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Deburring and Finishing Processes explained by AF Kenton a long-time process developer and OEM (Original equipment Manufacturer)
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ISBN - 978-0-615-85574-5
Evaluating Material Removal and Surface Modification Systems, by A.F. Kenton
Copyright 2013
Nova Finishing Systems ▪ PO Box 185, Hatboro, PA 19040 ▪ 215-444-9981 ▪ 800-444-4159 ▪ Fax 215-444-9982
www.novafinishing.com novafinish@earthlink.com
Table of Contents
Chapter 1 - Abrasives................................................................................................................................. 7
Introduction ............................................................................................................................................................................ 7 A Brief History of Abrasives ................................................................................................................................................. 7 Abrasives ............................................................................................................................................................................... 10
Chapter 2 - Classification ........................................................................................................................ 19
Surface Finishing and Preparation ..................................................................................................................................... 19 Classification: ........................................................................................................................................................................ 23 Type – Equipment Classification (first or first 2 numerical digits) ................................................................................ 24 Explanation of Location ....................................................................................................................................................... 26 Equipment ............................................................................................................................................................................. 35
Chapter 3 – Type 0 Equipment .............................................................................................................. 37
Alternative Deburring Systems .......................................................................................................................................... 37
Chapter 4 - Type 1 Equipment ............................................................................................................... 40
Automation: .......................................................................................................................................................................... 40 Wheel and Belt Systems ....................................................................................................................................................... 40 Human Factors...................................................................................................................................................................... 45 Variable Factors .................................................................................................................................................................... 45 Debris ..................................................................................................................................................................................... 46 Size/Diameter ........................................................................................................................................................................ 46 Automated Abrasive Wheel Deburring System ............................................................................................................... 47 Automated Abrasive Belt Machines .................................................................................................................................. 50 Non-woven ............................................................................................................................................................................ 51 Non-Woven Material Systems ............................................................................................................................................ 51 Selection ................................................................................................................................................................................. 58 Organic materials ................................................................................................................................................................. 60 Other Natural Materials ...................................................................................................................................................... 60 Abrasive and polishing compounds .................................................................................................................................. 66 Felt .......................................................................................................................................................................................... 69 Flap Wheels ........................................................................................................................................................................... 70 Discs ....................................................................................................................................................................................... 70 Comparison ........................................................................................................................................................................... 75 Inorganic Abrasive Belt Systems ........................................................................................................................................ 76
Chapter 5 – Type 2 Equipment & Mixed Technologies .................................................................... 82
Abrasive Blasting: ................................................................................................................................................................. 82 Air and Dust .......................................................................................................................................................................... 83 General ................................................................................................................................................................................... 84 Suction System: ..................................................................................................................................................................... 85 Safety ...................................................................................................................................................................................... 88 Pressure System: ................................................................................................................................................................... 88 Other Media .......................................................................................................................................................................... 93 Small Systems ....................................................................................................................................................................... 94 Cryogenics: ............................................................................................................................................................................ 96 Shot Peening Media ........................................................................................................................................................... 100
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Chapter 6 – Type 4 Equipment ............................................................................................................ 102
Wet Blasting or Water Hone: ............................................................................................................................................ 102 Water Jet: ............................................................................................................................................................................. 104 Ultrasonic Deburring ......................................................................................................................................................... 107 Abrasive Flow Media ......................................................................................................................................................... 112
Chapter 7 – Type 5 Equipment ............................................................................................................ 114
Thermal: ............................................................................................................................................................................... 114
Chapter 8 – Type 4 Equipment ............................................................................................................ 116
Chemical Milling: ............................................................................................................................................................... 116 Electro-Polishing................................................................................................................................................................. 117 ECD/Electro-Chemical Deburring .................................................................................................................................... 118
Chapter 9 – Type 3 Equipment ............................................................................................................ 123
Mass Finishing Equipment................................................................................................................................................ 123 The Barrel: ........................................................................................................................................................................... 125 Large Barrel Systems: ......................................................................................................................................................... 131 Medium or Open End Barrel Systems: ............................................................................................................................ 132 Open End Bottle .................................................................................................................................................................. 134 Small Barrel Systems: ......................................................................................................................................................... 136 Loading and Unloading Systems ..................................................................................................................................... 138 Vibratory Systems: ............................................................................................................................................................. 141 Separation ............................................................................................................................................................................ 151 Wet systems ......................................................................................................................................................................... 152 Bowl Shape Vibratory Mills: ............................................................................................................................................. 153 Vibratory Bowl System Eccentric Weight Control Adjustments ................................................................................. 156 Machine Capacity ............................................................................................................................................................... 157 Continuous Flow Tube ...................................................................................................................................................... 162 Multi Pass ............................................................................................................................................................................ 164 Compartment Processing .................................................................................................................................................. 166 Part Impingement ............................................................................................................................................................... 167 Unloading ............................................................................................................................................................................ 167 Dam Operations .................................................................................................................................................................. 168 Small Bowl Systems ........................................................................................................................................................... 171 High Energy Centrifugal Systems: ................................................................................................................................... 173 High Energy Barrel Systems: ............................................................................................................................................ 174 High Energy Disc Systems: ............................................................................................................................................... 177 Input/ Output ...................................................................................................................................................................... 179 Comparison of Disc vs. Barrel .......................................................................................................................................... 180 Other Mass Finishing Systems:......................................................................................................................................... 181 Drag Finishing .................................................................................................................................................................... 183 Spin Finishing ..................................................................................................................................................................... 184 Turbo-Abrasive: .................................................................................................................................................................. 184 Orbital Beam or Sonic Beam: ............................................................................................................................................ 187 Orbital .................................................................................................................................................................................. 187 Magnetic: ............................................................................................................................................................................. 188 Magnetic Disc Finisher ...................................................................................................................................................... 190
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Chapter 10 – Technology & Equipment Summary .......................................................................... 191
Conclusion of Equipment .................................................................................................................................................. 191 Surface Finishing Options ................................................................................................................................................. 195 EQUIPMENT CLASSIFICATION EVALUATION BY CATEGORY ........................................................................... 200 Equipment Burr Class Location ................................................................................................................................ 200 Wheel and Belt Systems 100 – 151 .............................................................................................................................. 204 Abrasive Blasting 250 - 253 ......................................................................................................................................... 204 Cryogenic Blasting 5200 - 5233 ................................................................................................................................... 204
Chapter 11 – Surface Finishing Standards ........................................................................................ 205
Surface Finish Quality Control: ........................................................................................................................................ 205 Other Terms and Measurement........................................................................................................................................ 207
Chapter 12 – Media ................................................................................................................................ 212
Media Supplies ................................................................................................................................................................... 212 Random Media ................................................................................................................................................................... 213 Media Size ........................................................................................................................................................................... 215 Preformed Shaped Media .................................................................................................................................................. 226 Steel media: ......................................................................................................................................................................... 231 Organic media: .................................................................................................................................................................... 237 Dry shapes ........................................................................................................................................................................... 238 Random Organic Materials ............................................................................................................................................... 239 Blended or mixed media ................................................................................................................................................... 244 Pumice .................................................................................................................................................................................. 244 Other inorganic additives .................................................................................................................................................. 245 Antique Appearance .......................................................................................................................................................... 245 Felt and Miscellaneous ...................................................................................................................................................... 246 Temperature ........................................................................................................................................................................ 246 Media Shapes: ..................................................................................................................................................................... 247 Media Guidelines ............................................................................................................................................................... 253
Chapter 13 - Liquid Systems ................................................................................................................ 254
Chemical Compounds ....................................................................................................................................................... 254 Liquid Flow Systems: ......................................................................................................................................................... 256 Additives: ............................................................................................................................................................................ 258 Chemical Accelerators: ...................................................................................................................................................... 260 Chemical Control/Monitoring: ......................................................................................................................................... 261 Alternative Processing Methods: ..................................................................................................................................... 264
Chapter 14 – Selection Guidelines & Cost Factors .......................................................................... 265
Waste Treatment: ................................................................................................................................................................ 265 Applications ........................................................................................................................................................................ 266 Quick Guideline Briefs For Mass Finishing System Processing ................................................................................... 266 Required Part Information for Proper Processing ......................................................................................................... 267 Equipment Requirements .................................................................................................................................................. 269 OPERATION COST ESTIMATE ...................................................................................................................................... 270
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Bibliography and Credits ..................................................................................................................... 275
Book ...................................................................................................................................................................................... 275 Articles: ................................................................................................................................................................................ 275 Seminar ................................................................................................................................................................................ 275 Contributors: ....................................................................................................................................................................... 276 Photo and Image Credits ................................................................................................................................................... 276
About the Author ................................................................................................................................... 280
7
Chapter 1 - Abrasives
Introduction
The purpose of this book is to cover the subject of all material removal processes or
surface finishing type modification equipment on parts and finished product. Basically this
subject matter involves the classification, explanation, and use of energy forces in a form of
negative actions to achieve positive results. In this case, surface finishing is the positive result of
the removal of material, which is actually a negative accomplishment. The information given is
technical, yet general purpose, with hands-on type applications designed to help one select the
best method and/or equipment to achieve the results one is looking for.
The title of this book is Evaluating Material Removal and Surface Modification Systems.
Most material removal processes and equipment use mechanical methods and solid abrasives to
accomplish surface profile modifications; however, there are also other methods and means of
accomplishing this task. Historically speaking, the term or word abrasives is well known and is
normally well understood to represent small solid materials capable of effecting other materials
when force of pressure is applied in relationship to one another.
The word “abrade” means to remove or modify the surface of an object with that of
another material object by physical movement or force. Most people equate abrasion with that
of a break down or the destructive action of one form of solid matter to affect that of another
form of solid matter in a relationship to those objects involved. In this process, the objects
involved get smaller and/or the overall object or larger objects normally get modified and
smoother. Given the consistency of the objects involved, there is a relationship or a controlled
rate of break down given the same amount of force, but that may not be necessarily true. In all
cases, abrasion is a removal process caused by the use of abrasives, which alters or changes an
edge or surface profile of one physical object with and by that of another.
A Brief History of Abrasives
The history of abrasive materials goes back a long way to the dawn of man. When one
thinks of the early man, he thinks of the cave man and his Stone Age mentality possessing only
the basic skill for survival. How man survived and became the dominant species here on earth
was through his intelligence and the use of tools, which were created or enhanced with the use
of abrasives. Archeologists indicate that even the earliest man used tools to help him kill his
food, cook it, and clothe himself. That means that man had the basic knowledge of how to make
things to help him help himself and that required the use abrasives.
Early man possessed few skills and he used what he could from nature; therefore, wood
and stone became his basic materials to make tools. With use, man began to modify these tools
by using harder substances to chip away at both wood and stone items. In time, blunt wood and
stone devices, when chipped and rubbed, became sharp cutting and piercing tools and
weapons. So very early on, man learned that rubbing or grinding of one object or stone against
that of another affected both objects, but more important he created and learned through trial
and error the early phases of abrasive technology and surface refinement.
Chapter 1 - Abrasives 8
As man improved his tools and weapons, he also discovered that his cutting tools had a
two-way action. That is, not only did the tool cut the object he was working on, but it sometimes
cut the person using the tool. In most cases a sharp edge was desired and care was exercised;
however, as people began to make other objects not designed to cut, the sharpness was not
desired and had to be removed or modified. A sharp edge in the wrong spot can cause failure of
the intended object or tool itself.
Edge removal processing really didn't get much attention until the Bronze Age and/or
when metal working became a more common tool making process, but even then creating the
sharp edge was more important than removing it. In those early days of metal working, the
creation of sharp edges on metals often produced end result of sharp, rough, or irregular edges
that reminded people of sharp or rough, prickly fruit and/or plants that protect themselves with
thorns or burrs. Consequently, at some point in history, these sharp, unwanted inorganic
fragmented projections also became known as burrs. Like their plant counter parts these burr
projections had to be avoided and removed before the tool or product could be used properly
and safely.
The creating of a sharp edge requires the thinning of materials being worked. Although a
lot of materials could be sharpened, they would not hold up over a long period of time. The
materials, which provided the best results, were metals, because they maintain a smooth
continuous surface with an acute angle; however, metals were also the most difficult material
that could be worked. To properly work metals and achieve the desired result one had to have
the knowledge of both the metal and the abrasive. Through mostly trial and error, it was
learned that different mineral abrasives and sizes had different physical effects or characteristics
to other materials and they produced different results depending on how these abrasive
materials were used or applied. In short, man learned about the hardness of one material in
relationship to affect that of another.
In the early days, most metal modifications and/or edges were accomplished by
blacksmiths using heat and hammers. Pounding and reshaping were the primary methods used
to obtain the desired shape and edge. After shaping, the final edge was dressed or worked by
hand using a flat grinding stone, a round wheel, or fine loose abrasives applied by leather and
lubricant. Because sharpening and the surface finishing process was achieved slowly, burrs
were not known to be a problem back then. If they were a problem, little is known or written
about them.
As mentioned, the knowledge of abrasive materials goes back a long, long way. Way
before the time of blacksmiths and metalworking. More than likely, stone finishing and wood
working trades knew how to use abrasives and this knowledge carried over into metalworking.
However, unlike these other trades, metal working and finishing presented special problems
not common in those other trades. The characteristics of stone and wood are not the same as
metal. Metal is tougher or stronger and more cohesive in thin sections than those of other
materials. The burr problem requires special handling or treatment and more aggressive
abrasives and procedures.
Chapter 1 - Abrasives 9
Just when man learned how to use abrasives in a more controlled and productive way is
unknown; however, there are stone monuments in ancient Egypt and other parts of the world
that that have been worked smooth and uniform and that is not found in nature. That means
that early-civilized man found ways to work and create relatively smooth surfaces through
repetitive means. However, the basic idea of using abrasives for creating smooth surfaces
probably came about by observing a number of exceptions in nature. More than likely, man
observed and tried to duplicate the erosive effects that water and waves had on stones in creeks
and shorelines or how desert sand and wind effected nature and manmade objects in arid
regions of the world.
Man could not duplicate the type of energy forces of nature and therefore probably had
to rely mostly on hand pressure and crude turning devices. To aid hand working, he used types
of cloth with or without hard support backing and other mechanical methods to apply greater
pressure to the abrasive in contact with the end product materials. The first known successful
mechanical method, other than hand and the grinding wheel, to apply a continuous force on
parts may have occurred in ancient China and Egypt. It is known that they did use barrel
tumbling methods with stones to work metal, but there isn’t much information on these
methods or processes.
The need and development of mechanical pressure for making contact between the
abrasive and the work piece resulted in new application methods and other materials being
tried for improving surface finishing speeds and results. At some point uniformity and
repeatability in both parts and supplies were discovered to be important factors. Due to scarcity
of uniform abrasive supplies and suppliers man basically used whatever was available to him in
either organic or inorganic materials and noticed that these different particle sizes and materials
produced different results. Because of the variance and characteristics of these different working
materials, they all became known as a media or a medium, which is a means of conveying or to
get to something else, or is a transmitting or transfer device. I guess you can also call this period
of time, early research and development.
Along with the understanding of abrasive materials, man discovered that the speed and
surface finishing end results could be manipulated using different mechanical contact devices of
cloth, fiber, or leather, which could be impregnated with abrasives. Most application methods
were mechanical rubbing or lapping type operations done by hand, but it was also observed
that finishing results were affected by the size and hardness of the abrasive particles used, and
the way in which the energy forces were applied. However, time was not considered a big
factor back in the early days of metal working, labor was relatively cheap and plentiful and
craftsmen took pride in their work.
In addition to the type of energy force, the process, and the mechanical contact device,
the transfer means of application and the moisture content associated with the use of the
abrasive were found to have an effect on final surface finishes. Lubricants and/or liquids were
used to improve the abrasive process and help prolong the life of these mechanical contact or
transfer devices, the abrasive, and to improve the general working conditions that man
Chapter 1 - Abrasives 10
experienced while working with these products. Liquids were used to reduce the dust and heat
transfer problem caused by mechanical actions necessary to get good finishing results.
So very early on in our civilization, it was discovered that a lot of different factors
affected surface refinement, and metal finishes and as technology improved over the ages, there
was a growing need for higher quality surface finishing for functional and mechanical
applications. Along with the need for abrasives for removing burrs and creating edges was the
need for smooth surfaces and/or low RMS 1 or flatness, which produces reflective mirror
finishes. To get smooth surface finishes required the use of finer types or sizes of abrasive
materials, more energy, and longer time processing. That is, the need to improve surface
features required different qualities or characteristics of an abrasive and the size of abrasives
was important to produce the desired result. Again, the method of application was also often
different as well as the processing time.
Mirror finishes were used a lot by people in the armies of old for a number of reasons.
The idea of a bright, shiny sword or metal armor, besides not only aesthetically pleasing, was
believed to have a defensive value to reflect light and interfere with the enemies ability to see
properly. Therefore besides fit, form, and function, bright finishes were desired on metals and
to accomplish the task of polishing required a wider range of finer, softer abrasives and
additives to prevent oxidation. It is interesting to note that a lot of abrasive technology
originated out of the needs of the military. So you see, the more things change, the more things
remain the same.
Abrasives
There has almost always been a need for different methods and materials to perform
special metal finishing tasks and that makes the abrasive industry and finishing one of the
oldest industries still in use today. Deburring and polishing are both material removal processes
that are relative to size. Polishing is more of a surface modification using little if anything
typically considered abrasive materials because of its small size, but their function is the same.
Both require the use of abrasive materials of different size, shape, characteristics, and methods
of application. For deburring, the general rule of thumb is the larger and harder the abrasive the
more material is removed in the shortest period of time; however, it also leaves the roughest
surface finish. For polishing, the best results are obtained using a series or progression of
smaller and smaller and softer abrasives. Naturally these are over simplified statements that do
not take into account part size, material, and what is the desired result.
The term abrasives, is a general or generic term used to describe a lot of different mineral
compounds. The word abrasive is not a specific item in itself because just about any physical
substance found on earth will effect or do material modification, if given the right tools and
pressure applied to an abrasive particles and the material being worked. Why I mention this
1 RMS means Root Mean Square. It is a standard unit of measure for surface profile or roughness. See
chapter 11
Chapter 1 - Abrasives 11
now is because an abrasive classification or product works a limited range of surface
irregularities and produces specific results. To a large extent, these surface modifications
depend on the material being worked. The material removal rate of all abrasives is normally
rapid at first then tapers off until no major material removal rate is noticeable and that is
because the abrasive particle size itself becomes smaller and less effective. This surface finish
situation may occur way before the desire finish is achieved.
As stated, in the past the abrasive material used for deburring were usually determined
by the hardness of the mineral or abrasive particle and the part being worked. Large hand-held
stones or files were used to rub or deburr material edges. For surface finishing and bright
finishes, leather or cloth and a fine abrasive paste or rouge where preferred to produce smooth
shinny metal. Technically, both deburring and polishing involves nearly the same abrasive
materials, but the amount and way in which the energy is applied to the abrasive and transfer
system determines the characteristics of the metal finish or end results.
Normally removal of a lot of material can best be accomplished on outside edges of a
part. That is because access to outside dimensions are relatively easy to reach and extreme force
can be concentrated and applied to an edge to remove material very fast; whereas, flat surfaces
require the same amount of pressure or more to produce relatively little noticeable material
removal. The reason for the difference is the amount of pressure spread over a point versus a
broad flat area.
An analogy of energy forces used here would be that of a riffle versus that of a shotgun.
Both guns work the same or do the same thing, but they are used for different applications. In
one of our abrasive applications, the process is done to remove the sharpness of the material,
the other is done to remove porosity of the material or to create a smooth surface. One process
requires the use of more rigid application of abrasive and the other requires a more flexible
application of those same abrasives or smaller abrasive particle sizes.
Abrasive pressure can be more easily concentrated in a rigid manner and there is less
resistance to the force of a metal edge than that of a surface area where pressure is spread out
over a relatively larger area. The cohesiveness or surface tension of metal is more difficult to
overcome in a broad flat state, given the same abrasives and tools. Normally application
considerations are not a problem and never in conflict. That is, we are talking about two
different requirements.
Edge removal is done for primarily safety and functional reasons and normally doesn’t
require a fine uniform surface finish. A flat surface is already safe and functional, but does
require surface refinement for better environmental protective treatments or coatings. A refined
finish will be a mirror image of that base metal, but will be capable of better adhesion qualities
or will produce more uniform molecular structure for a protective chemical treatment.
In most cases, function and/or longevity are the primary reasons for making parts out of
metal. Parts must conform to specific dimensions in order to work properly. The size and
outside dimensions are important for clearance to other parts, but these dimensions may also be
controlled by inside holes that fasten parts together to function as an assembly. Any overlap or
Chapter 1 - Abrasives 12
sharp edge may interfere or damage adjacent parts or materials. Therefore, edges must be
rounded or modified reasonably smooth and this amount of material removal is usually
determined by a combination of abrasives, friction, mass, and energy that work together to
modify the outer layer of the metal to conform to the finalized part and its working
environment.
The general surface appearance of metal appears relatively flat, but under magnification,
the physical surface profile of the metal is composed of uneven peaks and valleys. To deburr or
modify parts, an abrasive must be used that will remove or blend in these surface irregularities.
Very hard abrasive materials with large molecular crystals may produce a shinny surface
appearance, but they may also do more scratching or tearing on a micro level of the metal than
the smoothing or removal of the surface. Hard abrasive materials are actually better for
polishing when the material is of a very small particle size and/or worn down so that the edges
are rounded or removed. Worn or a round abrasive particles permit more mobility and a kind
of rolling action that is more desirable for burnishing, which is more of a lapping or deforming
of the surface irregularities than a removal process.
The smaller and harder the abrasive used with mechanical application devices, the more
pressure one can exert on the abrasive and this normally means the smoother the surface;
however, this is not necessarily true. Given the same size abrasive mineral, an abrasive harder
than the metal will work or create a profile of the metal nearly equal to the size and shape of the
abrasive particle used. That is because the abrasive may not break down, but will drag along the
surface of the part to be worked thereby creating a mirror image of its particle size. If the
abrasive is loose and able to roll, it actually flows with the profile and to some extent
compresses, laps, and/or deforms the peaks of the metal profile. This action creates a denser top
micro level surface that is more shinny or smoother, but the metal will still have an irregular,
less pronounced surface profile variation.
When an abrasive is used that is softer than the metal being worked, the abrasive will
break down or decompose as it is being used and generally will create a smoother over all
surface profile. That is, when the softer particles hit the profile, the particles meet resistance in
excess of their crystal size and strength and in the process of breaking down into smaller
particles; some of the metal profile is modified and/or removed. The rate at which the particle
breaks down and the crystalline molecular structure of the abrasive determines the overall
surface finish profile of the metal. If the abrasive breaks down too fast without any pressure
against the irregular profile, then there is little material removal. However, softer materials that
break down are normally smaller in particle size and are somewhat more flexible thereby
creating an overall smoother surface profile finish, but not necessarily a bright shinny finish.
To do a good job of metal removal the best abrasive materials are the ones that break
down and exposed new irregular or flat shaped sharp mineral crystals. This break down
characteristic seems to be a better gauge of a good abrasive than hardness; yet, hardness gives
greater life or longevity to the abrasive materials. Therefore, the measure of a good abrasive,
besides hardness, requires the knowledge of other characteristics such as the molecular
structure of the mineral, its crystal structure, and/or its chemical composition and in some cases,
Chapter 1 - Abrasives 13
its behavior in water and chemicals.
Hardness is still a very important factor to consider for abrasive characteristics, so much
so, that knowledge was protected and shared only with people who worked with abrasives that
were respected craftsmen or tradesmen. At times, these people had to share some common
information to gain reliable sources of good mineral sources and sometimes they had to trade
technical information as well. Like any trade or industry, there was and is a need to distinguish
materials and create standards. Because uniformity produces repetitive results the importance
of descriptive information for determining materials and hardness, a universal measurement
scale was desired and needed.
The classification of minerals seems to be pretty well clear cut and dry and is determined
by a relatively fixed chemical composition; however, there are different grade variations or
forms of hardness within a range of minerals that can be distinguish even within these fixed
grades. Minerals are naturally occurring compounds formed under the physical forces of
pressure and heat; therefore, different conditions can produce different variations of the same
mineral. This variation is normally distinguished by density, but it also can be a result of the sub
atomic molecular crystal structure caused by heat and pressure. Normally hardness and density
are closely related, but they can be different because of the atomic bonding structure.
The physical size of a particle is easy to identify and classify with mechanical means;
however, hardness and density are relative terms and can be difficult to classify using any fixed
set of standards or means of measurement. That is because there are a number of ways to
measure hardness, but no one single method works well in all cases over a complete range of
minerals.
In the early 1800’s, a hardness scale was developed by a Friedrich Mohs. The Mohs scale
rated all known minerals from 1 to 10, with the talc mineral as the softest at a 1 the diamond
being the hardest at a 10. The basis of this scale is the ability or relationship of one mineral to
scratch the surface of another. The original scale only showed or rated 10 common minerals of
the day. At a much later date a modified Moh’s scale was created that numbered minerals from
1 to 15. More recently, decimals were also added to create a more defined scale or relationship
of one mineral over another. The modified version of this scale is a fraction chart with the only
other numerical consideration as a .5 or a half whole number for determining sub category
hardness. Even though these other versions of this scale are acknowledged, unless specified as
the modified Mohs scale the measurement most people still use is the old 1 to 10 system.
More recent precision hardness measurement scales are the Brinell, Rockwell, Vickers,
and Knoop scales. All of these scales depend on resistance to permanent indentation of a
specific shaped contact tool device, such as a ball or pyramid, under pressure against the
mineral or material in question. The most common scale used in the USA, besides the Mohs, is
the Knoop scale that identifies minerals using a numerical value of 1 to 7000 for the same 1 to 10
Mohs classification. Even though the Knoop scale is more detailed, it is rarely used in the
abrasive finishing industry. All of these scales are excellent for determining metal hardness, but
Chapter 1 - Abrasives 14
because of mineral hardness, there are fracturing problems; therefore, most people still refer to
the original Mohs scale when talking about hardness.
In addition to the hardness of metals scales mentioned, there are still some other lesser-
known hardness scales which can be used or shared within the industry. The Scleroscope test or
scale is based upon the height of a rebound of a contact tool. Supposedly, this test measures the
loss or transfer of energy of the sample. Another test or scale is known as Microhardness. This is
a low-pressure indenture test similar to all of the other common metal tests; however, this is
done at low pressures and requires the use of a microscope. For softer materials, there is the
Shore Durometer scale or test that uses a spring loaded contact tool.
Other scales not commonly known or used by the general public are the eddy current test
that measures electrical properties, the Sonadur test that uses a sound resonance, and the
Eseway test that uses impact via an ultra sound sensor. None of these other tests are being used
to any extent in the abrasives industry so we will not go into them in any more detail.
Mohs Scale Of Hardness
Material Scale
Talc. …………………………………………….. 1
Gypsum. ……………………………………….. 2
Calcite…………………………………………... 3
Fluorite…………………………….…………… 4
Apatite………………………………………….. 5
Orthoclase…………………………………….... 6
Quartz. ………………………………………….. 7
Topaz…………………………………………….. 8
Corundum………………………………………. 9
Diamond……………………………………….. 10
I do not know of any study of metal or material hardness to correspond to the mineral
hardness and pressure or its relationship to the Moh’s scale; however, there is probably a
correlation. There is the Rockwell standard for measuring metal hardness, but again, there is no
relationship to the Moh’s scale. That means that there is no scientific relationship for selecting
one abrasive over another other than the recommendations from abrasive suppliers and most
abrasives that are used are determined by cost and availability which in turn is normally
determined by raw material suppliers. That also means that hands on experience knowledge is
one of the best sources for determining abrasive usage. The variable qualities of both materials
and abrasives make the selection and finishing process systems sometimes appear unscientific,
but there is a relationship. Most knowledge of abrasives, deburring, and finishing are just not
taught, but are picked up with experience.
Chapter 1 - Abrasives 15
Hardness of minerals is an important factor in material removal rates and processing
times. However, they are not the only factors. In fact, size and friability are very import in
relationship to the metal hardness. Because of specific gravity, resistance, density, and
molecular structure, a physical part is normally larger than the abrasive used and therefore
more resistant to significant physical changes. That means that an abrasive is affected and
subject to change as well as the parts surface finish; therefore, an abrasive harder than the
material being worked is desirable.
The stronger the crystal structure of the abrasive mineral and larger the size of the
particle the greater the amount of kinetic energy that is released. Not only do you have energy
from an outside source to create the pressure and contact with the part, you also have energy
from an inside source. Outside forces are easy to explain. That is the whole purpose of machines
and that is what all abrasive machines systems do. Inside kinetic energy is different. The latter is
similar to what happens in an earthquake or explosion. Besides the actual release of energy in
the form of heat, there is also violent radical molecular movement. Physical displacement and
forces are amplified in extremely short rapid movements of the remaining material on a
molecular level that creates tremendous pressures against whatever they are in contact with.
As abrasive particles break down and become smaller, they require greater outside
energy or force to do the same amount of material removal. That is both a true and false
statement. What happens is that because the abrasive particles become smaller there is actually
more surface contact, friction, and greater resistance. That breakdown process generally
produces less bulk and weight per particle. That in turn, reduces the size of the material
particles being removed. That is the true part of the statement.
Where the difficulties or false part of our statement, “same amount,” comes in is in the
load characteristics of the material removal process. Given the same density or hardness, the
larger mass will always affect the smaller mass first of either the size of the abrasive or the
materials surface profile irregularities. That means that the material removal rate maybe in the
same ratio of particle size to material removal, but the ability or load characteristics increase
making it more difficult to remove larger surface irregularities in mass. This is false according to
our first statement and goes back to an earlier statement that the surface profile can only be as
smooth as the smallest abrasive particle.
The molecular cohesive force or bond of an abrasive tends to lose its ability to remove,
carry, and convey other materials as they get smaller and this relates to mass and/or specific
gravity. However, this problem is somewhat overcome by the mass as a whole, which behaves
like a flexible solid. Then again, this size and mass behavior makes it more difficult to remove
greater surface irregularities without the use of more energy or force. All abrasives will work up
to a certain point and then slowly decrease, based upon the elements of weight, mass, and
density. As long as there is a transfer mechanism in place to apply pressure to both the part and
the abrasive, then there will be material removal. However, because we are talking about
normal working conditions or processing time, an efficiency point is reached way before the life
of the abrasive is used up. In short, the smaller the particle size, the greater the energy force
and/or pressure is required to maintain the same material removal rate.
Chapter 1 - Abrasives 16
With the exception of a flat smooth surface, irregularities in a materials surface profile
will always exist to some extent on a plane of reference, if only because of the porosity of the
material involved and the relationship of bonding molecules. In most cases, surface finishing
systems do not have to create a perfectly flat material profile. In fact, when parts require a heavy
coating over the finished part, a smooth finish is not the desired end result.
The size and/or amount of a surface profile irregularity can be reduced and will
continually decrease to a measured zero point or where the size of the abrasive will not work
efficiently. There are limits to abrasive mechanical methods or processes. At some point, which
depends upon the characteristics of the abrasive used, the break down rate or friability of the
abrasive becomes a more important factor than weight, mass, and density. The reason for that is
because the breakdown process releases kinetic energy forces and any movement of a solid
against another solid does surface modification.
This may still be a difficult technical concept to understand, because the relationship of
the abrasive to the material’s surface profile can vary greatly; however, a lot of common sense is
involved here. That is, at first larger, fewer, and heavier surface profile irregularities are
removed during a mechanical deburring process, then as the part’s surface becomes smoother,
material removal size becomes smaller in size and volume to both the abrasive and the material
being worked. That break down process gives the visual appearance of little or no surface
modification. In actuality, the material removal rate remains nearly constant, but physical
perception is deceived. However, if you go strictly by the weight of the part to the material
being removed, then this is a false statement. A lot of this measuring and evaluation depends on
what measuring scale you are using.
Typically, depending upon the deburring or surface finishing systems used, most large
irregularities that offer resistance to the abrasive are removed first, followed by smaller and
flatter surface features. The smaller the abrasive particle size, the deeper it can penetrate into the
material profile of the part; however, if the particle size is too small it too can get trapped in that
same profile if there is no larger particles to dislodge it. The smaller the mass, the less force it
has to do material removal and that also means the finer the surface finish. The only way to
compensate for this factor is to impart or increase more energy or weight to smaller abrasives
than is required for larger mass size. This particle lodging situation happens a lot with blasting
systems.
The only other way to get around the rule of particle size that affects the surface profile
rule is to allow the abrasive to float or give in relationship to the pressure applied to both the
abrasive and the material being worked. If an abrasive has the ability to be flexible, or allowed
to drag and/or be compressed along the surface of the material to be worked, it can accomplish
a finer surface finish than its normal particle size. However, because abrasives are basically
dense solids, there is little ability for this material to float unless you add air or water to the
process or to somehow bind the abrasive into a flexible or larger softer abrasive mass shape.
Then again, if any abrasive is permitted to free float without controlling the part contact, there is
no absolute assurance that this will still produce a uniform finish finer than the abrasive used.
Chapter 1 - Abrasives 17
It is necessary that the abrasive particle does change or break down in order to carry
away burrs, debris, or any surface irregularities. The result of not breaking down or becoming
smaller, is excessive energy imparted onto the abrasive that is transferred to the part causing a
condition resembling an orange peel surface. When that happens, the material surface becomes
more dense where impacting occurs and that creates a condition that is called work hardening
which is similar effect produced by heat treating materials. In an abrasive process, large
particles can deform the material surface being worked, given enough mass, creating either
visual or microscopic indentations and that can leave the surface rougher than what its surface
profile started out. This is another common condition that results from blast finishing systems.
As mentioned, the smaller the average size of the abrasive particles used to modify the
surface, the finer or smoother the material finish. Another way to produce smoother surface
finishes is to use softer or more flexible abrasives. A smooth finish can also be accomplished by
using some kind of liquid or some bulky filler mass as a means to cushion the abrasive or to
encapsulate it make it more flexible. Lastly, the slower the movement and pressure of the media
against the part or surface the finer or smoother the finish. Naturally, there is a point of
economics involved with all of these processes, so time is normally another factor or
requirement for finishing. The energy force factor must be considered in any material removal
system for speed and the finishing results desired.
At some point greater energy force or pressure and smaller particle sized abrasive is
required to perform finer or smoother surface modifications. When this point is reached, one
should consider the concept of step processing which is a condition where an abrasive ceases to
work efficiently to produce the desired surface smoothness. When that point is reached another
abrasive is chosen to produce the next finishing requirements. The point where the performance
of abrasive particles appears to decrease rapidly is when a new or different abrasive should be
changed in order to maintain efficient material removal rates. More energy or pressure can only
be applied to the abrasive up to the point where that energy can be transferred in relationship to
the material removal process or the required part finish.
To produce finer material or edge finishes requires smaller abrasive sizes and longer or
more aggressive processing times. It was mentioned that the fastest way to get to a smooth
polished finish is to prepare or refine the edge or surface features with coarse or larger abrasives
first. Depending on the roughness of the initial part and the finish required, the part or area is
then reworked with consecutively smaller abrasive grit sizes using a multiple number of steps
or passes until the surface finish is achieved. This step procedure is a slow process, but it is also
faster than using a single small abrasive size to accomplish the same finishing task.
With the exception of a measurable flat smooth surface, irregularities in material surface
profiles will always exist to some extent on some plane of reference, if only because of the
porosity of the material. However, the size and/or amount of the irregularity can be reduced
and will continually decrease to a point where the size of the abrasive media will not work
efficiently. Weight and mass are the most important factors to remove large amounts of surface
irregularities. However, a point is reached where weight and mass become a liability. At some
point, which depends upon the characteristics of the abrasive media used, the breakdown rate
Chapter 1 - Abrasives 18
or friability of the media becomes a more important factor than weight and mass. Technically
speaking, you cannot get a smoother surface feature better than the abrasive particle size you
are using, because the particle, if it does not break down into a smaller particle, will actually
produce irregularities that correspond to the physical abrasive particle size in use.
As mentioned, the only way to get around this rule of size is if the abrasive material is
allowed to float or give in relationship to the pressure applied to both the abrasive and the
material being worked. However, because most abrasive particles used are made into fixed
shapes or bonded to a rigid surfaces there is little ability to float, unless you add air or water to
the process. Then again, if abrasives are permitted to free float this may not produce a uniform
surface; therefore, contact pressure is very important in material removal rates and surface
finishes, where time is important. Now, that means that how energy is applied and transferred
to the abrasive particles and the parts being worked are also very important to material removal
processes.
Another factor to consider is the hardness of the materials being worked and the abrasive
particle hardness, because there are different friable breakdown rates or crystal structure of
abrasive materials. You need an abrasive that will wear away and remove surface irregularities
before the abrasive particles lose their ability to abrade and/or transfer energy. Energy force, or
how energy is applied to the materials surface must be considered in all surface modification
systems. There are a number of systems and options on how this energy is to be applied and
they all achieve different results.
The concept of energy or force uniformly applied to abrasive particles is an important
factor both in surface finish quality and the speed of the process. However, there are tradeoffs.
Consistency and repeatability are important. Therefore, not only does one have to consider the
abrasive and size to use, but he needs to know the finishing characteristics and quality in
relationship to the equipment or process, plus the economics that can be achieved using these
energy transfer systems.
19
Chapter 2 - Classification
Surface Finishing and Preparation
Before the age of mass production or standardized parts, most parts were custom made,
worked, and finished by hand. That normally meant that no two parts were actually identical
and not necessarily interchangeable. They may have looked and functioned the same, but
dimensional variations were common; therefore, finishing requirements were not that
important or critical, especially if the parts could not be seen. Appearance and being smooth to
the touch was probably more important than dimensional tolerances. If the metal part could be
seen, a mirror or reflective finish was usually desired, since this was normally a sign of good
craftsmanship. However, most metals and surface finishes that were exposed to the
environment and not protected were and are subject to oxidation. Therefore, no matter what the
appearance of the finished part, a protective coating was desired to cover the surface finish from
oxidation and deterioration.
Use of the word surface finishing opens up a whole new can of worms, which I avoided
earlier. Depending upon whom you talk with, the term “surface finishing” means different
things to different people. Depending upon the application or relationship to the person in
question, it can mean: preparation, plating, painting, coating, or our usage meaning surface
profile modification or the smoothness of the material. Each application or meaning involves
another industry or technology, which is different from one another and has its own set of rules
and requirements. Unfortunately, like so many of words in the English language, the proper
terminology depends upon the industry you are talking about and since they are all related, it
makes it extremely confusing at times. See conclusion chapter.
Surface finishing and surface preparation mean two different things, but to the average
person they are sometimes used interchangeably. A surface finish can mean the final result of a
manufacturing processes and/or the final appearance of the part at any stage of manufacturing
or it can be the final condition after any additional protective coatings are applied. In some
cases, a surface finish does not have to be protected and can be the same as that final
appearance of the part.
Surface preparation is the final surface appearance of the part prior to being coated with
some kind of protective film or coating. Surface preparation is never the final appearance of a
part, unless you consider thin chemical coatings or treatments. In the latter situation, a thin
coating such as anodizing or alodine, the part’s surface appearance or dimensions remain
unchanged; therefore, it is both a surface finish and surface preparation. It is the mechanical
systems and changing conditions or inconsistency of a part’s surface at any point is what causes
much of the confusion and usage of these interchangeable terms.
Now, although we have just tried to make a distinction between these two words,
common usage confuses them. That is, we have just said earlier that no matter what the
appearance, coatings are necessary to protect a surface finish from oxidation, but a surface
finish only represents a current condition of the part. That means that almost all parts are
Chapter 2 - Classification 20
finished to what is called a surface preparation condition. Interpretation of these words
basically now means that any metal part that appears to be metal is the surface finish or surface
profile; whereas, surface preparation now refers to perhaps a surface condition prior to being
coated with a thick film, or at least cleaned in some soluble solution. Perhaps another visual aid
is that a surface finish is usually a lot smoother than a surface preparation, because roughness
or porosity is a desired quality for most heavy thickness coatings or films to adhere too.
Before we get into equipment classification and energy force systems, let’s take a look at
the options for the common term surface finishing. In mechanical finishing, there are 3 types of
options. The option one chooses depends mostly on how the part is to be used, or in what
environment it will be working in. These options are as follows: 1. Surface preparation for
heavy or thick coatings such as paint or plastic based film products, 2. Surface preparation for
thin film chemical coating or treatments, 3. Polished or smooth finishes are for aesthetic
appearances or are done to reduce bacteria hazards and medical requirements. In most cases,
design engineers will specify surface finishing requirements based upon the end use criteria.
Once the surface finish requirement is determined, the method to achieve that surface
preparation needs to be selected. The following are some guidelines for surface preparations.
Surface Finishing Options
Type 1 Surface preparation for heavy thickness coatings
A. Surface finish will be the roughest of all options and the finished part will
exceed the parts final dimensions because of the coating.
B. Surface finish should be as rough as possible to increase the surface area for
good adhesion properties and/or wear characteristics or longevity of the coating.
RMS 35 or higher.
C. Roughness of surface should not exceed in height the profile of the thickness of
the film or coating to be placed on part.
D. Surface should be as clean as possible from debris, oils, and oxidation.
Therefore, cleaning should be done immediately before coating, but part(s) should
be dry.
Type 2 Surface preparation for thin film coatings
A. Surface finish normally requires a secondary modification and that will be the
final dimensions of the part, but it can be on the plus side of the tolerance
depending on the film or coating.
B. Surface finish requires a smoothing or modification of the part to improve
uniformity of the surface profile of the finalized processed part. Normal RMS
range is 12 to 20.
C. Roughness profile is not as critical for most chemical treatments; however, the
smoother the surface, the more uniform the treatment. See Type 1, C & D above
for non-chemical coatings.
Chapter 2 - Classification 21
Type 3 Polished finishes
A. Surface finish will be the smoothest of all the options and close to the final
dimensions of the part, but on the minus side of the tolerance. If a thin film coating
is still required, dimensions may exceed final part size.
B. This process is not considered surface preparation, but a modification
procedure or material removal process. The finalized part will either have a
textured pattern or mirror finish in the RMS range of 2 to 18.
C. Surface finish is mostly a question or porosity or for appearance sake; however,
coatings can still be applied for protective reasons.
In making a part, most manufacturing time is devoted to making the part. That is, a part
is made from raw material that can be molded, cast, or rolled into square or round bar, it is then
machined, milled, drilled, turned, ground, etc. In most cases, little thought or time is devoted to
the final surface finish of the machined part. That was the thinking in the past and this same
thinking process seems to have extended into the present.
Production facilities seem to spend a lot of time concentrating on the machining
operations and then rush the deburring and finishing operations. Too little engineering thought
is devoted to the final finish. Whereas, with some proper planning as to how a burr or
roughness is formed a lot of deburring and surface finishing can be avoided or lessened. The
combination of a good engineer and machinist, with the proper knowledge of feeds and speeds,
equipment, and tools can create a program that can eliminate almost all deburring and surface
finishing. See “Deburring and Edge Finishing Handbook” by La-Roux Gillespie 1997
Generally speaking, any part that is machined, formed, or worked usually results in
sharp edges and that is not normally an accepted finished part. Therefore, some secondary
operation or process is normally required to remove the sharp edges and/or smooth out surface
irregularities before the part can be used in its final application. A secondary operation means
that some form of energy or force must be used to remove or modify the part’s edges and
surface. What force one uses and how that force is applied is the understanding of deburring
and mass finishing.
In mechanical finishing, the concept of energy or force uniformly applied to abrasive
particles is an important factor both in the surface finish quality and the speed or rate of the
material removal process. In addition to speed one has to consider the factors of consistency and
repeatability and the economics that can be achieved using these energy forces. Other factors
are limitations of part size and shape as well as the abrasive used and the finishing
characteristics in relationship to the equipment. How energy or how equipment uses energy is
critical to the processing element, time, and the final results.
There are at least two elements or forms of energy that are used for material removal in
mechanical systems. These are: speed or velocity and pressure or friction. These are related
terms, but they can also be thought of as 4 elements. Speed and velocity are related to
movement. Pressure and friction can be related to compression and contact. So, in simple terms,
Chapter 2 - Classification 22
for material removal you need to move the part and abrasive under pressure in a uniform
contact fashion against one another.
That basically brings us up to finishing equipment. How energy or equipment uses
energy is critical to the processing element. Now, although there are two forms of energy
required, there are 5 basic energy or equipment systems that do surface finishing or material
removal, 6 if you consider hand operations. Of the original 5, only 3 are mechanical systems
which involve abrasives. The other 2 systems deal with liquids and temperature. These will all
be discussed at length shortly.
Naturally, manual hand work is all very labor intensive, time consuming, and surface
finish quality varies a great deal from item to item because of tools, methods, and the human
factor. This lack of uniformity and repeatability in early times was not normally a problem,
because most useable physical items or material goods were basically one of a kind type
products considered custom made and not made to with interchangeable parts. Therefore,
because of the time element and costs, surface finishing of goods were not a major prerequisite,
unless you were talking about items specifically to be shown and seen by royalty or people of
money. In the latter cases, a great deal of extra time was required and spent on surface finishes.
As machine assisted cutting tools came into use, burr removal became more and more of
a problem. Shortly after the industrial revolution began, the terminology used to describe the
process of sharp edge removal or surface refinement became known as deburring, or to burr,
and/or meaning the negative form of a burr. Burr, in turn is the analogy of the sharp thorny
projections of burr type plants previously mentioned. Many high speed production machine
systems using cutting tools create sharp edges and/or produce slivers or fragments of metal that
resemble, behave, and feel like the thorny burr.
Most metal working processes create burrs for a number of reasons. The primary reason
is the fact that when metals reach a certain thickness or rather thinness, they cease to behave like
the parent metal, but bend and/or behave like a flexible solid, yet stiff enough to create
problems of safety and possible performance of the part. One way to reduce this extra material
deburring removal is to use the proper cutting tool and speed in the machining operation. It is
possible to machine a part without any sharp edges or burrs, but it is usually more cost effective
to separate the fast machining operations or main material removal processes from the slower
secondary finishing operations.
Because time is money, most companies trade off production speed and incur the
problem of burr removal to a separate metal working process as a standard practice. The
deburring process then is necessary to actually finish the machine cutting operation, or to
improve the surface finish of the machined area, or to achieve a proper profile or edge.
Primarily the part must conform or meet fit, form, and function criteria within safe handling
parameters and maybe appearance. The actual removal process then is the burr removal or the
word deburr, even though we may be talking about surface preparation or finishing.
Hand powered tools and surface finishing was not known to exist or be of any
significance until the invention of steam powered machines. Even then, it was really electricity
Chapter 2 - Classification 23
and air powered equipment that became the main source of mechanical energy systems that
reduced and improved hand labor surface finishing operations. In the early 1900's, the
industrial revolution changed the way a lot of things were done. With standardized parts
and/or production lines came the need or requirement for the uniformity of parts and finishes.
Even with advent of powered hand tools, the surface or edge finish of an end product
depended upon who was operating the hand tool, the size, type, and condition of the abrasive
that were used or specified, and to some extent the inspection procedures which set the
standards of acceptability. The end results or finishing procedures still varied to some extent
depended upon the person and/or pressure applied to the tool, the abrasive, and the part. As
long as parts were not designed for close tolerance precision fit and as long as they looked
nearly alike, most of these finishing procedures were acceptable.
As quantities and/or volume of parts being produced began to increase, reliability and
quality of the part became a major factor. Therefore, it was necessary to develop new ways to
surface finish all parts alike and in the shortest amount of time, energy, and economically.
Hence, hand tools gave way to automated systems, except where work areas were too difficult
for efficient abrasive tools and procedures. A number of different ideas were incorporated into
technology applications to try to produce uniform finished parts, but most of these involved the
use of abrasive materials. Abrasives were and are the main source of mechanical material
removal systems.
In talking about abrasive deburring and finishing systems today, we are talking about a
great many different types of mechanical applications of abrasives and machine systems. All of
the abrasive systems developed have certain advantages and disadvantages depending upon
what has to be done to the part and the end result desired. The general basis of all of these
systems can be narrowed down into three different categories of machine applications or how
the media and energy force is used in relationship to the orientation of the part. That is, we
know that size, shape, and composition of the abrasive affect the final results of a part, but the
way in which the energy force is applied to the media and/or orientation of the part also effects
the final results.
Classification:
Because there is no central engineering organization that wants to get involved with
setting standards for determining all deburring and finishing systems, I created my own version
of a workable system for clarification and understanding of these material removal systems.
Before we begin to start to explain the equipment classification system, we also have to set some
other parameters as to what constitutes a burr or rough surface finish. Therefore, our
classification numbering system will cover the equipment involved, the size of the burr or
roughness and where or how the parts must be worked to achieve the results desired.
Instead of a single form of identification, we are talking about a number of separate
systems combined to create a single three or four digit classification number. This numbering
system works for all material removal systems, but it is not a good representation of extremely
small parts under a half inch in size and that will be discussed at length because of special
Chapter 2 - Classification 24
problems associated with size. Burr removal is functional or proportionate to the size of the
part; therefore, although this system is good for parts above a half inch in size or larger there is
a relationship to parts on a smaller scale. Again there is no precedence.
The equipment classification system will be composed of a single 3 or 4 digit
identification number. It will identify the energy system involved, the size of the burr or
roughness of the part and the location of the burr or where the work has to be done. Because
this information will be general in nature, to cover all systems, the classification system
developed throughout this book will show a numerical range for the equipment and not a
single digit number which can be developed for a specific machine systems. Then again, the size
of the media also affects the amount and size of the material removal process itself; therefore, a
numerical classification number also depends on the media being used and because of that, the
equipment cannot be isolated to a single number.
Type – Equipment Classification (first or first 2 numerical digits)
To classify all deburring systems and equipment, we will try to keep it simple and say
that there are perhaps five classifications, so equipment classification will begin with only the
numbers 1 through 5. Even though I said I was going to keep it simple, there is an immediate
problem. To classify all deburring and surface finishing systems, I have to start out with a Type
0 classification. This zero indicates that there is no equipment involved here and the work is
done by a manual hand operation. The zero plus five makes a total of 6 classifications.
Another problem here that needs immediate explanation is that some material removal
systems use a combination of methods or processes which are hard to classify with a single digit
classification; therefore, two digits may be necessary to properly identify the type of equipment
involved. An example of this is water honing equipment systems that use a combination of
water and abrasive; therefore, the number of this equipment begins with 42XX, which
represents both a liquid and a blast type energy system. That means that our classification
numbering system should be composed of a total of 4 digits, but in many cases only 3 digits will
show instead of 4 because we have dropped any classification number beginning with a zero.
Before we identify these 6 deburring systems in detail, there are some other important
factors to consider that determine or effect the equipment. Therefore, let us look at the last two
digits in our numbering system first.
Burr Class (second digit from right to left)
The next number in our classification number is a single digit that represents the class of
burr. I have created an artificial size range, which is based upon a general thickness
measurement and surface roughness based upon the RMS surface profile. Again, we start out
with the same zero problem. This zero digit is done to indicate that there really is no burr, but a
surface modification or finish is required or the determining factor rather than burr removal.
The system classifies 5 categories of burrs and stops at an arbitrary thickness I think is
appropriate. The zero plus five denotes 6 classifications of burrs and roughness.
Chapter 2 - Classification 25
Burr Location (last digit to far right))
The last number in the classification number denotes the location of where the work is to
be done or what area of a part is worked best by this equipment. This is a very general category,
but there again is a relationship, which is important. Again a zero indicates only surface
modification is required. The zero plus the three burr locations brings the total to four
classifications.
Explanation of burr class
“Class 0” burr indicates that while no burr is present, some further mechanical or surface
finish is required. In most cases this will involve burnishing or polishing, but textured finishes
may also be called for either on grounds of aesthetics or to improve adhesive bonding. No
assigned RMS will be given to this classification.
“Class 1” burr will be considered any material with a sharp edge that may or may not be
capable of cutting human flesh or a mating part or assembly. The equivalent surface roughness
would be 0 to 8 RMS. I am concerned here with the cutting of wire, cables, or tubing over a
period of time due strictly to weight, pressure, or movement against a sharp edge. Class 1 burrs
can usually be improved or modified sufficiently in a polishing or burnishing operation to
remove or modify the surface or edge enough so as not to create cutting possibilities. A surface
finish or 0 to 8 RMS is extremely smooth and normally requires no surface improvement, but
may require a polished reflective mirror finish. Jewelry and medical implants are common
surface finished parts.
“Class 2” is any burr or fragment of material that can be removed with ones fingernail
and resembles thin aluminum foil. Class 2 burrs can be removed with fine abrasive methods.
The equivalent surface roughness would be anywhere from 8 to 16 RMS. At or about a 16 RMS
is desirable for a good quality plated part.
“Class 3” is any burr that cannot be removed by ones fingernail and measures about .010
to .020 inches thick. Class 3 burrs require medium abrasive methods. The equivalent surface
roughness would be from 16 to 24 RMS and is the range of most parts that require a thin film
surface treatment.
“Class 4” is any burr that is .020 to .032 inches thick and is not considered parent metal*2.
This is relatively thick and rigid material and requires coarse aggressive abrasive methods. The
equivalent surface roughness would be from 24 to 35 RMS and is generally not suitable for thin
film treatments, but is acceptable for heavy thick coatings.
‘’Class 5’’ is any burr over .032 inches thick and is often referred to as parent metal.
Parent metal is any material that cannot be moved by hand without the use of a tool or is
something like a tear where the metal is distorted. Class 5 burrs should not be considered as a
candidate for normal deburring equipment or methods unless a great deal of time is available to
2 Parent metal is hard to define because it changes in relationship to the material in question, but generally
speaking it is a burr that can not be removed without excess multiple forces.
Chapter 2 - Classification 26
work the part. In fact, class 5 burrs should be returned to the supplier of the part or machine
center for rework. The equivalent surface roughness would be over 35 RMS, which is about the
finest surface finish that can be achieved using blast type equipment and methods. This surface
finish is good for all heavy thickness surface coatings.
Burr Classification
Class 0 burrs surface modification only, no burrs present.
Class 1 burrs are sharp edges which can cut one’s finger or cut wire or tubing over a
period of time and/or vibration. Approx. 0 to 8 RMS.
Class 2 burrs are thin irregularities of material which can be removed from a part with
one’s finger nail. Material thickness approximately 0 to .010. Approx. 8 to 16 RMS.
Class 3 burrs material irregularities that require greater pressure than the unaided hand
alone. Material thickness approximately .010 to .020. Approx. 16 to 24 RMS.
Class 4 burrs or material irregularities that require a lot of pressure and force on media
and part. Material thickness approximately .020. to .032. Approx. 24 to 32 RMS.
Class 5 burrs exceed .032 in material thickness and RMS surface profile roughness. Not
recommended for most deburring equipment or removal methods but RMS is good for
surface preparations or coatings.
Explanation of Location
Before we leave the realm of burr classification, we should also consider a second
number to indicate where the burr is located. To clarify that statement, we know in the
manufacturing process of producing a part that there are normally specific problem areas that
occur because of the way the part is produced. That is, we are concerned with burrs that occur
either on outside or inside dimensions. Internal burrs are primarily caused by drilling; If the
drill exits the part, they are considered outside burrs. As 0 above, so too do we carry a 0 for
surface modification even though we do not specify a location it will be the same as 3 or all
locations. The difference between 0 and 3 is that 0 will be surface profile improvement and 3
will be just for burr removal. The numbers are in the order of difficulty. Some deburring
methods are better than others in working these specific problem areas.
Burr Location
0 for surface modification only.
1 for outside dimensions.
2 for inside or internal dimensions.
3 for both inside and outside dimensional burrs.
Explanation of equipment classification
With the above information, we are ready to get back to our original intention of
classifying all deburring equipment systems. These systems are based upon the application of
Chapter 2 - Classification 27
energy in relationship to the part. The size, shape, and configuration of a part plays an
important role in the selection of one of three abrasive deburring or finishing equipment
systems, or the material removal systems based upon liquids or temperature.
For the mechanical abrasive methods we will classify them as either a type 1, 2, or 3
system. Type 1 systems uses abrasives in a parallel plane, or the main energy force is in contact
with a rotating transfer device that is controlled by pressure as it slides along the surface of the
part. Type 2 systems involve air born abrasives that are propelled or transfer energy forces at an
angle or perpendicular to the surface of a normally fixed part. Type 3 systems mix the
orientation of the part and the abrasive to achieve a mixture of nearly equal energy forces in an
x, y, and z axis movement under pressure. Because we are talking about all deburring and
polishing systems, we must also include here, type 4 liquid or chemical systems and type 5
temperature modification systems which involves heat or cold.
Equipment Classification
Type 0 system is for manual hand working of parts only. Energy is directed downward and
movement is back and forth or in a circular pattern with a fine abrasive.
Type 1 system is for relatively flat materials where the energy force is directed down and
parallel or horizontal in a wiping action to the materials surface via a wheel, disc, or belt.
Type 2 system is used primarily for surface preparation or textured finish to take a heavy
thickness coating. This abrasive blast equipment transfers energy force into solid abrasive
particles which are air or liquid born and directed perpendicular or at a slight angle to the
materials surface from a short distance away from the material being worked.
Type 3 system is used in mass finishing type equipment. Energy is transmitted uniformly into
abrasive particles or preformed shapes in a random combination or a mixed pattern of
movements relative to free floating parts within the mass.
Type 4 system is primarily a liquid energy transfer method directed through a liquid to help
modify part burrs and surfaces. This can either be a pressure system, a molecular reaction
system, or it can involve material transfer by an electrical current.
Type 5 systems is an air based energy transfer method that uses extreme temperatures to help
modify part burrs and surfaces.
Chapter 2 - Classification 28
Fig. 1. Type 0 Systems
Fig. 2. Type 1 System
Chapter 2 - Classification 29
Fig. 3. Type 1 Systems, continued
Chapter 2 - Classification 30
Fig. 4. Type 2 Systems
Chapter 2 - Classification 31
Fig. 5. Type 3 Systems
Chapter 2 - Classification 32
Fig. 6. Type 3 Systems, continued
Chapter 2 - Classification 33
Fig. 7. Type 4 Systems
Chapter 2 - Classification 34
Fig. 8. Type 5 Systems
Chapter 2 - Classification 35
Equipment
Type 0 system involves hand operations or the manual application of energy to the
abrasive device. Hand labor normally orients and works parts in one direction or uses abrasives
in a parallel plane to the material being worked for aesthetic reasons. By maintaining a rubbing
action or energy force in the same direction as the part or in the direction of the greatest amount
of material the abrasive or transfer device is more efficient than circular or cross movements.
Generally speaking all manual processing methods do not normally produce fast, good looking,
or smooth surface finishing results.
Type 1 system is the same identical method used by the type 0 system except the task is
accomplished using powered buffing wheels or belts to contact the part and this accomplishes
the same results, but faster than hand labor operations alone. The wheel or belt systems use
coated abrasives that travel over the part, or vice-versa, parallel to its surface. This movement
produces a long continuous sliding stroke or contact pattern with the part. With the exception of
pressure applied by the operator, less human labor is required and therefore processing is
normally faster with better results than type 0 systems.
The amount of material removal of type 0 and 1 systems is controlled by the amount of
pressure exerted on the transfer device and abrasive. For material removal, rigid systems work
best, but are hard to control. In both systems, flexible methods are usually favored for the
control factor and for polishing. Flexibility allows for more surface coverage, over lapping
patterns, orientation of the part, and the transfer device. It should also be noted that any long
fiber, grain, filament, or any fine abrasive with broad flat grain orientation will generally
produce more smoother, lower RMS, or shinny parts.
Type 2 systems are often called cleaning systems but are used mostly for surface
preparation treatments for coatings because they can produce the roughest surface profile
which is good for adhesion of paint and other heavy thickness coatings. In fact the finest surface
finish that can be achieved using this technology is only around a .032 RMS. Other benefits of
blast type systems is that they can also be used to stress relieve and work harden the surface
metal of parts.
With the advent of air pressure equipment, abrasive blasting became and still is a very
popular means of surface modification. In type 2 systems, the main energy force is transferred
to the abrasive that becomes air born and propelled in a controlled concentrated blast pattern a
short distance from the part being worked. Even though we have stated that these systems
apply force nearly perpendicular to the part orientation, the angle can vary to incorporated any
angle to the part, but the optimum efficiency angle is about 60 degrees. In a number of
automated or semi-automated systems the parts are in a fixed position. Movement of the part or
abrasive orientation is also within the realms of this definition.
Type 3 systems are very flexible systems. Unlike the above systems that basically work
with stationary flat oriented parts, type 3 systems do not require any prerequisites for handling
or fixturing of the parts being worked. Parts can move freely within these systems and the
equipment can use both loose random abrasives and/or preformed shapes in different sizes,
shapes, and compositions. Because of the multi directional energy forces, pressures and part
Chapter 2 - Classification 36
versatility, these flexible systems accomplish normally faster more uniform results more
economically. In this category are machine systems that rotate, shake, spin, and vibrate.
Generally speaking, these processing methods are considered mass finishing systems, because
they can accommodate a batch of parts in a work chamber with no special handling or
orientation. Mass finishing systems then refers to the batching of parts in mass in a machine or
work chamber with abrasives.
Type 4 systems cover a range of technologies. Energy and force are not directed or
transfer to another media, but is the result of molecular reactions or electrical movement. In its
simplest form, it can be nothing more than a liquid tank of water; however, normally a chemical
additive is required to create molecular movement. If that chemical is concentrated, it can cause
a reaction that will affect the sub atomic molecular structure of the material in the solution.
Typically in the plating industry, a controlled electrical current is introduced into a weak
solution that assists in transferring material coatings or to remove material. If acoustics are
introduced into the liquid to produce ultrasonic cavitation then the mechanical energy forces or
movement of molecules increases the effects of the chemical media. Lastly, water under high
pressure, liquids can be used to use to remove material.
Type 5 systems use air and extreme temperatures. Mostly we are talking about extremely
high or low temperatures. Extreme temperature processes create a condition outside the normal
characteristics of the material being worked and that makes it easier to remove the
irregularities. Heat can be used as a medium in a special piece of equipment designed to contain
a controlled mini explosion which melts or burns away fragments of material. On the opposite
side, there are other systems that use extreme low temperatures that freeze fragments to make
them brittle so that they can be removed more easily using some additional movement or
abrasive methods.
Deburring equipment and technology have advanced rapidly over the last several years;
however, this has not been the case in past history. Up until the late 1800’s processing methods
were slow to change from their introduction because labor was very cheap up until the mid
nineteen hundreds. As labor costs continue to increase more than the material costs they
stimulate new processing innovations. Now systems have changed and evolved over the years
in cost and speed of operation. There are now so many deburring and polishing systems that
one needs a score card to understand and determine which is best finishing system for what end
product. Hopefully, this information will help you with that determination.
There are many options and methods of deburring parts that are being used and each
method or system has advantages and disadvantages; therefore, the knowledge of these
alternatives can help one decide the best method or alternative equipment to use given the
proper circumstances and/or resources available. However, mass finishing systems are probably
the most versatile of all finishing systems because the abrasive media and equipment are so
diverse; therefore, this book will go into great detail on all mass finishing systems. However,
just briefly, there are now three basic types or generations of mass finishing systems that go
under the type 3 classification and that needs a little explanation. These finishing systems are
referred to as the 1, the barrel, 2, vibratory and 3, high energy centrifugal systems, and to some
extent there is a fourth related technology system called drag or spin finishing systems.
37
Chapter 3 – Type 0 Equipment
Alternative Deburring Systems
Hand-held tools and mechanical systems used to improve surface finishing were of no
significance until the introduction of steam power. Crude and cumbersome drives allowed for
limited material removal by turning rather large abrasive wheel and belt contact systems. It
wasn’t until the introduction of electricity and pneumatic air systems that the use of type 1
power tools became wide spread in the deburring industry. With the introduction of more
complicated part designs and functional requirements, plus standardized parts, automation,
and light weight portable tools, did productivity demands have a significantly effected on
finishing operations and the popularity of type 2 and 3 systems.
Even with the advent of powered deburring tools, the surface or edge finish of a product
depended upon the control of the tool by the operator, who decided what size, type, and
pressure to apply to the abrasive system and part. Most finishing operations are considered
dirty and supposedly do not require a lot of technical knowledge and because of that, work has
been delegated to the some of the most inexperienced workers. Unfortunately the human factor
effects the elements of pressure, speeds, and replacement tools and all of these elements effect
mechanical surface finishes. Sometime, the logic of some very complicated expensive parts
delegated to some of the most inexperienced operators leaves a lot to be desired. In addition to
working the parts, the human factor is also involved in the visual inspection procedures.
Without standard of acceptability, that also means that most parts can fall within a wide range
of surface finishes and/or profiles.
Most companies are more interested in precision dimensions than surface finishes;
however, as production quantities continue to increased and become more common place,
product uniformity and consistency demands also increase. Without adding more and more
people to meet these demands, most industries chose less and less work that is not machine
automated. For the repeatability factor, mass finishing systems are perhaps the best and
cheapest way to produce uniform surface finished parts in volume. Other alternative deburring
systems may still be required to work some difficult to reach areas, but mechanical abrasive
systems seem to be the basis of most material removal systems.
Upon reviewing the various deburring and finishing systems in use today, one
encounters many variations of the same systems we have classified. Each system has strengths
and weaknesses based upon a range of part sizes they can accommodate as well as production
volume based upon size and time. The classification system developed effectively sets limits
that reflects the manner in which the abrasive or medium utilizes energy input in relation to the
material removal rate and the parts orientation to produce specific surface finishing results.
Initially, I tried to organize alternative deburring systems into a logical progression from
the relatively simple to the more complicated systems. In this order most equipment systems
will usually give you some idea of costs, but technology and equipment accessories can get
involved and effects costs radically, especially the addition of automated material handling
Chapter 3 – Type 0 Equipment 38
systems. Therefore, simple systems can get quite complicated. This section will try to be a brief
glimpse of equipment and processes to compare material removal rates or surface modification
with mass finishing systems.
Hand Tools:
This category of deburring tools takes on two sub-headings. They are manual and
automatic. I did not break down automatic into semi or full automation. In most cases, parts to
be worked still have to be loaded and unloaded somehow; therefore, although the equipment
performs an automated function, the positioning and handling is not considered automated.
Truly automated equipment normally includes self loading and unloading systems.
Manual Systems:
The manual systems for deburring involve the use of physical manpower for its primary
energy source. That is, it requires a human to apply pressure to some form of tool to abrade or
polish some object which he holds or fixes in place. Then again, the tool can be fixed in place
and the part can be pressed against the tool. These systems are probably the oldest, most time
consuming, reliable, and maybe still the fastest of all metal removal systems.
However, besides fast and reliable, manual systems are also probably the least accurate
to control because they rely on the human factor and that is also true of all power tool systems
that are not automated. Repeatability of pressure, contact, time, and coverage can only be
accomplished by automation; however, even with power tool systems the application device
does wear out and changes its material removal performance characteristics with use. Therefore
hand and automated tool systems quality or finish can vary from piece to piece and operator to
operator over the same given period of time.
The most common tools in this manual category are the file, rubs, abrasive discs, belts
and/or sand paper. These hand methods can handle a wide range of from 0 to 5 type burrs in
our equipment classification numbering system. In addition to these popular contact devices is
a relatively new tool called an edge deburring or swivel tool.
I will start my classification system with this swivel deburring tool, because it does not fit
a logical progression of hand tools. This is a type 0, manual hand-held tool equipment
classification. Using our burr classification system, this device can only be used on class 1,2 and
maybe 3 burrs and only on outside #1 locations. That makes this tool a Type 0 system, with a
maximum burr classification of 3 in location 1, or is a 001 to 031 class tool.
This hand-held edge deburring swivel tool is nothing more than a handle with an
irregular bent shaped sharp squared off or sharp edged heavy carbide metal wire that is capable
of swiveling to the contours of the part to be worked and the force applied. It is something like a
file, but it maintains its position on the part by itself by way of a ball or bent hook like end piece
upon which pressure and contact are applied. Normally the operator of the tool holds the part
in his other hand so that he can turn the part and keep the tool on the edges of either holes or
the O.D. edges of the part. If you noticed, actually pressure is applied in two directions
simultaneously; therefore, some dexterity is required to operate this tool. While with hand held
Chapter 3 – Type 0 Equipment 39
sand paper or a file, pressure is usually applied in only one direction, or backward and forward
or in a circular motion over the same path using more energy than the swivel tool.
Fig. 9. Manual Hand Deburring Tool
This is a hand-held tool that is used to deburr the edges of a part. The tip or blade of the
tool swivels freely as it is pushed or pulled by the operator along the edge of the part. Because
of the configuration of the carbide tip, it tends to drag along the blunt edge of the part thereby
shaving the sharp edge of the metal. Most of these tools have inter-changeable tips for multi
function jobs.
Because hand tools such as the file and sand paper have been around so long, I don't
think it necessary to go into any explanation of these tools. However, I will say that new
developments in bonding techniques for abrasives in wheels, coated belts, and new fiber
materials, plus artificially made synthetics have made significant improvements to hand tool
products and accessories. Synthetic materials have especially improved the cutting ability, life,
and performance of all of these devices. This book and classification system will not cover any
of these manual systems, but they do fall within the limits of a 2-digit classification system such
as the swivel tool.
40
Chapter 4 - Type 1 Equipment
Automation:
Probably the most labor intensive and most popular form of deburring in use today are
wheel and belt systems which fall under our type 1 equipment systems. This type of equipment
covers the widest range of part burrs, hence its popularity. The reason for this is because these
systems use direct pressure and contact between a mechanical power or energy source, the
abrasive tool or transfer device and the parts being worked. Based upon our classification
system, this equipment handles 0 to 5 burrs in type 1 locations. Actually these systems can
probably work burrs a lot rougher than our classification range of up to 5; however, this is
excessive and inefficient use of manpower. Using our numbering system, this type of
equipment is normally designated a 1 and handles burrs 0 to 5, in location 0 to 1, or they have a
classification range of from 100 to a 151 system.
Note, the above classification is again general in nature, meaning that most applications
fall within this common realm of O.D. or surface profile applications. There are other variations,
such as small I.D. wheel systems that would be considered an equipment classification of up to
153; however, these systems are not within the normal application of this system. Most internal
deburring wheel systems are not as universal or easily dedicated to work all variations of I.D.
holes and have a very limited size range, because of the hole size and environment in which
they have to work.
The more rigid the abrasive tool or system, the greater the material removal rate given
the same pressure. That means that coated inorganic belt or rigid disc systems are much more
aggressive and can handle the upper limits of this classification better than can most organic or
synthetic wheel systems. That also means that belt and rigid disc systems are used primarily on
flat parts and outside surfaces. Organic wheel systems on the other hand can lap or polish parts
better because of the flexibility of the wheel. Also, because of the flexibility factor of most
organic wheel systems, they can handle both a portion of inside holes and outside dimensions
as well as a wider range of part shapes and configurations than can belts. Versatility sometimes
over comes speed.
Wheel and Belt Systems
General Information
I call wheel and belt equipment, forms of automated deburring systems, but in reality
they are more comparable to a hand tool. The only difference is the power source. That is,
energy is applied in some fashion to a rotating wheel and pressure is applied by a person to the
work piece, by hand, against the wheel or belt, or vice-versa. The industrial terminology for
hand-held work piece processing is called “off-hand,” because the work is done off one’s hand.
It is the person or operator who determines, by one's pressure and manipulation of the work
piece in relationship to a fixed position wheel or belt, the time in which the work will be
accomplished and to some extent the quality of the finished product. Hand-held tools are not
considered off-hand work, because the hands are not controlling the part, but the power tool
Chapter 4 - Type 1 Equipment 41
device. Because of the human factor this type of equipment is not a truly automated system, but
it is still a great improvement over a manually powered hand operations.
Semi-Automatic Wheel System
The machine system shown here is a basic double axial buffing machine, which has a
centrally located energy power source for rotating the wheels. In this case it is used for buffing,
but abrasives or solid non-woven or filament wheels can be used on this machine for deburring
also. I call this system, semi-automatic because it requires manual material handling and
finishing techniques.
Fig. 10. Semi-Automatic Wheel System
Do not under estimate the human factor. A skilled operator who knows and understands
the mechanics of pressure, loading, and/or the flexing of wheels and belts can normally out
produce a fully automated production line. Also, nothing seems to match the quality of the
surface finish as a good hand buffed part. A hand buffed part is still the industrial standard by
which all other processes are measured. All other methods and systems use or compare their
best surface finished parts to a hand buffed part.
Chapter 4 - Type 1 Equipment 42
Speeds/Energy Source
I suppose any electric motor can be fitted with any abrasive wheel, belt, or polishing buff
to work parts. But a lot of motors cannot hold up to the side pressure or end-thrust energy
forces exerted on the motor bearings by the wheel system by an operator; therefore, there are a
number of factors and operating conditions required for selecting a good motor. Most stationary
or hand-held wheel systems are heavy duty ball bearing motors that operate between 1200 to
3600 RPM. However, more important than RPM maybe the horsepower and bearings of the
motor. The speed at which a wheel turns or RPM’s relates to energy transfer and/or friction and
heat in most cases. Side pressure created by hand pressure of the part against a moving wheel
can affect the speed of rotation and bearings significantly. Without sufficient horsepower, one
may actually stop the wheel from turning completely by applying too much pressure against
the rotation force. Such a situation is not good for the part, the operator, the motor, or
production. Therefore, motors or equipment should be reviewed for adequate horsepower and
the application.
An important factor to consider besides the RPM of the motor is the speed of the outer
edge of the contact device. That is, the speed of the motor turns a wheel that is larger than the
shaft of the motor; therefore, the size or the diameter of the contact device in turn translates into
a higher RPM rate of speed than the motor or linear feet per minute. A 2400 RPM motor with a
12 inch wheel will produce a linear rate of travel or turn at twice the speed of a 6 inch wheel on
its outer edge. The optimum speed of most wheel and belt systems is approximately 1000
surface feet per minute.
The processing cycle time to produce an acceptable part is determined by the roughness
of the part, the pressure applied to the belt, the abrasive used, and the desired end results,
which can be expressed as follows:
1. Force or applied pressure x the distance traveled or surface feet per minute
= energy input.
2. Amount of material remove = energy input.
These equations relate material removal to energy input. They do not deal with the time
factor, which can be related to:
3. Rate of energy transfer = surface feet minute x pressure or force.
Cycle time is then inversely proportional to the linear surface feet per minute and the
applied pressure or force. That means that the temperature limit may be reached by the
operator, the abrasive, or the material, well before the part is complete.
Heat Gain
All type 1-equipment systems transfer energy from the motor RPM’s to the contact
device and then into the part in the form of heat. Too much pressure or temperature will
adversely affect the color or appearance of a part and may change the hardness of the metal
being worked. At extremely high temperatures, metals can oxidize and react like parts being
Chapter 4 - Type 1 Equipment 43
heat treated, resulting in either work hardening or loss of temper. In fact, the subject of
grinding, which we are not going to classify or explain, is designed for large amounts of
material removal. This equipment uses a multi pass means of lapping and liquid quenching the
part because of the heat transfer problem.
As mentioned, the optimum speed limit of most motorized belt deburring systems today
is equal to about 1000 surface feet per minute. The speed or cycle time of the operation is also
determined by pressure. That is, to achieve the desired end results, one has to remove the burr
or material to an acceptable condition. The more pressure you place on the work piece against
the wheel or belt the shorter the time cycle for the burr as well as the belt or wheel. However,
too much pressure can also cause problems and/or over correction, rework, and possible
damage to the transfer device, the work being done, and possibly the operator.
Another limiting factor for wheel speeds are the formulated dressing, lubricating, and
abrasive compounds that are used primarily on the organic fiber wheels. These compounds are
designed to deburr or polish and operate within a certain temperature range that is indirectly
controlled by the RPM speed at which a motor operates. As mentioned, pressure of the part
against the wheel system by the operator determines the amount of material removal and the
friction or the amount of heat generated, which is transferred to the part and operator.
That heat problem means that an abrasive or buffing compound used on a wheel system
must be formulated or selected to hold and transfer a proper mix of abrasive and lubricant to
work the part properly and that depends on the material and the finish desired on the part. Belt
systems don’t have the same exact problems as wheels, but they can to a limited degree use
lubricant compounds. On wheel systems, low temperature compounds may not hold the
abrasive in place to work at high speeds and pressure, whereas high temperature products may
not adhere to the wheels at slow speeds. Because belt systems are rigid, the heat can cause either
an adhesion problem where it can load up with debris or it will lose its own abrasive and can
become an ineffective abrasive tool.
For every action, there is an equal and opposite reaction. Energy transfer is one of these
reactions when type 1 equipment is involved. Besides the heat factor, vibration is also being
transferred to the operator and the part. As mentioned too much pressure can produce too
much heat and that will affect the operator, the tool (wheel or belt), and the part as well. The
heat factor refers mostly to relatively small to medium sized parts. Parts larger than a person
can handle in weight or length requires a fixtured tool or part plus a material handling system;
therefore, heat will not normally affect the operator, but the operator can affect the metal part.
Typically, burrs are on the outside edges of parts, and wheels and belts only work a relatively
small amount of material or surface area; therefore, heat is not normally a factor. However, to
work a large flat surface, especially buffing operations, heat is a major factor.
If a small hand-held part becomes too uncomfortable for a person to hold, he can't
properly control the part's surface finish. Also, if that operator presses too hard on the abrasive
wheel or belt, he may damage or compromise the transfer devices performance factor. That is, if
Chapter 4 - Type 1 Equipment 44
too much pressure is applied, a wheel will lose its uniform integrity and cease to work properly
and a belt will load up with the material being removed.
Normally, using a light amount of pressure on a proper wheel or belt will provide a
quick good clean abrasive surface finish. Too much pressure will create a glazed uneven coating
on the transfer device and part and slow down or stop the material removal system. If this
happens to belt systems, the best thing to do is to change the belt, but sometimes wheels can be
re-dressed. Operator technique and a proper balance of speed and pressure are required to
accomplish a good surface finish or deburred part with type 1 systems.
Heat Loss
Just as there is a rise in temperature due to the conversion of mechanical energy into
thermal energy due to friction, there is also dissipation. The three main ways to lose heat are
through conduction, convection, and radiation. To understand these methods, one can, to some
extent, overcome one force with that of another.
Conductive Heat Loss: is the process of energy transfer through that which is in contact
with the energy source, which is primarily another solid. Heat will migrate from its source and
will seek a balance within the material being worked to its ambient environment; therefore, it
will to some extent dissipate some of the heat within the part or material itself. If the part is in
contact with the transfer device, some of the heat will go into this device as well as the part.
Also if there is a work platform, this too will absorb some of the heat.
Other conducting factors that affect heat transfer are the materials being worked, the size
of the part or its surface area, and to some extent the characteristics of the abrasive product
itself. Those materials that conduct electricity also seem best for conducting heat. Copper and
aluminum are well known for their heat conducting properties. Some abrasives that break
down fast can carry away a lot more heat than more cohesive materials, Also, the more and the
larger the size of the material removed, the better the heat transfer away from the part being
worked.
Convection Heat Loss: is the heat energy transfer through air, a liquid, or solid. When a
transfer device is in operation, it does so in an ambient environment of air. The density and
weight of a solid effects the immediate molecules of air that indirectly passed on to that heat
energy to the surrounding air to a lesser degree. That means that the less denser air around the
work being performed is effected by the transfer device and it too absorbs heat. To increase the
efficiency of convectional heat transfer, water or liquid may also be used.
The physical geometry of the part itself also plays a part in how it holds or losses heat. A
thin flat part, like a heat sink which are specifically designed to loss heat, losses more heat faster
than a solid cylinder or rod, because the surface area is less. Therefore, the configuration of the
part or surface volume plays an important factor in heat transfer into the environment.
Radiant Heat Loss: is similar to convection heat, except it is primarily air born energy
transfer. Radiation is a transfer method not necessarily effected by the physical movement of
molecules, such as cohesive effect and movement of air around the transfer device or a
Chapter 4 - Type 1 Equipment 45
movement caused by the pressure of heavier to lesser density of air created by the density of
molecules as they expand. Heat transfer by radiation is actually more like a atomic molecular
transfer of heat, similar to or almost like a chemical chain reaction without physical movement.
Human Factors
The effects of heat and vibration on the human operator are important elements of both a
positive and negative nature. On the positive side, a good operator can out produce and is more
flexible than a fully automated belt or wheel system. On the negative side, a poor operator can
damage equipment, parts, and himself.
The human operator must be considered to be at least 50% of the overall performance of
type 1 equipment where material handling is absent. That means that most wheel and small belt
systems are primarily controlled by the operator from start to finish. That also means that the
working environment is an important factor to be considered. Operators are exposed to a
number of physical stresses related to this equipment. Safety from heavier debris and the close
proximity to the rotational force are inherent dangers that one must expect to face using this
equipment and precautions and care should be taken when and where possible. Prolonged and
constant handling of parts and pressure can cause white knuckle or carpal tunnel muscle related
physical symptoms in humans. Also, in proper air and dust collection systems can cause lung
related illnesses, all of which can incapacitate a human; therefore, operator comfort is not so
much a luxury as it is a necessity.
Variable Factors
Because of the speed at which a wheel or belt system operates, a lot of material can be
removed in a relatively short period of time. Of course, the amount of material removal has a lot
to do with the type and size of the abrasive wheel or belt used. That makes these systems very
versatile and capable of handling all types of burr classifications. However, it should also be
known that there are some variable factors that also cause slight variations that effect surface
finishes using these systems.
A new rigid wheel or belt, before it is broken in or used for production will operate more
aggressively before it stabilizes. That is, it will remove a great deal of material and produce a
rather rough finish in comparison to parts worked by this same system a short time later. This
difference is more noticeable on belt system than on wheels, because most flexible wheels use
what are called a rouge or lubricating sticks to coat or treat the wheels which effect material
removal. Belts on the other hand already have the abrasive added to the contact device.
Rigidity or stiffness of a transfer device tool initially increases contact pressure; therefore,
the amount of pressure to the work pieces needs to be constantly increased over the life of the
tool to maintain the same cutting or deburring rate and surface appearance of the part. In either
case, there is a noticeable difference in first piece parts versus a part taken from production at a
later time in either a fully automated system or parts done by hand. Because of this known
problem of uniformity or surface finishes, most first piece parts are often set aside and then
reworked with this same tool after the wheel or belt is broken in.
Chapter 4 - Type 1 Equipment 46
As a wheel or belt is used, there is still an ongoing break down of both the abrasive
particle size on the transfer device tool and the material being worked. Again, this effect is more
noticeable on belts than flexible wheel systems, because you are normally always adding an
abrasive paste to a wheel whereas a belt uses up what it has.
Debris
In any mechanical abrasive process there is an end product, that being a finer surface
finish of the materials you started with. With the exception of precious metals, most of this finer
end product of metals and abrasive is completely useless and has no value. In fact, it is a
liability and/or necessary evil. If abrasives don’t break down, they don’t work. If parts don’t
conform or function properly they don’t work properly. Therefore, the whole principle of
deburring is based upon negativity, or the negative destruction of both the media and the excess
material or burr to achieve a good positive acceptable result.
The debris created from deburring operations has to go somewhere. In most cases the
heavier particles fall on the floor, but a large amount of the debris is so fine that it drifts in the
air around the work area and in some cases, some gases can be given off from the materials
being worked or the abrasive binder. In large amounts of volume to air ratio, or given a little
amount over a long period of time, this debris material can become hazardous to one's health.
Therefore, pre-cautions are necessary in a work environment to protect the employees. That
means that the operator and those nearby should wear a protective air filtering device to protect
their health, and/or a dust collection system should be installed near the machinery work area to
suck out and vent the contaminates to a safe collection source.
Size/Diameter
As mentioned above, the wheel or belts selected to perform material removal plays an
important part in obtaining the desired results. Solid rigid wheels and belts made of inorganic
materials seem to cover a wide range of abrasive grit sizes and use different bonding agents in
their composition. These transfer tool devices can vary in diameter but are relatively thin in
relationship to the material to be removed because of the heat transfer problem mentioned
earlier.
Most standard off the shelf rigid inorganic wheels are relatively thin and under 1 inch in
thickness. If they are thinner than 1/8 of an inch and solid they are known as cutting wheels.
Some solid wheels can be up to 2 or 3 inches in width, but this is not common. As a contact
device surface area increases so too does heat transfer become more of a problem; therefore, it is
usually easier to work with small surface areas than larger contact systems. This smaller size
also permits working more detailed areas of a part and normally greater flexibility of part sizes.
Besides rigid inorganic wheel systems, there are both organic and inorganic composite or
flexible filament wheel systems. The flexible inorganic composite systems can be made to
handle very wide parts with some minor contours, but they are mainly used for flat sheet metal
parts with a lot of shallow holes or special applications. These automated deburring machine
systems work and look something like a street sweeper, but the parts pass through a series of
Chapter 4 - Type 1 Equipment 47
abrasive rotating wheels on both the top and bottom sides of the part as it passes through the
machine. Adjustments can be made to the brushes to apply the proper pressure for surface
finishes and compensate for brush wear. Most of these brush type systems use water and
cleaner to properly process parts. Like any machine with moving parts, the machine is
completely enclosed, vented, and in most cases uses water to control dust and temperature of
the parts and the environment of the operation.
Automated Abrasive Wheel Deburring System
Most common automated deburring systems are designed for processing relatively flat
sheet metal parts and/or in-line production. Also, due to the violent nature of the material
removal process and energy forces at work, a lot of these systems are designed to be run wet in
order to keep dust and debris confined. In fact, most machine systems are completely enclosed
for safety reason so no human can come in contact with any of the moving parts; therefore, little
can be seen of the actual wheels and mechanisms that do the work as seen in the following
machine systems. With few exceptions and because of costs, most machines are built or
dedicated to in line high volume production or parts that are relatively similar in size because
adjustments, other than the deburring wheels, to such a machine is costly due to down time and
tooling.
Fig. 11. Automated Abrasive Wheel
Chapter 4 - Type 1 Equipment 48
Fig. 12. Automated Abrasive Wheel Machines
Below are two versions of in-line abrasive wheel systems. The normally larger “dry”
system is used for deburring or polishing machined parts that have more surface variation. The
smaller “wet” systems are used for sheet metal parts, or in this case printed circuits. In a
number of cases units can be made to use both dry and wet technology for processing parts.
This can also include provisions for cleaning and drying parts.
Fig. 13. Dry system
Chapter 4 - Type 1 Equipment 49
Fig. 14. Wet system
Some automated belt deburring systems can also be made to be very wide and can move
or feed parts. These systems have greater heat transfer problems than the wheel systems
because there is more contact area than the brush systems. However, in most cases no human
touches the part until it comes out of the machine and this heat is dissipated relatively fast. Care
is still required in handling these parts. The main problem of these machines is the fast
accumulation of debris and the need for frequent and proper cleaning. It should be noted that
fires and explosions have been known to occur in cases where poor maintenance is practiced.
Most of the big automated belt systems are designed to handle large sheet metal parts 3
or 4 feet wide. They also have the ability to control the amount of pressure or tension on both
the top and bottom rollers, as well as the backup padding under the belt to effect surface
texture, on the part as it moves through the machine. Because of the amount of material removal
most of these large belt systems have dust collection systems built into the equipment to collect
debris particles. Optional wet systems are also available and that helps cut down on a lot of the
debris problems.
Chapter 4 - Type 1 Equipment 50
Automated Abrasive Belt Machines
All automated abrasive belt systems can only process flat 2 dimensional sheet metal
parts. These systems are capable of deburring the top and bottom of holes in relatively thin
sheet metal and they leave a textured grain appearance on all parts. The main feature of these
machines is their wide abrasive belts and their in-line adjustable pressure sensitive conveyors.
Shown below are both the dry and wet systems.
Fig. 15. Dry system Wet system
Probably the fastest high-speed material removal system is accomplished with solid inorganic rigid wheels.
However, most of these wheels are not used in offhand applications. That is because it is difficult to maintain a
consistent, even pressure between the wheel and the part without mechanical assistance. Hand-held parts will cause
rigid wheels to bounce or chatter against a part and results in a rough and possibly irregular surface finished part.
This condition is also a safety issue to the operator; therefore, most of these systems are automated so that constant
pressure can be applied to both the part and the wheel.
As mentioned, greater resistance causes greater heat; therefore, most of these automated
solid inorganic rigid wheel type systems use liquid lubricants to speed up processing by
maintain proper working temperature and to remove debris. These systems do deburr, but are
more commonly used for what is called lapping or grinding a part to a specific thickness. The
term lapping is used to indicate a multi step, back and forth, movement or layering process to
remove small amounts of material until the desire thickness is achieved.
I mention these grinding wheels here, but I will not go into a lot of detail on them. They
are not part of standard deburring or surface finishing practices. But, because they do remove
material they should be mentioned. Usually these systems produce a very smooth, flat surface
finish or work type 0 burrs. This type of operation is not normally used for mass production
Chapter 4 - Type 1 Equipment 51
because parts are usually handled one at a time. There are some flat disc lapping machines with
multiple spindles that can do large volume production; however, parts are still feed one at a
time into the machine. Therefore, this type of equipment is not common in high volume parts
production unless dimensions are critical to the part's performance. These machines are
normally used for making precision part's rather than to do deburring.
Non-woven
There is a relatively new category of light weight solid wheels and belts which are used
for offhand applications called non woven products. These are very abrasive materials and are
composed of both organic and inorganic materials. Because these products can be very
aggressive and don’t load up with debris they are used on up to a type 3 burr, but they can also
work other lesser burrs. These non-woven abrasive products are composed of synthetic
polyurethane fibers in a flexible foam like fibrous composite imbedded with inorganic
abrasives.
Non-Woven Material Systems
As abrasive go, non-woven products are a relatively new comer to the deburring industry. This material
is composed of minerals, resins, and fiber that are made into wheels, sheets, belts, and other composite
materials. The formulation provides great rigidity and flexibility for a very effective and efficient abrasive
medium.
Fig. 16. Mineral, Resin and Fiber:
Synthetic fibers and abrasive particles are combines and bonded to form a conformable,
three-dimensional, open-web material
Surface Finishes
Mineral type
Grade
Finishes Generated (Micro-Inch Range) Coated Abrasive
Grade Equivalent Aluminum Stainless Steel
A Course 130-150 62-72 80-150
A Medium 80-100 32-40 150-180
A Very Fine 16-35 6-12 220-320
S Super Fine 8-12 4-6 320-600
Chapter 4 - Type 1 Equipment 52
These non-woven wheels are made with different percentages of abrasives as well as
different abrasive particle materials and sizes. Naturally the finer and softer the abrasive, or the
smaller the percentage of abrasive in the wheel the finer the surface finish. These wheels are
normally always run dry and they produce less heat to the operator in offhand production than
do the inorganic solid wheels. Non-woven wheels are basically solid and rigid, but they have
some flexibility to them that gives them better off-hand control than other inorganic rigid
wheels. Also, because of the rate at which the wheel breaks down, they produce more dust or
debris and that carries away more heat, which is transferred into the debris.
Non-woven products have greater rigidity than most fabric or flexible brush type wheels
but the material characteristics of this type of abrasive material also gives them greater contact
control and contour flexibility. This semi cushion type quality allows the operator to get more
coverage and better pressure and/or performance of material removal and surface finishing of
the part. That means that less heat, energy, and vibration are transfer to the operator than with
inorganic rigid wheels, bit less than flexible organic wheels. Depending on the part in question,
these wheels probably remove as much material in the same amount of time as some coarse grit
solid wheels, but hardness of the material or part does play a big factor in this generalization.
The biggest advantage of the non-woven wheel is that it won't load up with the work removal
material, because it breaks down at a relatively fast rate and as mentioned, they do produce a
lot of dust and material debris. There are tradeoffs.
Filament and wire
In talking about inorganic composites, we were talking about basically rigid wheels.
There is also another category of inorganic wheels, which are considered flexible brush and are
not non-woven. The flexibility of brush wheels is a direct result of the construction and density
of fiber materials in a radial pattern. That is, most of the wheel is composed or encompasses a
greater portion of air than actual filaments. These fibers or strands can be made from metallic
wires, and abrasive filled nylon or polymeric composite materials that are extruded. These
materials are then cut to length, shaped, formed and/or crimped, and then fastened in a radial
or straight pattern configuration series or uniform rows of fiber.
Fig. 17. Deburring Wheels
Chapter 4 - Type 1 Equipment 53
Fig. 18. Filament Brush Systems
Most industrial filament brushes are made up of individual strands or filaments in a
radial or circular construction, but reciprocating flat brushes are also available. Filaments are
made from straight or crimped cut metal wire, encapsulated wire and polymers, or non-metallic
composites of abrasives and polymers of round or rectangular shape filaments. Because of the
wide variety of materials and sizes, a simple wheel is very complex; therefore, the following is
terminology, specifications, and application information.
(a) Geometry of conventional circular filamentary brush,
(b) wire filament geometry, and
(c) nylon/abrasive filament geometry.
Fig. 19. Filament Geometry
Chapter 4 - Type 1 Equipment 54
Fig. 20. Brush Characteristics
Chapter 4 - Type 1 Equipment 55
The advantage of brush filaments is that they bend under pressure and this again helps
the operator to have better control of the wheel and the part. These wheels are better at working
recesses than non-woven products, but are still not good on parts with a lot of deep recesses and
holes. That is because the actual deburring work is done at the end of the filament or that
portion of the filament that is in contact with the part. Basically, if the fiber is flexible enough, it
can and will drag along the surface of the part creating an overlapping uniform smooth pattern.
Filament and wire wheels are also used to create textured artistic patterns on primarily metal
parts.
Naturally, the straighter and thinner the filament, the more flexible the brush and the
softer and finer the material removal pattern. Also, normally the fewer the number of filaments
the softer the wheel. On the opposite side, the thicker the filament or the greater the number of
filaments, the greater the rigidity and the more material removal capability; however, to
increase stiffness, some wire wheels are composed of knotted or twister groupings or bundles of
wire. As mentioned earlier, new unused wheels or flatter, squared off end bristles remove more
material or work faster before they are properly broken in. Speed or RPM’s of the wheel and
size are also important considerations.
In addition to the actual material specifications of the filament is the pattern or how the
filaments are held in place and how they are grouped in different pattern variations. Besides
wheel brushes are cup, end, internal, wide, and maybe very small micro brushes. Each of these
brush systems are constructed or fabricated to perform different functions and/or work specific
application problems. The older and more common brush wheels used for deburring are made
from metal wire and the most common shape is called the circular or radial brush. The
following are recommended applications.
Chapter 4 - Type 1 Equipment 56
Filament Power Brush Material Applications
Of the 5 basic types of filament brushes, there are 4 charts and/or recommendations based upon work piece materials. Wheel and wide brush
charts are used interchangeably. (Courtesy of Osborn Brush)
Wheel Brush End Brush
Selection
Guide
Selection
Guide
Matching the WORKPIECE material to the brush
material
Matching the WORKPIECE material to the
brush material
The Best Brush
Material Is:
The Best Brush
Material Is:
CRIMPED WIRE Aluminum Brass Copper Iron Plastic Steel Stainless
Steel
Wood
CRIMPED WIRE Aluminum Brass Copper Iron Plastic Steel Stainless
Steel
Steel OK OK OK BC NR BC NR OK Steel NR VG BC BC NR BC NR
Stainless Steel VG OK OK OK NR OK BC OK Stainless Steel VG VG VG VG NR VG BC
Nonferrous OK BC BC OK VG OK OK OK Nonferrous VG BC BC NR OK OK OK
KNOTTED WIRE KNOTTED WIRE
Steel NR OK OK BC NR BC NR OK Steel NR NR NR BC NR BC NR
Stainless Steel NR OK OK OK NR OK BC OK Stainless Steel NR NR NR VG NR VG BC
Nonferrous VG BC BC OK VG OK OK OK
TY®
ENCAPSULATED
WIRE
TY®
ENCAPSULATED
WIRE
Pliant Polymer NR NR NR BC NR BC BC
Pliant Polymer NR NR NR BC NR BC BC NR Rigid Polymer NR NR NR BC NR BC BC
Rigid Polymer NR NR NR BC NR BC BC NR
NATURAL
FIBERS
NATURAL FIBERS
(With Abrasive
Compounds Only)
Tampico- Treated Tampico VG VG VG VG BC BC BC
Untreated VG VG VG OK VG BC BC OK
- Treated VG VG VG VG OK BC BC NR SYNTHETICS
Sisal VG VG VG OK OK OK BC NR Abrasive Nylon BC BC BC BC VG BC BC
SYNTHETICS
Nylon OK OK OK NR OK OK OK OK
Abrasive Nylon BC BC BC VG VG BC BC VG
Chapter 4 - Type 1 Equipment 57
Filament Power Brush Material Applications, continued
Cup Brush
Internal
Brush
Selection
Guide
Selection
Guide
Matching the WORKPIECE material to the brush
material
Matching the WORKPIECE material to the
brush material
The Best Brush
Material Is:
The Best Brush
Material Is:
CRIMPED WIRE Aluminum Brass Copper Iron Plastic Steel Stainless
Steel
Wood
STRAIGHT WIRE Aluminum Brass Copper Iron Plastic Steel Stainless
Steel
Wood
Steel BC BC BC BC NR BC BC BC Steel VG VG VG VG NR VG VG NR
Stainless Steel VG VG VG VG NR VG BC NR Stainless Steel VG VG VG VG NR VG BC NR
Nonferrous VG VG VG NR OK OK OK VG Nonferrous VG BC BC VG OK OK VG NR
KNOTTED WIRE CRIMPED WIRE
Steel NR OK OK BC NR BC NR NR Steel VG VG VG BC NR VG BC OK
Stainless Steel OK OK OK VG NR VG BC NR Stainless Steel VG VG VG VG NR VG BC OK
Nonferrous BC BC BC NR NR OK OK NR Nonferrous VG BC BC VG OK VG VG OK
TY®
ENCAPSULATED
WIRE
TY®
ENCAPSULATED
WIRE
Pliant Polymer NR NR NR BC NR BC BC NR Pliant Polymer OK OK OK BC NR BC OK NR
Rigid Polymer NR NR NR BC NR BC BC NR
SYNTHETICS
SYNTHETICS Abrasive Nylon BC BC BC BC BC BC BC BC
Abrasive Nylon BC BC BC BC VG BC BC BC
Legend
BC
is typically the BEST CHOICE for the
combination
VG
is typically VERY GOOD for the
combination
OK is typically SUITABLE for the combination
NR is NOT RECOMMENDED for the combination
Chapter 4 - Type 1 Equipment 58
Fig. 21. Filament Brush Applications
Selection
Brush type is determined by how the strands of filaments are held in what position or
arrangement. Basically there are five types of filament brushes: wheel, cup, end, internal and
wide brushes. The brush selection is determined by the type of work to be done, the equipment
to be used, and it’s RPM speed, and the surface profile or finish desired. The composition of the
filament strands is determined by the workpiece material, equipment RPM and the finish
required. The size of the brush is determined by the part’s size and configuration, equipment
RPM and the finish required
Typically the larger the brush diameter, the more efficient the brush. However to select
the maximum allowable size, you must consider RPM machine speed. RPM speeds over 6000
should not exceed a 6” O.D. Shorter filaments have the ability to flex and conform to irregular
surfaces better.
Chapter 4 - Type 1 Equipment 59
Fig. 22. Brush Types for Applications
Getting back to composite filament brushes, the most common synthetic wheels are
normally made from nylon with either a silicon carbide or aluminum oxide material added to
them to make the flexible filament more abrasive. These brushes consist of about 40% of organic
material and can be made with a number of different abrasive particle sizes. The coarsest, most
abrasive size is about a maximum grit size of 46 to the smallest of about 500 grit. Because of the
relatively low melting temperature of around 600 degrees for nylon, these brushes have limited
applications for deburring. This may sound like a high temperature, but it is relative to
pressure, meaning that it can easily exceed this temperature very quickly at the contact point.
Consequently, these wheels are used more for cleaning purposes along with straight nylon
material fibers, polymeric, polypropylene, and the natural fibers of tampico and palmyra.
Most brushes have relatively short bristle lengths which are easier to control and work
better than longer ones because pressure deforms the bristles. The inherent flexibility of all
filament and wire wheels allows them to work extremely well on contour parts and again type 0
to 1 burrs. However, because of their construction, they can produce noticeable patterns or
textures on the finished parts and may leave flat surfaces rougher than they were before they
were worked. Then again, some of these finishes are considered artistic in themselves and can
be found to decorate trucks and the most notable use was on the Spirit of St. Louis airplane.
The deburring performance of such brush wheels depends on the overall diameter of the
fiber, the width of the bush, the type of material, the length of the fibers, and the number of
fibers filaments, and the wheel or design application. A general rule of thumb is the larger the
diameter of the filament and the shorter its length the rougher the surface finish produced and
the more material removal capability. Also the greater number of filaments a brush has the
more uniform and finer the finish pattern or texture.
Chapter 4 - Type 1 Equipment 60
Organic materials
Lastly, there are the flexible organic cloth type wheels. These wheels have greatest
amount of flexibility and that does not lend itself to a great deal of material removal. These
wheels may also have the greatest amount of construction and material variations. Generally
speaking, most of these wheels are used to deburr and polish, or buff, type 0 burrs but can be
used for some minor deburring on type 1 burrs.
The amount or aggressiveness of the organic wheel or material removal depends mostly
on the compound used with the wheel rather than the actual construction of the wheel. Organic
fabrics are composed of strong, almost hollow, inter-connecting and woven cellular fibers that
tend to have greater flexibility and therefore softer qualities than solid, rigid inorganic
materials. This flexibility lends itself to surface refinement, rather than material removal.
Fig. 23. Organic Wheel Materials
The following are some of the more common compositions and materials used to make buffing wheels.
Flannels
Domet flannel (with nap on both sides) and Canton flannel (nap on one side and twill on the other) in
various weights are used where other fabrics fail to produce a high enough luster. Coloring of jewelry products
is a typical application for such buff materials
Sisal
Sisal is a natural hemp fiber used for fast-cut buffing of steel and stainless steel. It is a coarse fiber
twisted into strand groups and frequently woven into a fabric. It has a much lower thread count than cotton
muslin, sometimes five by seven per inch, and offers the advantages of greater surface defect removal.
Combination Sisal/Cloth buffs are effective designs. The sisal plies are often cloth covered to omit the tendency
of the sisal to cut the cotton threads of adjacent cloth plies. Alternating cloth and sisal improves compound
retention, reduces unraveling and moderates cut. Kraft paper alternated with sisal also has applications.
Other Natural Materials
Occasionally, other materials are used to form buffs. For example, woven wool buffs are
used on plastics, soft metals, and sterling silver. Sheepskin buffs are used to avoid surface drag
or smear when buffing metals that contain lead. Russet (bark-tanned) sheepskin is used for cut.
White alum (alum-tanned) sheepskin is used for color buffing.
Chapter 4 - Type 1 Equipment 61
Pieced Buffs
Pieced buffs are less expensive because they are made from lower priced materials. The
buffs are made of colored segments, unbleached segments, and occasionally bleached material.
Combination Buffs
Often different materials are combined, especially sisal and cloth, and occasionally paper
as well as cloths of different specifications.
Synthetic Fibers
Unwoven nylon and other synthetic fibers, because of their water resistance, may be used
wet or dry or with wax or grease lubricants. Buffs made of synthetics are usually operated at
low speeds, Typically 2,500 sfpm, to prevent melting and streaking of surfaces.
In the finishing industry, the term polishing basically refers to metal removal and is done
with anything that modifies a surface profile which is the same definition we use for deburring.
That also means that almost anything can be considered an abrasive, even the smoothest
material that can be used to rub or contact another surface. To make some distinction of
terminology, the finishing industry uses the word buffing to refer to a specific desired
brightness or high luster surface finish, but this does not necessarily mean a smooth surface
finish.
The most common, general purpose, polishing wheels are made from cotton, but can be
muslin, canvas, felt, or leather. Wheels are fabricated in layers sewn together or held together
with adhesives of silicate of soda or animal based glues. The quality of the wheel is determined
by thread count per inch in the fabric, which weights between 2.5 and 3.5 linear yd./lb. of 40-
inch wide materials. These materials can be treated before or after assembly of the wheel.
Harder and stiffer treatments provide faster cutting and deburring. Softening makes them more
flexible and provides longer life. Some treatments provide better adhesion for lubricants and
compounds. Most treatments are done to the buffs to make them fire resistant and retard
burning.
Buffing wheels are normally die cut and pieced together in layers like a sandwich.
Without a means to hold the layers together, the buffs unravel or fray easily. However, in this
condition, they are cheap and good for polishing. Most wheels are sewn together in various
ways. Concentric sown wheels tend to be stiff near the stitch section, then loosen after the stitch
wears through and this may cause an uneven textured surface on the finished parts. A spiral
stitch results in a more uniform density of the wheel and produces more constant results.
Square sewing creates more pockets to retain more buffing compound. Other sewing patterns
are radial, radial arc, tangent, parallel, ripple, zigzag, cantilever, and petal. These patterns
provide strength and longevity to the wheel and also increase its cost.
Chapter 4 - Type 1 Equipment 62
Organic Wheel Fabrication
Fig. 24. Wheel construction
The following shows the sewing patterns and/or fabricating construction of most of the buffing wheels
in use.
Unsewn Buffs
Conventional, full-disk buffs are made with die-cut cloth
disks. Unsewn, conventional full-disk buffs may be used for luster.
Loose disks are turned to allow the threads of the material to lie in
different directions. This results in more even wear, avoiding a
square shape after being put into use. One disadvantage of this
conventional design is that the fabric can fray or ravel. When held
against a wheel rake, a cloud of threads may fly off. This shortens
buff life, increases compound consumption, and adversely affects
finish. Also available are solid bias sisal buffs, with every other
layer being cloth, and rebuilt buffs made from reclaimed material.
Conventional Sewn Buffs
Conventional, full-disk buffs for heavier buffing (cut)
are sewn in various ways. Closer sewing is specified for cutting
harder metals and for removing deep imperfections.
Concentric dewing causes a buff section to become
harder as it wears closer to the sewing and softer after wear causes
the sewing to break through. Spiral sewing results in more
uniform density. Square sewing produces pockets that help the
buff wheel to retain more buffing compound. Radial sewing,
sometimes called sunray sewing, and radial arc sewing provide
other variations. Tangent, parallel, ripple, zigzag, cantilever, and
petal sewing are used for similar reasons. Special sewing, other
than spiral, which is done on automatic machines, involves more
labor in the buff manufacturing process, thus increasing the price
per buff.
Folded or Pleated Buffs
Folded buffs consist of circles of cloth folded twice to
form a quarter circle, resulting in a “regular-pocket” buff (18 ply),
or, for more cut, three times, to form eighths of a circle to
constitute a denser “superpocket” (34 ply). The segments are laid
down to form a circle, with each segment overlapping the previous
segment. They are sewn around the arbor hole and partway to the
periphery. The folds form pockets that hold compound and flex
sufficiently for contour-following capacity. Folded buffs share
three design deficiencies: lack of center ventilation, a tendency to
fray, and waste of material in the unused center.
Pleated Buff
Airway buff cloth may be accordion pleated to present
more angles of material to the surface of the product to be finished.
Pleating results in more cloth angles to reduce streaking and
improve coloring characteristics. Better cutting is also achieved in
some applications.
Packed Buffs
Buffs may be packed with spacers consisting of cloth or
paper inserted between the larger diameter plies. The same spacer
principle is used between buff sections. Both measures result in a
softer wheel face. The packed buff construction is effective in
contour buffing applications.
A version of the packed buff, for threaded, tapered
spindles (2-12-in. diameter), is used in the jewelry industry. The
center is hardened, usually with shellac. The sides of the buff may
be reinforced by leather disks.
Pieced Buffs
Pieced buffs may be used in place of sewn full-disk
buffs. They are made from remnants of cloth left over in the
manufacture of other textile products. Such buffs require one of
the types of sewing used for full disks in order to stay together in
use. The chief virtue of pieced buffs is their higher value owing to
the lower cost of materials. They usually are sold by the pound
(see Table).
Chapter 4 - Type 1 Equipment 63
Approximate Weight - Spiral Sewed Pieced Buffs
REGULAR
Approx. 1/4 in Thick
HEAVY
Approx. 5/16 in. Thick
Extra Heavy
Approx. 3/8 in. Thick
Diameter
(in.)
Lbs. Per
100
Sections
Sections
Per 100
Lbs.
Lbs. Per
100
Sections
Sections
Per 100
Lbs.
Lbs. Per
100
Sections
Sections
Per 100
Lbs.
4 7.4 1351 8.2 1220 11.1 900
5 11.5 870 12.8 781 17.3 578
6 16.6 602 18.4 543 24.9 401
7 22.1 452 25 400 33.0 303
8 29.4 340 32.7 306 44.1 227
9 36.5 274 41.3 242 54.8 182
10 46.0 217 51.0 196 69.0 145
11 55.6 180 61.7 162 83.4 119
12 66.3 151 73.5 136 99.5 100
13 77.7 129 86.2 116 116.6 86
14 90.2 111 100.0 100 135.3 74
15 103.5 97 114.8 87 155.3 64
16 117.7 85 130.6 77 176.6 57
17 132.9 76 147.4 68 199.4 50
18 149.0 67 165.3 60 223.5 45
Conventional construction wheels and sewing patterns may also incorporate folds or
pockets of fabric and/or gaps. These segmented pockets hold compound and flex for greater
contour following capability. There are also the pleated patterns that provide more cloth angles
to reduce streaking and improve coloring capabilities and cutting in some applications. There
are also what are called packed buffs. These are wheels that are packed with spacers of either
cloth or paper inserted between larger diameter layers or plies of fabric. All of these wheels
have a relatively small I.D. hole that can have flanges.
Fig. 25. Organic Wheel Designs
In addition to the stitching or sewing pattern of organic buffing wheels, there is the arrangement of the
fibers and how those fabric materials are held or gathered together
Chapter 4 - Type 1 Equipment 64
Fig. 26. Cloth Buffs
Bias buff (left) versus conventional buff (right). Thread configurations of bias buffs
alternate warp and filler threads. Biasing provides design efficiency by exposing all thread ends
to the surface being buffed, reducing fraying of the fabric.
Bias pattern construction wheels are more frequently used than conventional buffs
because they naturally run cooler and therefore resist burning. As mentioned, a lot of cotton
buffing wheels can catch on fire with or without lubricants or compounds. Temperatures
produced in buffing can exceed the combustible ratings of most fabric materials and that is why
most buffs are treated with fire retardant chemicals. That still does not insure that fire is not
possible in buffing operations; therefore, care should be taken in and around such high
production work areas.
The main construction difference in fabric buffing wheels is the orientation or layering of
the plies of fabric composing the wheel. Less expensive construction wheels use a simple X Y
pattern which is capable of unraveling. Most production wheels use bias material threads which
are held at 45 degree angles when assembled. This construction orients all the fabric ends so
that they face the outside edge from a large I.D. or center section that supports the inside edge.
This popular wheel is also convoluted with puckered pockets. The higher the number the
greater the cloth content, density, and convolutions. Another wheel is the open-face cloth buff,
which prevents loading and streaking. The bias sisal wheel is good for longer life, the open cloth
bias wheel and the open double cloth wheel is good for contoured parts, the spoke unit or finger
wheels have great cutting power as well as contour capabilities.
As you can tell, there are a number of buffing wheels with special applications unique to
each design and/or construction; therefore one requires some knowledge of these variations and
applications to select the proper buffing wheel that will hold up to the part or application
necessary.
Cloth bias buffs in order of increased
density from closed Face (left to right:
0,2,4,6) to open face (far right) design. Open cloth sisal buff Spoke unit or finger sisal
buff.
Chapter 4 - Type 1 Equipment 65
Fig. 27. Organic Wheel Applications
Below are some of the more common applications for wheels shown.
In most cases, to get a good quality finished part requires a number of different wheel
applications or abrasive qualities not found in one wheel alone. As mentioned, each wheel has
certain qualities and/or advantages over that of another. Therefore, in most production facilities
there is more than one polishing station and these are normally set up with different wheels to
achieve different results. That means that most parts can or should be worked with more than
one wheel abrasive or polish. For production speed, a part is done in steps or stages until it is
acceptable and the fastest way to achieve this is by various steps rather than can be
accomplished in one operation only.
Chapter 4 - Type 1 Equipment 66
Abrasive and polishing compounds
To accomplish either a deburred or buffed part using flexible organic wheels requires
that the wheel to be coated with either an abrasive compound or rouge. Some wheels are treated
with chemicals to enhance their performance, but they still need an abrasive or rouge
compound applied to the wheel to do the type of surface finishing work required. The wheel
provides the mechanical energy for the abrasive or rouge to work. Compounds normally come
in a solid bar form that becomes a semi liquid form coating when applied to a moving wheel
system. These compounds must be periodically applied to the wheel to replenish or improve
the working performance of the wheel or compound. The type of wheel is also important in the
retention and performance of the compound.
The compound in bar form contains a binder and an abrasive. Most binders come from
animal or vegetable materials that can be made into fatty acids, tallows, or glycerides, and will
produce saponified water-soluble soap film which will dissolve when combined with alkali
cleaning solutions. Petroleum, mineral oils, and waxes can also be used, but are unsaponified
and are more difficult to clean than water-soluble products. Besides cleaning, binders control
frictional heat or slip, lubricity, degree of hardness and/or resistance, and the adherence
properties of the compound.
To apply the proper compound to the wheel, the solid bar is pressed against the flexible
soft wheel buff and the friction generates heat that liquefies the compound and transfers it to
the wheel. Some newer automated methods spray a liquid compound on the wheel or parts as
they travels through a number of wheels. Typically, an abrasive compound would be composed
of a pumice, fused alox, or silicon carbide. An intermediate step or compound might be "Tripoli"
or fine silica, and a final polish would be an iron oxide, aluminum oxide, or chrome based
compound.
Aluminum oxide compounds are the most popular products used in deburring and
buffing and are normally white in color. There are a lot of different grades of aluminum oxide in
use. It rates an 8 or 9+ in its various oxide forms on the Mohs’ Scale. When this raw material
product is heated at low temperatures of 950 degrees centigrade, it is considered fused
aluminum oxide or calcined alumina and is still considered soft material and is used for buff
polishing of all materials. At temperatures of 1250 or 1850, this product is used more for its
cutting qualities. Naturally, the larger the abrasive grain size, the faster it will cut, but the
hardest fused aluminum oxide is generally used in the making of abrasive belts.
Silicon carbide is the hardest material used in a compound and it rates a 9.6 on the
original Mohs’ Scale and is normally used for abrasive cut down. It is made from mixing coke
and silica in an electric furnace at approximately 1900 to 2400 degrees centigrade. It is used
primarily for abrasive cutting processes and can be gray in its color or compound. Another cut
down compound is Tripoli. It is a name used for naturally occurring microcrystalline silica. It is
used for cut down of mostly non-ferrous materials of aluminum, brass, copper, zinc, and other
white metals. Because this is a silica product, it requires protective breathing precautions of a
Chapter 4 - Type 1 Equipment 67
mask and/or ventilation. This is a relative soft material rating a 7 on the Mohs’ Scale and can be
yellow in color in its compound form.
Besides abrasive cutting compounds are buffing compounds, which really don’t remove
material as much as they modify surface finishes by lapping or micropolishing. Chromium
oxide, also called green rouge, is used for buffing and can achieve mirror finishes and/or color
finishes on stainless steels, chromium, and nickel. Its oxide is rated a 9 on the Mohs’ Scale. Iron
oxide or ferric oxide is also called jeweler’s rouge or red rouge is also a popular buffing
compound. It is 99% pure iron oxide and is used a lot on non-ferrous metals of brass, copper,
gold, and silver and is usually red in color. It is a lot softer oxide rating only a 6 on the Mohs’
Scale.
Abrasive and Buffing Compounds For Organic Wheel Systems
To determine what compounds to apply to organic wheels, the following guidelines are
recommended. First, what is the hardness of the material to be worked? Second, what is the
hardness of the abrasive in the compound? Third, what is the RPM speed of the equipment
being used? Fourth, what is the desired surface finish? In addition to these questions, one
should also know the size of the abrasive particles and temperature range of the compound.
Hardness of Abrasive Materials
Abrasive Type Chemical Symbol Mohs’ Scale
Aluminum Oxide (fused) AL2O3 8-9+
Aluminum Oxide (calcined) AL2O3 8-9+
Tripoli-silica SiO2 7
Silicon Carbide SiC 9.6
Iron Oxide Fe2O3 6
Chrome Oxide Cr2O3 8-9
Wheel Speeds for Hand Buffing, sfm
Cutting Down Luster Buffing
Carbon and Stainless Steel 8,000-9,000 7,000-9,000
Brass 6,000-9,000 6,000-9,000
Nickel 6,000-9,000 6,000-8,000
Aluminum 6,000-9,000 6,000-7,000
Zinc & Other Soft Metals 5,000-8,000 6,000-7,000
Chromium - 7,000-8,000
Chapter 4 - Type 1 Equipment 68
Production Buffing Techniques
Material to
Finish
Satin Finishing Cutdown Buffing Color Buffing
Aluminum Aluminum oxide greaseless
compound light head of
Dry Tripoli bar. Loose or
ventilated buff or string wheel,
3,000 to 5,000 sfm
Tripoli bar or liquid
compound loose or
ventilated buff, 6,000 to
8,000 sfm
Rouge silica unfused aluminum
oxide bar or liquid compound loose
or low-density ventilated buff, 6,000
to 8,000 sfm
Brass Aluminum oxide greaseless
compound. Loose or ventilated
buff, string wheel 3,500-5,500
sfm
Tripoli bar or liquid
compound. Ventilated
loose or sewn buffs. 5,500
to 8,000 sfm
Rouge silica unfused aluminum
oxide bar or liquid compound loose
or low-density ventilated buff, 5,000
to 8,000 sfm
Hard
Chromium
Aluminum oxide greaseless
compound. Loose buff 5,000 to
6,500 sfm
Chromium green oxide or unfused
aluminum oxide bar or liquid
compound, loose or ventilated buff,
5,000 to 6,500 sfm
Chromium
Decorative
Plate
Lubricated silica greaseless
compound, loose buff, 3,000 to
4,500 sfm
For burnt areas:
Combination fine fused
and unfused aluminum
oxide bar, loose or
ventilated buff, 6,500 to
8,000 sfm
Chromium green oxide or unfused
aluminum oxide bar. Loose or
ventilated buff, 6,500 to 8,500 sfm
Copper Aluminum oxide greaseless
compound. Loose or ventilated
buff string wheel, 4,500 to 6,000
sfm
Tripoli bar or liquid
compound.
Loose sewn or ventilated
buffs, 5,500 to 7,500 sfm
Rouge, silica, or unfused aluminum
oxide bar or liquid compound, loose
or low-density ventilated buff, 5,500
to 7,500 sfm
Copper
Plate
Aluminum oxide greaseless
compound. Loose or packed
buff, string wheel, 3,000 to
5,000 sfm
Tripoli bar or liquid
compound.
Loose or ventilated buff,
5,000 to 8,000 sfm
Nickel and
Alloys
Aluminum oxide greaseless
compound. Loose or ventilated
buff, 5,000 to 7,500 sfm
Tripoli bar or liquid
compound.
Loose sewn or ventilated
buff, 5,000 to 8,000 sfm
Chromium green oxide or unfused
aluminum oxide bar or liquid
compound, loose or ventilated buff,
5,000 to 8,000 sfm
Nickel
Plate
Decorative
Aluminum oxide greaseless
compound. Loose or ventilated
buffs, 4,500 to 5,500 sfm
Lime bar, or chromium green oxide,
or unfused aluminum oxide bar or
liquid compound, loose or low-
density ventilated buff, 6,500 to 7,500
sfm
Steel and
Stainless
Steel
Silicon carbide or aluminum
oxide greaseless compound.
Loose or ventilated buff, 4,500
to 6,500 sfm
Aluminum oxide bar or
liquid compound.
Ventilated, sewn, sisal
finger or Tampico buffs,
8,000 to 10,000 sfm
Chromium green oxide and/or
unfused aluminum oxide bar or
liquid compound, loose or ventilated
buffs, 8,000 to 10,000 sfm
Zinc Aluminum oxide greaseless
compound. Loose or ventilated
buff, 5,500 to 6,500 sfm
Tripoli bar or liquid
compound. Loose
ventilated or sewn buffs
Silica or unfused aluminum oxide
bar or liquid compound, loose or
low-density, ventilated buffs, 6,000
to 8,000 sfm
Chapter 4 - Type 1 Equipment 69
In more advanced automated systems, parts may be spray coated with a liquid form of
rouge as they pass on a conveyor belt line into a fixed series of buffing wheels. The liquid
compounds used are all water based products or oil/water emulsions. Stability of the product is
achieved through density, viscosity, and suspension. Because this is a liquid compound that is
accurately proportioned per part, wheel speeds can be lower and uniformity is more consistent
to the operation. In general, liquid systems are a lot more simple to operate and maintain and
maybe the trend form in the future for all systems; however, these are automated systems and
the initial coast is a whole lot more than using bar compounds.
As mentioned, in wheel systems it is the compound that does the actual material removal
or surface modification, the wheel only provides the pressure and/or mechanical energy that
acts somewhat like a catalyst in the operation. That is, it helps the operation, but it is not the
primary agent in the process. Pressure, friction, type of wheel, and compound is what produces
a polished or abrasive surface finish. Again, a lot of different compounds and wheels produce a
wide variation of finishes.
As long as we are talking about finishes again, let me say that nearly all flexible wheel
systems produce a luster on parts. As mentioned earlier, these wheels can be composed of
different materials, thickness, length, texture, and/or grades that produce highly reflective mat,
textured, or satin type finishes. There are also the composite synthetic brush type wheels that
produce excellent material removal or polishing type results, but not generally a mirror finish.
Reflective surface finishes can be achieved using abrasives and other means; however, to
achieve a reflective mirror finish requires a soft wheel and compound with a lot of lubricity to
improve the material surface profile of the material being worked. A smooth, flat buffed surface
is normally required and desired for medical parts to avoid contamination from microscopic
organisms and sometimes on high tech parts for precision performance.
Felt
Now, after making that statement, I am going to make an exception to what I just said.
Another good polishing wheel that is not exactly soft and is an exception to rigid wheels are
those made of hard organic cotton felt. There are a number of grade densities of felt that are
manufacturer that are determined by pounds. The harder grades of organic felt material have
some minor flexibility even though they are basically stiff rigid wheels. That means that these
solid rigid wheels are similar to non-woven materials in characteristics and performance but are
not considered as such because they are not composed of a blend of mixed abrasive materials
and synthetics.
Felt wheel products are made in different densities and the harder the felt the longer it
lasts. Also, density determines how these wheels perform. The problems with these wheels are
the same as those of solid inorganic wheels; it is difficult to maintain constant, even contact with
a part without a chattering effect. Therefore, a lot of felt wheels are very popular for small
power tools and especially the jewelry industry for achieving mirror finishes. Because of the fine
quality of this material, these wheels can be used with or without rouge.
Chapter 4 - Type 1 Equipment 70
Flap Wheels
The flap wheel is another type of radial wheel and is composed of separate individual
square flap segments of coated abrasives of fabric, sisal, and cloth material that are set at a right
angles to the direction of rotation. Because of this construction, the wheel tends to be more rigid
and therefore more aggressive. Basically they behave the same as filament and wire wheels, but
are more easily controlled and normally produce smoother results.
Fig. 28. Types of Inorganic Flap Wheels
Discs
Disc type abrasive products look and behave like wheel systems; however, unlike radial
wheels, they work on one of their flat sides, instead of the width of the edge or face. The
abrasive is only coated on one side of the disc like a belt system. They are similar to a flap
wheel, but they do not work with the tips of their edge and they do not rotate like radial wheels.
The disc can be flexible or rigid, but normally that is a function of the backing or support
backup mounting plate. The hand tool that use discs are also more difficult to control, because
they are used at right 90 degree angles to the work piece and that causes them to follow a
changeable circular pattern. That is, the pattern is a variable factor influenced by the rotation of
the disc and controlled by the operator that can be anywhere from perpendicular or an almost
flat angular drag. Also because of the circular pattern, it is very difficult to create a uniform
surface finish.
This system uses a single disc or a flexible flap type of construction and it operates in
close full contact with the work piece. That means that when the abrasive wears down the disc
will have to be replaced. That also means that the surface profile will also change, because the
abrasive has also changed. The working part or flap of these wheels are made from coated
abrasive belt products and can be backed up with either rigid or flexible formed materials for
better control and contact.
Chapter 4 - Type 1 Equipment 71
Besides the abrasive type sandpaper belt materials being the same as a disc, the shape
and behavior characteristics are definitely different from a radial wheel system. When a disc is
mounted vertically fastened to a fixed motor and platform system, the results are good for
working thin edges of parts, but not large flat areas. Even this type of equipment and processing
method does not produce good uniform material removal or deburring results. This problem is
even more noticeable when using a handheld portable power tool on larger flat parts. The
circular shape of the disc and the pressure an operator applies to it in a free or non-rigid plane
of reference normally creates an irregular surface finish or angular drag pattern. Material
removal is accomplished in a circular manner, but because of the speed and the control factor,
only a portion of the disc is in contact with the surface profile at one time, thereby creating an
overlapping half moon pattern. In other words, the portable hand tool or disc grinder is good
for large flat parts, but it still produces uneven results and patterns because of the control factor.
Beside circular disc, there are now some triangular shaped discs with holes in them to
help relieve the heat and remove debris or what is called loading caused by excessive pressure
to a disc. Loading is the condition where the abrasive and the material being removed from an
almost flat profile thereby not allowing the abrasive to be in surface contact with the material to
be worked. As mentioned previously, in order for abrasives to work, they must themselves have
a surface profile capable of material removal. Technically, the use of a disc is not a normal
finishing system, because of the control factor. Most disc systems are used for small part lots or
reworking materials.
Chapter 4 - Type 1 Equipment 72
Fig. 29. Inorganic Abrasive Disc
The transition from radial deburring wheel systems to belts uses another type of wheel know as the
disc. Instead of using an in line wheel face, the disc uses a single side or uniform abrasive face that operates in a
circular rotary pattern 90 degrees to the movement of the tool. Instead of working a relatively small section of
part with good visual reference, the disc covers a much wider area and obscures the work section, then again,
the radial wheel is used to work smaller off hand parts and disc are primarily used on much larger parts.
Instead of taking parts to the wheel, the wheel is taken to the parts.
The most common disc construction uses a thin abrasive belt product, normally round in shape and designed
for quick changes by snap on fasteners, screws, or glue. The more rigid the disc construction or the support
backing the more aggressive the wheel system. There are now some solid triangular shaped discs for reciprocal
type equipment and a new triangular AVOS disc with holes that allow operators to actually see the product or
problem area they are working. These new design discs tend to generate less heat and use less power.
Chapter 4 - Type 1 Equipment 73
Other variations of the disc, besides the standard flat are: slotted, scalloped, raised bump,
and stars. Some more bulky configurations are square or round pads, cross, and butterfly.
Another shape that is used to work I.D holes are the cartridge rolls, cylinders that are uniform
or tapered, and cone shapes. We have already talked about the flap wheel, but I guess it can be
classified as either a wheel or a disc belt. They can also be constructed with an inter mix of non-
woven pads, designed to remove a lot of material in a short period of time, from type 0 to type 3
burs. Wheels using the non-woven materials as filler, produce excellent polished finishes, but
not a buffed finish.
Each of these shapes are constructed to handle special applications or work difficult to
reach areas for deburring.
Perhaps I should mention that up to this point, we have talked about RPM’s and rotation
as the power source to accomplish material removal… There is another way and it is common
with these disc type transfer or contact devices. There are what are called reciprocal motor
systems. These systems work in a back and forth motion and are more closely related to a
vibration method. Technically, both the contact device and the power source remain relatively
stationary, but because of the fast back and forth movement of less than an inch, the system
creates an over lapping pattern for which the abrasive can work and modify the part.
The reciprocal systems are used a lot at home to improve surface removal. They are not
normally used in industry for production because they are relatively limited in their abilities
and applications. They cannot designed to handle burrs over a type 2; therefore, this equipment
would have a maximum range or classification of 100 to 121. This is the only application of
reciprocal power source equipment.
Chapter 4 - Type 1 Equipment 74
Fig. 30. Inorganic Abrasive Shapes
All abrasive belt construction wheels and standard reciprocal shapes start out as flat and nearly square
shapes. They are then either cut into special shapes and/or folded into special shapes. Following are a few
common applications.
Chapter 4 - Type 1 Equipment 75
Before I go much further, I think I should say something about discs versus belt systems.
I grouped wheel and belt systems together because they are used to work parts or materials in a
horizontal or parallel plane to the surface of the materials they are working. That is, the surface
profile material of a part is moved perpendicular to its original position or along the same
parallel plane as the part. Wheel and belt systems use abrasives and compounds differently, but
achieve nearly the same results.
In operation, wheel and belts do not behave the same, but discs and belts use the same
abrasive materials and do behave the same. The only difference between belts and discs are
their shape and the way the energy forces are applied. Belts normally work a broad flat area in
one direction and produce a uniform surface finish. Most discs can work with their whole
surface diameter, but normally operators use just their edge and rarely achieve 100% contact.
This method of operation produces a swirl pattern and this is normally never uniform. The
reason for this problem is the way the transfer device tool is held and the difficulty of the
operator to apply pressure and control over the tool and the surface being worked. Therefore,
discs are used more for heavy material removal in small areas and in excess of type 4 burrs. As a
general statement, disc systems are almost used more like a cutting tool instead of used for
surface finishing.
Comparison
Earlier, I began this section talking about type 1 systems which are both wheel and belts
and then I proceeded to tell you a lot about wheels. Even though these systems are related by
the way they work or move horizontal or parallel to the materials surface profile, they are
different to some extent. Belts have different characteristics from wheel systems. Wheels seem to
be softer, more flexible, because they are composed of a lot of loose materials separated by air
and therefore they are used more for buffing or what I think most people call polishing,
meaning to produce a bright shine. However, polishing terminology used by wheel people
means material removal and buffing is the proper term for a bright surface finishing.
Belts are more rigid and seem to have greater surface contact and abrasive density and
that relates to more material removal or deburring than wheels. I would also say that probably,
wheels work better on contour parts and belts work better on flat sheet metal type parts. Belts
also do not use a lot of compounds to control material removal and surface finishes therefore
they tend to be simpler systems. Once a belt is selected you are pretty well locked into a
uniform finish, depending upon the abrasive used, that a belt will produce. Again, you do have
the break in situation factor were the belt is more aggressive initially and then stabilizes.
What I just said about belts being a simpler system is and is not exactly true. Although
the contact belt is relatively simple compared with the wheel systems, belts have a couple of
variables. First of all the belt has a power source motor not necessarily directly in contact with
the belt. Usually the system has a drive wheel or contact wheel, the belt itself, and an idler or
tension-tracking wheel, all of which are designed to control the belt. So, even though we are
talking about a wheel versus a belt, we are also talking about other mechanical features that
Chapter 4 - Type 1 Equipment 76
control the process. That makes the actual equipment system more complicated mechanically,
but the application and/or results are simpler or easier to obtain.
Inorganic Abrasive Belt Systems
Although powered by motor and wheels, belt systems are mechanically more
complicated, but produce more consistent finishing result. Belts work like wheels in that they
operate in a linear mode, but tend to be more rigid and have greater surface area. Besides the
type and size of the abrasive construction of the belt, the hardness of the contact wheel also
effects the final surface finish of the part. Compounds are not as important in obtaining final
results. All belts have at least two wheels and most use three. Work area is either against a
contact wheel or a stuff contact backup point between the contact and tracking wheel.
Fig. 31. Contact Wheels
Surface Material Hardness and
Density
Purpose Wheel Action Comments
Cog Tooth Rubber 70-95 Durometer Heavy Grinding Very aggressive, retards
dulling
For heavy stock removal
such as gates, risers, etc..
Standard
Serrated
Rubber 55-95 Durometer Medium to Heavy
grinding
Excellent stock removal,
not as severe as cog
tooth
Not as aggressive as cog
tooth, depending on land to
groove ratio. Most common
type
Plain Face Rubber 40-95 Durometer Light to medium
grinding
“Middle-of-the-road”
type wheel, finer surface
roughness than above
For flat surfaces or where
belt might be punctured
with serrations
“X” Shaped
Serrations
Rubber 35-70 Durometer Polishing to light
grinding
For very mild contours
and light stock removal
More applicable for
nonferrous parts
Flat Compressed
Canvas
Available several
densities from
extra soft to extra
hard
Polishing Varies with density from
light stock removal to
fine polishes
Bench-type grinder
oriented. All around wheel
Flat Solid
Sectional
Cloth
Available five
densities, 50 to 90
plies per inch
Polishing Uniform polishes for
contoured work
Excellent for all types of
finishing. May be preshaped
Flat Buff Section
Cloth
Variable Contour polishing Conformable for
polishing contours and
irregular shapes
Adjustable for width and
density
Chapter 4 - Type 1 Equipment 77
Like wheel systems, belts use pressure applied both to the part and the transfer tool
device or belt. Therefore, motor requirements are nearly the same and can be inter changeable.
Unlike the wheel system, the surface finish using a belt cannot be regulated to any great extent
by compound additives, but it can be regulated by changing the contact drive wheel under the
belt. Given the same abrasive belt using a soft contact wheel versus a hard wheel, the belt will
work faster to remove more material the harder the contact wheel; however, that will also result
in a rougher surface finish. Cloth and soft contact wheels have greater contour capabilities and
will result in finer surface finishes.
Fig. 32. Inorganic Abrasive Belt Applications
Belts are manufactured to include different abrasives and sizes, backings, bonding, splices, and types of
flexing. Abrasive grains are classified into grades or grit sizes ranging from 16 coarse to 1500 fine. Two systems
are normally used: FEPA for aluminum oxide and silicon carbide abrasives and CAMI for zirconia alumina (see
chart. Typical applications and speeds are as follows:
Chapter 4 - Type 1 Equipment 78
Fig. 33. Suggested Surface Speed and Abrasives for Various Metals
Material Operation Abrasive Grits Belt
Speed Lubricant Contact Wheel Type
Hardness/
Durometer
Hot and
Cold Rolled
Steel
Grinding
Polishing
Fine
Polishing
ZA,A/O or
CAO
ZA,A/O or
CAO
A/O
24-60
80-
150
180-
320
4,000-
7,000
4,000-
7,000
4,000-
7,000
Dry
Dry or Light Grease
Heavy Grease or
Polishing oil
Cog tooth or serrated
Plain face rubber,
canvas
Plain face rubber,
canvas, cloth
70-95 duro.
40-70 duro.
Medium
Soft
Stainless
Steel
Grinding
Polishing
Fine
Polishing
ZA or A/O
ZA or A/O
A/O or
S/C
36-60
80-
150
180-
240
3,000-
5,000
3,000-
5,000
3,000-
5,000
Dry
Dry or Light Grease
Heavy Grease or
Polishing oil
Cog tooth or serrated
Plain face rubber,
canvas
Plain face rubber,
canvas, cloth
70-95 duro.
40-70 duro.
Soft
Aluminum Grinding
Polishing
Fine
Polishing
ZA,A/O or
CAO
A/O or
S/C
A/O or
S/C
24-80
100-
180
220-
320
4,000-
7,000
4,000-
7,000
4,000-
7,000
Light Grease
Light Grease
Light Grease or
heavy grease
Cog tooth or serrated
Plain face rubber,
canvas
Plain face rubber,
canvas, cloth
70-95 duro.
40-70 duro.
Medium
Soft
Copper and
Copper
Alloys
Grinding
Polishing
Fine
Polishing
A/O or
S/C
A/O or
S/C
A/O or
S/C
36-80
100-
150
180-
320
3,000-
7,000
3,000-
7,000
3,000-
7,000
Light Grease
Light Grease
Light Grease or
heavy grease
Cog tooth or serrated
Plain face rubber,
canvas, cloth
Plain face rubber,
canvas, cloth
70-95 duro.
40-70 duro.
Medium
Soft
Nonferrous
die casting
Grinding
Polishing
Fine
Polishing
ZA,A/O or
CAO
A/O or
S/C
A/O or
S/C
24-80
100-
180
220-
320
5,000-
7,000
5,000-
7,000
5,000-
7,000
Light Grease
Light Grease
Light Grease or
heavy grease
Cog tooth or serrated
Plain face rubber,
canvas, cloth
Plain face rubber,
canvas, cloth
70-95 duro.
40-70 duro.
Medium
Soft
Cast Iron Grinding
Polishing
Fine
Polishing
ZA,A/O or
CAO
A/O or
S/C
A/O or
S/C
24-60
80-
150
150-
240
2,000-
5,000
2,000-
5,000
2,000-
5,000
Dry
Dry
Dry or Light Grease
Cog tooth or serrated
Serrated or plains
Plain rubber
70-95 duro.
40-70 duro.
Soft
Titanium Grinding
Polishing
Fine
Polishing
ZA or S/C
S/C
S/C
36-60
80-
120
150-
240
1,000-
2,500
1,000-
2,500
1,000-
2,500
Dry
Dry or Light Grease
Dry or Light Grease
Cog tooth or serrated
Plain face rubber,
canvas
Plain face rubber,
canvas, cloth
70-95 duro.
40-70 duro.
Soft
Tensioning devices are important in belt performance and the proper running or
centering of the belt. These devices are slightly crowned in the center and should not be a flat
Chapter 4 - Type 1 Equipment 79
tension wheel for the proper tracking or positioning of the belt. If the tension on this
idler/tension wheel is too tight a belt may wear or deteriorate very fast and created very rough
finishes. Too lose a belt may slip and therefore not work properly, but in some cases may be
good for processing contoured parts. A proper tension is dictated mostly by the type of contact
wheel that is selected for a desired finish which the contact wheel is designed to produce.
Belt Composition
The abrasive belts or discs are made from sandpaper. Other than the fact that there is no
sand or paper involved in making these belts, this statement is correct. The generic name of
paper is used to describe some coated products; however, these are actually compositions of
either man made or natural fiber materials and are developed from paper type products. In
addition to these paper based products are cloth materials which are stronger and normally
water resistant. Fabric materials seem to hold abrasives better and generally last longer than
paper.
Cotton again is the choice of most abrasive belts or discs; however, polyester fibers offer
greater tensile strength, last longer, and are more resistant to fraying and tearing. Common
abrasive particles used are garnet, flint, and emery. More recently, the newer man made
materials of aluminum oxide, silicon carbide, zirconia alumina, and ceramic aluminum oxide
are becoming more popular. New synthetic inorganic materials and bonding agents are being
developed everyday and are producing faster, longer life products.
The backing or bonding agent used to attach the abrasive to the belt is very important.
Typical binders are glue, phenolic and urea resins. Glue bond products are less resistant to heat.
Resin over glue are used for good flexibility and all resin bonded products give the maximum
durability and aggressiveness. Generally speaking, the greater the thickness of the bonded
coating, the less flexible the belt.
Lastly, the orientation of the abrasive on the belt or disc is also becoming a very
important issue. Up until very recently, most belt materials were and are random shaped
particles that conformed to a specific particle size that are basically glued together and bonded
to a flexible belt material. Most belts use a system called open cut distribution of random
dispersing of the particles to the backing material or giving the belt about 50 to 70% abrasive
coverage. This is normally a single layer on a flat surface. There have been some recent
developments that can actually orient the abrasive particles to allow the greater mass or full
abrasive coverage to be in contact with the paper material, thereby producing more uniform
products and finer surface finishes. This system is what is called close cut and is complete
coverage and can have a specific pattern or orientation of abrasive applied to the belt.
In addition to dispersal is now a new manufacturing belt process that can micro replicate
a specific size and shaped particle and create an orientation pattern on a belt in multi layers
similar in appearance to that of a metal file. The abrasive micro replicated composites are a
patented and complex process that creates a precise replicated abrasive shape and pattern. As
the abrasives wear, they expose other layers of abrasives until a color change becomes
noticeable with wear thus indicating the belt needs to be replaced. This construction and pattern
Chapter 4 - Type 1 Equipment 80
uniformity produces faster, more exact cut rate, and even surface finishes throughout the longer
life and higher cost of the belts. The abrasive orientation also reduces loading problems or
produces more debris and or liquid removal. Naturally, the more complicated or complex the
bonded product, the more expensive the belt.
Construction of the more common, open cut, coated abrasive belt products can take one
of four forms. They are as follows:
1. J construction is flexible lightweight cloth belts used mainly for contours.
2. X construction is heavier than J weight and is used for heavy stock removal.
3. Y construction is a newer coated abrasive belt that is stronger and more rugged
than X weight.
4. S construction is a special material designed to make wide belts.
The faster a standard abrasive belt is run, or surface feet per minute, the more heat is
generated causing it to deteriorate faster also. Too fast a belt speed will cause excessive loading
of any material being removed to stick to the belt and will stop abrading entirely. Sometimes,
the abrasive in an over loaded belt can be restored with a hardened metal dressing wheel.
However, the simplest means is to let the belt cool down and then contact it again very hard
and for a short duration with another part. Pressure causes the fracturing of the abrasive grain
and exposes new crystallized material.
To prevent over loading, improve the finish, extend the life of the belt, and to increase
aggressiveness, lubricants can be used on a dry belt. Like the buffing wheels, grease sticks can
be applied before the work has begun to the belt and during its operation. These lubricants do
not decrease material removal and they do retard over loading as well as provide finer surface
finish results. Normally liquid coolants or water is not used with belts except in the larger
automated systems mentioned earlier.
Chapter 4 - Type 1 Equipment 81
Fig. 34. Inorganic Abrasive Belt Construction
Abrasive usage and belt construction has come a long way since early times. Up to recent
times, abrasives were selected based upon hardness and size. Past refinements of belt materials
have centered on the application medium backing and/or bonding along with harder synthetic
abrasive materials. Today’s technology has now gone into the design and replication of the
abrasive shape, it’s construction, and how this shape is arranged in patterns. While higher rates
of abrasion are not necessarily achieved, more consistent surface finishes; cooler temperatures
and longer belt life are the results at slightly higher costs.
Three-dimensional structures uniformly
distributed over the entire surface
82
Chapter 5 – Type 2 Equipment & Mixed Technologies
Abrasive Blasting:
Abrasive blasting is a type 2 equipment system for class 5 burrs only, primarily at 0 and 1
locations, but can handle some 2 locations; therefore, I’ll give it a 3 rating. That makes this a 250
to 253 system. It is probably one of the most popular forms of surface preparation or finishing in
use today. It is also probably one of the oldest finishing systems. In short, this system duplicates
the effects that occur more slowly in arid wind driven deserts. That is, abrasive blasting uses air
pressure to propel an abrasive or non-abrasive particle at materials that require some kind of
uniform surface finish. The results are good clean parts with a textured, indented, or irregular
increased surface area profile finish, provided that either the abrasive is harder or the energy
pressure is greater than the material being worked.
About the best surface finish that can be achieved using this equipment is somewhere
around a 32 RMS. To achieve that fine a surface finish requires special fine media and a good
dry air source. As mentioned earlier in the section on abrasives, it is difficult to achieve a surface
finish finer than the size of the abrasive particle that one is using. That means that the particle
size and how the energy is applied determines the surface profile of the material being worked.
Blast type systems cannot properly process abrasive particles finer than 320 girt, which is equal
to around 32 to 35 RMS.
In addition to media particle size, a part finish can vary to some extent by just the
positioning of the part in relationship to the direction of the air pressure and/or blast pattern. If
parts are done at a consistent and proper angle to the abrasive blast gun nozzle, the results are
good clean, relatively smooth material finishes with a semi gloss type appearance. If the part is
worked in a direct line of sight or close to 90 degrees to the abrasive, the results are more
dimpled rough surface finish. The first method is considered surface finishing and the second
surface preparation. In the first method, processed parts normally can be used in an as is
situation and/or chemically treated; whereas, the second method requires the part have another
operation, or is used mostly for good paint or coatings adhesion.
The elements of the abrasive, pressure and positioning are the determining factors using
blast equipment. The best results are achieved when the blast pattern produces a scrubbing
pressure wave type action, determined by weight, pressure, and volume, of the media. If the
work or gun nozzle is not positioned at the proper working angle, you might want to compare
this type of technology to that of the blacksmith of old, because what you may get is a pounding
or hammering of the surface by a lot of small particles. The wrong angle will peen the part and
produce work hardening as well as reduce the life of the media.
Abrasive blasting is not a true deburring system per se, because it really doesn't remove
the burr as much as it modifies it so that there are not a lot of sharp edges. That is a common
problem in all abrasive blast systems, because the size of the particles being used, their shape,
and the random energy force controls the pattern of the surface profile and that matches the
Chapter 5 – Type 2 Equipment & Mixed Technologies 83
abrasive being used. A better descriptive word or terminology for this type of equipment is
surface cleaning or preparation.
After making this statement about cleaning, I should tell you that actually the part or
parts being processed should be washed or cleaned prior to being worked by blast type
equipment. The reason for this cleaning is that dirt, oils, greases, from parts processed will
eventually be re-deposit on the materials being worked. Because most of these systems are
closed loop systems the abrasive particles doing the surface modification are re-cycled and
reused; therefore, any abrasive will become a carrier or act as a transfer agent for the
contaminates and find their way back onto parts later on in the processing.
Most blast systems are generally used in a closed loop cabinet and are not really
conducive to high volume production environments because of the problem of processing one
part at a time*3 which is the same problem that the automated buffing or polishing production
lines encounter. Again, the more automated systems can handle larger volumes of parts if they
are tied into a conveyor belt or material handling system, but that still requires loading and
unloading the holding device or fixture that positions the part.
In most cases, abrasive blast systems are faster and cheaper per piece using manpower
than wheel buffing systems, again depending upon the size and configuration of the parts.
Small hand-held parts still maybe faster with a wheel system. However, the surface finish or the
end result is also very different. Wheel systems are normally used to produce bright shinny
parts as an end result; whereas, blast systems are used to produce a satin or frosted appearance
on parts and/or parts that have to have other surface finishes or coatings put on them.
Perhaps the greatest advantage blasting has over a buffing wheel type systems is that the
abrasive blasting can work more detailed parts and/or more recessed machined areas than can
fixed diameter wheel or belt systems. Blasting is a more flexible system because you do have the
capability of using multiple nozzles that can achieve almost complete coverage of the part
except where or how it is mounted on the material handling system. Again automation can
possibly re-position part orientation.
Air and Dust
Besides the need for an air supply system to operate blast equipment, another companion
piece of equipment is also necessary to operate the system properly. Besides the actual blast
cleaning equipment, which is usually a closed loop cabinet, there is the need to vent the dust,
dirt, and debris to the outside or a safe containment source. This is called a dust collector.
Naturally this device slows down and filters the air to an acceptable condition before releasing
it and stores the solid fine waste while the main bulk of the abrasive is re-cycled prior to the
dust collector. Depending upon the volume of the machine system, the spent air can normally
3NOTE: An exception to all of this are some machines that have accessory baskets that rotate on an angle
inside the cabinet. This system accommodates and upsets a batch of parts while the gun nozzle is fixed. Parts
tumble either continuously or on a timed cycled.
Chapter 5 – Type 2 Equipment & Mixed Technologies 84
be allowed back into the work environment. Larger systems need special handling and disposal
procedures.
Another companion piece of equipment required is an air supply system. Most
companies already have air compressors for other needs within a machine shop; however, it
there is no source to create air pressure that is also needed. Naturally that also means the
necessary plumbing of pipes to transport the air to the location of the equipment and a
sufficient volume of pressure and air supply. On top of all of this is the need for in line filter
systems to eliminate an accumulation of water or moisture associated with compressed air
systems, plus possible oils. The drier the air, the better the operation of the equipment.
General
It is difficult to image anyone not knowing what abrasive blasting is or what it does.
However, just to be sure, let me say this, it is a mechanical means to surface finish all materials
by way of using air pressure and fine abrasive inorganic or organic particles. Unlike the
mechanical wheel/belt systems that do surface removal by means of applying direct contact
pressure from an abrasive transfer device to the work piece, abrasive blasting applies pressure
to the air born abrasive particles only, not another transfer device.
In blast equipment, abrasive particles abrade by way of an impact or a one way type
scrubbing action caused by mechanical energy and resistance, resulting in friction, abrasion,
and heat. The abrasive impact pounds and/or shatters the abrasive as well as the effecting the
surface of the part or object being worked. The impact pressure of the particles dislodges
surface materials on the part being worked and again there is kinetic energy that is released
when the abrasive media breaks.
Instead of a continuous contact pattern that may produce a grain type appearance,
blasting is a more mobile means or fine random contact of material removal with no major
discernable surface finish pattern if done properly. At the same time, there is definitely a
textured finish to all materials being worked.
Abrasive blasting creates a satin, glossy, or dimpled finish appearance similar to the
effects produced by wind driven sand on objects in a desert.
I imagine that somewhere way back in history that this observation resulted in the idea
for sand blasting. Such a system could have been tried with some success using a gravity feed
type system suspended above the work to be processed. But without the pressure, such a
system would have been a long drawn out process. I have never heard or read where this was
done, but it is possible.
Speaking of pressure, that is the main difference between the two commonly used air
blasting systems available to do this type of finishing. There is the vacuum or venturi system
referred to as suction and the pressure system. Both systems perform relatively the same
amount and type of work; however, the vacuum systems have been around a whole lot longer,
are good for small to moderate production volume, and are a little less expensive.
Chapter 5 – Type 2 Equipment & Mixed Technologies 85
Fig. 35. Abrasive Blast Systems Comparison
Below is a comparison of the two main operating systems used in abrasive blast
finishing. The end results achieved using this equipment are nearly the same; however,
there are mechanical, internal, and pressure differences.
Suction System:
This system works by using a high pressure air line and an abrasive feeder line, both of
which connect to a nozzle or gun type device that mixes the air with the abrasive particles. That
is, they unite the two separate lines within what is called a gun. It is called a gun because of its
resemblance and function as one. Air and abrasive are combined within this mixing chamber or
a metal Y fitting design in a ratio of 2:1. That is, the air line is normally twice as large as the
abrasive feeder line right before the point of discharge through a nozzle.
Air pressure in this type of system can be used to regulate speed or pressure of the
abrasive, but pressure or air volume can also be regulated by means of the abrasive feeder line
itself. This system is designed in such a way that allows air to enter the system by way of
another hole opening on a metal tube over which the flexible hose connects to the abrasive
reservoir. If the hole is fully uncover by the hose, you will get almost all air flow only. Fully
closed, you will get all media. This adjustment regulates abrasive volume at any pressure.
Chapter 5 – Type 2 Equipment & Mixed Technologies 86
The Venturi suction system works by both negative and positive pressure. It allows high
velocity air pressure to pass over the abrasive feeder line. That movement in turn creates a
negative pressure over the abrasive feeder line and that basically sucks the abrasive through the
smaller hose and combines it with air pressure at the back of a nozzle, resulting in a positive air
flow. The gun nozzle is a tapered smaller orifice, which then speeds up the combined flow and
sprays out the abrasive under positive pressure in a relatively narrow focused and/or fixed
pattern of discharge. During this mixing of the abrasive and air some energy or pressure is lost
in this negative suction process, but because of the nozzle restriction, it is again speeded up.
As the air pressure and abrasive are increased in the system the resistance of the nozzle
also increases. That means more wear and tear on the nozzle. Naturally, the I. D. hole of the
nozzle determines its spray or work pattern and if the hole increases by abrasion, so too does
work area increase and pressure must be adjusted accordingly. Along with pressure is air
volume. One affects the other. This is a cause and effect relationship or catch 22 that should be
known for proper control. Because of this wear rate, nozzles have to be watched and replaced
periodically. This should be done when the I.D. of the nozzle becomes 1 ½ times its original
size.
The nozzle in a blast gun behaves something like a drill bit. That is, it is a perishable,
disposable tool. It can be used up to some point, then it loses its ability to work properly. In
most cases this is a quick change, fixed rigid insert, usually made of hard high tensile strength
tungsten carbide or boron carbide steel, or hard ceramic, positioned in the nozzle assembly or
gun. The gun, in turn is small and flexible enough to be a hand-held mechanism; however, it is
still restricted in movement by the attached air and abrasive hoses. The maintenance and
replacement procedures for these nozzles are simple easy to use mechanisms that make this
system appealing. Hoses also wear out, but have a great deal of life compare to the nozzles.
Probably the next most frequent replacement item are the hand gloves and maybe the glass
observation window in the cabinet which can get obscured because of the abrasive.
As mentioned, the actual spray pattern or work zone of the gun is controlled by the
inside diameter or hole in the nozzle, and the distance from the work piece, and the air
pressure. In suction systems the inside hole diameter of the nozzles range from 1/4 of an inch
I.D. to 7/16 of an inch. As the I.D. becomes larger so too does the amount of air pressure and
volume required to do the same amount of material removal. The larger the I.D. the greater the
spray pattern or coverage area that can be worked in proximity to distance in one pass. Usually
straight through bore I.D. hole nozzles are used for close up work, or 10 to 12 inches in distance.
Tapered nozzles are better for distance beyond that and are tapered from the larger inlet to
smaller exit. In most cases, the outlet is also tapered at the reverse angles to direct the spray
pattern. For working parts with I.D.’s there are some nozzles that have multiple side vents. See
charts.
Chapter 5 – Type 2 Equipment & Mixed Technologies 87
Fig. 36. Abrasive Blast Comparison,
Pattern and Pressure
Suction-Blast Air Requirements (SCFM)
Pressure (PSI) 30 40 50 60 70 80 90 100
¼” nozzle, 3/32” air jet 6 7 8 10 11 12 13 15
¼” nozzle, 1/8” air jet 10 12 15 17 19 21 23 26
5/16” nozzle, 5/32” air jet* 15 19 23 27 31 37 38 42
7/16” nozzle, 7/32” air jet 31 38 45 52 59 66 73 80
*Unless otherwise specified, this nozzle is
supplied.
4 SCFM = 1 compressor horsepower
Pressure-Blast Air Requirements (SCFM)
Pressure (PSI) 20 30 40 50 60 80 100 120
1/8” nozzle 6 8 10 13 14 17 20 25
3/16” nozzle* 15 18 22 26 30 38 45 55
¼” nozzle 27 32 41 49 55 68 81 97
5/16” nozzle 42 50 64 76 88 113 137 152
3/8” nozzle † 55 73 91 109 126 161 196 220
* Unless otherwise specified, this nozzle is
supplied.
† This nozzle supplied on FaStrip cabinets.
4 SCFM = 1 compressor horsepower
Compressors should be sized to the next larger
nozzle to allow for nozzle wear.
GUN Distance from Workpiece
ID 6" 12" 18"
1/4" 1-3/8" 2-5/8" - 2-3/4" - 1"
5/16"* 1-1/2" 3-1/2" 1-3/4" 4-1/2" - 3-3/4"
7/16" 2" 3-3/4" 2" 4-1/2" - 3-3/4"
Hotspot Brush-off *Standard nozzle
Nozzle Distance from Workpiece
ID 6" 12" 18"
1/8" ¾” 1” 1” 1-1/2” - 1-1/8”
3/16"* 1-1/4” 1-3/8” 1-1/2” 2” 1-5/8” 2-1/2”
¼" 1-1/4” 1-1/2” 1-7/8” 2-¼” 2-1/8” 2-3/4”
3/8”† 1-5/8” 1-3/4” 2” 2-1/4” 2-1/4” 3”
Hotspot Brush-off *Standard nozzle
Chapter 5 – Type 2 Equipment & Mixed Technologies 88
Safety
Because of the abrasive characteristics of blast type processing and the velocity of
discharge of the abrasive, the operator must or should wear protective clothing and rubber
abrasive resistant gloves. In self contained closed cabinets, all of these safety features are
supplied as standard equipment. Blast systems designed to be used outdoors, or in large open
environments, or enclosed blast rooms, need extra safety protective clothing and air breathing
systems. All of these systems are regulated by OSHA and EPA rules that make safety
equipment and/or clothing necessary for an operator of this type of equipment in all
environments. However, the biggest concern or emphasis is on air born breathing apparatuses
rather than physical injuries from the blasting.
Initially sand blasting systems were the most popular form of abrasive blasting out doors
and had few regulations. However, sand is a composite of different minerals and it is composed
mostly of silica. Under current regulations any material containing silica requires safety
precautions due to its carcinogenic properties and because blasting is primarily an air based
system, that requires air breathing devices. Eye protection gear is also required and a major
concern against air born particles. Lastly, because all parts and materials contain residue debris
these contaminates as well as spent abrasives must be disposed of properly and not just left on
the ground at an unprotected blasting site.
In manual closed cabinets, safety or protective gloves are designed or permanently fixed
to the cabinet in such a way as to make the systems completely air tight. In these manual type
cabinet operations the operator can move the gun nozzle, fix it or the part in place, or turn the
part in a close proximity to the gun nozzle within the sealed cabinet. Normally one hand holds
the part and the other hand directs the gun or abrasive at the part. The operator observes what
he is doing through a glass window in the sealed cabinet and does not need special eye wear,
because that too is fixed into the cabinet. The closed loop cabinet system also has a continuous
flow of air, which sucks the debris and finer particles into the dust collector and the larger
media is re-cycle by gravity feed to and from the bottom of the machine.
Nearly all debris is in the form of a dust and goes into a collection system which must be
purged and disposed of on a periodic bases per regulations and/or specifications of the
equipment manufacturer. Caution and proper maintenance is required for debris and dust
collection. If not properly done or performed, explosions and fires can happen. The use of
aluminum oxide and working of metals such as aluminum and magnesium are very susceptible
to these types of problems.
Pressure System:
As the name implies, this is a systems that combines the air and abrasive particles into a
single feeder line and has a much more simple nozzle discharge tube. With fewer parts and
lines, this type of system usually works up to four times faster than suction systems
because you can get greater pressure and twice as much velocity to the particles and/or
Chapter 5 – Type 2 Equipment & Mixed Technologies 89
discharge with much less air pressure. In fact, air pressure is the only way to regulate a pressure
system.
Pressure systems have a higher abrasion ratio or factor than suction systems, because the
abrasive particles are pushed by a positive energy force rather than pulled by a negative
vacuum system. That means that there is more energy or force to the abrasive particle at the
discharge nozzle and that allows the operator to work at lower air pressures. That also means
that the gun hose will have to be replaced more frequently, but because of reduced pressures,
nozzle should wear longer.
No air is wasted in this positive flow process system, which is the direct use of air
pressure to the blasting nozzle gun. Besides higher energy impact of the abrasive, other benefits
are longer media and nozzle life and shorter time cycles and maybe better control and
performance than with the suction type systems and at these reduced air pressures. Therefore,
long range cost savings usually warrant the extra cost of this type of system. Pressure systems
will remove heat treat scale at 60 PSI where the suction system may not, even at a higher
pressures.
The spray pattern or nozzle inside dimensional holes are usually smaller than suction
systems. The I.D. range is normally from 1/8 inch to 3/8 of an inch and the spray pattern is
smaller and more controllable. Other than the method of applying pressure to the abrasive, the
operation and re-cycling of these systems are the same.
Chapter 5 – Type 2 Equipment & Mixed Technologies 90
Fig. 37. Abrasive Blast Systems
Abrasive blast equipment only provides the mechanics to effect product. That is, the
equipment cannot work or clean a part properly without manual or mechanical movement to
either the part or the equipment in relationship to the part. Therefore, movement is very
important in abrasive blast systems. Most inexpensive systems are consider a closed loop
cabinet where the operator opens a door inserts the part(s), closes the door, put his hands
through the cabinet gloves to get to and hold the parts, and then looks through a glass
window as he processes the parts. Visuals show the typical requirements of a closed loop
abrasive blast system and two small-automated barrel tumbling systems.
Chapter 5 – Type 2 Equipment & Mixed Technologies 91
Fig. 38. Automated Abrasive Blast Systems
Because of the human factor and dwell time, parts may not get a uniform surface
finish; therefore, when volume or uniformity are of concern, material handling or movement
systems are desired over human processing. These systems can be as simple as a rotating
barrel or table, some form of in-line movement, multiple or moving nozzles or any
combination of these methods. The following illustrations depict some of the more common
material handling systems. The letter G represents parts being processed.
Chapter 5 – Type 2 Equipment & Mixed Technologies 92
Abrasive media
Besides the equipment to provide the pressure or work energy, the abrasive blast media
is the next most important ingredient in this mechanical system. Here we begin to change the
terminology of the word abrasive or abrasive particles and use the more common term for most
mechanical processes to media, because not all materials used to modify or do material removal
are solely abrasives.
Again, different sizes and hardness of media materials produce different results. Early
on, the use of sand was the most commonly used media because of its known abrasive qualities
and/or characteristics. It was also abundant and cheap. It was so common that most people still
refer to this equipment and technology as sand blasting. However, it was also discovered that
sand media had a relatively short life expectancy. That is, it could only be re-cycled about once
or twice at about 60 PSI air pressure before it is completely used up or loses its mass and/or
ability to abrade.
Air pressure controls the speed or impact energy of the particle and/or material removal
rate as well as the rate of decomposition of the media. A real low air pressure may get you a
second or third re-cycling of sand media, but because of material volume and general
maintenance and up keep, sand is not cost effective or commonly used or recommended for
abrasive blast systems. Then again, if you lived out in a desert, it probably would be your first
choice.
Abrasive media selection should depend upon the type of abrasive or mineral, its size,
shape, density, hardness, and friability and not cost. Unfortunately cost often dictates the
media, instead of the other way around. Other features to consider depend upon the amount of
air pressure one wants to use, the attrition rate of the media (which includes media size), the
angle of the gun nozzles, and the type of material and/or surface finish desired. It should also be
noted that by re-cycling the media over and over again, the pattern or texture of the finished
product will change, because the media will also change. That is, with use and re-cycling, media
will get smaller and smoother with use which is the same condition experienced with wheels
and belts, but not as dramatic a change.
The greater the angle of the blast guns, from 90 degrees, the greater the life of the media
and the greater the volume of media impact to the stationary work part, which also produces a
smoother surface finish. The material removal rate efficiency of the media is greatest between 45
and 60 degrees. As a rough guideline, large glass beads at high velocity provide a deep matte
finish; whereas, low velocity produces smoother, brighter surfaces. A smaller particle size will
generally produce a brighter smoother surface. When the size of an abrasive particle is doubled,
so too is its kinetic energy. When velocity is doubled, its kinetic energy is quadrupled. The more
common abrasive media in use today for most metal modification or burr removal is aluminum
oxide and glass beads.
Chapter 5 – Type 2 Equipment & Mixed Technologies 93
Other Media
Some media used in this equipment is not really designed to be abrasive. Glass bead is
manufactured from lead free, soda lime type glass that contains no free silica. This material is
then made into a preformed ball shape that produces a much smoother brighter type finish than
angular abrasive. Glass beads hardness is about a 6 on the Mohs scale and can be re-cycled
maybe 30 times at 60 PSI. The media is virtually chemically inert and therefore it is a happy
medium for high efficiency and an environmentally acceptable method of metal cleaning or
surface finishing when properly controlled. Glass beads are the most common, general all
purpose media and comes in a wide variety of sizes. See table showing comparison chart of
other impact abrasives for cleaning, finishing, peening, and to some extent deburring
applications.
The heaviest abrasives used for blasting are from three main metal groups and are steel,
malleable iron, and cast iron in either round shot or angular grit. Steel can be recycled 200 times
or more, whereas, cast iron may be between 50 to 100 times and malleable iron falls somewhere
in between these two. The hardest material is normally cast iron with a Rockwell C scale of up
to 65. Both iron materials cost less than steel and break down faster and tend to be more
aggressive than steel, but the life of steel makes it more cost effective.
Steel shot is significantly heavier than glass bead and therefore achieves similar surface
appearance on parts, but it produces a more noticeable dimpled pattern in a shorter period of
time. Even with this heavy media, little or no burr is effectively removed and therefore this
system remains a class 0 to 1 deburring system. Steel grit, silicon carbide grit, and garnet all
produce fast results but because of the irregular angles of this media, the surface appearance is
very dull. They are normally used to prepare or produce a rough surface texture which is good
for secondary coatings to adhere.
Aluminum oxide is probably the most popular abrasive media in use today because of its
costs, its longevity, and its hardness. Besides glass beads, this media is probably the most
common abrasive used in blast finishing and surface preparation. At 120 pounds per cubic foot
of material, it is heavy and carries a lot of kinetic energy to the work piece. It rates an 8 on the
Mohs scale.
More gentle abrasive media for blast finishing are the organic materials of walnut and
other shells plus corn cob. These organic materials are usually used in smaller machines or to
work non-ferrous metals and plastics. Choosing the right media is not that difficult. There are
relatively only a few options. However, as I say that, I also know that wheat starch, rice hulls,
nut shells, fruit pits, sodium bicarbonate, ceramics, plastics, nylon and other synthetics have
been used with good success. Perhaps the most important factor to remember is the larger the
media particle the more material it will remove and the softer or finer, the smoother the surface
finish.
There are some special applications that may be of interest using abrasive blasting
techniques. I mentioned corn cob as a soft gentle media, its specialty is in the use of paint
stripping. However, more recent plastic media is now more commonly used to strip paint,
Chapter 5 – Type 2 Equipment & Mixed Technologies 94
especially on aircraft. In fact special blasting gun nozzles for aircraft are now available to that
includes a method of sucking or collecting the paint particles and abrasive debris in a vacuum
type glove or bag type mechanism that hugs the surface of the material being worked or
stripped. Instead of a cabinet that uses a gravity feed mechanism to recycle, this seems to do
everything all in one and this produces a cleaner working environment. Actually the system is
the same as a normal closed loop cabinet; however, the active or mobile head mechanism is
open on one side to work the material and the hoses to and from the head are longer and further
removed from the actual power and feed source.
Small Systems
Another special version of the pressure type equipment are small bench top systems. The
working cabinet of these systems are a little bigger than a bread box, or close to two feet square.
Some of these cabinets are even equipped with microscopes. This system deserves some special
attention because it has a number of special features. Like their big brothers, these systems do
require the work cabinet and a dust collector. Unlike the bigger systems, these systems cannot
normally use air, but requires very dry air sources, of carbon dioxide, or nitrogen, which also
should be filtered for sub micron particles.
Because these are small systems, the nozzle or gun is also very small and looks
something like a pencil that can easily be handled with one hand. The normal nozzles of these
unites are very small, with an I.D. orifice of .005 up to .045 and are made of tungsten carbide or
a synthetic sapphire. Other sizes and configurations are also available. The maximum flow rate
of media is around 40 grams of material per minute. Naturally because of this small size and
volume, production is usually limited to deburring, cutting, and drilling of small high tech
parts, used in the electronics industry, but is also used for deflashing, cleaning, etching glass,
and working small areas in other industries.
Perhaps the biggest difference of these small systems, besides their air supply is the
media and its applications. The media used in these systems are fine powders of aluminum
oxide, silicon carbide and glass bead that can vary in size from 10 to 50 micron in size. Because
of the size of this fine material, the supply source or feed of this material must first be vibrated
before it is feed into the blast system. Also, the media is not re-used; rather it flows into the dust
collector. The relatively low volume of media and debris does not load up the system very fast.
Chapter 5 – Type 2 Equipment & Mixed Technologies 95
Fig. 39. Small Abrasive Blast Equipment
Equipment size makes a lot of difference in finishing results, time, and area coverage. Although the
media remains nearly the same, the abrasive particle size is normally a lot smaller and the results are therefore
proportional.
There are four variables affecting the cutting speed in small abrasive blast systems, which can be precisely controlled for
maximum efficiency. They are: (1) distance to nozzle from the work piece, (2) rate of abrasive flow, (3) propellant gas pressure, and (4) the
type of abrasive used. Although the figures below demonstrate experiments conducted on glass, the relationships are similar to other
materials.
Fig. 40. Technical Data of Variables Affecting Cutting Speed
Chapter 5 – Type 2 Equipment & Mixed Technologies 96
Cryogenics:
Another variation of abrasive blasting or type 2 equipment was initially developed for
very soft and flexible products in the synthetics industries. Normal abrasive blast systems will
not economically remove the burr or deflash rubber and plastics parts because of their
flexibility; therefore, temperature is used to change the quality characteristics of the parts being
worked. Under our classification system, this is both a type 2 and 5 system, because it uses both
direct particle energy transfer and temperature to effect class 0 to 5 burrs in 0 to 3 location.
Because the abrasive method of operation is somewhat secondary to the environmental controls
our classification will be a four digit number to reflect how the equipment is different from
abrasive blast equipment and that makes this a 5200 to 5253 system
This burr classification covers a wide range of surface finishes and may need some
explanation. Cryogenic blast equipment is used primarily to clean parts. Most cleaning systems
do not normally effect the existing RMS of a part, because media made with gases or semi
liquids will flow or deform upon impact with the material being worked. As long as the
material being worked is harder that the media, there is no or little surface profile change. Some
soft materials may still achieve a slightly higher RMS due to the media mass and impact energy
of even these soft materials.
Type five equipment systems represent the newer technologies that use cryogenics or
below freezing conditions to effect material removal behavior. The equipment operates in a
closed loop system just like abrasive blast systems, but it is designed to operate at extreme cold
temperatures. There is a definite advantage in operating at temperatures below 32 degrees
Fahrenheit, especially with organic materials and soft flexible materials such as rubber or
plastic. These systems are especially good on molded parts. That is because thin parting lines,
flash material, and/or minor burrs on primarily molded parts become stiff, rigid, and weak at
low temperatures. The advantage of this lower temperature is that it takes less energy or impact
pressure to remove these thin and normally flexible burrs.
You might like to relate this equipment system to that of a functional refrigerator or ice
making cabinet in that the work environment and parts are processed at below freezing
temperatures, but the operator stands outside the cabinet without special protective clothing.
The parts are loaded into the machine and pre-treated with liquid nitrogen, before being
worked. The blast media must also be pre-treated before being used. The cabinets are made
with double wall construction and insulated as well as the gloves to conserve the working
temperature. Care is still required in handling parts in the cabinet as well as after they come out
of the machine.
These systems are very expensive due to the fact that this equipment uses liquid nitrogen
and requires some additional features and items not common to air blast systems. Some early
cryogenic equipment that are no longer used, use to also makes their own blast media which is
CO2 gas in a solid pellet form. The carbon dioxide media use to act and behave just like organic
abrasive particles. The most interesting feature about this media was that there was no waste or
residue from the media itself. Any remaining media not destroyed in the impact soon
Chapter 5 – Type 2 Equipment & Mixed Technologies 97
evaporated afterwards. The only material left was the excess flash or burr. Problems and costs
are associated with these systems.
Most of the media used in cryogenic deflashing systems today is plastic or nylon and
again used on rubber and plastic products at low temperatures. There is virtually no use of this
technology for working metal, because of cost and inefficiency. The media can be propelled by
air or airless blasting mechanics. Also, it should be noted that the actual processing time of parts
should include a pretreatment phase of cooling the part as well as the media. In addition to the
liquid nitrogen machine systems, there are also some machines that still use CO2, dry ice or just
normal frozen water, or wet ice to operate, naturally these are less expensive systems and they
don’t operate as efficiently.
Fig. 41. Cryogenic Blast Equipment
Cryogenic blast equipment is used primarily on soft, very flexible materials such as
rubber and plastics, but it can also be effective for cleaning very viscous covered materials. The
system operates like a normal abrasive blast system except the work chamber environment or
main ingredient functions at extremely cold temperatures. Surface finishing is not as important
as removing excess, unwanted materials that normally occur with molding processes. The three
main elements of the system are: velocity or pressure of the media, which is normally plastic
shot, for the proper length of time, and at a low enough temperature to stiffen or freeze the
excess materials.
Chapter 5 – Type 2 Equipment & Mixed Technologies 98
Wheel or Airless Blasting:
This equipment still falls under the classification of type 2, blast cleaning equipment.
However, what makes this equipment different from air blast systems is that it is not propelled
or controlled by air pressure but a mechanical energy force. The impact energy transfer system
puts this equipment into a class 5 burr removal system in 0 and 1 locations. That makes this a
250 to 251 system. This system does the greatest amount of molecular material modification,
produces the roughest surface profile, well over 35 RMS, and it can handle a 52 burr, but it will
not remove it in a good clean and smooth way, which is typical result of all blast systems. This
system is used primarily for surface preparation or treatment rather than deburring.
What makes this equipment so different from blast equipment is that it is propelled or
controlled by mechanical speed or velocity of a wheel mechanism alone. This system utilizes a
mechanical spinning wheel movement or energy force to propel heavy weight media at high
velocity speeds against a machined part or casting to descale, modify, or treat the parts surfaces.
Remember our earlier statement. When velocity is doubled, kinetic energy is quadrupled. These
systems are capable of blasting parts with 2600 lbs. of steel shot per minute over a broad work
surface area, for as long as the media supply can hold up. Again, there is deterioration of the
media that must be considered, but most parts are worked in a relatively short period of time.
This equipment behaves almost exactly how the old blacksmith process worked, but
without the heat problem. This is not so much an abrasive blast type system as it is a malleable
surface conditioning process. The energy forces produced by weight and the high velocity of
steel ball, pellet, or grit media does treat and change the hardness of the metal and/or relieves
molecular stress from the manufacturing or machining operation of the parts being processed.
Instead of effecting the molecular structure of the part as is accomplished in heat treating, this
system uses impact weight to condense the outer molecular structure of the part in question.
What happens here during this process is the surface becomes microscopically
condensed and/or harder due to the dense re-arrangement of the molecules of metal. This can
be achieved to some extent by using air blasting equipment, but wheel blast systems are special
machines designed to employ the use of malleable impact knowledge technology or the
movement and flow of metals under pressure to strengthen and/or stress relieve parts and
weldments. The process can also be referred to as shot peening and the machines are called
wheel or airless blast cleaning equipment.
This system uses primarily mechanical energy forces caused by a rotating blast wheel
which can be controlled by a fixed or variable speed motor from 1800 RPM to 3600 RPM. The
blast wheel can be positioned or moveable and reversible, or there can be multiple wheels
within the system fixed above or below the work piece. The blast pattern produced by the
wheel within the machine can be adjusted; however, its greatest efficiency is located directly
below the impeller and slightly to the side opposite the center line of the wheel rotation. The
actual release point of the shot is at the 11 O’clock position prior to the throw line or where the
media leaves the impeller.
Chapter 5 – Type 2 Equipment & Mixed Technologies 99
Fig. 42. Wheel or Airless Blasting Equipment
Wheel or airless blast equipment derives its energy from a wheel that transfers RPM’s
to the velocity of the media at a designated rate, direction, and force. The media hardness,
weight, and mechanical forces involved in turn effects the materials being worked. Because
of the greater media weight more energy can be transmitted to the work and larger work
pieces than other blast systems.
Chapter 5 – Type 2 Equipment & Mixed Technologies 100
Because of this energy force, the work chamber and parts being processed by this
equipment have to be rugged and thick, or else they may be distorted and will self destruct by
this process. The machine cabinet is normally made out of ½ to 1 inch thick manganese which
has good work hardening characteristics itself and becomes harder with use. There are even
more expensive impact resistant construction metals available for longer life than the
manganese. In addition to the special emphasis on the construction of this equipment, like the
air blasting systems, these systems still require all of the same support accessories. That is, they
require an air supply, the dust collection, and the abrasive material handling systems. The
media used is normally larger than that found or used in air blast equipment.
The terminology cleaning is often referred to, for this type of equipment, is not exactly
the same as air systems or water based systems. Cleaning here usually refers to the descaling of
heat treated parts, which are commonly processed by these systems. As stated, these machines
are designed to produce clean work hardened parts, but because they do effect dimensions of
the part or parts, they also produce uniform surface conditions which looks similar to a sand
blasted finish.
This type of equipment is not specifically engineered to do any deburring but is again
only a surface modification processing that does reduce surface problem areas and burrs.
Because of the tremendous energy forces and aggressiveness of these machines, these are rather
large and heavy duty machine systems constructed with thick plates. Therefore in order to
justify fabrication costs and construction large volumes and/or part sizes or special surface
treatment problems are necessary to support the high costs of fabrication.
Unlike sand blast equipment, most wheel blast cleaning machines are almost fully
automated, except for the loading and unloading of parts by an operator. This automation is
almost necessary due to the high energy forces of the media and impact debris. The machine is
designed to isolate the work chamber to work normally one part at a time on a horizontal
turntable and unless the table has a special fixture for moving the part, only one side of the part
can be worked at one time. Some of these machine systems are designated as batch equipment
and processes a small volume of parts. The work chamber of these batch machines allows the
parts to tumble freely like the sand blast barrel type systems or they have a flexible chain type of
convey belt that operates vertically within a closed chamber. There are still other machines
specifically designed with more than one wheel and blast chamber to work some rather large
parts or continuous parts and more than one side of a part at a time. However, a great many
machines are fully automated for continuous straight pass through or rotary table type systems
because of the potential safety problems or forces the operator can be exposed too. See
application diagrams below.
Shot Peening Media
Shot peen or blast media varies from abrasive blast media in that it is less abrasive and is
normally larger, more uniform in size and shape and therefore heavier. That is because the
desired end result is to work harden or modify a part surface and not necessarily remove
material. The more spherical the shape the better the surface finishing results and the more
Chapter 5 – Type 2 Equipment & Mixed Technologies 101
uniform the surface treatment. Broken or sharp edge particles can damage a parts surface
resulting in an uneven non-uniform treatment.
Fig. 43. Peening Media
102
Chapter 6 – Type 4 Equipment
Wet Blasting or Water Hone:
This is a type 2 and 4 equipment system that handles class 0 to 5 burrs from 0 to 3
location. Since this is a dual energy related system and its main source of energy comes from
liquid under pressure, therefore, I have inverted the classification number to reflect that
environmental relationship. That makes this a 4200 to 4253 system. Just like the cryogenic blast
equipment, this classification number covers a wide range of surface finishes, because it is used
more often for cleaning parts than producing surface finishes. Like all blast systems, the surface
finish will normally exceed 32 RMS; however, because of the liquid element, the energy forces
and abrasive particles will flow and/or deform on impact. That means that there will be little if
any surface modification, provided the parts are harder than the abrasive used in the process.
Wet blasting equipment uses an abrasive and a liquid energy transfer method system;
therefore, the proper terminology for this system or process is called water honing. This
equipment is basically the same as abrasive pressure blasting systems; however, because we are
dealing with a liquid system and an extremely fine abrasive this process generally produces
smoother surface finishes because it has more flexibility and/or buffing action to the media. The
energy of the particle size is, to a large extent, absorbed by or into the liquid; therefore, the
impact of the media to the part isn’t as great as an air blast system. In fact, the blast processing is
similar to cleaning parts with high pressure water or heavier more viscous water. This process
produces less contact impingement than air blast systems and generally produces no
compressive stress or work hardening on parts.
In most cases, the finer media used in a wet system would not be able to be processed by
normal air blast systems because of its surface tension. That is, small media can reach a point
where it behaves like glue or wants to become a solid again and air pressure alone would not be
enough to keep it flowing. Given the same media size particles, pressure, and time used, a wet
system produces results that are smoother, brighter, and have more shine; however,
contaminates and/or oxides can still produce dull gray finished parts.
Lastly, even though the wet system does not require a dust collector, the pumps, and
controls necessary for wet blasting normally makes this equipment more costly than air blast
systems.
Actual operation and costs are comparable, but there are more maintenance problems.
Then there is the need to treat or change the liquid system periodically. Like the air blast system
that self purges out smaller particles in a dust collector, a wet system has to use liquid filters.
Chapter 6 – Type 4 Equipment 103
Fig. 44. Wet Abrasive Hone
Wet abrasive hone equipment looks exactly like an abrasive air blast system except the
cabinet system is watertight. The closed loop cabinet and operations uses water instead of
air to move the media which is an extremely fine abrasive powder and this results in less
material removal and a finer surface finish to parts.
Chapter 6 – Type 4 Equipment 104
Water Jet:
This is a type 4 stand alone system, suitable for class 2 and 3 burrs to handle in type 1
location only, but it can do some work in 2 and 3. Because this is a limited pass or has very little
dwell time on a specific area of a part, it has relatively no effect on the RMS surface finish or
profile of that part. This equipment has limited applications and range that will make this a 421
to 431 system.
It has been known for some time that water alone does do material removal work of soft
or soluble materials. High pressure water jet systems have been used for some time for cutting
metal similar to either plasma or flame cutting equipment. Water pressure systems are not
commonly used for deburring, but there are trends that indicate they are gaining popularity as
more machines are being used that have improved surface coverage to do deburring. They are
not to the point of a dishwasher, but they are getting there.
Water jet technology will not radius existing edges, but it will remove lose fragmented
burrs effectively. Usually these machines are specifically designed to wash or clean parts first
and deburr as a secondary operation. The first machines specifically designed to do deburring
were introduced in Germany in 1974. A typical water jet deburring machine system operates at
pressures of about 5000 to 9000 PSI. At pressures greater than these, this equipment is used for
cutting; but just the same, care must be exercised not to dwell on a part for any extended period
of time for even at these pressures materials will be worn away or cut to some extent, especially
softer non-ferrous metals.
There are two principle methods of operation for water jet deburring equipment. The
more common system that is more effective, uses a rotating nozzle holder, fitted with two
nozzles that rotate at high speeds of 200 to 850 RPM and moves in a set direction which is
computerized to create multiple over lapping patterns. The other basic system is used more on
flat parts and uses a set of broad fan like nozzles that again travel or move the part in a set
pattern. Because the latter spray pattern is more spread out, it has less concentrated pressure to
deburr the parts, but it lends itself to continuous pass through type systems.
Water jet technology is relatively new, therefore the pumps
are also new and still being developed and improved. That means that there may be
significant maintenance time required to keep the system functioning properly. However, the
greatest equipment wear is in the nozzle orifice, with the broad flat fan spray nozzles being
effected first at about 100 hours of operation.
To improve or protect both the part from wear and oxidation and the nozzle life,
chemical detergents and inhibitors are added to the deburring liquid. Some more powerful
water jet cutting equipment utilizes extremely fine abrasive media to improve or speed up their
cutting ability. Therefore, the addition of abrasives is likely to be more common in the not too
distant future of water jet deburring equipment as well. Again, the major problem is the wear
resistance of the nozzles. Material limitations and the extremely high pressures wear the nozzle
orifices relatively fast, therefore, improvements in this area are expected.
Chapter 6 – Type 4 Equipment 105
As long as we are talking about primarily a water system and before we move on to more
abrasive removal type equipment, we should talk about ultrasonic applications. The water jet
uses straight water under pressure to deburr or modify materials. In the near future, these
systems may include the use of very fine abrasive particles or liquid enhancers to give more
density, bulk, or energy to work faster. It is a lot more difficult to excite or agitate water or
energize water to do material removal; however, it can be done on a microscopic level.
Water Jet Deburring
Water is the simplest and cheapest medium that can be used to deburr, but great
pressures are required for abrasion to take place by way of a narrow jet or focused
concentration of water. The molecular structure of water allows it to penetrate the densest of
materials and modify whatever it comes in contact with; therefore, pressure, pattern
concentration, and dwell time determines the effectiveness of material removal of water jet
equipment.
Fig. 45. Methods of obtaining broad jet coverage
In essence, the following methods are used to achieve the extensive deburring and
cleaning of component parts.
Spraying with rotating nozzle holders, fitted with circular jet nozzles
Spraying with flat jet nozzles arranged in a row
Chapter 6 – Type 4 Equipment 106
Ultrasonic Deburring/Polishing:
In lieu of inline water pressure created by pumps, water can be mechanically excited or
energized without great inline pressure. Boiling is one way to energize water and electro-
magnetic excitement is also possible. Ultrasonic cleaning system have been know and used for
years as the best method to clean the porosity of all materials and as we said earlier, cleaning is
actually the removal of semi-solids. There is no one machine system designed and marketed
today as yet to do straight ultrasonic deburring in a liquid tank system. However, it can be
done, but the results are normally better accomplished faster, cheaper, and easier using other
methods; therefore, there is no equipment and no rating.
To clarify my statement, ultrasonic tank systems can and have been used for cleaning
and that is a material removal system for contaminates and soils. It should also be mentioned
here that a test of a good ultrasonic cleaning system is to place aluminum foil into a tank to
check its power. A good system will put holes in the foil; therefore, with the proper
concentration and direction of energy, ultrasonic applications can remove or modify solids on at
least a small scale. Deburring can be accomplished using this technology and therefore should
be mentioned with or without a rating system. Remember, before the laser was invented, there
were only forms of the incandescent light bulbs.
Ultrasonic cleaning utilizes the principle of electro-mechanical energy to power or
energize water to remove soluble material contaminates. To create that force, an electric current
or a modulated electric current is introduced to a quartz crystal called a transducer. A pulsed
current causes the crystal to expand and contract very rapidly and that transmits a low power
radio signal that effect the water molecule. Present equipment operates at a range of 23 kilohertz
to about 80 kilohertz, but its energy is measured in watts.
Ultrasonic crystals are normally manufactured in a cone shape to direct the energy to the
large end of the transducer which is sealed to the underside of a liquid tank. Because we are
dealing with solids, the electrical connections and the seal must be properly bonded. The
electro-mechanical energy then focuses energy up through the transducer and the tank wall,
and that in turn agitates the water molecules and creates standing energy waves inside the
liquid.
Present technology says the lower the frequency, the more powerful the energy is
transmitted in standing waves. That means that unless a part is moved, there will be gaps or
voids of no work on the part in question; therefore, some newer systems use a modulating
frequency range than one set power output. The water is effected by the ultrasonic energy wave
vibrations and causes the water molecules to break down and implode similar to how solids
release kinetic energy. As this implosion occurs there is also very violent movement occurring
in positive directions as well as negative movement. This violent movement on a microscopic
level produces an extremely good mechanical movement or action to clean all material
immersed within the agitated liquid.
The terminology cleaning is more associated with using ultrasonic energy systems than
with deburring. That is because this process equipment uses mostly chemicals to get a reaction
Chapter 6 – Type 4 Equipment 107
with the materials being worked. That is, the liquid in the process is more of a controlled
chemical action and reaction rather than a mechanical abrasive system. To do any abrasive
deburring and/or polishing using this equipment or system requires a delicate balance of a
solution capable of suspending an abrasive particulate. An alternate method would be to
somehow move the liquid just enough to keep the abrasive in suspension and not interfere with
the ultrasonic energy that produces energy waves. Remember, the energy wave force only
effects the water molecules that in turn moves the particulate. Therefore, that also means that
any abrasion must be relatively light.
Ultrasonic Deburring
Water based systems are very effective methods for cleaning or dissolving soluble materials; however, it
is rarely used to deburr parts without using a great deal of pressure. Yet, on a microscopic level, water agitated
by ultrasonic does exert great energy that can do minor material removal. Ultrasonic equipment at present is
only used for cleaning and not deburring.
Fig. 46. How Ultrasonic Deburring Works
In an ultrasonic cleaning system, cavitation bubbles form and
grow under the influence of negative pressure in the rarefaction portion of
the sound wave. As the sound wave progresses, negative pressure is
replaced by positive pressure in the compression portion of the sound
wave, causing cavitation bubbles to implode, which releases mechanical
energy in a “jet” or shockwave. This energy release enhances and
facilitates cleaning processes
Chapter 6 – Type 4 Equipment 108
Ultrasonic orbital system
There is now a machine system on the market that claims the right to be called an
ultrasonic orbital system. Unlike the previous mentioned ultrasonic systems, this system uses
primarily solid forms to transmit energy and behaves like a reciprocal motor. Like other
previous ultrasonic systems, we are still talking about relatively light deburring, but this
equipment is used mostly for very limited polishing work type applications or class 0 burrs in
type 1 locations.
The equipment still falls under our classification 4 system; however, it is a modified type
4 system or 4 and 2 system, making this a 4200 system only. The RMS range is very limited
using this equipment. The surface improvement range will only be about 0 to 8 RMS. That
means that normally parts being processed have to be smooth or under 20 RMS before they are
processed. Even this number does not describe this machine system adequately, because the
liquid used in this process is really a slurry of liquid and a fine abrasive that is energized
perpendicular to the work piece.
Typical applications are for polishing molds and finishing blind cavities. The equipment
uses contact pressure, combined with a unique blend of liquid, abrasives, and a moldable rigid
tool. As mentioned, this equipment behaves similar to a reciprocal disc system and employees
both mechanical and electro-mechanical energy forces. Material removal rates normally do not
exceed .0005 of an inch or less and can achieve surface finish improvements of 5:1 to 10:1 and as
smooth as 4 micro inch.
The machine system looks something like a hydraulic press. The main work tool is a
special shaped transducer attached to a probe type extension which in turn holds a piece of
graphite or glass that works the part. The transducer behind the tool is electrically excited and
produces mechanical energy forces that are transmitted to the end piece tool. This end piece is
then placed onto the part that has to be worked. The probe and the stationary part are then
immersed in a fine abrasive slurry. When the tool is activated the graphite or glass end piece is
ultrasonically agitated and because of the contact pressure, it molds itself into the work piece
and in so doing it also modifies the work piece. There is some periodic movement of the tool up
and down in order to bring new abrasive slurry to work the part. The neat thing about the
probe is that it does not require a pre-shaped tool or special alignment. Everything is done and
functions automatically.
The abrasive slurry that is used in conjunction with the ultrasonic probe uses a 300 mesh
or finer abrasive material. Normally, silicon carbide is used; however, a lot has to do with the
hardness of the material being worked. In some cases harder materials and fine diamond
abrasive must be used. A lot of the materials used are diluted forms of materials used in the
next category of equipment called Extrudehones or abrasive flow systems.
Chapter 6 – Type 4 Equipment 109
Fig. 47. Ultrasonic Polishing
Proper finishing of molds and blind cavities has
historically been a labor-intensive, time-consuming and
expensive procedure. The ultrasonic process achieves a
polishing action by vibrating a brittle tool material such
as graphite or glass into the Workpiece at ultrasonic
frequencies and relatively low amplitudes. The
polishing action occurs as the fine abrasive particles in
the slurry abrade the high spots of the Workpiece
surface, typically removing 0.0005 inch (0.013 mm) of
material or less.
The extent of polishing required is determined by the initial
surface roughness of the Workpiece and the finish required after
polishing. Typical surface improvements range from 5:1 to 10:1;
finishes as low as 4 μ inch(0.1 μm) Ra can be achieved.
In orbital polishing, controlled material removal occurs by the Workpiece
being oscillated orbitally in the horizontal plane while being fed vertically into a
containment cylinder of abrasive media. The advance rate of the Z axis (vertical axis)
is controlled in an adaptive mode, where the Z axis federate is predicted on pressure
feedback. As the Workpiece is inserted into the media cylinder, pressure rises
causing the media to conform to the geometry (of virtually any reasonable
configuration) and to become semi-solid, three-dimensional sandpaper, improving
surface finish and removing burrs.
Chapter 6 – Type 4 Equipment 110
Abrasive Flow:
Abrasive flow or extrude hone technology is relatively new and follows the pattern of
abrasive materials as the main source of material removal, but in a modified form. The abrasive
media is a cross between a liquid and solid that flows under pressure. Because the media is
unique, I am showing this process and equipment as a separate category, but it may be
considered an extension or progression of the wet blast system previously mentioned. That is
evident by the use of the terminology honing which is used to describe wet processes of
material removal.
Really this is an abrasive flow machining process. However, because of heavy viscosity
or cohesiveness of the abrasive media used in this system, this is more an extrusion process than
a true honing system, hence the name. For sake of classification, I will call this a 4 and 2 or 42
type system, which handles class 0 to 4 burrs in type 3 locations. That makes this a 4200 to 4243
system and a surface finish from 10 to 24 RMS depending on the processing media.
This equipment utilizes a mechanical means of using abrasives in a semi-solid form
closely resembling putty or silly putty. Because of the flow characteristics of the media, this
system tends to work best in confined internal passageways or inner dimensions, but with
proper fixturing, external areas can also be worked. Positioning of the part and the proper
control and direction of the semi-solid media is very important to achieving the desired
finishing results.
Under hydraulic pressure the media is energized or forced to move or flow through a
fixed stationary part. The abrasives are dispersed and suspended in a gelatinous putty like
polymer matrix that flows under pressures from about 100 PSI (7 bar) to 3,200 PSI (200 bar).
Normally the higher the pressure the faster the flow and material removal, but it also depends
on the viscosity of the media. Because of part design and material construction some parts may
not be able to take the high pressures exerted by this equipment; therefore, there are some
limitations as to what parts can be efficiently processes using this technology.
The abrasive hone works something like the hydraulic cylinder which is used to move
the media. That is, the whole machine behaves like one big hydraulic cylinder, except in this
case the work chamber is completely filled with media and is under pressure, or the media is
directed or allowed to flow through the part and then exit. The movement applied to the heavy
viscous abrasive material is forced through and/or around the fixtured part in a two stroke up
and down flow cycle of the hydraulic cylinder. The resistance and pressure of the abrasive in
the media putty then modifies the part where the media is allowed to flow. If the media does
not flow, that section of the part will not be worked; therefore, this will not work blind holes or
dead end passages.
Chapter 6 – Type 4 Equipment 111
Fig. 48. Abrasive Flow Machine Process Schematic
In a standard abrasive flow process, two vertically opposed cylinders extrude abrasive media back and
forth through passages formed by the Workpiece tooling. Abrasive action occurs wherever the media enters and
passes through the most restrictive passages.
The major elements of the process include:
The tooling which confines and directs media flow to the appropriate areas;
The machine which controls the media extrusion pressure, flow volume and if desired, flow rate;
The media, which determines the pattern and aggressiveness of the abrasion action that occurs.
By selectively permitting and blocking flow into, or out of, Workpiece passages, tooling can be designed to provide
media flow paths through the Workpiece that restrict flow at the areas where deburring, radiusing, and surface improvement
are desired. Frequently multiple parts or passages are processed simultaneously.
In a linear abrasive flow system, flowing abrasive media moves through workpieces in only one
direction.
Some advantages:
The tooling need only provide a seal at the inlet to the Workpiece allowing simpler tooling and
more convenient loading.
The outside of the Workpiece is not surrounded by media during processing, which means easier
unloading and cleaning.
Media removal from the processed passages of the part can be accomplished in the processing
station, collecting and returning it via the same hopper and in the same location stream as the processed
media.
Since media can exit freely from the part, there is less flow resistance that isn’t performing useful
work, consequently processing is faster and less heat in produced in the abrasive media.
Chapter 6 – Type 4 Equipment 112
Fig. 49. Abrasive Flow Variation
Another newer variation to this abrasive flow system is a faster one way machine that
automatically re-cycles the spent slurry. Tooling is very important and/or can be selective in
working some areas and not others. That is, it can restrict flow to only the area that needs to be
worked. Tooling is not only for holding the part, but to restrict and direct the flow of the putty
like media. Tooling can channel the pressure and/or abrasion to the burr area of the part
provided the part is adaptable to the parameters mentioned and can accept the pressure,
frictional heat, volume, media, and multiple strokes. This technology is especially good and
useful for deburring parts that have a lot of internal, deep, inter-connecting cavities.
Abrasive Flow Media
The media used in an abrasive flow process is a very special synthetic polymer putty like
material that can vary in viscosity to achieve different results. The more solid, denser, or lower
the viscosity of the media the slower the movement and the coarser the surface finish and
higher the material removal rate. The higher the viscosity, the faster the process and the finer
the finish. Media viscosity, extrusion pressure and passage dimensions determine the media
flow rate, which are calculated by dividing the flow volume by the processing time.
The abrasive used in the polymer is typically silicon carbide with a particle size of .0002
up to .060, but boron carbide, aluminum oxide, and diamond can also be used. Time cycles of 1
to 2 minutes are common, but finer results may take up to 7 minutes per cycle. The life span of
the media depends upon the amount of materials processed and its efficiency will decline until
it needs to be replaced in a couple of weeks.
In addition to deburring parts, there is yet another slight variation to this equipment
called an orbital polishing machine. As the name implies, this equipment is designed
Chapter 6 – Type 4 Equipment 113
specifically to polish. The equipment to do this work is similar to the deburring equipment,
except that there is a mechanism that produces a horizontal oscillation between the tooling, the
work piece, and the slurry. The speed of oscillation and orbital amplitude is 400 to 1200 RPM
and the tooling is usually made of nylon or polyurethane. The height or amplitude of the
oscillation determines the amount of material removal; however, this dimension cannot exceed
the height of the surface variation to be worked. The polymer slurry used to polish is of a higher
viscosity than that used to deburr and does not flow while in use from one chamber to another,
rather it moves or flexes in place.
Like the previous technologies, the abrasive flow machines or Extrudehones are still a
one on one type machine system. That is, the number of parts that can be processed are
determined by the tooling fixture or fixturing. This type of system is adaptable to production
line technology, but requires a lot of automated material handling systems which can increase
productivity by loading and unloading and/or the use of multiple cylinders for processing.
Also, just like abrasive blast type systems that require a dust collection system, the abrasive
hone type system may require the use of a clean and wash cycle as part of its production to
remove the polymer residue. This does not have to be built into the machine or dedicated to this
specific manufacturing process, but is recommend for high volume production. Therefore, this
equipment can and is quite costly.
114
Chapter 7 – Type 5 Equipment
Thermal:
This is a good opportunity to explain another relatively new technology called thermal
deburring. This system is classified as a type 5 equipment process, but it can only work up to
class 2 burrs effectively in 3 locations, and it will not affect the overall surface finish of the part.
That makes this a 500 to 523 system classification. Although heat is involved only, this system
processes parts or produces parts similar to abrasive extrusion, except the work medium is
primarily an air plasma instead of viscous solid. This system is good for parts with the same
deep internal holes, cavities, and/or hard to reach burrs.
Deburring takes place in the same uniform manner as how the flow of abrasive putty
material works its way through a part, except instead of a semi-solid abrasive material as the
work tool, the tool here is heat caused by pressurized air and combustible natural gas. In fact, it
is not a mechanical process of burr removal at all. It is a short thermal heat cycle induced system
and/or controlled combustion system that burns away excess burrs. If you define the word
burn, it is a very rapid or violent form of oxidation similar to an explosion.
In the case of thermal deburring, a batch of parts can be placed loosely in mass into a
basket or fixture which then goes into a work chamber that is sealed with a clamping force of
200 to 400 pounds. For more uniform finished parts, placement or orientation of the part is
sometimes helpful for processing. If the parts are not restrained, they may fly out of the
container during the rapid combustion and/or subject to possible damage.
These systems are relatively small or accommodate small parts. The larger work chamber
machine systems measure about 10 inches by 6 inches; therefore, capacity is limited. Smaller
systems are more powerful and efficient. The work chamber when sealed is filled with natural
gas and oxygen which are pumped in under pressure and then ignited. The mixture of gas to air
can be from 2.5:1 to 9:1. Some machine systems feature a dual shot capability. The result is an
instant combustion like explosion, burn, or oxidation, which reaches temperatures of 6000
degrees Fahrenheit that lasts approximately about 2 milliseconds. This heat burst is so intense
that sharp edges and burrs vaporize into an oxide powder and gases. Normal processing time is
usually less than 1 minute.
Why the heat effects the burr instead of the part is because of the high ratio of surface
area of the burr to part mass. Also, the time cycle is so short that the heat cannot penetrate or
damage the rest of the basic part. However, there can be a residue oxide coating from the burr
that can and will deposit on the part during the cooling cycle. Large burrs may produce small
molten round ball like weld splatter and excessive burrs may just round off like an incomplete
molded shape.
Because this is not a mechanical system that uses pressure and resistance to remove the
burr, what you get is a slightly modified version of what you started out with. That is, flat
surface areas will not be effected nor improved by this process. The only areas that will be
effected are the sharp edges or burrs created in the machining of the part and should this be an
Chapter 7 – Type 5 Equipment 115
irregular burr varying in thickness, the finished product may still be similar to an irregularity.
Almost all applications are on metal parts, but with proper adjustments, plastic can be worked
also.
Thermal Deburring
Temperature has an interesting effect on all materials. Earlier we discussed cryogenics that made soft
flexible parts stiff, brittle, and weak for media to work easier. Now we come to the opposite category. Extreme
high heat temperature for a short duration can literally evaporate solid materials. The following explanation
describes this process more thoroughly
Fig. 50. Thermal Deburring
116
Chapter 8 – Type 4 Equipment
Chemical Milling:
This is not so much a physical piece of equipment as it is a process, just as the name
implies. This is classified as a type 4 process that uses chemicals for the removal a class 0 to 3
burrs in 3 locations. That makes all chemical processes variations of a 400 to 433 system. It is not
a mechanical abrasive process. That also means that basically what you start within the way of a
surface finish is what you are going to end up with but with slightly less material or an etched
part and it can be bright and shiny or dull. If the part is rough or around 35 RMS (average of the
surface variation determined by a profilometer measuring root mean square), it will end up
roughly the same or maybe slightly better. This is because this process involves the reaction of
chemicals and solids, which dissolves or removes small amounts of material in an etching type
operation controlled by the concentration of chemical, temperature, and time. A good part of
the actual material removed goes into solution, heavier debris settles to the bottom of the tank,
and some material is transferred into heat and gas.
Using a straight chemical process, a number of parts can be grouped together in a batch
type operation, tumbled in a basket, or just immersed in the acidic or caustic chemical for a
relatively short period of time. Even though I have just explained this process of material
removal, there is almost no use of this technology for deburring purposes because of the
hazards involved and/or the lack of good controls over the process, chemicals, and parts. There
is a slight variation of this process used called ECD or electro-chemical deburring which we will
talk about shortly.
On the positive side, this is the first technology we have talked about that can be
considered a type of mass finishing process if it utilizes a rotating chemically resistant barrel
system of operation. However, in a straight chemical process, most parts have to be oriented for
the work to be done properly and requires the use of good liquid circulation or part movement.
This form of batching can also utilize a material handling system that works in batches or
continuously, but again due to the hazards and lack of controls there are no machine systems
designed to do a straight chemical milling process.
There is one popular form of chemical milling, machining, or deburring to work class 0
burrs which is used to produce electronic computer circuit boards. Technically, we are talking
about a cutting operation here rather than deburring, because the end product is composed of a
flat composite material that has basically no observable burrs. Why it is still considered as a
deburring process is because we are dealing with extremely fine micro burrs. This is a popular
method for burr removal in the computer industry. Control is achieved with masking materials
that are required for precisely controlling where the chemical will perform its work to create
good clean clear and isolated or delineated circuit lines and pads. Printed circuit boards are
sensitive to electrical current, so normal plating methods are not used. Burr or material removal
is limited to microscopic burrs over a wide broad area.
Chapter 8 – Type 4 Equipment 117
When chemically milled parts are done, they must be rinsed in order to stop the reaction
from taking place. If the rinse process is done improperly, too much material removal may
cause more problems or create more burrs than they correct. Therefore, time, temperature, and
the concentration of the chemical is important in controlling the rate of material removal or burr
or it will create a larger burr problem.
Technical knowledge of metals and chemicals are very important because of reactions
and/or the release of gases and by products. This technology is primarily a liquid system, which
involves a series of cleaning, rinsing, chemicals, and more rinsing tanks. This system requires a
large processing area and support equipment to maintain safety and the integrity of the
chemical processes. Such systems are more often associated with plating type company
operations rather than an in house manufacturing operations, unless it is part of a large volume
parts producer. This is true, primarily due to the major fact that this industry is controlled by a
lot of safety regulations involving both people and the environment. Again, this process is very
specialized, regulated, technical, needs a lot of support, and is relatively expensive.
Before we leave the category of chemical processing, we should say that we are talking
about plating industry processes. However, most plating companies are concerned with putting
on a coating, not taking something off. To be short and sweet, the difference between a straight
chemical systems and the next subject of electro-chemical deburring is the use of an electrical
current. Like thermal deburring, electro-chemical deburring will attack burrs or irregularities
first. The speed of material removal depends upon the chemical, its temperature, current
density, fixturing, and the metal alloy to be worked; however, the addition of electricity does
speed up material removal and does make it a more controllable deburring process than
straight chemical milling applications.
There are a number of variations in electro-chemical deburring. It can be used with or
without acidic solutions and stationary electrodes to remove metals. Often the parts are
passivated or surface hardened against oxidation during the deburring process, because of the
chemicals used. The parts can be fixtured, racked, or tumbled in a barrel. There is one process in
mass finishing that uses graphite ball media in a barrel, with parts that can conduct an electric
current, and an electrode. As the barrel rotates, the balls both act as an abrasive as well as a
conductor of the electric current, which works with the chemical to remove the burrs.
Electro-Polishing
Nearly all forms of chemical surface modification all fall under the same equipment
classification range of 400 to 433. Electro-polishing is a form of electro-chemical deburring that
uses an acidic electrolyte and an electrical current that can be used on most metals, but will not
work well with alloys containing silicon. It is actually a deburring system, but it leaves the
entire surface of the metal bright and shiny; therefore, it is sometimes used just for the final
appearance of the part. This process differs from electro-chemical machining by using a heated
chemical bath combination of phosphoric and sulfuric acid chemicals and requires a anode and
cathode plating technology or fixturing of parts in a bath.
Chapter 8 – Type 4 Equipment 118
The process works by using an electric current to create a very thin monomolecular film
of gas that builds up on the part, and any burr or material sticking up through this gas tends to
burn off. Besides burrs, high profile surface features or material peaks are first effected in this
process. Given enough time, other significant material removal will occur on flat surfaces
because of the chemicals involved. Metal surface finishes will normally be brighter on all areas
of the part. Surface finishes will not be as smooth as mechanical processes, but they may look
better.
ECD/Electro-Chemical Deburring
Another deburring process using liquids is called electro-chemical deburring or ECD. It
is the most popular form of chemical deburring, because it is fast, accurate and can handle up to
class 3 burrs. It is different from the electro-chemical polishing I mentioned earlier, because the
liquids used are not strongly acidic and do not etch or passivate the metal. This material
removal process is also very selective and is different because electrical current does most of the
work.
In an ECD process, the liquid is a simple 20% salt solution of sodium nitrate or chloride
mixed with water which is called an electrolyte and has a pH of around 7 or is neutral. The
solution only conducts a direct electrical current and/or a flow of electrons and metal ions from
positive to negative anodes. In addition to an electrical flow the electrolyte is also designed to
flow under a pressure of 5 to 40 PSI. The liquid flow and current can be adjusted to increase the
speed of the deburring process, which is extremely fast. Parts are normally processed in
seconds, but material handling takes up significant time.
Fixturing is very important in this process. The normal gap between the part and the
anodes is approximately .020 to .060th of an inch, but can be .010 to .020. The smaller the gap,
the faster the process works; however, the gap depends on the size of the burr, liquid
flow, current, and time. Opposite the fixtured part is an electrode designed to conform to the
finalized size and shape of the parts dimensions. To activate the process, a direct low voltage
electrical charge is introduced into the liquid bath tanks via the anodes and directs a flow of
electrons that travel through and from the part through the liquid to a negatively charged
anode. This process is very fast and selective. Deburring is localized to where or what has to be
removed. That means that tooling plays a major role in deburring.
In all cases, the parts to be worked have to be fixtured onto a specialized rack type
system which is then immersed into an electrolyte solution. Then, an electrical current, which is
reduced through a rectifier, must be allowed to complete an electrical circuit which dissolves
the burr. There are no other physical changes to the part or liquid during this process. However,
the fixtures and solution must be cleaned and properly maintained continuously. Chemicals
used vary with the metals being used, but surprisingly a lot of these products are proprietary.
Also, this process can only be used on metallic parts. Most machine systems are automated to a
point where the operator loads a fixture while another fixture is being processed.
Chapter 8 – Type 4 Equipment 119
The results of ECD processing are fast, from 10 to 30 seconds, and can be controlled a lot
better than straight chemical milling or electro-chemical milling, but the additional support
equipment and material handling can be a whole lot greater and more costly than the other
systems. Some variations of this process move the parts or have moving electrodes or brushes to
pass over the burr area instead of moving the liquid and some even use an electrode mesh that
is laid on the part and dissolves in the burr. The benefit of ECD is in precision control of the
material removal process, plus the chemical solution is very inexpensive and is relatively safe;
however, the accumulated waste and debris must be neutralized before disposal in solid waste
fills.
Fig. 51. Electro Chemical Deburring
Electro chemical deburring (ECD) works almost identically to thermal deburring except that it operates in a
chemical liquid bath. Temperatures, but mostly opposite electrostatic charges work in opposition to each other to
remove loose or thin sections of non-parent material. To operate efficiently, the positioning and/or tooling
representing the anode or cathode are very critical to the performance of this type of system. (see diagram) Unlike
chemical milling, which takes a long time cycle, ECD works in seconds.
Burlytic ECD Process
There is another variation of ECD with the trade name called Burlytic deburring. This is a
more forgiving process similar to what is used in the plating industry and is almost identical to
the first electro-chemical deburring/milling process I described earlier. This system uses a large
Picture
Shows the sectional view of a simple EC
deburring fixture where we deburr the intersecting
holes on the Workpiece (10)
A) The lower fixture with the baseplate (1), the
Workpiece locator (4), the electrode with the
connecting bus bar (10) and (2), the
electrolyte connection with the internal
cavities (3)
B) The upper fixture consisting of base (5),
positive anode contact (8), anode spring (6)
and electrical connection (7).
The entire fixture will be attached to the
machine feedhead, advanced to make contact, and
will charge the part positive. If applicable, it will
also place the electrodes in relationship to the
Workpiece. Retracting the upper fixture after the
deburring cycle is completed will clear the lower
fixture so finished parts can be unloaded and
undeburred parts loaded.
Chapter 8 – Type 4 Equipment 120
tank systems and rather simple tooling procedures. Unlike normal ECD, the Burlytic process
electrolyte chemical is run at ambient or cool temperatures and is somewhat of a selective
deburring system over that of ECD and requires no special tooling. Also the electrolyte does not
need to be pumped under pressure, but must be agitated and the electrical current application is
different. Instead of low voltage over a given period of time, this process uses high voltage in a
pulsed method of operation. Actual time to do the material removal is about the same. ECD
does work faster, but because of the method of current distribution, the actual material removal
rate is about the same.
The Burlytic process is a computer controlled system; therefore, it is a more expensive
than ECD. Its actual tooling is quite simple and inexpensive; therefore, its overall operating
expenses are less than ECD and it can also work a wider range of both ferrous and non-ferrous
metals. The process produces normally bright polished looking finishes with surface refinement
or smoothness of 4 to 8 RMS thereby making it a little more versatile than ECD.
Fig. 52. ECD Processing Equipment Systems
The term electro-chemical deburring can also be referred to as electro-chemical machining. The process
utilizes the flow of an electrical DC current through a liquid chemical bath or tank. The difference between most
systems varies how the parts are attached to fixtures and/or electrical connections, power requirements, time, and
the liquids used. Below are two widely used systems
Chapter 8 – Type 4 Equipment 121
Fig. 53. Burlytic Process
Small ECD System:
As indicated, most ECD systems require a lot of space and to some extent support
equipment. There is one slight exception to this type of system. There is a small hand-held one
man machine that can do the same job, but only one piece at a time. This machine's tank is
roughly 2' square by 6" deep and contains and re-circulates an electrolyte salt solution. Attached
to this tank is a rectifier generator that conducts the electrical current between a hand-held
wand and the part. The wand is hollow and allows the solution flowing through it to complete
the electric circuit. The part to be worked is placed in the work tank against a metal base plate
and the wand is then placed on or near the burr to be removed. The liquid flow and a metal gap
between the tip of the wand and the metal part and plate permits an electrical current to
disintegrate the material as the wand passes over it. It is a relatively small, inexpensive simple
system that works or behaves like a welders torch, except with a liquid.
About the Burlytic Process The Burlytic process uses a patented electrolyte solution
and a computer controlled energy source to achieve a
new level of performance in electrolytic deburring. The
electrolyte has a high electrical resistance. When a
machined part is immersed in the solution and a low DC
voltage charge is applied between the part and a
stationary cathode, an electrostatic charge is
concentrated at the sharp features (burr) on the part. In
high-density areas of the electrical field, burrs are
dissolved and carried away by the electrolyte. By
applying voltage in controlled pulses it is possible to
provide polishing action over an entire Workpiece or
focus the deburring activity to just the edges of the part.
Chapter 8 – Type 4 Equipment 122
Fig. 54. Small ECD System
As an alternative to large processing tanks is a small portable mini ECD deburring system that
is good for low volume or multiple configuration parts. This unit is not as powerful as larger systems,
but it has universal applications and does not require special tooling. Rather, this system relies on a
hand-held guided electrode wand or stylus that serves as the tooling. The electrode is a brass and
plastic tube assembly that is easily replaced or modified for special applications. All work is
performed within a 25 inch square x 5 inch high tank and powered by a separate generator
attachment. The electrolyte solution is normally a non-hazardous sodium nitrate that works well with
most metals
123
Chapter 9 – Type 3 Equipment
Mass Finishing Equipment
We have finally reached the classification of type 3 mass finishing equipment or
deburring mills. The latter name of mills is not commonly used, but that is their function to
grind or exert abrasive pressure in a free or loose state via mechanical energy forces and gravity.
It is the only equipment or machine systems to employee energy flow patterns to move the
entire mass of abrasives and parts as a single unit, hence the origin of the name. It is also the
only system that uses gravity as a primary pressure source of energy along with mechanical
energy movement applied to the largest size of abrasive media in an unrestricted free flow
pattern.
The type 3 systems can handle from 0 to 5 class burrs primarily at mostly number 1
locations or the O.D.’s of a part, making the equipment range from 300 to 351 in our
classification system. I am tempted to give them a 353 rating; however, solids going through
holes is not normally a good idea, because of the possibilities of media irregularities and or
multiple shapes getting stuck within the part being worked. However, even though they are not
recommended for internal deburring or surface modifications, they are still better than type 1
systems and maybe type 2, with the exception of abrasive flow systems. These systems can
achieve close to a 4 RMS surface finish starting from around 35 RMS in multiple sequential step
processing. Anything above 35 RMS is not recommended for processing.
The terminology or mass finishing reference is due to the fact that a large volume of parts
can be processed in a batch or continuous flow with or without abrasive media in a free tumble
process movement or X,Y & Z dimensions within a work chamber. The handling of parts in
mass is one of the biggest advantages of this equipment over all other systems. It is versatile,
quick, easy, and requires relatively little direct or indirect labor, just machine time.
These systems normally do not require any special preparations for cleaning or holding
the parts, but can be adapted for special applications. Most systems can process a wide diversity
of part sizes, shapes, materials, and weights. The size of the part processed is only limited by the
size of the machine and the range of the surface finish is only limited by the abrasive media
shape and particle size. Most machines in use are manually loaded and unloaded, but fully
automated systems are available. The primary purpose of automation is to lift the media and
parts to the height of the work chamber for processing. Most machines will unload without
much help.
The equipment provides the mechanism to apply abrasive energy forces to the mass, or is
the vehicle used to remove material, or to get to a certain designated surface finishing point
and/or achieve the desired end results on parts. Mass finishing systems transfer or use energy
forces that are applied to a work chamber to create uniform energy patterns within the mass
that effect the parts and materials placed into the work chamber of the equipment in
relationship to abrasive materials and gravity. It is a mechanical abrasive process. How the
energy or force is applied to the abrasive determines the speed or processing time cycles and
Chapter 9 – Type 3 Equipment 124
that distinguishes the difference between these mass deburring systems, but there are still some
other factors besides energy considerations as well.
Generally speaking, mass-finishing equipment can be broken down into 3 generations of
technology improvements or types of equipment. These equipment systems are the barrel,
vibratory, and high energy or centrifugal systems. There are other machine variations or
systems that use the same abrasives and use mechanical energy forces, which are indirectly
related to these systems, but unless the parts can be processed in mass, they are not a true mass
finishing system. For those reasons mentioned, the following systems or equipment will be
listed in their order of historic lineage, speed of operation, and price.
What primarily makes these machine systems different from one another is their speed of
operations and this is the result of the technology used to exert energy forces to the abrasive and
parts within their work chambers. All these systems can produce nearly the same end results;
however, it is a question of time. As a general rule, the rotating tumbling barrel system takes the
longest time to process parts. That is followed by vibratory systems, which improves processing
times by a factor of 10 and then there are the high energy centrifugal system that improve
processing time by another factor of 10 over the vibratory equipment.
The use of gravity is very important to mass finishing systems. If it weren’t for gravity,
none of these systems would work. Gravity is translated into weight, force or friction, and
pressure. All mineral abrasives have different weights and molecular density and that is
expressed as a value known as specific gravity for all materials (see tables for abrasives). Parts
too have weight, density or harness and size, but these are variables that are not distinguishable
with a scientific constant. The greater the weight of the mass the greater the force, friction, and
material removal. That greater the concentration or density of the abrasive and parts, meaning
the height of the mass, the greater the downward pressure and friction in the work chamber.
The speed of the mass movement and how the energy is applied is also important. The
only thing the equipment does is to create a flow pattern or movement to the solid abrasives
and parts in a uniform pattern. Basically you have a solid mass moving in a limited or restricted
work chamber and this exerts energy on a smaller sized particles and mass and that produces
pressure resulting in friction. It is the weight of the mass that exerts the pressure on the parts
and the larger the abrasive shape and particle size of the media the more the material removal.
What you put into a machine determines what comes out of it. What media you use determines
how the parts and mass are modified. By increasing the speed of rotation or gravity one
increases the energy forces and improves the pressure and speed of material removal process.
All mass finishing systems have some form of a work chamber or container for the work
mass. The barrel is nothing more than a large sealed container that is turned, rotated, or moved
on a stationary frame in a fixed position. It turns or rotates the contents within at a speed that
does not exceed the force of gravity which is 32.174 ft. per second square. Vibratory systems
move or oscillate the work container and contents inside from an outside energy source that
creates a moving vertical amplitude that does not exceed a half an inch in height and creates a
pressure of about eight times the force of gravity. High energy centrifugal systems use both
Chapter 9 – Type 3 Equipment 125
external and internal forces to apply pressure to its work contents also. An internal disc spins
the mass and that transfers energy directly to the parts, up to 25 times the force of gravity. The
high energy barrel systems uses counter rotating barrels to increase the pressure up to 30 times
the force of gravity within the work chamber and that is then transferred to the mass and parts.
Naturally the more advanced high energy centrifugal systems have the shortest finishing
time cycles and are probably the most aggressive systems now, but they are also the most
costly. Although vibratory systems are somewhat slower, they have quick unloading or
material handling advantages over the manual high energy systems. The barrel systems are still
popular because of slightly lower prices than vibratory and they get good polishing results even
though they are slow.
A lot of engineers compare the processing technology of mass finishing systems to that of
a three-legged stool. That is, the equipment provides the mechanical energy forces, the media
performs the work, and a liquid4 keeps everything functional. If one of these three factors is not
performing well, the parts to be processed will not achieve the desired end result. Therefore, of
all of the systems mentioned so far, perhaps mass finishing equipment is the most difficult to
master, because of the three variables.
Some people even call mass finishing systems technology black magic or black art and is
one of the reasons why a number of companies do not like to use this type of equipment or
processing system. That is because it is possible to work a batch of parts which will be
processed the same and uniformly, but the next batch or another batch some time later can have
some variation if something in the process has changed. Like any new piece of equipment, there
is a learning curve. It takes time to master all the variables. Even though there may be problems
from time to time, these systems usually out perform all other methods of deburring by a long
mile in relationship to cost savings or processing costs per piece.
As mentioned, the main advantage to mass finishing equipment is the fact that parts can
be handled or worked in mass and can produce consistent uniform finishes per batch of parts, if
done properly. These parts do not have to be racked, placed in a fixture, orientated, or done one
piece at a time. Also, the parts do not normally have to be cleaned prior to placing them into a
machine. The liquid and chemical used in the processing can usually handle most contaminate
problems. Therefore, mass finishing systems lend themselves very well to high volume
production and a wide range of part sizes and materials without much labor and maintenance.
The Barrel:
Now, at some early point in history it was discovered that a true bowed barrel shape
allowed people to move great weight from place to place fairly easy. Because of the round
barrel shape, only a small portion of the barrel actually touches the ground, acting like a big
wheel, and that allows for relatively easy movement over flat surfaces. In the movement process
4NOTE: Besides a liquid as the main source of cleaning or lubrication, small dry inorganic
or organic particles can be used to take the place of liquids and chemicals.
Chapter 9 – Type 3 Equipment 126
it soon became evident that the rotating barrel also had the ability to effect the contents inside,
especially loose objects not tightly packed. In most cases, especially food stuffs, this was not a
desirable intent of the barrel design. On the positive side, it was thought to be a good probable
means to effectively work surface conditions of objects and modify sharp edges within the
barrel. By simply holding the barrel in place and allowing it to rotate with abrasive and
materials inside, it became a tool to work other harder materials, formerly worked by hand.
That concept created the advent of mass finishing barrel tumbling systems for deburring parts
which remains one of the principle methods of working parts even today.
Operating Principle of the Barrel
A barrel system works by rotating a closed work chamber containing parts and abrasive
media in a one directional mode of operation. As the barrel rotates, a work action or slip of the
mass occurs inside the barrel by the raising of the contents or work load to a height where
gravity over comes inertia and any cohesive properties of the mass itself. This movement creates
a spill down zone or a continuous slide in primarily one direction or motion, but some side
movement and/or tumbling action can take place. The original bowed wooden barrel had some
minor compression and greater side tumbling capabilities than the more recent straight barrel
designs built for efficiency and longer wear.
Most barrels used in production are built symmetrical for simplification of construction
and made from metal that can be coated, not like the bowed wooden barrels of old. To improve
the action or movement within this type of equipment, large barrel systems have broad flat
hexagonal sidewalls that create a greater degree of lift or aggressiveness to the media and parts
within. A single uniform curved barrel surface is constantly trying to rebalance the load within,
whereas rotating flat areas create a more rapid pulse type movement to the workload. Most
smaller barrel systems are made in a round shape for cost purposes.
Prior to the decline of popularity of all the barrel systems, some barrel designs began
tapering or bowing the ends of the tumbling barrel to get more x and y movement and
compression or friction to the work mass. Another innovation tried was to vibrate the barrel
while turning it in order to speed up or improve upon barrel processing times and finishes.
Unfortunately, most of these innovations could not significantly improve processing times to
justify the cost of these features.
Chapter 9 – Type 3 Equipment 127
Fig. 55. Mass Finishing Systems Barrel Tumbling Equipment
Barrel tumbling systems go way back to ancient times.
They are simple, they are easy to operate, and they have
been around for a long time and will continue to be
around for a long time. Probably the only new addition to
the barrel system over the years was the introduction of
electrical power. The diagrams below illustrate the
principles of operation and a picture of a large single and
double compartment machine system.
Barreling Action
Capacity
The actual working capacity of a barrel is approximately 50% of the volume size within
the barrel. That is, a normal 5 cubic foot barrel holds two and half cubic feet or approximately
250 lbs5 of media and work mass. Of the weight and volume, only about 50 to 60% of the work
mass is parts; therefore, the classification of capacity is somewhat confusing. That is, some
manufacturers rated their equipment by working capacity based upon parts and some used the
size of the work chamber to identify their capacity. In either case, the standard unit of measure
was based upon volume rather than weight or liquid capacity.
5For this example, we used 100 lbs. equal one cubic foot; however, media does vary for 55
lbs. minimum for plastic, 90 lbs. avg. for ceramic, to 330 lbs. for steel.
The tumbler corners lift the load until it
reaches a point where it slides down the hill.
The bumping and scraping against the stones
(or themselves) abrades the parts. At least 90%
of the work is done in the upper 1/3 of the
load
Chapter 9 – Type 3 Equipment 128
As the barrel system rotates, the actual active work zone in the barrels work chamber
only occurs on the top level of the media or about 1/3 of the mass inside. The other 2/3 of the
work mass is virtually dormant or inactive. Typically, the load level or capacity of a barrel, at
60% of its volume, with the liquid level one inch below the mass level should produce an
abrasion rate of 150 surface feet per minute.
Fig. 56. Barrel Processing Equipment
Speed
The speed at which a barrel rotates is very important, because the slide of work load
depends upon the diameter of the barrel, the R.P.M.'s., the height of the media and work load
mass, and the height of the liquid level. The normal speed of rotation of our example machine is
very slow with an optimum speed of around 27 RPM's or about 150 SFPM (surface feet per
minute) for polishing and good part finishes. Processing cycle time depends on the size of the
barrel and also affects the surface finish of the parts. See chart:
R.P.M. for Barrel Diameters
RIM or
Surface
Feet/min
40
36
32
30
28
24
23
20
17
16
15
13
12
11
50 4.8 5.3 6 6.4 6.8 8 8.3 9.5 11.5 12 13 14.7 16 18
60 5.7 6.4 7.2 7.6 8.2 9.8 10 11.5 13.6 14.3 15.3 17.6 19.4 21.4
70 6.7 7.4 8.4 8.9 9.5 11.3 11.7 13.3 15.9 16.7 17.8 20.6 22.6 25
80 7.6 8.5 9.5 11.3 11.7 12.9 13.3 15.3 18.2 19 20.5 23.5 25.8 28.6
100 9.5 10.5 12 12.7 13.6 16.1 16.7 19 22.7 24 25.6 29.4 32 35.7
120 11.4 12.7 14.3 15.2 16.3 19.4 20 23 27 29 31 35 38 43
135 13 14 16 17 18 22 23 26 31 32 35 40 44 48
150 14 15 18 19 20 24 25 29 34 36 38 44 48 54
165 16.2 18 20 21 23 27 28 32 38 39 42 48 53 59
180 17 19 22 23 25 29 30 35 41 43 46 53 58 64
200 19 21 24 25 27 32 33 38 45 48 51 59 64 71
225 22 24 27 29 31 36 38 43 51 54 58 66 72 80
250 24 27 30 32 34 40 42 48 57 60 64 74 81 89
Chapter 9 – Type 3 Equipment 129
A good barrel system has a speed control that can regulate the RPM’s of the barrel. This
is important because some burrs, if subjected to a energy forces of a normal deburring cycle
speed, can be deformed and or rolled over to one side quickly, making them more difficult to
remove later. That means that a good machine operator will first start the machine at a lower
speed to avoid this problem and then increase its speed 10 to 15 minutes later.
Small barrels require faster speeds to equal the same amount of SFPM. Faster speeds
maybe desirable for deburring parts, but these faster speeds may overcome the force of gravity
and interrupt the constant even slide zone within the barrel and that in turn may cause part
impingement, pitting, or an orange peel effect, and/or damage to the parts being processed.
Instead of the parts tumbling, they may get air born and get pounded or showered with heavy
particles causing impact damage. Where the part surface finish is not important and shorter
time cycles are more desirable this may be acceptable process, but it is not the best use of the
equipment. Continued use at high RPM’s will shorten the life of the media, by breaking it up
faster, and/or effect the inner walls or liner of the work chamber as well.
The standard barrel systems efficiency to deburr or polish depends on the ability of the
work mass (parts and media) to slide down a slope created by gravity. As mentioned, if the
slope is broken up by too fast a speed the parts may become air born causing part damage
and/or the barrel system becomes ineffective. Too slow a speed does not hurt the parts but it just
makes the time cycle longer. When faster speeds are desirable, make sure there is a greater
quantity of water and chemical compound in the barrel to give more cohesion to the mass and
this will also soften or buffer the impact or hammering effect of the media on the parts.
Barrel tumbling systems have been around a long time, but are not as popular as they
once were, mainly because of their slow speed of parts finishing, operator intervention, and the
need for material handling. However, they probably still produce the best polished parts of any
mechanical system using dry organic materials, that is because barrel systems produces long
smooth slide patterns against the part, similar to the effects of a buffing wheel. Barrel systems
are still very popular for burnishing or bright finishes. Steel ball burnishing media is also use for
work hardening parts, especially the smaller systems that operate on rollers. Because these
systems are considered closed loop, they work well where chemical treatment of parts or harsh
chemicals are desired. Lastly, some of the older chemical compounds that foam a lot seem to
work better in barrel systems and produce better end results than the newer chemical
formulations that go into more aggressive finishing equipment.
Liquid
The reason for the popularity of barrel systems is due in part to their simplicity and the
heavy construction of the work chamber barrel. They hold up to a lot of abuse and weight as
well as strong chemical concentrates. This type of machine can handle a large volume or liquid
content and the chemical factor is used very effective in metal burnishing. The normal water
and compound solution for a barrel system is one gallon per hundred pounds of media. For
deburring, less water or a level of 1 to 3 inches below the mass level is desirable. For burnishing,
more water is preferred or 1 to 3 inches above the mass. Care is required when using strong
Chapter 9 – Type 3 Equipment 130
chemicals, especially when unloading the barrels after processing is complete. Be sure to slowly
pre-release any sealed hatch cover prior to opening due to chemical reactions and/or pressure
caused by heat generated during processing.
Getting back to the ruggedness of the equipment, perhaps we should spend a little time
on the work chamber liners. Because barrels are designed to abrade parts, the abrasive materials
and parts used in the process also abraded the wall construction of the work chamber. Early on,
barrels were made completely out of wood and some were designed to run with water in water.
These systems date back to ancient Egypt and China, but there are still some in use today that
uses a barrel design that permits water to flow in and out of the barrel. These systems have
limited use and are used mostly for cleaning and to some extent polishing.
Inner Wall Construction
More heavy-duty barrel construction is from metal, but some are still lined with wood.
This wood acts as insulation and allows a buildup of heat and it also cushions heavy parts so
that damage is less likely to the part. These wood lined barrel systems are still in use today and
are preferred for gentile light weight parts and dry organic media processes designed to polish
plastic parts and restoring clarity to clear cut plastic.
Naturally woods is not a good barrel liner for abrasive deburring work or long wear.
They should not be used for extremely heavy parts unless the deburring or polishing media is
greater than 80% of the mass volume. Wood liners also have to be replaced often to prevent
more serious damage to the outer metal barrel itself. Such maintenance repair or replacement
work does become quite costly. Therefore, for more aggressive abrasive processes a one-piece
interior coating or a more flexible abrasive resistant liner is recommended or necessary to
prolong the life of the work chamber.
The first practicable abrasive resistant liners used to coat these work chambers were
made from neoprene rubber based materials. Unfortunately these liners don't stand up to a lot
of the chemicals used in the processing of parts with the media. Eventually, most of the liners
then changed to PVC or polyvinyl chloride based materials. These worked exceptionally well;
however, their life span was not as great as the neoprene. Next came the urethane liners that are
now the most popular of all the liners used for all mass finishing equipment. These latter liners
last extremely long and are chemically resistant; however, the PVC materials still seem to give a
little better traction to help the media rotate. Therefore, you will still see some PVC and to some
extent neoprene liners in smaller barrel system.
Barrel systems are still popular for removing a lot of material on outside surfaces and
rounding edges, or putting a radius on parts over a long period of time. Time cycles may take
days. On the positive side, barrels still produce maybe the closest finish to a hand buffing
operation than any other mass finishing machine system. On the negative side, besides speed
being a factor, the one directional mode of operation also affects material finishes. That is, in the
actual tumbling operation very little media gets into the inner dimensions of a part. That means
that the outside edges of a part get worked very hard or aggressively while the inside
Chapter 9 – Type 3 Equipment 131
dimensions get barely touched; therefore, barrels are not recommended for deburring parts
with machined recessed surfaces, slots, or grooves.
Large Barrel Systems:
There are three basic designs of barrel systems in popular use. They all rotate parts in a
one directional mode, but how they do it is slightly different. The most common system, as
stated above, is usually a hexagonal barrel attached to a frame with a shaft secured to the center
portion of the outside barrel or it can be a through shaft axle type. This barrel can be one, two,
three, or more closed compartments with secured access hatch covers on each to allow multiple
parts processing at the same time. Each work chamber can have a different media and part;
however, if they are different, then the processing time cycles may also be different.
Probably one of the most annoying problems of a large barrel machine is the loading and
unloading of the barrel. Because barrel systems are the oldest form of mass finishing machines
around, most large production systems did not and still do not have very good positioning
controls. This positioning problem is also a result of the chain and sprocket drive design. That
automatically means that there is linkage and gearing that behaves like a digital system, or that
there are just so many spaces and voids where the barrel can stop. The number of gear teeth and
size of the linkage determines the position of the barrel and there are just so many teeth. To load
these machines, there is only one access hatch to the work chamber and it must be in the right
position for both loading and unloading. The problem of not being in the right position results
in spillage and time delays.
To position or jog a barrel takes a quick button push of an on-off electric switch and
visual attention. That action creates a short jerky movement of the barrel. Because of the weight
and load position of the mass within the barrel and the lack of a good dead stop or brake, the
barrel tends to want to re-position or move itself back to its original position after its power is
cut. That means that positioning is not always easy to control; consequently, as mentioned,
there may be rapid lurching and missed positioning of the hatch cover which can cause
problems and time delays as well as extra clean up.
To load the machine, the barrel must be manually jogged or stopped at least 45 degrees
to its upright position for optimum loading. Media and parts must then be brought up to that
level of the opening and hopefully the container is not larger than the hatch opening. Large
barrel systems should take at least a minimum of 50 pounds of parts and maybe up to 1000
pounds or more per batch. All large systems should have hoist or material handling accessory
assisted systems.
The height of the barrel opening can vary to some extent, but it is usually at least 4 feet
from the floor level and even at this height, repetitive motion and weight can be strenuous if
this is done manually. To unload parts, the access hatch must first be stopped again at the top
side, then the access hatch removed and/or replaced with a screen hatch cover. In any lower
position, or straight down, the inner contents of the mass will exert a pressure that will interfere
with removal of the hatch as well as cause a possible safety problem to the operator. Another
problem of the hatch cover is that it only allows access to the barrel, a barrel with its opening
Chapter 9 – Type 3 Equipment 132
straight down may not completely unload its contents, because a hexagon shaped barrel will
retain parts and media on the flat section adjacent to its hole opening.
After the appropriate processing time to work the parts, the barrel or work chamber is
stopped, then jogged or rotated by a drive mechanism and positioned perpendicular to gravity.
Without the use of gravity, barrel systems cannot work. With the screen hatch cover in place,
the barrel can be slowly rotated allowing its contents to be spilled or jogged again to direct its
liquid contents, debris, or media to the ground, a screen deck, or container. The fastest way to
unload and separate parts is to dump everything onto a separator screen deck. With a screened
hatch cover in place smaller media can go through and the parts will still be left in the barrel,
but the restricted opening can still leave some media mixed with the parts. In lieu of the hatch
cover application, some barrel machine systems have provisions for detachable screen decks
built into the machine below the barrel.
Because of liquid problems, most big barrel machines have a specially designed area with
sloping floor and drains. Provisions must be made to catch or direct the liquid, media, and/or
parts. As mentioned, to speed up material handling operations, the entire contents of the barrel
are dumped onto a separate screen separation system. In all cases, problems of liquids and the
positioning control system does not making dumping of the processed liquid or slurry simple.
Also, in most cases, the liquid can contain chemicals and contaminates which again presents
problems for the operator and maybe in and out plant environment. For more immediate safety
reasons, operators wear a lot of waterproof safety clothing and possibly a respirator. Because of
the viscosity and chemical composition of the affluent, special plumbing and holding tank
systems are common. This is normal procedure for large machines over 5 cubic foot capacity or
more.
Medium or Open End Barrel Systems:
I chose to call this section of machines medium size capacity or open end barrel systems,
because the typical machine in use is relatively small to medium at about 5 cubic foot capacity
which is about the most common. This is a popular machine system because it works well in a
manual mechanical mode with human physical power supplying most of the machines loading
and unloading movements. There are larger systems which have automated tilt features of up to
9 cubic feet, but the majority of machines in use are of a medium size capacity.
This design variation of a barrel system has only one axis point and is normally always
open on the other end. This can be considered a cantilever mount design, which looks like a
cement mixer; however, unlike the mixer, this barrel has a greater number of flat sides and like
the mixer, it is slightly larger at the bottom mount area than the top. Most of these systems are
designed so the barrel work chamber and motor are inter connected in a fixed position and
attached via a bevel gear. The motor is mounted and moves on the opposite side of the tilt
mechanism from the barrel. In this position the motor acts as a counter weight and somewhat
offsets the weight in the work chamber. Still, some machines have additional weight added to
the motor area to offset the mass weight within the barrel.
Chapter 9 – Type 3 Equipment 133
The biggest advantage of this equipment is the quick loading and unloading capabilities
of the machine system. The barrel can be emptied very quickly and manual loading is normally
about the same height as the horizontal barrel or at a person’s waist level, before the work
chamber is re-positioned in the operational mode. The tilting mechanism on all cantilever
systems allows for quick dumping of parts and media. Positioning or tilting of the barrel is done
by hand and can be adjustable from straight up to straight down, or complete turned around
until fixed into position.
Because this dump and load system is normally done manually, these machines are not
big systems like the horizontal units; rather, they are maybe 5 cubic foot maximum to about 1
cubic foot in capacity. The manually lifting and controlling of the work chamber or weight
movements basically determines the sizes of these machines. That also means that a lot of these
systems are used for drying or polishing of parts with organic materials, because organic media
is lighter in weight.
The work chamber or barrel normally operates on a 45 degree diagonal line of rotation.
Actually they can be adjusted from zero to 90 degrees or at any point in between as long as the
parts and media don’t fall out as the barrel rotates. This angle produces a media or mass flow
that is similar to a vortex pattern common in all mass finishing equipment. While in operation,
the one directional cascade of the mass is the same as horizontal machines, but the slide pattern
of the media in this machine, can vary anywhere from 60 to 30 degrees. At 45 degrees, the slide
zone within the barrel movement maybe slightly greater than that of a horizontal barrel system,
but there is not as much weight or mass; therefore, time cycles maybe slightly greater than
horizontal barrel systems.
These systems usually operate without a cover or sealed hatch because the media does
not reach the opening while in operation, which is not true of the bigger horizontal systems. In
this operating position the opening allows for quick visual inspection of the parts and
processing without stopping the machine. The machine is fixed in place or stationary while in
operation, but it can have wheels and is easily moved around to different shop floor locations.
Another versatile feature is that the machine is capable of tilting 180 degrees thereby allowing
the machine to be loaded on one side or very close to another machine, processed, and dumped
to the opposite side.
When parts are added to these open end barrel systems, there is a tendency for the flow
pattern to change and because of gravity the parts seek the bottom of the greater portion of the
elongated mass within the barrel system. Unlike cement mixers, most of these machine systems
normally don't have vanes to upset the parts, but they could have them. In fact, fins or lifters
can help achieve better mixing of the media and parts provided the parts do not get stuck on
them or damaged due to contact.
The main reason for these machines not to have lifters is because of the possibility of part
damage due to the parts hitting the next moving lifter. A movement of the lifter vane is opposed
by the gravity and flow pattern of the mass and therefore two opposing forces produce a great
deal of force and possible damage. If the parts and lifters are completely submerged under the
Chapter 9 – Type 3 Equipment 134
media, then the risk of damage is drastically reduced. The flat sides of the typical barrel
normally provide sufficient energy and mass movement within them as to not require lifters.
Open End Bottle
Another problem with any barrel design is that mass movement within the work
chamber is somewhat restricted. That means that part separation can occur in relationship to the
mechanical motion and gravity if the parts are extremely heavy. Speed will only improve part
movement and media pressure on the part to a certain degree, beyond which there is no
improvement and inefficiency. To make barrel system more aggressive there is a special shaped
barrel system called a bottle tumbler. These barrel systems have work chambers with large
bottoms and small top openings similar to that of a bottle, hence the name.
In addition to increasing the mass mixing or rotation of the parts, the bottle shape design
also produces greater, more uniform compression forces on the mass within. As the load rotates
in primarily one direction there is also much more tumbling motion in X, Y and Z directions
caused by the shape of the barrel. Therefore, these barrel systems are sometimes referred to as
triple action machines.
Bottle tumbler machines are not very common because of the higher fabrication costs of
the work chamber. Also this bottle shape design was introduced about the same time as other
more aggressive deburring systems became available. Another reason for their scarcity is
because their actual working capacity is about 1/3 rd of their rated size. That is, if the machine is
called a 3 cubic foot machine, its actual working capacity with parts and media is about one
cubic foot.
Barrel Shape Designs and Applications
Most barrel tumbling systems operate in uniform of symmetrical shaped horizontal barrels. When
barrel system use a vertical of angular rotating position, they tend to have a larger dimensional configuration at
the bottom of the work chamber and a narrower open top. Better surface finishing results can be achieved with
a horizontal barrel system, but they are not as user friendly as tilt barrel barrels. Also, parts having a greater
length than width or thickness have a tendency to tumble end over end in tilt barrel designs which result in
excessive wear on outside dimensions and ends. Therefore, the bottle-shaped tilt barrel design creates a more
aggressive triple action flow pattern within the work chamber and mass resulting in shorter time cycles and a
more uniform finish to parts.
Chapter 9 – Type 3 Equipment 135
Fig. 57. Tilting Tumbler Machines
The tilting tumbler is a versatile machine suitable for
wet or dry barrel finishing procedures. An old favorite for
finishing, it offers the advantages of fast loading and
unloading as well as rapid inspection. This is especially useful
with runs of short duration.
This particular machine features a tapered octagon
shaped barrel for maximum tumbling action. The barrel is
metal and watertight. If necessary, the barrel can be lined with
wood or seamless vinyl.
The tilting device will swing the barrel a full 180˚, the
barrel is automatically locked in any position.
The tumbling dryer machine combines tumbling
action and heat to dry and clean parts with corncob grain or
sawdust. A heated barrel speeds drying time and lengthens the
life of the drying agent (corn cob grain or sawdust).
Open-end bottle or triple action barrel
mixes parts and media similar to a horizontal
barrel
Chapter 9 – Type 3 Equipment 136
There are some very small open end barrel systems that are less that 1 cu. ft. capacity in
size, but most of these machines are not what I would call industrial production machines,
unless you are talking about very small parts less than a half inch in size. Because of cost factors,
these small systems are made at a fixed angle and the whole unit, with the motor, is picked up
and tilted to empty the contents. Again, because of these limiting factors, most of these
machines are typically used as parts drying systems, but they can also be used to perform wet
deburring operations as well.
Small Barrel Systems:
The last type of barrel system is for smaller machine systems, usually under 1 cubic foot.
These barrel systems can be just smaller versions of their big brothers, but more often than not,
they normally run on rollers and bars, which are turned by a separate power source. That is,
there is a separate power rail system that rolls and turns the barrels as they sit on the rotating
rails and that bar movement turns the barrels. The barrels are separate and only held in place by
gravity.
Like the medium barrel systems the weight of the barrel and its contents basically
determine the maximum size of these systems. That is, you can only lift just so much weight
onto one of these power rail systems unless you use a secondary material handling or lifting
device. Most of these barrels are made of one piece, light weight, molded polypropylene. For
ease of loading and unloading, the barrels have a large hatch cover opening on the side of the
barrel. Most of the power rails are designed to accommodate one to eight of these barrels at a
time. These detachable barrels do not normally exceed one cubic foot capacity in size and can
get down to .10 cu. ft. The versatility and light weight of these systems make them popular in
the jewelry industry and/or used a lot for small parts batching.
Chapter 9 – Type 3 Equipment 137
Fig. 58. Small Barrel Tumbling Systems
All of the tumbling systems on the following page operate with removable barrels.
The upper right system uses a central shaft that clamps the barrels and holds them in place.
The other unit’s barrels rotate by riding on rails that turn the load. They are held on by
gravity.
Chapter 9 – Type 3 Equipment 138
Loading and Unloading Systems
Loading and unloading of these machines is always a slow process in that the media and
parts must be placed in the machine and then dumped to sort out the media from the parts each
time the machine is used. That is because the systems with hatch or door mechanism have a
somewhat restricted opening to get parts and media into and out of the barrel. By the way, and
that also means that an additional operation must be performed that requires another accessory
piece of equipment. Without a separating screen or sorting device the separation of parts from
media can be very time consuming operation. As mentioned, some large barrel systems may
have a special door hatch cover that can be replaced with a screen to allow media to fall out and
the parts stay in during a slower rotation cycle, prior to unloading, but I have never seen a very
fast effective system.
Most large barrel machine systems have accommodations for flat screens to be installed
slightly under the rotating barrel. Besides the screen deck, two containers are required. One to
catch and hold the media and the other for the parts. This feature permits all the contents of the
barrel to be dumped at one time and allows the machine to be refilled and started again while
sorting can take place below the horizontal barrel. While this is technically possible, moving
equipment in close proximity to an exposed rotating piece of equipment is now regulated by
OSHA standards and may no longer be an acceptable condition.
Self powered mobile screen systems may be utilized and acceptable to speed up
unloading; however, because of the safety cover or cage around the machine that must be place
before the machine is started, even this accessory may be a problem or restricted during
machine use. Therefore, sorting must take place either immediately upon dumping, before the
machine is restarted, or moved to another location for separation. Dumping the entire contents
of the barrel usually saves time; however, not always. No matter what unloading system is
used, there is going to idle machine down time.
Another interesting feature about parts separation is a great reliance on hand picking of
parts out of the media mass, especially when the media used is nearly the same size as the parts
or larger than the parts. It is an extremely slow process. That is, it is slow if the parts are smaller
than 3/8 of an inch and when there is a large quantity of parts involved. When parts are big in
comparison to the media is the fastest method of separation. However, more often than not,
people tend to think that they can manually separate parts from media faster than accessory
devices. In most cases this is a false assumption.
Flat screen separators are the most common separating devices that are used and as
stated earlier, some of these are built onto large barrel systems. These manual or stand alone
screens are good separation systems up to a certain point. As stated, when there is a big
difference in part size and media, separation is relative quick and easy. When the parts are less
than twice the size of the media, or the hole size of the screen opening is less than twice the size
of the media there may be difficulty in properly separating parts from media. The most
important thing to remember is to get a screen with the greatest amount of open area in
relationship to solid part of the screen.
Chapter 9 – Type 3 Equipment 139
Mechanical Screen Separators
To improve separation there are automated stand alone systems which are designed to
vibrate by themselves and are usually mobile or easy to move around. These systems are
relatively fast, provided there is a substantial size difference between the media and the parts. If
there is not a big difference in size of media versus parts, separation maybe a little more
difficult, especially in separating parts smaller than the media.
Media that has been worn or random media may still get through these screens and mix
with the smaller parts.
Another problem of flat screens is that even with vibration assisted shaking of the screen,
there may still be problems of media laying or sitting on top of parts. If a part has a recess
configuration, media can get stuck in these areas or just rest on top of the part during
separation. Therefore, in nearly all cases, even with screen systems, manual hand labor and
monitoring may still be required for complete and proper part separation.
The only sure way of removing all media from a part is to upset the part during the
separation process from the media by rotating the entire mass before allowing the part to exit
the screen. The rotary screen looks like and is a large diameter perforated tube that turns on
normally powered rollers. Because of media and part size, a number of screen tubes maybe
require. However, a rotary screen separator can handle a lot of volume, heavy loads, and is
All screen systems are designed to
separate parts from media. For large
volume production, powered vibrating
screen systems are favored over manual
systems, especially where large
volume and weight are involved. In
most applications, the parts are larger than
the media. Normally, for speed, all the
contents of a mass finishing system
machine are dumped onto the screen deck,
which has a raised edge or border to funnel
and direct the parts. Some systems are
extensions to existing internal screen
ramps or decks. Most screen systems only
use one size screen to separate the parts
from the media, but multiple screens can
be used to sort the media for critical
tolerance problems either with the parts or
the media. All of these systems have a
place for containers(not shown) to collect
parts and media separately.
Some of the more common screen
hole sizes And/or standards are shown
here.
US std Tyler Micron Size Inch Size
Mesh Mesh Approximate Approximate
4 4 4760 0.185
6 6 3360 0.131
8 8 2380 0.093
12 10 1680 0.065
16 14 1190 0.046
20 20 840 0.0328
30 28 590 0.0232
40 35 420 0.0164
50 48 297 0.0116
60 60 250 0.0097
70 65 210 0.0082
80 80 177 0.0069
100 100 149 0.0058
140 150 105 0.0041
200 200 74 0.0029
230 250 62 0.0024
270 270 53 0.0021
325 325 44 0.0017
400 400 37 0.0015
Chapter 9 – Type 3 Equipment 140
much faster, more efficient, and can take up less floor space or be much shorter than a flat
screen system. Therefore, if efficiency, speed, and space are a factor, one should consider the
rotary screen separator over other systems, provided the parts volume warrants the extra cost of
such a system.
Tubular Rotary Screen Separator
This screen system is made from the same flat stock as standard screen separators, except
the material is rolled into a tube. This shape has many advantages. One, it is fast and two; parts
and media get tumbled as they pass through a rotating screen in a gravity feed operation. That
means that it is difficult for the screen to get blocked by media and parts shed most excess
media on top of them.
Fig. 59. Tubular Rotary Screen Separator
Chapter 9 – Type 3 Equipment 141
A couple of comments about barrel finishing that may be of some interest. Of all the mass
finishing systems used, barrel finishing equipment costs are normally cheaper than other
systems. They also have longer media life than other systems, primarily because they are slower
than other systems. That also means that longer time cycles involving chemical additives are
subject to more discoloration or darkening of the metal parts due to chemical reactions. Lastly,
because this is a closed loop system, parts may come out dirtier or with more debris than other
processes; therefore, they may still need a secondary rinse or cleaning.
This is about as far as I want to go with the barrel system. There have been some new
developments with what are called high energy barrel systems; however, I want to cover them
under another heading called high energy systems. But, before we leave barrel systems I should
say something about a another transition machine system that is not made any more. At one
time, there was a barrel machine that not only rotated but also used a shaking or vibration
motion that could work independently of or simultaneously to the rotational motion. These
machines did not produce a good vibratory action, but they worked well in the unloading
and/or separating operation when the machine was stationary. Again, the advantages and
technology did not warrant the extra expense.
Vibratory Systems:
Unlike the barrel, the work chamber of a vibratory system does not rotate or move to any
extreme degree. Instead, the work chamber is suspended on springs under its outer edge,
flange, lip, support platform, or work chamber so that the work chamber can float freely about
in a limited way. Rather than apply energy to rotate the work chamber, the energy force is
directed to the work chamber by way of an eccentric weight attached to power drive shaft
normally located centrally under the work chamber.
The free-floating suspension system of springs and the off balance eccentric counter
weight tilts the work chamber to create a continuous circular movement. At a cross section static
point, the work chamber is lifted and dropped in short vertical movements to compensate for
the off balance eccentric weight and that creates an energy flow pattern or rhythmic movement
to the eccentric weight*6. The energy and force is transferred from the work chamber to the
contents through the solid media and parts mass to create a mechanical movement and
pressure, which performs a grinding or milling action within the work chamber.
In addition to this physical work action movement caused by the eccentric energy forces
are some other internal vibrational harmonics caused by the design of the work chamber, the
construction materials, and by the media. These other forces are relatively weak secondary
energy forces to the main energy pattern of the eccentric movement. Most of the dissimilar
harmonics are caused by the media; however, chamber design and construction materials can
also effect energy transfer. Again, energy forces travel best through a solid and excite or vibrate
the work chamber and that energizes anything within that chamber. This is energy force is more
6 NOTE: There is one mechanical energy system that uses electro-magnets to create the same material flow
as that produced by an eccentric, but this is only found on tub type machine systems.
Chapter 9 – Type 3 Equipment 142
obvious or can be better seen in how a fluidized bed system or ultrasonic system works, except
this is physical movement of solids and/or transfer of mechanical energy.
The vertical height or amplitude movement of a vibratory work chamber is normally less
than one inch above and below the stationary top or the spring line at the work chamber base,
which serves as the centerline for the movement. The movement of the work chamber is a direct
function of the eccentric weight mechanism and work mass. An eccentric weight is specifically
designed to produce a movement or force away from a central axis of the drive shaft as it turns.
This creates a certain continuous moving energy wave, point, or position that causes a positive
and opposite negative constant moving radial bump type force away from the center axis of the
drive shaft.
The physical weight and/or location of the eccentric determines the amount of amplitude
or force of this energy bump within the machine. Therefore, amplitude adjustment is normally
accomplished by the adding or subtracting of weights in relationship to the total work mass, but
it can be a matter of just moving and fixing the weights out away from the center of the rotating
shaft or at angles to opposing weights. It is possible to add too much weight or amplitude
adjustment to a machine system process. Too much weight will produce an uneven flow or no
flow of the media mass within the machine and will cause the mass to bounce in place and
possibly damage the parts being processed. Too little weight will just increase processing time,
but will also produce a generally smoother type surface profile finish.
The movement of the eccentric weight produces or generates an X force of tremendous
energy which is up to eight times the force of gravity. That force moves the media mass out
from the center of the machine to the outside vertical wall of the work chamber in a radial
pattern. The eccentric also produces a Y force that creates a vertical lift exactly where the
eccentric weight is under the work chamber and another sub-secondary force of lesser energy
directly opposite the eccentric. Actually, the eccentric energy forces produce an equal xy pattern
that moves the media up before it tumbles backward as it also moves in a confined limited way
until it reaches the outside wall.
The backward movement of the media is a result of the eccentric weight energizing the
media mass, lifting it, and then letting it settle back down in a new position. Actually, because
the media cannot move as fast as the eccentric weight, it passes its energizing vertical point and
begins to settle and to fall backward before the next energy wave moves it again in a continuous
manner. So even though the work mass appears to be and is in constant motion, the energy
forces are really short energy bursts or pulses that create a wave or movement within the work
chamber.
Chapter 9 – Type 3 Equipment 143
Fig. 60. Vibratory Systems
Fig. 61. Vibratory Energy System
All vibratory mass finishing systems operate
by creating an out of balance energy force which
creates an energy flow or pattern within an attached
work chamber. This energy is created by a motor,
with either eccentric weights attached to a vertical
drive shaft, or it turns a belt or flexible shaft that
turns another shaft with eccentric weights attached to
the work chamber.
Above pictures show the construction of a
direct drive motor system which is centrally located
in the machine with its eccentric weight attachment
assembly. Depending upon the machine and work
load, weights can be added or removed. Also shown
is the typical mechanical flow pattern created by the
eccentric weights within a vibratory bowl system.
A tub type unit has its drive shaft and
eccentric weight assembly located horizontally below
its work chamber. Most tub systems are run by belts
(not shown).
Chapter 9 – Type 3 Equipment 144
The energy force from the offset eccentric weight is a single point or line within a 360
degree circle. That means that there is more dead space than impulse; therefore the greater
media movement within the work chamber is away from the energy wave or opposite the
rotation of the eccentric weight. When the media reaches the outside wall of the machine it then
moves in the direction of least resistance, which is up and slightly in the opposite direction of
the eccentric weight movement and this causes a spiral action. The equal X Y forces produce a
circular movement to the media within the work chamber around the outside wall and down to
the center of the machine or mass. This movement also produces an even continuous circular
horizontal and vertical orbital movements flow to the media. Too fast of an RPM speed of the
motor or too heavy an eccentric weight versus the weight load ratio will cause the load to
vibrate in place and be ineffective.
The energy forces produced by a vibratory system are a lot stronger and faster and
energizes the entire work mass than a barrel system. Barrels rotate and rely on gravity to create
pressure from the movement of the media and this is only active in one third of its total mass at
a time. Therefore, vibratory systems are more efficient and more powerful, and at the same
time, the way the processing energy is applied to do the work makes the equipment safer, more
user friendly, and requires less space than a barrel machine of the same capacity. Barrel systems
are normally enclosed with a stationary safety cover because its movements are greater than one
inch and cannot be touched or handled during its operation without some possible harm to
one's hand or operator. It is possible to put one's hand on to a vibratory machine and actually
into the media and/or work mass without any major problem for safety while in operation.
As you can tell from this description of mechanical energy forces, the barrel needs a
hatch cover secured at nearly all times on the larger horizontal systems to retain the work mass
while in operation. A vibratory system usually operates without any top or security device,
because it always operates in an upright position. In fact the larger machine systems have no
means to hold the work chamber to its machine base except its weight, the weight of the
contents, and either an external or internal method to hold the springs in place. An optional
cover device can be used to quiet the machines noise when in operation and/or to hold down
dust if the machine is using dry media. The noise is actually a result of the media movement
within the machine.
Most vibratory systems use motors that operate between 950 RPM to 1800 RPM. These
can be fixed or variable speed motor systems, with the most common speed for deburring at
1400 RPM for large machines and 1725 RPM for smaller machines. Greater speeds do not seem
to produce the results of this speed range without some negative results. Like the barrel
systems, the greater RPM's usually result in part damage and/or impingement.
Higher RPM's and/or energy requirements may be desirable for heavy weight to load
ratio processing or doing what is called burnishing. Some steel burnishing machine systems
operate at 3600 RPM and this is only done because of the weight mass that retards its actual
movement. That is, steel media requires a lot of energy to get it to move and continue moving;
therefore, the RPM of this work mass is probably the same as ceramic in slower RPM machines.
Chapter 9 – Type 3 Equipment 145
Like barrel systems, slower RPM speeds are also not recommended only because it takes longer
to accomplish the same results.
As mentioned in the footnote, there is one vibratory tub type machine system that uses
electro-magnets to energize and create the vibrational energy forces. It looks and operates the
same as eccentric motor system, but it uses electro-magnets to create a physical pulse movement
to the work chamber. Because the movement is linear this system has only been used on the tub
designed equipment systems. The system also requires the use of a separate variable voltage
transformer and control panel to regulate the movements and adjust the amplitude of the
electro-magnets.
Burnishing is not a material removal system per se, but it is like the sand blasting system
in that it modifies rather than removes the burr. Any material removal is a result of metal
flexing or fatigue, but most of the burr is still there, rolled over to one side or flattened. This
process uses a non-abrasive preformed ball shaped media of steel or porcelain and does require
a lot of energy to move this weight mass and get good rotation. Because of this weight mass
element, most of these machine systems are built special to handle the extra stress, weight, and
power requirements. Because porcelain ball media is lighter, it can be used in almost all
vibratory machines to accomplish burnished parts, but it will take longer than steel because of
its weight. See the section on media for specifics.
Noise and Vibration
The noise factor can be quite significant in vibratory equipment depending upon the
media and the amount of liquid being used. That is because this type of machine normally
operates with an open top work chamber and it is so much more aggressive than barrel type
equipment; therefore, sound covers are sometimes used to cover the machine in operation.
These sound covers can be either permanently attached or lowered into place to encompass the
top of the machine or the whole machine. Another solution is usually to dedicate a separate
room to isolate the noise and/or vibration. Noise and vibration are really two separate problems.
Although sound can be annoying, vibration can be just as disturbing or worse, both to
people working around the equipment area and to other machine systems. That is, vibration can
travel a significant distance with enough force that it upsets delicate equipment and
instruments within the same building. In fact, it is recommended that large machine systems be
given their own cement slab to isolate the vibrations from other nearby equipment. In lieu of a
separate slab, cushion type isolators are also recommended, but are never as effective as bed
rock type isolation.
Vibrational energy forces must go somewhere and if a machine is not designed properly
and this energy is not transmitted to the work load and/or chamber properly, this force will
travel the shortest route possible. This often means that it will back up or down into the whole
machine stand or base. This will also mean more functional problems than normal for the
machine in a relatively short period of time. If the media does not get moved and work
properly, something else will get moved or be effected and this is normally negative reaction.
Chapter 9 – Type 3 Equipment 146
A good abrasive deburring operation produces about 80 decibels of sound vibration or
more with ceramic media. More aggressive machines operate at higher decibels, but all noise
levels can be adjusted or controlled by the use of media and liquid. Then again, noise indicates
the aggressiveness of the system. To intentionally decrease the sound level by changes in media
or liquid levels will effect time and performance also. Therefore, sound levels are a good
indication of the process operating properly. However, government rules and regulations do
require protective head or sound gear at or slightly above the 85 decibel vibration level for
anyone working in or near this type of environment.
A vibratory machine does process parts a lot faster than that of a barrel. If a barrel takes
10 hours to work a part properly, it would take a vibratory system maybe 1 hour to do the same
job. Deburring cycles of 10 to 15 minutes are common. Also, this type of machine produces
more uniform finished parts because of more equal X - Y energy forces applied through the
abrasives in direct contact with the parts. This difference in surface finish appearance is
especially noticeable if the parts have internal cavities or recesses. Surface finishes are uniform
wherever the media can reach or make contact.
There are two basic variations of vibratory machines. What I am referring to here is the
work chamber configuration, commonly called a tub or bowl. There is also a difference in the
way energy forces are applied and the types of parts that can be processed. However, as the
names implies, one is designed like a bowl, donut, or angel food cake mold; whereas, the other
is a rectangular tub shape.
Most bowls use a center cone section to separate the media during its circular rotation
and this also directs the flow of media and parts into a continuous circular channel or creates a
dual movement function. The tub is already a single channel and moves the mass
predominately in one direction. Both vibratory machine systems produce a two directional
movement to the media or an X - Y motion to the media mass while it circulates.
There are some comparable differences in the time cycles of a bowl versus a tub type
system. Given the same size machine capacity and media weight, tubs produce 20% to 30%
more energy forces that result in slightly shorter processing time cycles. The major difference
can be accounted for due to the fact that the channel depth is normally greater in a tub than a
bowl, thereby allowing greater weight and pressure on parts at the bottom of a tub than can be
gotten in a shallower bowl channel. Weight is a big factor in processing times. The more media
and parts you can get into a machine the shorter the time cycles, because the greater the mass,
the greater the weight, and the greater the pressure.
Besides cycle times, there are also some significant implications of the work chamber
shape in regards to the parts being processed. The biggest difference is usually in the size or
length of the parts capable of being processed. Tub units can process rather long parts that
tumble freely, but retain their orientation within the mix occasionally hitting or touching one
another or the tub walls. Whereas, in a bowl unit, the parts move in an equal X-Y spiral motion
and are less subject to part and/or wall contact, provided that they are smaller in size than the
bowls channel width.
Chapter 9 – Type 3 Equipment 147
Flat parts are a special problem with tub or bowl type units. Both designs have relatively
flat walls, especially at their top opening. Tubs have two short flat walls and both have smooth
curved surfaces. Flat, two dimensional, parts and flat walls do like each other a lot; therefore,
they are not a good combination for wet processing. Water can create or cause problems with
what is called surface tension between both the part, the work chamber, and water resulting in
adhesion between parallel surfaces and especially parts. Water adhesion is a situation where
water loses its memory and thinks and behaves like glue. This is a problem with flat parts, light
weight parts under a ½ inch in size, or parts with at least one large flat surface, but it is not a
concern with most other machined parts or applications.
Most large machine systems are designed so that their work chambers have serrated or
textured areas near the open tops to allow the breakup of water surface tension on parts. This
design helps the problem of surface tension between the parts and the machine wall, but it
doesn't help part on part adhesion problems. Sometimes a quick temporary fix for water or part
adhesion problems is to add a little alcohol to the process to reduce surface tension. In any case,
the bottom line is that flat designed equipment and parts do not lend themselves to good
uniform deburring in a wet mass finishing processes.
Material Handling Systems
Another major difference between a tub and bowl is the material handling system. In
fact, in most manual or semi-automatic mass finishing systems the bowl has more advantages
than a tub system and even some high energy systems because of parts handling capabilities.
That is because a bowl machine is normally designed with a dam or ramp which leads or
diverts the work mass to a raised screen deck that will separate the media back into the bowl
and allow the parts to be directed to a container outside the machine. This is the most efficient
separation system available in mass finishing, even today. However, for additional costs
automated systems will outperform even this simple design.
A bowl machine system behaves more like a continuous flow type processing machine
than a closed loop batch type system than most other mass finishing systems. That means that
the machine can continue running uninterrupted thereby allowing the machine operator to
dump a new load of parts in the same media, if they are compatible to the media being used.
That saves a lot of machine down time. In barrels, tubs, and high energy systems, finished parts
have to be dumped onto a separate screen deck and then be re-directed to a container. After
this, the media and new parts must be put back into the machines work chamber and unless this
material handling system is automated, this is a lot of indirect hand labor.
Tub Shape Vibratory Mills:
We will start with the tub type unit, because this was developed and introduced before
the bowl type machines. The tub design is actually made into the shape of an elongated letter
"U" that maybe tilted slightly at an angle and some may have one long wall slightly curved.
The tub is suspended on springs under the flange or lip at the top of the letter U. The
other distinguishing feature that identifies tub type machines is how the machines are powered
Chapter 9 – Type 3 Equipment 148
or energized to create the vibration for mass motion. Because there is no real name designation
identification to the tub shapes, I will give them my own identification, which is not part of any
equipment classification system:
Type 1A is the basic tub shaped machine. We will keep it simple and just say that this
unit is powered by a single rotational shaft attachment with an eccentric weight that is slightly
off center to the work chamber and runs length wise underneath the tub. This off center
eccentric is indirectly powered by a belt driven motor7, a flexible coupling, or a constant velocity
coupling from the motor to the shaft. Belt systems alone retard the free floating tub; therefore,
these drive systems are normally only found on smaller less expensive machines. On some
larger machines, weights can be added or subtracted to improve the amount of vibration or
amplitude of the vertical motion of the machine. This offset eccentric position produces energy
forces that bring media and parts up one side of the long tub wall and falls down to the other
side. During the process, the media movement pattern is slightly deformed or elongated and
not symmetrical as it rotates the whole mass. In this processing, there is good side motion and
part movement or tumbling. It is not exactly an equal X - Y motion, but it is close and it does a
good job.
Fig. 62. Tub Type Systems
The basic tub type mass finishing vibratory system produces
an energy wave or pattern that has a primary flow pattern as well as
a secondary pattern. Where the energy is applied to the work
chamber determines the flow characteristics of the media and parts
within. The first illustration shows the longer primary flow pattern
of the media and the smaller circular lines show the action within
the media mass. The eccentric weight moves the work chamber in a
circular pattern. Energy is transmitted to the media and parts, which
flow in a predetermined pattern, which allows the smaller, and
usually lighter media to move faster than the larger parts. This
movement causes a scrubbing or abrasive action against the surface
of the parts as they too move. The action or movement is very
uniform throughout the entire work mass.
7NOTE: One exception to this is a machine that is powered by electro-magnetics that
vibrate up to 3600 cycles per minute manufactured by a company called Vibrodyne. This unit
requires a separate control panel that includes a variable voltage transformer.
Chapter 9 – Type 3 Equipment 149
Fig. 63. Typical Tub Type Configurations
Type 1B tub looks the same as 1A, but it is a dual shaft machine with two eccentric power
drives, located or attached along the outside of the long tub walls. Naturally there is more
aggressiveness to the work mass and the results are slightly shorter time cycles. There is also a
greater capability to run heavier parts and for those parts to be lifted or moved higher in the
work mass which is better for recovery or unloading by hand or a lifting mechanisms. Some
Chapter 9 – Type 3 Equipment 150
dual shafts machines are powerful enough to run heavy steel burnishing media applications,
but steel ball burnishing is not normally done in a tub because of the weight factor and the
extreme power requirements.
Type 1C tub is an overhead cam type machine which has its eccentric weight system
attached and located to the top side of the machine. This system can also be a single or dual
shaft system. This machine is capable of working extremely large parts and does lift them up to
the top surface of the work mass. These overhead machines also seem to have slightly different
media performance against the part. The action is more of a scrubbing motion rather than a
beating action found in type 1A and 1B tubs. Generally speaking, this action results in an overall
smoother surface profile or finish to the part.
Type 1D is a Continuous In-Line Tub. These machines are another separate category or
modification of the basic tub type system. As the name implies, this machine system uses a long
tub type work chamber, but it is designed to re-circulate the media like a bowl machine. The
machine is designed in such a way that the media and parts are feed into one short side of the
machine, they travel down a slightly inclined channel, over a screen deck and come out the
other side. Parts are continuously moved in the long direction of the machine as they circulate
or processed in the short direction of the tub until they exit over a screen where the parts are
separated from the media. The media is then conveyed back to the front of the machine and is
reused and is continuously recycled, hence the name.
Because of all the mechanics involved these machines usually run from a five cu. ft. at 12"
x 72" up to a size of 125 cu. ft. or 48" x 288" or bigger. The big advantage of this type of
equipment is that parts can be feed into the machine and processed without touching each
other, they can also be integrated into a continuous production line. The disadvantage is the
machines large size and the large volume of media that is required and that means less
flexibility of using different media without significant down time for change over.
Continuous Tub Type System
Another variation of the tub type system is the continuous, in-line or linear flow through
system. This system operates like all the other tub systems except the tub is usually longer to
increase dwell time in the abrasive and it is slightly inclined to make the media and the parts
flow in a specific direction. As the mass exits the machine, it is dumped onto a screen deck that
separates parts and media. The media is conveyed back to the start of the machine in a
continuous loop. This machine system is rather large due to accessory conveyers and
separators, but parts maintain good separation and therefore it works well with automated
production lines.
Chapter 9 – Type 3 Equipment 151
Fig. 64. Continuous Tub-type System
Separation
I have mentioned how large parts can be processed and removed from all the different
work chamber tubs mentioned above; however, I did not say anything about smaller parts.
Smaller parts of less than 1/2 inch in size require a special material handling system rather than
the hand pick type method. Part separation can become very time consuming as well as cause
machine down time. Therefore material handling or unloading deserves a lot more attention
than meets the eye.
On nearly all tub type units, one of the short walls of the tub contains a door mechanism.
When the parts are properly deburred and ready to be unloaded, the operator can open a hatch
or door which empties the complete machine. The media and parts are then dumped onto a
conveyor or a secondary screen device which is normally use to separate the parts from the
Chapter 9 – Type 3 Equipment 152
media. The parts go on to their next process and the media is put back into the machine for re-
use or another media is put into the machine for processing with different parts. That means
that the machine is idle until it is re-started with the next load. All of this handling requires
additional manpower and/or labor as well as time.
Wet systems
A brief statement here about the liquid application during the mass finishing process.
This subject will be covered in detail later. All of these tubs, bowls, and high energy systems
have drains and inlets for adding chemicals and liquids. Some can be complicated devices for
monitoring the chemicals and/or contaminates. In most cases, they are simple systems. In some
machines, you have a continuous flow of liquid in and out of the work chamber and mass at
about the same flow rate. In other batch type operations, you can put a set amount of liquid in
and retain it for nearly the entire cycle, this is especially true of nearly all barrel systems.
Normally, it is suggested that if you use the batch type system in vibratory equipment, just
drain and rinse the media mass for the last 5 or 10 minutes with water. This rinse can also be
done with the barrels, but you must stop them first, drain, and re-fill them with the clean rinse
water.
In all machines, you have a main source of liquid input that may or may not be
connected to the work chamber and maybe a series of smaller exit drains at the bottom of the
work chamber that are inter connected. Normally the more amount of liquid into and out of a
machine the nicer looking or the cleaner the parts. With proper compound additives used in
processing, the parts do not require further cleaning or assistance to stop chemical reactions or
oxidation. Strong chemical solutions may be used to work parts faster; however, most
commonly used products are extremely weak or diluted so that they can be disposed of down a
drain. However, even the weakest compounds must be checked with local disposal procedures.
Some deburring wastes and/or metals require special handling. Stainless steel is made with
chromium which can go into solution and may have to be handled differently. See section of
liquids.
An adequate amount of liquid into a machine is determined by the machines size. That
is, large machines require a greater flow of liquid than do smaller machines. In most cases, you
want to see a good amount of liquid in the media mix to keep everything flowing freely. Too
much water flow will slow down the deburring action of the machine system. A good guideline
is about 5 to 10 gallons of liquid per hour in machines over 5 cubic foot capacity. You do not
want to see a lot of debris or a heavy milky solution. Also, you do not want to see liquid
splashing out of the media mix. In the later case, you may want to check your drain system to
make sure they are not clogged and retaining liquid. For that reason, a good drain system
should be able to discharge twice the amount of the maximum input. There are exceptions to
almost everything I am saying here, but until you learn the basics, it is difficult to explain these
variables.
One last thing about drains, the actual size of the holes in the drain plate covers
determines the size of the parts that you can work. That is, the larger the drain hole, the less
Chapter 9 – Type 3 Equipment 153
likely it is to get clogged and the faster the liquid drains. But, if you have a drain hole of say 3/8
inch diameter, that is about the minimum size of the part and/or media you can run in this
machine before it too goes down the drain. Lastly, there are some cases where it is desirable to
run a dry organic media mix. Normally this media is relatively small. That means that the
drains will get clogged very easy; therefore, special precautions must be taken to seal the drains
before using the machine with this dry organic materials.
Bowl Shape Vibratory Mills:
Motor systems
As tub type units are mostly distinguished by the location of their power drives, so too
can the bowls; however, the round bowl shape is the dominant feature of these systems.
Although these two designs visually appear quite different from one another, they actually
function almost identical, in that the media and mass still travels up the outside wall and down
toward the center of the machine. The bowl design has a more noticeable center section,
whereas, the tub center is within the work chamber or mass itself. The bowl shape design
feature actually creates a more linear flow to the mass that can be controlled easier than a tub
type machine system. Although we are talking about linear, which is normally considered
straight, the bowl shape is a circular channel through which the mass travels around in a
straight flow line.
Unlike the tubs, that have their power drives and eccentric weights mounted in a
horizontal position parallel along the tub bottom or walls, bowls have their drive and weights
mounted in a vertical position through the center of the machine. That means that a tub unit
accentuates the moving energy bump in a vertical plane, whereas, the bowl does the same thing
on a more horizontal plane. The tub machines are slightly more aggressive because the eccentric
moves in harmony with gravity forces and therefore intensifies the movement and forces of the
mass.
Most large bowl systems have only two options on their power drive and they have
nothing to do with the way energy is applied to the work chamber. The distinction is that the
motor system is either a dual shaft direct drive, or an indirect driven pulley and motor system.
Dual does not mean two separate shafts, but one shaft or axis that goes complete through the
center of the motor or machine. In both cases, there is usually a top and bottom shaft with
eccentric weights. In a sense, the dual shaft mechanism behaves like a gyroscope with limited
intentional vertical movement to which the work chamber center line or center of gravity is
attached.
The direct drive, dual shaft motor system has weights attached to both motor shaft ends
and is positioned or attached directly to and through the center hub of the work chamber. There
are two indirect drive systems that use a transfer system. In one, the motor drives a belt and
pulley system with upper and lower weights attached to or through the center hub to activate
the work chamber. The other indirect drive mechanisms use a constant velocity, flexible
coupling do the same thing as the belt. The flexible coupling seems to be the more common
system in use today. Both indirect drive systems make repair and replacement of motors and
drives easier than direct drive systems, because they are easier to get at.
Chapter 9 – Type 3 Equipment 154
A direct drive system uses a dual shaft motor which is rigidly attached vertically within
the machines work chamber or center hub section, making the power source and work chamber
one. That means that the assembly above the springs is extremely heavy because of the motor
weight, bowl construction, liner, and media within the work chamber. Most of these bowl
machines are designed in such a way that even without the eccentric weights in place, the
greater weight of the machine is the motor system which is centered or slightly below the
bottom level of the work chamber. This is done to offset the weight of the media mass within
the bowl.
As mentioned, the direct drive motor location also means that the motor is more difficult
to get at and repair if anything should go wrong. It even means the changing or adding of
weights for amplitude adjustments is also a little difficult. Belt and coupling systems have the
motor located to one side or attached to the chassis of the machine and that makes replacing
parts and adjustments a lot easier. On smaller equipment or the centerless hub machine there is
only a single shaft and lower eccentric weight attachment. Both machine systems operate the
same but there are more adjustments and performance factors that make the dual shaft system
more desirable and controllable.
Fig. 65. Vibratory Bowl System Direct Drive
The following semi-transparent visual of a typical direct drive vibratory bowl system and placement of motor, weights, in enclosed chassis which is accessible by a door. Top weights are accessible by removing top cover shown closed. Also shown are suspension, drain, and exit or screen deck ramp systems.
Chapter 9 – Type 3 Equipment 155
Adjustments
In the bowl design the energy forces are somewhat different than the tub. Although the
eccentric counter weight systems are attached differently and the forces are applied differently
they behave similar, in that the media moves in the opposite direction to the eccentric weights
movement. In the tub, the eccentric weight is attached directly parallel to the tub. Whereas, the
counter weight system of the bowl effects and directs the energy perpendicular to its
movement. A bowl moves or tilts down to one side in an act-reaction type energy force
movement, perpendicular to wherever the eccentric energy force is directed. This causes a
constant circular spiral motion perpendicular to the bowls level orientation.
Besides the moving or adding and subtracting of weights, there is no control or
adjustments to a tub machine to adjust the x - y flow or motion of the media within. A bowl
system has much more control over how materials are processed because there are weights on
both the top and bottom side of its eccentric shaft whose angles can be adjusted in relationship
to one another. These weights are also balanced in relationship to the mass within the work
chamber. Positioning of the eccentric weights does make a difference in the x - y movement or
way in which the media and parts behave in the machines work chamber.
In a bowl design, the bottom weight controls the vertical mechanical action of the
machine and because of that, the bottom weight always leads the top weight in the direction of
rotation. Adjusting the bottom weight controls the amplitude or vertical lift motion of the
machines media or work mass. The top weight controls the degree of the rotational loop or roll
action which is the distance or amount of horizontal travel in relationship to its vertical lift
movement. In other words adjustments can be made to control either a very tight short spiral or
a long spiral of the work mass.
Naturally, a tight spiral is desirable for what is called single pass processing and/or even
multi-pass machine systems; however, too tight a spiral can cause more part on part contact.
The tight spiral or slow feed rate adjustment concept is incorporated into some machines for the
sole purpose of only allowing a part to pass or move in one direction and exit the machine. That
means that any batch type machine system can be adjusted and utilized to make it a continuous
in line or pass through type system. Part movement in and out of a machine can be controlled or
regulated to process parts to a pre-designated time cycle determine by the weight system alone.
The closer together the top and bottom weights are to each other the tighter the spiral. The
maximum adjustment is 180 degrees apart for a long spiral. See diagram for details.
Chapter 9 – Type 3 Equipment 156
Vibratory Bowl System Eccentric Weight Control Adjustments
The amount of bowl movement or aggressiveness of a machine system over 2 cubic feet
capacity is controlled by adjustable top and bottom eccentrics weights sometimes called a
flywheel. These weights control vertical lift or height of the bowl movement. This is called
amplitude. Weights can be added or subtracted to compensate for the workload within the
bowl. The heavier the mass, the more energy is required to move it. Too much energy may
damage parts.
The relationship or position of the top and bottom weights is adjustable within 180 degrees of each
other and controls the rotation or spiral of media and parts mass. The maximum effective range of the weight
separation is approximately 150 degrees. Other than adding weights, the bottom weight position is normally
and the top one is the one that is changed because it is easier to access. Because the bottom weight cannot be
seen when adjustments are made to the top, there are normally markings to indicate the position of the bottom
weight. Adjustments of weights control the speed, travel or movement of the mass around the bowls channel
and the amount of roll or spiral and/or separation between parts. The closer together the weights, the tighter the
spiral. Because machines may differ in the direction of rotation, the bottom weight always leads the top weight.
(See diagrams)
Fig. 66. Counterweight Adjustment
Although we have talked about the power drive system of bowl machines first, a more
common way to distinguish bowl type systems is in the actual shape or fabrication of the bowl.
This shape description does distinguish them from tub type machines, but bowl machines are
also designed different from one another. When these machines were first introduced in the
Chapter 9 – Type 3 Equipment 157
early 1950's, fabrication simplicity was the rule that controlled costs and designs. Therefore,
most bowl machines were built with flat bottoms and sides, which were molded or lined with a
heavy 1 to 2 inch coating of urethane. As indicated earlier, flat walls, water, and flat, light
weight, two dimensional parts don't get along very well for uniform processing. Therefore,
eventually most bowl designs eventually evolved into the more common curved wall
machines.
Most bowl systems now use the curved wall shape, not only to keep media and parts
from adhering to the sides of the bowl, but this shape also aids in the performance of the media
mass. Because of the media flow within a bowl is directed up the outside wall and down toward
the center cone section of the bowl, a curved wall restricts and/or compresses the media mass
exerting more pressure and energies to the mass which abrades parts faster. In a normal straight
wall channel bowl design, the media loses energy and pressure as it expands in the vertical lift
of the media. If the media is restricted near the top of the bowl before it falls into the center, it
retains greater more uniform pressure transfer to the mass.
Machine Capacity
Besides shape as a determining factor for performance, it also determines the capacity of
the machine system. That goes for both tubs and bowls. In the mass finishing equipment
industry there is no uniform code to determine capacity. What seems rather clear cut to the
average non-user is not that simple for comparison purposes. This problem may be related to
the working capacity of the barrel systems. What is said to be a 5 cubic foot capacity machine
maybe the total fill volume or the proper working capacity for parts, not the size of the work
chamber.
To determine capacity size, one must take into account a number of factors. Capacity can
be given in size, weight, volume, or liquid. It can also be given as the total mass, the media or
part mass only. Another confusion is the relationship of the media to the parts ratio or
percentage. That difference means that because media and parts vary in density or weight a
machine can have several different capacities depending upon which media you want to use to
determine a standard unit of measure. Simple?
As mentioned, the terminology of working capacity can be different from machines total
capacity. This term usually refers to a machine in a condition that would be considered ideally
loaded to perform at its optimum processing cycle. In a vibratory system, this ideal work
chamber capacity is usually 2/3 to 3/4 full of both parts and media. Again, this can be a variable
condition depending upon what media and materials will be necessary to do proper deburring
and/or processing. Therefore, be careful when trying to compare. You may be mixing apples
and oranges.
One more note about size. When determining what size part that can be worked in a
bowl machine is not determined by the overall size of a bowl; rather, it is determined by the
channel width of this type machine. The maximum part size that goes into a tub should be at
least an inch or two shorter than the total length of the tub and the part will probably be in
Chapter 9 – Type 3 Equipment 158
contact with the walls of a work chamber. In a bowl machine, the part length should not exceed
the short width of the channel for good uniform finishing.
Parts in any machine system should be is smaller than the channel width so they will not
be in contact with the wall or work chamber. To exceed the width of a channel is possible;
however, that means that the part will always be in contact with either the outer or inner wall of
the bowl. That also means that the part may not get good rotation which may result in a non-
uniform finish and excess wear to the work chamber liner. Curved walls help minimize the
amount of contact with any part shape or configuration.
Besides curved walls effecting the performance of vibratory machines, there are other
shapes that have processing advantages and disadvantages. As mentioned, tub systems use
primarily the application of energy forces to distinguish design variations. The following are
some of the variations in bowl designs.
Work Chamber Bowl Channel Designs
The following illustrations show a progression of bowl configurations from early square
designs to the more common curve pattern. Fabrication is from the simple to more complex.
Curved designs increase the amount of pressure on the media and parts to work more
aggressively throughout the complete cycle or movement; whereas, the square design
encounters more resistance and uneven flow patterns. Even the curved bottom bowl loses
energy and pressure as the mass rises up the outside wall of the bowl’s channel. Normally, the
greater the restriction and movement the more aggressive the abrasion of the parts and the
shorter the time cycle.
Fig. 67. Bowl Designs
Arena Bowl Shape
Now, in addition to curved walls to get additional pressure to the media there is an
elongated bowl system called the arena bowl, also known as the race track design. This bowl
design can have curved walls, but its main source of media compression comes from its shape.
This design was one of the first machines created to compete with in line continuous tub type
Chapter 9 – Type 3 Equipment 159
machines. The longer channel length permitted greater dwell time before the parts exited the
machine in one pass.
Supposedly this machine produces the same horizontal and vertical X - Y motion as any
other vibratory system; however, just like a race track, the mass runs faster with less rotation in
the straight away in longer channel section of the bowl before the turn increases pressure
around the shorter curves. Parts have a tendency to bunch up at the short ends of the machine
and this increases pressure that can cause somewhat uneven processing and possible part
impingement or damage.
Originally, this machine was designed with one motor or direct drive located in the
center of the machine to power the whole machine. This did not provide enough movement and
action and a second eccentric drive system was used with one motor located at the opposite
end. Later, the motor was relocated to the center of the machine and drives went to both
eccentric systems at either end of the machine. In more recent years, the arena bowl has also
been modified into a two motor and eccentric system to increase the power and performance of
the machine.
Fig. 68. Vibratory Bowl Equipment Variations
Arena Bowl – A variation to the
standard bowl is an elongated work chamber
bowl that looks similar to a racetrack or arena.
On of the advantages of this design is to give
parts more separation and more travel or dwell
time before a part makes a complete trip
around the bowl. By adjusting the eccentric
weights, parts can be made to exit the machine
in one pass. Also, instead of continuous
pressure of the curved bowl design the
configuration concentrates greater pressure at
the two end areas of the bowl. When two
motors and eccentric systems are used in this
machine, the increased vibration improves the
aggressiveness of the media and material
removal process for shorter time cycles.
Chapter 9 – Type 3 Equipment 160
Spiral Bowl
As long as we are talking about bowl shapes, it might be a good idea to tell you about
two more bowl configurations. One is called a spiral bowl and is shaped like a lock washer. This
design along with the eccentric movement pushes the media mass up an inclined fixed bottom
plane until it reaches an offset portion of the bowl. Once at the top of the offset, the media drops
back down and starts all over again. At the point of the offset, a screen deck or exit screen is
attached so that parts can continue and media be returned to the bowl channel without stopping
the machine
The greatest advantage of this bowl design is the ease of parts separation and unloading.
This design is also a good one-pass continuous cycle type system, which is dedicated to parts
that enter the low end of the machine and exit at the top. The media movement and motion is
controlled by the top eccentric weight, which governs vertical movement or dwell time cycle.
On the negative side or in more common use the machine is very aggressive because the drop
off increases a more violent work action in relationship to the parts and that may cause some
minor marking or damage to some parts, which may or may not be desirable.
Fig. 69. Spiral Bowl
This is a true bowl design; however, instead of the bottom of the bowl being uniformly level, this bowl
design tapers or rises like a lock washer. Naturally at a certain point the bottom drops off and the media begins
a new travel cycle. The advantage of this design is that it is much easier to unload parts without losing any due
to being trapped anywhere. This machine can also be adjusted for a single pass cycle. Another advantage of the
drop off is to concentrate pressure on the parts and shorten processing time; however, the drop can also cause
possible damage to delicate or critical dimensions.
Chapter 9 – Type 3 Equipment 161
Centerless Bowl
Another less common bowl design is called a centerless bowl. This is a bowl that
essentially does not have a typical center cone or hub section. The center portion of this bowl is
slightly raised to some extent, but not enough to be considered a center cone. Technically
speaking, without a center hub, parts can be processed larger than channel width.
When this machine is in operation, the media flow is basically the same as a machine
with a center cone, in that there is a center gap where the eccentric energy is so intense that it
causes the media to flow back out before it can come together. A slightly raised center section
aids in a more even flow and compression of the media.
This machine design has the greatest curved walls and compression of any vibratory
machine being made today. These extremely curved walls do provide more uniform
compression and pressure on the media to work faster. On the other hand, there is no top
weight eccentric; therefore, there is no control on the vertical rotation or spiral. Adjustments are
made with the bottom eccentric weights only.
Centerless Bowl – This is one of the more unusual bowl system designs. This machine is
called a Centerless bowl; however, there is a raised lower center section, but no central core or
hub. The advantage of this design is to create a greater curvature to the bowl walls to increase
pressure on the work mass which shortens processing time. The lower center section allows for
a little easier access to the mass and it also allows for processing some longer parts than the
normal channel width, but it is not normally recommended. Other than the bowl design, the
machine works and behaves like a standard bowl system
Fig. 70. Coreless and Conventional Centerless Bowls
Chapter 9 – Type 3 Equipment 162
Continuous Flow Tube
Just as tub machines have continuous pass through systems, so too do the bowl
machines. There is one machine system called a tubular vibratory finishing system that looks
and behaves similar to a bowl machine; however, instead of a straight through or circular one
pass system, this machine looks like the coils of a water cooler or spiral spring. The machine has
a series of completely enclosed tubes in a double spiral that allows the media and parts to travel
down three circular levels and then back up to the same entry level.
This design minimizes the need for large floor space like the continuous tub system and
increases travel distance in a relatively short space. Typically, these machines range in size of 6
to 16 cubic foot capacity and require 5 to 6 ½ feet diameter of floor space. In this design, parts
are feed in the top of the machine near where they exit. Separation takes place on the top side of
the machine in an open space of 5 ½ to 7 feet in length.
Part size is limited to the diameter of the tube, which is either a 4 or 6 inch inside
diameter. Tube construction is almost one inch thick made from a reinforced molded rubber
product. Parts longer than the inside diameter of the tube can be processed; however, that
means that the parts will be rubbing against the tube I.D and therefore can possibly get stuck.
The tube design exerts excellent compression or working pressure on the parts provided the
correct working level of media is maintained. Media level is critical to proper functioning of this
machine system. If the is not maintained and filled to the proper working capacity, the media
and parts will not complete its closed loop flow.
Continuous Bowl Type Systems
Just as the vibratory tub type machine systems have their continuous in-line flow
through system, so too do bowls. As mentioned a couple of times, eccentric weights can be
adjusted in such a way to increase dwell time or the time it takes a part to make one complete
revolution of the bowls channel. Long cycle times are possible in almost all bowl systems
and average around 15 to 20 minutes. Unlike the tub that requires a large space for conveyors,
bowls take up less space for in-line production systems. That means that machines can also
be arranged empty into another machine with different media or longer time cycles
Chapter 9 – Type 3 Equipment 163
Fig. 71. Tubular Vibratory Finishing System
This machine looks something like a vibratory bowl system, but instead of an open
processing channel, this machine uses interconnecting spiral tubes to form an extra long
continuous work chamber. There is one short area at the top of this machine where media
and parts can be seen and/or loaded and unloaded. This design is probably the ultimate
design for media compression. Besides the above features, this machine system looks and
behaves like a normal vibratory bowl.
Chapter 9 – Type 3 Equipment 164
Multi Pass
In recent years, a number of manufacturers have developed another continuous flow
through bowl system called a multi pass bowl type machine. This machine looks more like the
standard bowl systems than the tube type machine. Also, unlike the tube system design, the
multi pass systems are all top load media and travel systems. Instead of one large channel, these
machines can have a number of smaller channels or a smaller continuous spiral type channel in
the space of one big over all work chamber.
Basically, the multi pass is a regular normal bowl machine with a least one continuous
spiral channel or two side by side segregated channels. This design allows for the use of more
than one media or where parts can travel in one continuous flow through these two media
processes. Normally the channel width and depth are a lot less than the standard bowl design
and processing takes longer because these machines don't get as much pressure on the mass;
therefore, they are better adapted for running small sized parts.
The advantage of this machine system is that if there is more than one channel, more than
one media can be used for processing the same part. The channels can be configured in such a
way that the part(s) can move back and forth from one channel to another by themselves. That
also means that a two or three step process might be performed on one type of part in one
processing machine cycle. As mentioned earlier, separation and processing time can be achieved
or adjusted to suite the process by re-arranging the eccentric weights to permit longer time
cycles or dwell time of the parts in the media.
Chapter 9 – Type 3 Equipment 165
Multi-Pass Continuous System
This is another variation of a vibratory bowl type system. Again, this machine looks and
behaves the same as a normal vibratory bowl. The only difference is that this bowl is designed
to have a single continuous spiraling channel, but gives the appearance of a number of smaller
width channels, side by side. Actually, the machine can be designed to have more than one
separate channel with inter connecting ramps so that more than one media can be used to
process a part before it exits the machine. The main advantage of this system is increased part
separation and a dwell time of up to 30 minutes or the optional second step media operation for
a finer surface finish. On the negative side, part size is normally smaller due to the reduced
channel width.
Fig. 72. Multi-Pass Configurations
Chapter 9 – Type 3 Equipment 166
Compartment Processing
Not related to the bowl shape is another interesting design patented by a company to
keep parts separated from one another is a free floating separation device that looks similar to
an old fashioned Merry-Go-Round. This device fits into the bowl of their machine system to
separate individual parts and is used to minimize part impingement or damage. This device
uses a single one piece unit fixture that has a series of rotating mobile compartments that are
attached to the center of the machine like a spooked wheel.
A single part is designated per compartment and allowed to circulate within the closed
work channel and the limits of the fixture spacing. The compartments allow for the circulation
of the part and the media, which is confined to or within that compartment while it in turn
circles the channel width of the machine. This device keeps parts separated so that there is no
part on part contact and at the same time provides enough space for a uniform finish to the part.
The fixture or compartment sizes are usually made to order and are not normally adjustable to
accommodate different sized parts. These compartment systems are usually dedicated to
specific parts and/or product lines.
Vibratory Bowl
Fig. 73. Part Separation Partition System
figure 55
The biggest problem of all mass finishing
systems is the problem of unwanted marks or
damage due to part on part contact. This is more
noticeable on heavier or larger parts than our
category B size. The ideal processing method is to
run parts through a continuous in-line system
with sufficient space between parts to enter and
exit. If a continuous system cannot maintain
enough part separation then one can use a fixed
partition to insure individual part separation and
integrity. In a tub type machine system, inserting
and fixing the position of the partitions is
relatively easy because of the common rectangular
shape. However, every partition system still needs
to allow media to flow or travel from one partition
to another. Without this interaction the energy
forces and weight mass involved will destroy the
partitions. One of the more popular batch type
bowl separation systems is the floating merry-go-
round. This system looks like a spoked wheel
which is inserted into the channel width and it is
allowed to travel and move with the work mass.
Chapter 9 – Type 3 Equipment 167
Part Impingement
I keep talking about part contact or part impingement, but I have never spoken in length
about it. Basically, impingement is a condition where one part contacts another and in so doing
results in some form of marking or damage to both parts. This condition can be caused when
the process or eccentric weights are not adjusted correctly or there are too many parts to the
volume of media and/or where amplitude is too great. The word impingement is used primarily
to describe a condition of marks on polished parts or where aesthetics are concerned.
Sometimes impingement or part on part contact is a desired process where parts alone
are used to deburr each other without the use of media. This latter processing method, the word
impingement isn't even used to describe the process; rather it is referred to as part on part
processing. This processing method is used a lot on flat small parts and/or where media
separation or lodging is a problem. The results are often parts with a bright finish, no burrs, and
no extensive labor for separation, but these parts may still have marks on them.
In most cases, impingement is not desirable condition. Normally parts are processed in a
ratio or percentage of parts to media. These figures can vary, but the normal percentage for
deburring can be 50:50 to 60:40, media to parts. For polishing, it can be anywhere from 70:30 to
90:10, media to parts. Why this is important is because of the nature of the efficiency of the
abrasive process and part impingement. That is, at a percentage of more parts to media than
described, part impingement is likely to occur. This condition can cause damage and/or is not
aesthetically pleasing.
Unloading
Probably one of the most import features of mass finishing parts in a bowl system is the
unload mechanism. This device is extremely simple and yet quite unique to vibratory bowl
systems only. Bowl systems are the only machines that are capable of unloading themselves
without secondary pieces of equipment or expensive automated material handling systems.
That also means that the machine does not have to be shut down and the media reloaded as
long as the next batch of parts are the same or does not require a different size or type of media.
That is because the media always stays in the machine even when parts are taken out of the
machine.
To do this type of unloading, there are three different design variations that work or aid
in the process for internal parts separation as well as the old standby complete dump via the
door hatch mechanism. There is the interrupt-dam, the inclined-ramp and the reverse dam.
They all require the use of a raise screen deck above the media and are normally fixed within
the work chamber channel. For this system to work properly, the parts must be bigger than the
media so that the media can pass through the screen deck holes back down to the work chamber
channel. The longer the deck the more thorough the separation of the media from the parts.
Generally speaking the deck only encompasses less than 1/3 rd the diameter of the bowl
or channel and can extend out another foot or two beyond the bowl so that a container can be
positioned underneath. The gap between the media and the upper screen deck can be anywhere
Chapter 9 – Type 3 Equipment 168
from 4 inches to 12 inches or more. If parts are extremely large, they can stick out of the media
during rotation and can interfere with the screen deck and vice versa. That means that they can
become stuck on the underside of the deck and if not caught in time, they may damage to part,
deck, or both.
Some screen decks and dams are designed as separate inserts that fit into special mating
parts or locking devices built into the machine. Also, there are some bowl designs which have a
bump or raised bowl section on the bottom of their channel to meet a dam half way. This design
helps smooth the incline up the ramp to improve media flow, but it also reinforces the rigid seal
of the dam. The greater the perpendicular angle of the dam, the less efficient it is to properly
circulate the total mass. Dam type separation systems work very well and efficient, but because
of the interrupted flow of the mass they still may not achieve 100% parts separation; therefore,
be aware of part stragglers.
Dam Operations
When a dam is activated and properly in place, it stops the flow of the work mass
causing it to take the path of least resistance. Dams are designed to stop the flow of media and
parts around the work channel and divert the flow up to the raised screen deck until it reaches
and travels over it. In all cases, the dam must close and seal the channel and direct the media up
to and over the screen deck. The dams can be made straight up and down vertical, flat or
horizontal, or most are made to interrupt media at an angle. When not in use, most dams are
located slightly in front and hinged to the screen deck in the same horizontal position; however,
they can also be separate from the deck or be located on the bottom of the bowl and raised up.
A lot of dams are set in place manually by a big leverage type handle located on the
outside of the bowl connects the dam and the lever directly opposite the dam through the work
chamber. Manual dams cannot be set in place to work when the machine is not running,
because it is impossible to physically seal off the channel properly through a stationary solid.
Even when the machine is running, the manual dam can only be started or inserted just so far,
then the force of the work mass will complete the activation or seal. Again, manual insertion of
the dam is sometimes difficult and may take a lot of physical muscle; therefore, a growing
number of machines are being automated to do everything hydraulically. Without a complete
channel seal, you cannot get proper separation.
Dams can be manually activated or automatically powered. On some machines the work
flow rotation can be stopped and the motor and media flow reversed. This stopping and
reversing the rotation can actuate the dam, which makes it easier to insert or automate the
unloading sequence. The interrupt dam works best on flat bottom machine systems. The reverse
dam works exactly the same way as the interrupt dam except the machine comes to a complete
stop first and then the motor and media is reversed, after a time delay. The dam is inserted into
the work mass and the movement of the media completes the sealing of channel and diverts the
mass onto the screen just as the interrupt dam system.
Chapter 9 – Type 3 Equipment 169
Fig. 74. Vibratory Bowl Internal Screen and Dam Systems
The same screen systems that are used on barrel tumbling systems can normally be used for part
separation on vibratory systems provided they have an exit door that is reasonable located or matches the screen
height. However, in addition to the exit door, most vibratory bowl systems have a screen separation system
built into each machine and that does not require the emptying of the entire contents of the machine. Although
these separation systems are built in, they do not have to be used until the processing is complete. To
accomplish unloading and separation, a dam or lever can be activated to close the processing channel and
redirect the mass over a screen deck and exit parts to outside the bowl.
There are a number dam and screen designs that are used. The system below shows a basic dam that is
inserted when needed. Note: to active a dam, the machine should be running, because of the density of the
work mass, it is not possible to properly place the dam and close the channel. When the dam is placed to block
the channel, the media builds up or is directed up a ramp to the deck. That means that the dam interferes with
the flow pattern of the work mass and creates an uneven weight distribution which can interfere with all the
mass exiting over the screen deck. The problem of part accountability is almost non-existent with the spiral
bowl design (bottom) because the dam and screen are nearly the same or it is a continuation of the bottom
channel profile and that does not interfere with the basic flow pattern of the work mass.
The inclined ramp is only found on spiral bowl
systems where the channels are all slightly inclined like a lock washer and is described above. Because of
this inclined design, this dam is more like a bridge or an extended bottom channel which serves as a
screen deck that exits the machine. This system requires a lot less energy to move the media mass and is
the best system for achieving almost total separation of the media from the parts. That is because there is
no interruption of the materials part flow and everything must pass over or through this dam
unrestricted. All the other dam systems may trap parts and/or not result in 100% separation because of
blockage and mass flow. Even with this screen system there is still a possibility media can fall into the
parts container if there is a large number of parts with media resting on top of them.
Chapter 9 – Type 3 Equipment 170
Lastly, there are still a number of machines in use that do not have any kind of internal
parts separation systems. The lack of a separation systems on these machines may be due to the
size and/or configuration of the parts that need to be worked or just a cost factor. To unload all
of these machines, there is still the old reliable stand by door or hatch that purges the whole
contents of the machine. All big machines with or without dams have a door to quickly
changing the media in a machine before refilling and starting the next batch of parts. This is the
same way a big barrel machine is used. The dumping of a machine's contents onto a secondary
transfer device or screen is a fast method of unloading and separation. A word of caution. If
these big doors are used too often, there is a tendency for wear and tear and the watertight seal
may eventually leak and become a problem due to constant use.
Let me take a quick minute here to go over another area related to separation. Just in case
you are unaware of the differences and the need for different screen sizes and holes, I thought I
would cover this subject a little. As stated, in mass finishing systems you normally want a
screen that has holes smaller than the part, but large enough to allow the media to fall through.
When the media is nearly the same size as the part, round perforated holes are preferred over
square or diagonal wire mesh because it controls the exact dimensional limit of the part being
separated out of the media. Sometimes a long or elongated slot is also desirable for long parts,
but wire mesh has or accepts a lot of part and media variation.
Screens are used to let media pass and parts to stay on top of a screen separation system.
Normally parts cannot have a smaller dimension than that of a round hole unless it has a shape
to it or is extremely long. Sometimes the physical limitations of screen sizes can be fooled and
the parts captured by the way in which the media and mass enters the screen. Most undersized
parts will fall through a round hole; however, there are a good percentage of parts that can be
recovered provided they are at least twice as long as they are wide. Long thin parts are best
separated through long slots.
When parts are smaller than the media, it may be necessary to do what is called reverse
separation. That is a condition where the media stays on top of the screen and the parts fall
through. Movement of the separation screen is necessary to direct the media to a separate
container. During this screen separation, or machine processing, or unloading of the machine
the media may get broken or chipped. That means that there is still a possibility of media chips
still getting into the parts. If this happens, the ceramic or plastic chips can be blown away with
air pressure. This type of separation process is usually done away from the machine discharge,
because time and attention needed to this operation.
The key for getting excellent separation under normal working conditions is to have the
largest amount of open area to the solid portion of the screen or frame material. That usually
means that wire mesh should be the preferred screen; however, as mentioned, it is sometimes
difficult to determine odd shaped parts or media through square holes. The relationship of the
hole size to part size is important as well as the moving of the mass over the screen separation
system.
Chapter 9 – Type 3 Equipment 171
Most of the screens that come with standard bowl machine designs have a hole opening
size of 1 to 1 1/2 inches. Naturally, that means that the parts being separated should be larger
than the size of the hole openings. Additional screens or other screen hole sizes can be
purchased for smaller size parts to fit the deck. However, most screen systems lose their
efficiency below 1 inch in size. That is mostly due to the heavy thickness and construction of the
deck system itself. That basically means that the ratio to open area is less than 50%, which is not
good for part separation. On top of all of this is always the problem of storage, maintenance, the
changing, and the wear and tear on fasteners.
Lastly, smaller ferrous parts may be more easily separated from the media by use of
magnets than screens. Manual magnets can be used to separate large parts from a machine
while the mass is in motion. Other magnetic systems can be adapted to remove parts from the
media when place above the existing screen system. The more automated systems look
something like a chain conveyor and are not normally built into machines but are accessory
systems that attach to or are in close proximity to the existing separation system.
Small Bowl Systems
Perhaps a brief note should be added here about small vibratory deburring machines.
These machines are usually one cubic foot or smaller and are becoming very popular for a
number of reasons. The cost of this equipment is relatively inexpensive because a lot of the
materials are plastic, but they perform almost as well as their big brothers. The major design
difference, besides a one piece bowl construction, is that they do not normally have an
adjustable counter weight eccentric system on both the top and bottom side of the motor. This is
done for fabrication simplicity and costs, but it works and functions nearly the same as the large
machine systems.
Some of these machines are built so cheaply that they do not hold up to long term
industrial use. Make sure you check machine specifications, especially the motor, and warranty
to compare systems. Normally you do not want a machine system with a motor smaller than 1/4
horsepower, and if they do not advise you of the horsepower, you know these machines are not
meant to last. Machines below 1/10 horsepower are for infrequent or light duty hobbyist use. On
the positive side, because of this inexpensive construction, these machines do not normally need
any maintenance or lubrication, as do the larger systems.
The biggest advantage of these smaller machines, besides costs, is the ability to do batch
work on parts smaller than one inch and are extremely good on parts under a half inch in size.
To unload most of these machines and/or their contents the machine must be manually dumped
onto a secondary screen type device. However, there is one finishing system that can separate
parts from the media in less than 30 seconds without dumping the entire contents of the
machine onto a secondary piece of equipment or screen. This patented device is called an
"Inseparator" and it can separate parts down to .030 in size, provided one uses the appropriate
media.
Most of these small machine systems are easily convertible from wet to dry media
operations very quickly. Lastly, these machines seem to polish parts almost as well as hand
Chapter 9 – Type 3 Equipment 172
buffing. The only major difference is their limited capacity; therefore, they are very popular
with small parts manufacturers and jewelers.
Fig. 75. Small Internal Parts Separation System
Most small vibratory deburring systems usually use a cheap and dirty separation screen on top
of a 5-gallon bucket to separate parts from media. There is only one internal separation system and
that is considered semi automatic. It is a frame and interchangeable screen system called an
“Inseparator” that operates like a basket. It is a very fast manual put and take-out system that claims
100% part separation in less than one minute. Because of the size limitations of this equipment, this is
especially good on small parts under category B or 2 inches in size down to .030 minimum.
Chapter 9 – Type 3 Equipment 173
High Energy Centrifugal Systems:
This type of equipment is considered the third generation of mass finishing machines. As
vibratory systems were a significant improvement over barrel type machines, so too are high
energy, centrifugal systems over vibratory. If it takes a barrel system 10 hours to properly work
parts, it might take a vibratory unit 1 hour to do the same job, and a centrifugal system 6
minutes. That’s fast!
Surprisingly the motor speed or RPM’s on these machines are actually slower than that
of most vibratory equipment, yet we call these high energy systems. That is because, even
though high energy motors operate at slower speeds, they use a different principle of applying
energy forces than vibratory machines. That is, instead of indirectly applying energy forces by
an eccentric, that lifts and drops or bumps and grinds, high energy systems apply a constant
force directly to the whole media mass at once. Vibratory is just that, it vibrates, oscillates, or
pulses by moving the mass in short movements and uses gravity to help it create a flow pattern.
High energy systems apply a direct, constant, circular energy force of great pressure to the
media, therefore, it operates faster than vibratory systems.
High-energy systems move the media mass in a constant sliding type motion and this
creates uniform pressure greater than gravity itself within the work chamber. That is, because of
the speed of rotation, an artificial gravity of its own is created greater than natural gravitational
forces. Rather than the short impulse movements that are found in vibratory equipment, high-
energy centrifugal forces move the mass and maintains a uniform pressure greater than gravity.
You might want to compare the appearance and function of this system in action to that of an
amusement park Ferris wheel ride on its side, or better yet, the ride where the bottom drops
away after it reaches a high speed of rotation.
Upon analyzing this high-energy equipment, the movement relates closer to that of an
abrasive belt or wheel system than it does how vibratory equipment works. Yet, like the
vibratory, the flow within the work chamber is similar to the toroidal action of that equipment.
What is different about high energy systems is the movement of the media or height it attains as
it is lifted by the velocity of the rotation before gravity over comes the vertical height and
pressure. Again, while this motion and action is similar to vibratory, the force is more constant,
uniform, and greater.
Like the mass finishing systems previously mentioned, there are variations to the
centrifugal systems as well. There are basically two types of high energy systems in use today.
These are the barrel and the disc finishing systems. The barrel systems look something like the
original barrel type machines of old; however, there are some noticeable differences. Whereas,
the disc finishing systems look like a big food blending machine without the stirring devices in
the bottom.
Chapter 9 – Type 3 Equipment 174
High Energy Barrel Systems:
Like the old barrel systems, these machines can be rather large and are completely
enclosed for safety reasons. The machine will not operate without the safety cover being closed
and this cover seals off all access to the moving barrels inside. Because this system uses counter
rotating barrels, there are a number of high-energy forces and stress factors that requires a well
engineered machine with proper safety precautions. This is not a machine that can be taken
lightly.
As previously mentioned, instead of one large barrel rotating very slowly, the centrifugal
systems consist of a number of smaller barrels which are designed to spin in the opposite
direction of the main rotational force. That is, the carriage frame that contains the barrels rotates
in one direction up to 250 RPM and the barrels are also powered to rotate in the opposite
direction up to 60 RPM. The speed of the counter rotating barrels can be anywhere from a 1:1
ratio to a slower 4:1 ratio of turns of the barrel to one revolution of the carriage.
Naturally, the more turns of the barrel the more G forces, gravitational forces, applied to
the work mass within. These counter rotating movements can produce up to 30 times the force
of gravity to the barrels contents. This system creates the greatest pressure of all mass finishing
systems and makes this the fastest deburring equipment available. Unlike vibratory equipment
that have equal X-Y forces and works with gravity, centrifugal systems have X-Y-Z forces. The
dominate Z force is gravity and pressure.
The first machines to use the high energy centrifugal forces came out in the 1950”s and
saw limited use because they were very big and tall machines that required a lot of space.
Besides big in height they had relatively small barrels and little working capacity. Also, because
this energy principle was new, these early machines experienced problems due to the high-
energy forces and material failures.
Chapter 9 – Type 3 Equipment 175
Fig. 76. High-Energy Mass Finishing - Centrifugal Barrel Systems
Most centrifugal machines are equipped with 4 barrels spaced evenly on a heavy-duty spinning turret.
Position or the direction of spin can be horizontal or vertical and it can spin like a paddle wheel, boat, a roulette
gambling wheel, or a windmill. As the turret is rotated in one direction, the barrels rotate in the opposite
direction affecting a 1:1 ratio. When turret speed exceeds60 RPM, the barrel is subject to high compressive
forces of up to 30 times the force of gravity. This speed causes the work mass to slide to the furthest inside wall
of the barrel. The energy and pressures created in this process produces extremely fast material removal or
surface modification
far exceeding
either normal
barrel or vibratory
systems.
Today, the barrel systems seem to vary in the design of the securing devices and/or
arrangement and size, shape, and access covers of the barrels. Most systems use an equal
number of balanced barrels, the most common number being four, but it is not necessary to run
all the barrels at one time or even put or keep them in the machine. These barrels are normally
mounted horizontal or length wise, parallel to the floor, but smaller versions can be mounted
vertically on a rotating disc. The newer horizontal barrel systems seem to favor a slightly tilted
barrel system where the barrels are mounted on a diagonal line inclined toward the main
central axis. This latter configuration supposedly helps create a figure 8 type flow inside the
sealed barrels which results in a better flow pattern, more travel, and/or a supposedly better
finish and shorter time cycles.
Chapter 9 – Type 3 Equipment 176
Fig. 77. Barrel Finishing Systems
Most barrel finishing systems look and behave similar
to the older barrel methods of years ago, except for speed.
However, internally within the barrel, the work action is
completely different because of the high gravitational forces at
work; therefore, construction requires more precision and
balancing for safety and performance. With some slight
changes in the shape and alignment of the barrels within the
machine, different workflow patterns can be achieved. As
mentioned, 1,2, or 3 barrels can be used in these systems. There
are also smaller 2-barrel systems that require a lot less space
because they spin on a flat vertical wheel or plane. Barrel
shapes and size vary a great deal, but because of the aggressive
nature of these systems most work chamber barrels utilize a
replacement liner concept.
Chapter 9 – Type 3 Equipment 177
Besides the technologies used for the counter rotation and securing of the barrels in this
equipment, the basic function of the machinery is the same as a standard barrel system. That
means that material handling or the loading and unloading are exactly the same as previously
mentioned; therefore, extra barrels are recommended for faster more efficient use of these
systems. Also, because of the higher energy forces and heat generated by these systems
chemical reactions are more common and that creates pressure in the barrels that must be
relieved prior to the opening of the door or hatch on the barrel.
High Energy Disc Systems:
These machines are relatively simple and that makes them easy to operate. The most
complicated part of this machine is the precision dimensions required in manufacturing and
fitting the bottom disc to the work chamber. Like a vibratory machine, these machines all sit
upright in operation, but like the cement mixer type barrel system, they can be dumped. The
smaller machines can be operated without a safety cover and needs no special precautions.
Most of the smaller machines, less than 8 cubic foot capacity, can be dumped by hand. The
larger automated systems normally are fully enclosed for safety and because of the material
handling design and conveyor systems.
The work chamber design on this machine system is very simple, with either straight or
slightly curved walls which always stay stationary. There is no true center cone section to this
work chamber like the vibratory machines; therefore, there is no channel width to restrict the
size of the part entering the bowls shape. But, because of the media flow, parts should not
exceed half the bowls diameter in order to get uniform finishing.
The only moving part on this machine is a conical dome shaped bottom disc of the work
chamber, from which the machine derives its name. This bottom disc turns at speeds of 80 to
300 RPM which equates to a peripheral velocity of 800 to 1200 surface feet per minute. This is
nearly the same speed at which a buffing wheel operates. The action or motion within the work
chamber of the disc machine is similar to that of a vibratory machine, except the media travels
in the same direction as the rotation of the bottom disc. Therefore, this system can be considered
a direct drive action type machine system rather than the indirect drive reaction type vibratory
machine systems. Also, we are talking about higher speeds of media rotation that increase the
weight and/or pressure of the media work mass to accomplish more material removal in a
shorter period of time. This machine system is approximately 10 times faster than most
vibratory equipment, but not quite as aggressive as the high energy barrel systems.
Chapter 9 – Type 3 Equipment 178
Fig. 78. High Energy Mass Finishing Systems Centrifugal Disc Systems
How It Works
Most centrifugal disc finishing machines look similar to conventional bowl systems. However, instead of
the bowl moving by an eccentric weight, the bottom of this machine looks like a dish or disc, hence its name, which
spins and the outside walls stay stationary. The is no large or raised center cone to this machine. Although the
RPM’s of this machine are less than vibratory equipment, the spinning disc subjects the media and work mass to
greater energy and compressive forces of up to 25 times the force of gravity at a low noise level. This machine
works fast, but not as fast as the centrifugal barrel system. One advantage over the barrel system is the size and
capacity of the work chamber can handle more and larger parts than the barrel. The illustration shows the mass
and flow pattern within the work chamber.
A typical disc finishing machine system can normally be manually tilted and its contents dumped out
(at left, below). A fully automated system (below, right) has material handling capabilities: (1) container
movement, media and parts loading plus liquid input systems. (2) is the bowl type work chamber in both its
normal working condition and (3) its dump mode. (4) shows the screen separation system and (5) the rinsing
system.
Chapter 9 – Type 3 Equipment 179
There is one more interesting feature to the disc machine which should be talked about
and that is precision gap of the bowl and spinner (disc). Abrasives and precision is not
commonly talked about in this industry, but relatively speaking, these machines are built with a
high quality control standards and have a gap of .020 in width between the rotating disc and
the fixed outer bowl. This tightly controlled gap is still subject to particles lodging and that can
affect the wear of these mating parts. This can be a major problem with any small parts or
media, but can happen with any size due to the nature of the material removal process itself.
Input/ Output
Without sufficient water flow to cool and lubricate the gap, this machine can seize up
very easily, because deburring generates friction and heat. Unless that heat is dissipated,
materials will expand to absorb that heat. Dry processing can also present special problems of
heat and particle size; therefore, it is not normally recommended for dry organic processing, but
there are variations of this equipment specifically designed to run dry media. Care and
maintenance of this inherent problem determines the life and/or replacement of these disc parts.
Because of this gap problem on all disc systems, there are a number of approaches to
compensate for this potential condition. The most interesting is the liquid input and drain
system for wet processes. Most disc machines add liquid from the top and drain out the bottom
through the gap. Some companies use this bottom gap to add water and compound up through
this gap to the media mass while in operation. The idea is to reverse the liquid flow pattern to
remove debris from this critical dimension area.
The bottom input systems can use a side drain above the gap plus it uses a center drain
which exits down through the center drive shaft. The size and location of these drains
determines the amount of liquid that can be used in this equipment. All liquid systems that
carry away debris have inherent problems that can cause blockage; therefore, there does not
seem to be any real clear advantage to either liquid drain type system.
Chapter 9 – Type 3 Equipment 180
Fig. 79. Disc Gap and Drain System
There are two basic gap and drain systems in use with disc finishing systems. Type A is the more common
method of circulation, where liquid and compound enter into the top portion the machine and drains through the
gap between the disc and the stationary wall, to the exit drain under the spinning disc. The number 1 shows the
flow of the work mass and 2 the flow of the liquid. In type B systems, the liquid enters the work chamber through
the gap from below, which is the reverse of type A and exits via the hollow center shaft. This method B supposedly
balances the disc hydraulically and allows for generally smaller gap dimensions under .020 with this up flow
design and this also reduces seal failures. The flow pattern shows entry and movement of the liquid within the
mass only. Both systems may also use an extra drain positioned near the bottom of the outside wall. In either case,
the gap is subject to lodging by particles smaller than gap because of pressures exerted by the high gravitational
energy forces at work.
For dry organic processing in disc machines, the input system is basically the same,
except air can be introduce or blown through the gap. This seems to work fairly well; however,
better provisions must be made to cover the top and purge the air and collect the air born dust
particles. Most machines are not interchangeable to run wet and dry systems. That is because
liquid drain holes are too small and therefore are not easily adaptable to be able to handle the
proper flow of air in a dry system. Basically, what you are talking about is a special modified
design that reverses normal drain systems and increases the flow to accomplish dry processing
with the minimum of problems.
Comparison of Disc vs. Barrel
There is little over all processing time difference between the high energy barrel systems
and the disc systems from part input to separation. Perhaps the main difference between these
machines is the material handling and/or the work load capacities. The centrifugal barrel works
faster, but material handling time makes it slower than the total time and labor of a disc
machine. The larger barrel system may require special handling and the positioning of the
barrels for both loading and unloading, plus the labor needed to take off the hatch cover, dump,
and separation nearly equals the amount of time required by the disc machine to do the same
amount of work. To get around this down time problem, extra barrels can be purchase to load
and unload while the machine is still in operation.
Chapter 9 – Type 3 Equipment 181
As to capacity, the disc machine normally can handle a lot more volume and larger parts
than the barrel system. The barrel on the other hand seems to work faster and achieves better
results using dry organic polishing media and can work smaller parts than the disc. Therefore,
you make the call. Again, there are tradeoffs. A fully automated disc finishing machine system
can easily be more cost effective and efficient provided there is enough part volume to justify
the cost of the automation. Then again, such a machine is a lot more costly as are all the
centrifugal machines versus the vibratory equipment. They basically all do the same thing, it’s
just a matter of time and money. The question is, what do you want to do? What volume? In
what time frame? And how much can you afford or are willing to pay?
Other Mass Finishing Systems:
This section is really an extension of the mass finishing equipment, but these systems are
variations that are distinct enough to warrant their own categories. In other words, these
machine systems are not as popular as those above, but there are advantages enough to mention
their differences and/or their advantages or disadvantages. The major link or similarity is that
they can all use the same abrasive media that is used in mass finishing equipment.
Spindle and Drag Finish Machines:
These are two different related technology machine systems and are somewhere in
between a disc machine and a vertical high energy barrel system. These machines usually fall
under the terminology of mass finishing equipment; however, the machine can only handle one
part or a group of parts per fixture or spindle. These machines are all classified as type 3
equipment systems and can handle up to class 5 burrs very effectively, but only on 1, outside
locations. So, like the vibratory and high energy systems, these are also 300 to 341 systems.
This is not a free tumbling parts system that is used in mass finishing. The parts are
rigidly attached or allowed to move within a confined space of only the fixture or how it is
attached to the fixture. The number parts or group of parts able to processed at one time is
limited to the number of spindles a machine has. The only similarity to mass finishing
equipment systems is the abrasive media that is used in processing and to some extent the way
that media is used. However, the resistance and pressure caused by fixtured parts speeds up
processing or finishing time a great deal and can be somewhat selective in where the greater
material removal takes place.
Every part has to be loaded and maybe unloaded manually to or from a fixture. There are
not too many universal fixtures that can handle all part sizes and configurations; therefore, a lot
of the processing depends on the design of the fixture and part. Once a fixture is designed, there
is the need to reasonably balance the weight and position of the part or parts onto the fixtures so
they are as nearly balanced as possible so they get properly finished.
Because of a lot of direct labor time is involved, most of these machines have extra
spindles for loading and unloading during processing. The fixturing of the parts or spindles
takes about the same amount of time as the loading and unloading of high energy barrel
Chapter 9 – Type 3 Equipment 182
systems, the only difference is the number of parts that can be processed. Although this is a time
consuming problem for material handling, processing time is relatively short.
Most of the bigger machines look something like a standard vibratory machine. The
system contains a work chamber that sits vertically like a vibratory or disc machine, but they
have armatures called spindles that hang down from an independent separate mechanized rack
type device, or it can have motorized attachments that fastens to the outside of the machine. The
spindles are hand loaded and/or unloaded with parts and the fixture is placed into the tub or
barrel only when the media is in motion. Instead of parts being placed inside a machine and
allowed to be process freely, parts are fixed onto vertical spindles and these spindles are then
placed into a normally wet media mass.
There are at least two main differences in the drag finishing systems. Most systems rotate
the work chamber while others rotate the parts. In very early systems, vibratory equipment was
used and parts immersed into the work flow. Then, specific versions of this equipment were
designed so the tub or bowl rotated and the spindles with parts stay stationary. In either system,
the violent movement of the stationary spindles and parts caused media to fly out of the work
chamber upon impact with the fixtured spindles and parts. Because of the great resistance of the
media around the parts as well as up the walls of the work chamber, most of these older
machines had high protective barriers around the bowl or machine.
These early drag machines produced a disruptive media flow and that resulted in an
uneven effect or material finish on the parts. To compensate for this effect, some stationary
spindles were manually reversed, or the parts were rotated on the spindle. Other drag systems
that use a stationary work chamber, reverse the part rotation of the parts for an equal amount of
time in the opposite direction to get more uniform surface finishing. Because of this reversing
and manual attention problem, the fixtured spindle systems began to get motorized and
automatically rotated the parts in the work chamber
Rotating or spinning the parts allowed these machine systems to use slower work
chamber rotation speeds and/or media movement. By rotating the part more energy is
transmitted to the part instead of the media. Eventually, this processing became known as spin
finishing. Drag finishing is exactly the same process; however, instead of the parts spinning in
place, they are drag through the media.
Newer spin finishing machine systems look and operate differently from the older
systems. Most of the spin finishing machines have their motor located on the top of the machine
and the spindles and fixtures are designed to come down from the top into the work chamber.
Then, either the work media is raised up to the parts or the parts are lowered into the media.
Some spindles can rotate the parts in place within a moving barrel, rotate the part on the spindle
only, or some machine systems actually drag and spin the parts through stationary or moving
media one way and then reverse the spinning.
There seems to be a number of new variations of this equipment. Some early machines
perform or function as mentioned above and in some cases, the spindles go up and down as
well as spin. In some machines, the spindles don’t rotate but the media can be rotated in both
Chapter 9 – Type 3 Equipment 183
directions. Some spindles hold the parts rigidly in place so they cannot move, others allow the
parts to be attached to the spindle having but a single point of contact; thereby allowing the
parts to move in a limited way. Speed of rotation also varies. The tendency now is to rotate the
media slow and spin the parts fast. Some systems spin the parts and the barrel up to a 6:1 ratio.
This is an extremely fast speed and material removal system.
Most drag systems run large parts in wet systems and used with large abrasive media.
The newer spin finishing systems are equally impressive and do primarily smaller parts using
dry organic systems for polishing. The aggressiveness of any drag or spin finishing system
lends itself to polishing work and the use of dry organic materials; therefore, the latter systems
are very popular with jewelers right now.
Drag Finishing
Drag finishing is an older technology than spin finishing. Neither process is a true mass
finishing process because both require the placing of parts on fixtures, which is a hand type
operation. However, the process is usually classified as a mass finishing because it uses the
same abrasive media. The main difference between the two systems is that in drag finishing, the
media is in motion and the fixtured parts normally remain stationary and in spin finishing it is
just the opposite. Because parts are rigidly in place, drag resistance is normally greater than spin
systems. To achieve a uniform finish requires the equal movement of the media in both
directions or a slow rotation of the parts either manually or automatically.
Fig. 80. Drag Finishing
Technically speaking, almost any previously mentioned mass-finishing system can be
used as a drag or spin finishing system, that is because any systems can be adapted to handle
fixtured parts. But, the bottom line is that all of these machine systems require the use of
spindles to fixture parts in order to increase pressure and speed up the material removal
processing times by creating greater resistance and pressure against the abrasive media. In turn,
Chapter 9 – Type 3 Equipment 184
that fixturing time requires labor and that limits production volumes. Again we have a trade off
of speed or time versus labor in the way of material handling and volume.
Spin Finishing
Spin finishing is the natural progression of drag systems. That is because parts must be
turned to achieve uniform results. To increase or improve results, why not spin the parts at
higher speeds? Most spin systems still move the media and some also incorporate an automatic
reverse cycle to rotate the parts. The spin can be accomplished in either a horizontal or vertical
motion to the fixtured parts and the spindles can also move up and down in the media to give
an x and y axis movement to the parts.
Fig. 81. Spin Finishing Equipment
The selection of media is the same criteria used for other mass finishing systems;
however, because of energy forces and fixturing, most media used is relative small in size and
therefore, more random abrasive particles can be used than the more expensive preformed
shaped type media. Also, as mentioned, smaller size media lends itself and this type of
equipment to smoother, lower RMS surface finishes, and/or polished finishes.
Turbo-Abrasive:
This is another variation of the spindle machine systems; however, this machine system
uses exclusively dry inorganic media and can handle up to class 4 burrs and is also classified the
same as other mass finishing equipment as a 300 to 341 system. The turbo-abrasive performs
Chapter 9 – Type 3 Equipment 185
similar to drag and spindle systems, except that the spindles and fixtures rotate only and
operate horizontally completely within a fixed media and barrel container. There is another
more important technology used in this process that contributes to its increased performance
and that is what is called the fluidized bed concept.
This fluidized bed principle introduces air into a mass of solid relatively small particles
and that changes the characteristics of the media mass to behave like a liquid. Once the air is
shut off, the media mass again behaves as a solid; therefore, air pressure is used to adjust the
resistance of the media to the part. Air pressure plays a considerable role on the speed of this
operation. Instead of controlling the speed of the parts movement to shorten time cycles and
processing, air pressure can be used to regulate to some extent the same task. Air pressure is
sometimes used in pulses to improve material removal rates and too much air will slow down
the operation. Another result of too much air pressure is that it also purges the media of smaller
particles and debris caused by the operation.
Like drag and spin finishing equipment, all parts must be fixture onto spindles. The
turbo-abrasive machine can be made with one or more spindles up to eight depending upon the
size or range of the parts that need to be worked. The most common size range of parts are from
a half inch to about 4 inches in size. The high speed of the spindle rotation can be adjusted to
5,850 surface feet per minute and/or produce metal removal rates of .08 to .2 thousandths per
minute.
The media used to perform most turbo abrasive deburring is a combination of alumina,
zirconium, and titanium, plus other variations of this mixture. Like the air blasting systems, an
air supply is needed and some form of dust collection is required for this equipment which is
built into this machine system. The abrasive particle size still plays an important part in material
removal rates and again air pressure must be compensated for this size and weight factor. These
fast cycle times do not result in a lot of heat generated because the induced air pressure also acts
as a coolant and dissipates the heat; therefore, no precautions are necessary in the handling of
parts coming out of the process.
Chapter 9 – Type 3 Equipment 186
Fig. 82. Turbo Finishing
TF-500 Turbo-Finish Machine with
horizontal spindle for processing 1-4
parts simultaneously, each of which
can be up to 20 inches in diameter
Large turbine discs with fir tree slots
deburred and finished with turbo abrasive
equipment
Close-up of Fir-tree slots on turbine disk
or ring prior to processing with Turbo-
Abrasive equipment
Assorted consumer articles and hand-tools
processed with Turbo-Abrasive equipment
Fir-tree slots in same turbine component
after Turbo-Abrasive processing
Chapter 9 – Type 3 Equipment 187
Orbital Beam or Sonic Beam:
This machine came way before the turbo-abrasive system, but it used a similar concept.
That is, they both insert the part into a media mix after the media is energized. This machine
design was a radical departure from mass finishing concepts and never really caught on as a
viable processing system because of limited applications; therefore, it is no longer made. The
technological approach used was unique and worth mentioning. The motor or energy source
was also unique and was the first system to be powered by electro-magnetic solenoids. Using
our classification system, this would have been a type 3 system that could only handle up to
class 2 burrs, or maybe class 3 in 3 locations, making this a 300 to 323 system.
In this machine system, processing is specifically designed to handle two separate
energized systems at one time. The machine looks something like a telephone pole with two
cross beams or a dual cantilever mechanism. The media mass is contained within two stationary
square containers on opposite sides of a horizontal beam. There is no resemblance to a normal
mass finishing work chamber. There is no center cone section, eccentric, or spinning disc.
Rather, the small random shaped abrasive media is rotated within a square container which is
energized from below caused by electro-magnets that are energized or rapidly pulsed to create
a mechanical movement. Normally a large single part was fixtured to each side of another
horizontal beam that energized and vibrated. The parts are immersed into stationary tubs, or
the tubs were raised up to the parts. Because of the high frequency of the energy transmitted to
the media, the mass became fluidized and the parts buried themselves into the media.
This machine system had a very brief introduction in the mass finishing industry and
saw very limited use, around the late 1960’s or 70’s manufactured by the former Wheelabrator
company before it was broken up. This was not a very popular machine system, but it might be
considered the first type of high energy system and it was the first use of a electro-magnetic
machine system. It was also the first vibratory system capable of deburring deep inside holes
and cavities commonly found in automobile transmissions castings. Unfortunately no visuals
are available on this equipment.
Orbital
This machine uses the name orbital, similar to the last machine system; however, it is a
much smaller system that works completely different. It looks and behaves similar to a paint
shaker and it is also called a shaker-mixer. It is a type 3 system that can handle up to class 3
burrs in 1 locations. That makes this a 300 to 331 system. The only difference between a paint
shaker and this machine is that the work chamber is a clamping device that holds a sealed,
removable container that moves in and out as it shakes back and forth. This system and
movement is essentially a modified barrel system, except the barrel/ container moves back and
forth in a violent action, but it does not make a complete revolution.
The work chamber is a separate sealed container or barrel, just like a can of paint. The in
and out action of the drive shaft, which is also shaking back and forth, creates a figure 8
movement of materials within the work chamber or an orbital pattern, hence its name. Because
of the violent nature of this action, this machine is completely enclosed. Because of the energy
forces involved, most of these machines are relatively small in size making it acceptable to
jewelers and other small parts manufacturers.
Chapter 9 – Type 3 Equipment 188
Fig. 83. Orbital Shaker-Mixer
The orbital machine system resembles and works similar to a paint shaker. The energy forces produced
by this equipment move back and forth and in and out which creates a figure 8 movement within the work
container which is detachable from the machine. When in operation, the machine cover completely encloses the
shaker movement.
Magnetic:
Probably the newest technology principle used in mass finishing systems today utilizes
magnets to energize the work mass to do burnishing only. Common terminology for this system
is a magnetic tumbler; however, it is actually a centrifugal system that primarily uses special
small stainless steel rod media. Magnetic systems were first introduced into Europe in the late
1980’s to burnish and to some extent minor deburring of small parts.
Because of the limited size and power of these systems they can only work class 1 burrs,
maybe class 2 in 1 locations. This system falls under our type 3 mass finishing classification and
rates a 300 to 321. I am tempted to make this a 4300 to 4321 system because more than half the
work chamber mass volume is liquid, but it is the media that actually does the surface
modification work or effects the part.
The system has no observable moving parts; however, it works by spinning magnets
below a cover plate or platform on which the work chamber rests. Except for an outside raised
lip restriction on the top plate of the machine, the work chamber is not physically attached or
fastened. Rather, it is held in place by the magnetic attraction of the media inside the bowl and
the magnets below.
The machine system uses strong rare earth rotating permanent magnets fixed to a
motorized rotating disc that operates at 1725 to 3600 RPM in close proximity to the media mass.
Chapter 9 – Type 3 Equipment 189
The energy force of the magnets has a limited range to influence both ferrous and to some
extent non-ferrous metals of drawn stainless steel wire; therefore, these systems are very small
or perhaps a better word would be shallow and can only handle small parts. Anything over 2
inches in size would be a difficult task for this equipment.
The work chamber of these machines are filled with mostly water and chemical to
approximately 2 to 4 inches of work height. The most common media used is special stainless
steel pins on or about .5mm x 5 mm maximum or small light weight ferrous materials that
would take less than 1 pound to fill a large 8 inch diameter size machine system. Existing small
steel or stainless steel balls will not work. The proper proportions of media to liquid in the work
chamber is very critical to the proper operation of this equipment, but the most important factor
is the extremely thin and long stainless pins or cut wire which is very expensive.
Even though the media is special, it is still subject to problems of discoloration and or
darkening if not properly treated or maintained. You may have noticed that we have been
talking primarily about stainless steel media and magnetism. Normally stainless steel is not a
magnetic material; however, when any metal is drawn to such a small size, its molecular
structure changes or becomes aligned. This alignment makes all materials then subject to
magnetic influences.
This machine is primarily a burnishing system that uses stainless steel metal pins or cut
drawn wire to initiate surface finishing by way the pressure and impact created by metal
movement within a liquid mass, thereby energizing the solid contents of the work chamber.
Because of mass and attraction, this system will not work properly, if the parts are made out of
ferrous or magnetic metals.
Chapter 9 – Type 3 Equipment 190
Magnetic Disc Finisher
The magnetic disc finisher has no noticeable moving parts. It works by spinning permanent magnets just
below a non-magnetic cover plate on which the work chamber sits. There is no fixed attachment of the bowl to the
cover except for the magnetic attraction of the magnets and the media within the container. It works by the
spinning magnets, which in turn moves the stainless steel cut wire pins within a container of liquid. Normally
stainless steel is not magnet; however, when the material is drawn or its atoms become aligned it is magnetic.
Because the media is metal, it is non-abrasive. That means that this system is used primarily for burnishing, but it
can remove excess some material because of the small media size and force. Even though there is x & Y movement
to the media the parts may not rotate well in this system; therefore, a number of systems have an automatic reverse
or spin cycle.
Fig. 84. Magnetic Disc Finisher
This centrifugal machine system behaves more like a disc finishing machine which
produces a lapping work flow pattern type action. A good magnetic system also generates a lot
heat to the work chambers contents to uncomfortable levels within 15 to 20 minutes. These
machine systems are being used mainly for burnishing type work, but they also do light
deburring by impacting parts or removing loose burrs. By mixing the steel with other materials
in a ratio capable of being driven by the steel, some abrasive deburring can be accomplished.
This is a good system for burnishing jewelry and small parts, but they are extremely limited to
small mostly non-ferrous type parts .
191
Chapter 10 – Technology & Equipment Summary
Conclusion of Equipment
At the beginning of this book, we talked about the history of abrasives and the
application of abrasive methods to improve and remove surface variations. Primarily, we were
mainly concerned with creating and deburring of sharp edges resulting from the working of
metal parts. Basically, we said that there were a number of ways to achieve surface modification
or metal removal, and we arrived at a classification system that used 6 different applications of
energy to do material removal.
Very early on, we tried to set parameters to indicate the amount of material removal or
treatment by indicating at least three forms of acceptable standards for conditioning or surface
finishing modifications in relationship to the surface profile of the material being worked. Those
surface modifications being, surface preparation or the conditioning of the surface to accept a
thick protective coating, the removal of excessive burrs and the preparation of the surface to
receive a thin protective coating, and the smoothing or polishing of a surface profile.
To achieve these three forms of surface conditioning or modification, we came up with a
classification system that identifies 6 types of processing, 5 use equipment. The first system, or
our type 0 system, is a manual hand labor method of applying or supplying physical force to an
abrasive to do surface modification or material removal. This type 0 system involves no
equipment but does involve an energy transfer device; therefore, we include it within the
system, but give it no numerical value or a zero rating. In addition to the use of hand labor,
three other systems involved the use of mechanical forces and abrasives. Two involve the use of
non-mechanical methods. All of these systems involve the use and transfer of energy to apply
force or molecular changes to the parts to be modified.
Technically speaking, energy can be transfer through a solid, liquid, or air. Naturally the
greater the weight or mass, the greater the amount of energy that can be transferred and the
greater surface modification that can be accomplished in the shortest period of time, normally
that also results in the roughest surface profile of the finished part. Therefore, the greatest
amount of material removal can be accomplished with rigid solid abrasives, then liquids, and
then air. Next, the size and composition of the abrasive is then the next factor in the amount of
material that can be removed. Lastly, how the energy force is transfer to the part is the last
factor that determines surface removal rates and speed of operation. How energy is applied is
the criteria for our equipment classification system.
All of the mechanical abrasive equipment systems are energy transfer devices designed
to increase the speed and velocity of the abrasive in relationship to the parts and this increases
pressure, which improves abrasion and material removal. The increase in speed or velocity in a
linear straight-line mode is different from rotational energy forces, meaning that speed does not
necessarily result in greater pressure. Pressure is more easily achieved when it encounters
resistance at high-speed centrifugal forces. The formula for centrifugal force is: force equals the
mass times velocity square divided by the radius (F=mV2/r), or force equals the mass times
Chapter 10 – Technology & Equipment Summary 192
gravity (F=mg). So, if you double the RPM's, you double the velocity and quadruple the
gravitational forces or pressure. If you double the radius or diameter while keeping the velocity
constant you would get half the gravitational force. Double the RPM's and double the radius,
you double the velocity and gravitational forces.
The most economical way to increase the speed and pressure of mechanical abrasives
systems is by increasing the gravitational forces using the principles of rotational devices or
centrifugal forces. For every action, there is an opposite reaction. Along with increased speed
comes friction and heat. Systems that use air and liquids dissipate most of their heat via these
methods and therefore most parts are relatively unaffected by the heat of the processing. At
some point, all of these systems can reach an upper limit were heat will affect the part
processing; however, more than likely the equipment will reach its functional level or limitation
before the parts will.
All of these systems achieve increased pressure by wheel movement in a direct or
indirect application or transfer of energy. Although rotation is directly involved in type 1
systems, the speed of rotation is not as important as the pressure on the abrasive transfer device
by the operator. Type 2 systems are the most indirect method or use of speed, because rotational
forces have to be converted to air pressure, which in turn energizes the abrasive. The
application of rotational energy is most notable in type 3 high-energy mass finishing systems.
In type 1 equipment systems, the energy of rotation is applied to a solid or transfer
device, be it a wheel or a belt, in direct contact and/or works parts parallel to the surface profile
of that part. This is almost the identical motion and action used by manual hand labor
operations, except this system uses primarily a flexible powered transfer device. Without
automation assistance, man is still the primary source of applying the pressure to the transfer
device and this effects the final surface finish because of his manipulation and use of this
equipment. Because of the simplicity of the equipment and/or tools, this system is probably one
of the most popular methods of achieving material removal and modification. Of all the
mechanical systems, it is the oldest and cheapest methods, excluding manpower, with one of
the widest ranges of material modification; therefore, it is still a very popular method of
achieving surface profile modification.
In our type 2 equipment classification, the energy of a solid is applied by air pressure and
projected at the surface profile of a part in close proximity to the energy release point. This is a
indirect method of energy contact or transfer which is diffused at nearly a perpendicular angle
to the part to be worked. Because of the angle of attack of the solid abrasive, this method
normally increases the surface profile of the part being worked and produces rougher surface
profile results, no matter what media is used; therefore, this equipment is used primarily for
surface preparations. Unlike type 1 systems, where the pressure being applied is by human
manipulation of the equipment, man only controls the position of the part in relationship to the
abrasive flow and the pressure is constant to what settings are used or required by the human.
In type 3 equipment systems, we return to the energy of rotation of a solid applied by a
solid in a direct contact method that uses rigid solid abrasives in a free floating mass that is
Chapter 10 – Technology & Equipment Summary 193
capable of multiple applications of pressure and angels of attack by the media shape. This
equipment uses the largest form of abrasive particles and greatest amount of energy force than
any other system. It also has nearly no human interaction that controls the part finish, except
selection of what abrasive to use. This is the most aggressive method of uniform material
removal of the entire surface finishing systems and it does not require automated material
handling systems to work large volumes of parts. This equipment is used primarily to remove
excessive burrs and surface modification for plating applications and smooth surface finishes.
Type 4 equipment systems use a liquid to transfer energy to a solid part and this can be
done in a number of ways and/or in combination with solids or air. Because of the density and
cohesive effect of water molecules, which are very small, water by itself is a poor medium for
transferring high-pressure energy and has little abrasive force by itself. Water needs a great deal
of energy input to get an effective output and again, because the molecules are small the effect is
less than that obtained by solid abrasives. Any 4 digit machine systems beginning with the
number 4 means that these systems do not removal as much material as the basic 3 digit prime
number system which follows this first digit. In our equipment classification, a four digit
number beginning with the number 4 means that this is a combination method process which
normally produces smoother surface finishing result and is less aggressive for removal a lot of
material.
Type 5 systems are not good primary equipment systems that do a lot of material
removal. Type 5 systems use temperature extremes to do limited burr removal and not good for
surface modifications. Basically you have extreme heat and cold that can only effect relatively
relative thin sections of materials and are not good on surface profile modifications. On the high
heat side, energy transforms thin solids into vapor or lighter, less dense material deposits, but
can work difficult to reach areas. On the cold side, a negative energy system weakens thin metal
and plastic materials, making other solid applications or combination systems work more
efficiently to removal flash and burrs.
Presently mass finishing equipment is the most popular means of deburring and surface
finishing of parts and the least expensive overall process for doing surface modifications. It is
also popular for producing bright shiny burnished and to some extent polished parts; however,
when aesthetics are in question, probably the hand buffing type wheel systems are still the most
popular and produce the best looking results. For external or heavy coatings, blast systems are
the most popular processing method. For hard to reach and micro to small light burrs, liquid or
chemical and thermal systems seem to be more effective.
Simplicity seems to be the key to getting people to use tools and the less direct labor the
greater the probability of the system to be used. That also means the more automation and/or
material handling systems get tied into other equipment finishing type systems, the more
common deburring done by hand and mass finishing systems will likely decline in large
production facilities. Yet, the demand for smoother polished parts may actually increase due to
the concern of material porosity and medical concerns; therefore, surface refinement may
become a greater requirement than deburring.
Chapter 10 – Technology & Equipment Summary 194
The reason for the possible decline of deburring may be because the simplicity of mass
finishing equipment is only over shadowed by the complication of abrasive media selection and
the variables that control surface finishing. Actually, newer equipment systems and processes
are becoming more specialized, less complicated, and easier to work with. It is the media, not
the equipment, that really determines or makes mass finishing systems a precision instrument
or predictable processing method of achieving the desired end result of a part finish. A finishing
system is only as good as one’s knowledge of the media and/or the control one has over the end
process.
As automated machining centers increase their programming capabilities, which
improves their accuracy and performance, they may eventually include deburring tools. That
means, there will be less need or requirements for material or edge removal, but more concern
for surface finishes. There are still a lot of deburring and polishing applications that automated
machine tools or programming systems can’t work properly; therefore, I think there will always
be a need for abrasive mechanical systems. Even if the volume of deburring applications
decreases, polishing applications will probably increase because of bio medical concerns.
Generally speaking, most machine centers cannot achieve the uniform surface profile
finishes or smooth edge radii or blending requirements that mechanical system can. Also, if the
machine center can achieve the desired deburring results, the speed and time required to keep
up with production volume may not be competitive to a mechanical secondary operation.
Lastly, without sophisticated follow up machine systems to monitor surface profiles and
tooling, machine centers will constantly turn out parts that will vary slightly from one piece to
another. Tooling and wear is a major factor that must be taken into consideration and that
affects uniformity of finished parts.
So, where do we go from here? Let’s review our equipment classification system and
take into account what a novice person may want to consider when they are in need of
producing a better surface finished part. What equipment should be used? What are some of the
standard parameters required or should be taken into consideration when selecting how to do
these secondary operations? What determines how I finish this part?
One of the first things to take into consideration for determining equipment is the size of
the part. Another factor is the configuration of the part and what has to be achieved as the final
surface profile. Actually that was two factors; however, the second part of that factor may have
to be clarified. That is, what has to be achieved is largely determined by how the part will be
used. Engineers will usually specify what surface requirements are needed based upon the
environment the part will be used in and how the part is to be used. That means that there are
usually 3 different parameter options. We have mentioned these options earlier, but it may be a
good time to review these again.
The three main options for a part finishing systems are as follows: 1. Surface preparation
for a heavy or thick coating, such as paint or plastic based film products, 2. Surface preparation
for a thin film chemical coating or treatment, 3. A smooth, or bright, good looking aesthetic
finalized surface appearance on a part. Once one of these factors has been determined, then the
Chapter 10 – Technology & Equipment Summary 195
finishing equipment can be determined. There are exceptions to almost all processes as to what
is best and that is determined a lot of times by what one has to work with in the way of
equipment in house. However, because we are not locked into this limitation, we will make
recommendations based upon our classification system.
Surface Finishing Options
Type Description
1 Surface preparation for heavy thick coatings
2 Surface preparation for thin film coatings
3 Polished finishes
Our equipment classification system is a generalization for all finishing equipment
systems and parts processing. In the following chart, the numbering system is basically listed in
the order of how technology has evolved to some extent; it reflects costs and the order of the
aggressiveness. Variations, supplies, and improvements in this equipment have provided or
designated us with a “Range” or limitations. In the last column of our chart, I have included
“Surface Finishing Options” as a quick reference guide. This series of numbers appears in the
order of the equipment’s best performance capabilities from the list above. Both designations
are generalizations and are only suggested as a reference. There are some additional charts to
follow which may also be helpful for narrowing or selecting the finishing system for your
particular application. Again, this is not absolute.
Deburring Equipment Classification - Surface Finishing Options
System Range Option
Wheel and Belt Systems 100 – 151 3 - 2 - 1
Abrasive Blasting 250 – 253 1 – 2
Cryogenic Blasting 5200 - 5233 2
Wheel Blasting 250 – 251 1
Wet Blasting 4200 – 4233 2
Water Jet 4200 – 4231 2
Ultrasonic 4200 – 4211 2 - 3
Abrasive Extrusion 4200 – 4243 2 – 3
Thermal 500 – 533 2
Chemical 400 – 433 2 – 3 – 1
Mass Finishing Systems 300 – 351 2 – 3 – 1
Spindle/Drag Finishing 300 – 351 3 – 2 – 1
Turbo-Abrasive 300 – 351 2 – 3 – 1
Orbital/Sonic Beam 300 – 323 2
Orbital 300 – 331 3 – 2
Magnetic 300 – 321 3
Chapter 10 – Technology & Equipment Summary 196
The primary systems used to achieve type 1 surface finishing options or preparations are
classified as type 200 equipment systems. This also includes 4200 and 5200 systems to some
extent. These are all blast type systems and are also know primarily as cleaning systems that
produce parts with finishes that have a greater over all surface profile or surface area which has
better coating adhesion qualities. Blast finishing systems normally leave surface finishes
rougher than what one starts out with.
These same surface qualities can be achieved to a lesser extent by using very coarse
grades of ceramic media in mass finishing equipment and abrasive belt and wheel systems, in
that order.
Type 2 surface finishing options are more general applications of all three types of
equipment classifications. That is, using a medium to fine grade of abrasive in any one of the
designated equipment systems mentioned will produce results which are normally acceptable
for thin chemical films or treatments. Naturally, the finer the abrasive used, the lower the mass
and pressure which results in a smoother surface profile or finish to the part. A smoother
surface profile is more desirable for thin uniform coatings because there is less surface profile
exposure to the environmental elements. Rough surface profiles are susceptible to uneven
coatings and penetration by material protrusions.
Type 3 surface finishes can also be accomplished using all three abrasive equipment
classification systems; however, all 200 equipment systems should not be used, unless you are
looking for a frosted texture or satin type finish. A better result can be accomplished with 4200
systems. That leaves all 100 and 300 equipment system as the primary means of achieving
polished, low RMS surface profile finishes. Again, a low surface profile reduces the effect of
biological agents and eliminates possible contamination problems.
Now, before we talk about aggressiveness, which relates to time, I think we need to talk
about volume. If you do not have a lot of parts that need a secondary finishing operation, your
options are either limited or not, depending upon how you look at things. Small volumes of less
than a dozen or so parts are normally limited to hand type operations, because most systems are
not built to handle so few parts. That means that parts are either worked by hand or processed
using wheel or belt type systems. If the part configuration is relatively simple and has easy
accessibility to the area that needs to be deburred, then relatively more parts can be processed
probably more quickly by hand than can some automated systems or even mass finishing
equipment. Total time is a big factor for determining cost effectiveness or feasibility. Other
factors include equipment maintenance, wear, and set-up time.
The complexity of a part configuration and accessibility are also important factors to
consider in determining equipment. Whereas, we have shown that volume is not the sole
determining factor for equipment selection, this same statement has its opposite counterpart.
That is, if a part has a complex geometry or the burrs are located in difficult to reach areas and
are time consuming to work by hand, then there may be enough repetitive business to justify a
lot more expensive processing system. Most complex configurations of parts have internal
cavity burrs that cannot be easily reached or seen and that is why we have incorporated this
burr location into our numerical classification system.
Chapter 10 – Technology & Equipment Summary 197
The numbers 0, 1, 2, or 3 appear as the last digit of our equipment designation system.
However, there are really only two choices here. Again the number 0 means that no or little
material removal is necessary. As far as I know, all equipment systems will deburr outside
accessible #1 locations relatively easy; therefore, you will not normally see a machine system
ending only with a number 1 type location. As mentioned, the most difficult areas to reach are
internal number 2 dimensions. This problem and location is especially noticeable with
mechanical abrasive systems, because solids do not move well in confined spaces. The number 3
is the ability to work both area locations. There is no one system that does both ID and OD areas
equally well.
Our equipment classification system distinguishes aggressive features or traits by the
second to last digit in our numbering system. This number reflects or determines the range or
capability for material removal, with the number 5 being the highest classification of material
removal. Again, material removal in excess of .030 is possible with a number of these machine
systems, but it is not recommended and not the efficient use of the equipment. Burrs or material
removal in excess of .030 are best accomplished with better machining practices.
Aggressiveness of a mechanical machine system relates to time. The more aggressive a
machine the faster the equipment or the greater the pressure is applied to the process.
Remember, the machine system is only an energy transfer device to the medium that does the
material removal. Therefore, in larger mechanical machine systems, the larger, heavier, and
more rigid the mass or solid the media used by the equipment, the more aggressive the
equipment system. So, aggressiveness can relate more to the solid abrasive than it does the
equipment, but how the energy is directed and how much energy is transferred is the function
of the machine system.
Now, because of progress and machine improvements, there are a number of variations
in equipment and system designs that determines equipment aggressiveness. In type 1, wheel
and belt systems these differences are somewhat clear, cut, and dry. There are relative no or
little use of solids by these systems; however, the wheel or belt itself does behave like a solid
form of media, or is the transfer medium. Besides this factor, other variations or improvements
to these systems are mostly in the form of automated material handling systems. Speed or
RPM's of the drive wheels can only achieve a fixed rate of energy transfer. The operator applies
or determines the pressure to the part or work and that causes heat which is a factor that is
effected by pressure. Besides pressure, the other controlling factors are the compound additives,
coolants, and abrasives that determine a system performance.
In blast type systems there are more aggressive control variables. Also, there are different
parallel blast systems technologies operating side by side. The aggressiveness of blast
equipment is determined by the amount of energy transfer or pressure. There are just two ways
to apply energy to air born particles and only one way with the addition of liquids. The greater
the pressure and the heavier and larger the media, the faster, more aggressive the equipment
system.
Chapter 10 – Technology & Equipment Summary 198
To determine the aggressiveness of blast systems is to look at the media that is used with
the equipment system and the amount of force used to energize the media. The amount of
material removal of these systems is greatly affected by the size and type of the media used on
the part or material being worked. Increased pressure means that the part and media size is or
will be significantly modified as pressure increases, but coverage or dwell time will decrease. So
blasting has to take into consideration two factors for aggressiveness, not just the aggressiveness
equipment, but that of the media being used.
In mass finishing systems aggressiveness is also a product of pressure and these
differences are known as generations of equipment or the form or type of energy used to
perform the work, such as barrel, vibratory, or centrifugal. Although these systems use energy
differently, pressure is determined by the application of rotational energy forces or factors of
gravitational forces and by the use of larger heavier media. As with blast equipment, media is a
major factor that effects the amount of material removal, time, and the surface finish.
Unlike blast systems, mass finishing technologies are significant progressions and
warrant different names or titles. The energy forces transferred to the parts are different in a
barrel, vibratory, and high energy systems. Each system works by almost a factor of 10 times
faster than its previous name sake or generation of equipment. The end results are almost
identical but the processing speed is the major determining factor plus cost of the equipment.
Once a part is processed, it is of little use until it is sorted or isolated by itself. Separation is
another factor that enters into time cycles; therefore, processing time is not solely dependent on
speed or aggressiveness of the equipment. Material handling is always something to be
considered.
Perhaps one the better deburring equipment systems is the abrasive flow type machine.
These systems combine or utilize the attributes of solids and liquids in direct contact with the
part. The energy transfer medium behaves similar to a solid but it flows more like a liquid. This
is an extremely efficient and somewhat aggressive deburring system that does well on surface
profile material removal. Because of the flow characteristics of the heavy viscous slurry media,
this is the best system for working parts with internal cavities and dimensions
The down side of abrasive flow equipment systems is that they are slow, require special
fixtures, and require some massive support equipment and pumps; therefore, it is probably the
most costly equipment system of all that are listed. Some variations of this equipment produce
excellent or improved surface profile finishes, but generally most of these machines for
removing hard to reach burrs.
The technologies of thermal and chemical deburring systems would seem to be more
easily controlled or regulated than blast or mass finishing equipment, because they do not
involve the mechanical systems or the use of a solid media in relationship to the part. These
systems use the mediums of air and water which are less dense energy transfer system;
therefore, the equipment is used more for selective type material removal work than the more
difficult task of surface profile modification.
Chapter 10 – Technology & Equipment Summary 199
Adjustments or aggressiveness to these systems involve primarily one energy transfer
system which should not vary significantly; however, volume and the mass or part size is more
of a controlling issue or factor. Relative to other equipment systems, parts processed by these
methods are generally smaller and the process removes less material than other deburring
systems mentioned. Even though these systems are rated very aggressive in our classification
chart, they are rarely used for major deburring or surface modification. These systems are
similar, but a lot less costly than the abrasive flow machines that do almost the same type of
material removal.
As you can tell, there are degrees of aggressiveness and there are variable factors
influencing the use of different deburring or finishing system. There are a lot of gray areas here
and/or variations. Therefore, enclosed is another evaluation chart that is a little more detailed
than the equipment classification chart only. This should help you decide a little better the
strengths and weaknesses of the different type of equipment and material removal processes
involved.
Like all good flexible processing systems, there are a lot of variables that enter into this
more detailed chart. That means that selection depends upon how you want to use the
equipment. Naturally, the more uses or variation in parts you have or want to process through a
machine system, the more down time will be experience in set up time or change over down
time. No system is completely idiot proof. The more variations you have or want to have, the
greater the flexibility of the equipment system and the greater the chance of encountering
additional problems. With that thought, below is a more detailed chart for equipment selection
and part processing:
Chapter 10 – Technology & Equipment Summary 200
EQUIPMENT CLASSIFICATION EVALUATION BY CATEGORY
Equipment Burr Class Location
System
1 2 3 4 5 0 1 2 3 4 5 0 1 2 3
Wheel & Belt G VG G G G G G VG G P
Abrasive
Blasting *
G VG G S P P VG G P S
Cryogenic
Blasting
G G S G S P S G P S
Wheel Blasting G VG VG G S S S S G P
Wet Blasting G G VG G S S P G G S G
Water Jet G G G G S S P G G P
Ultrasonic G S VG G S P G G
Abrasive
Extrusion
P G S G G G G S S G VG G
Thermal G S G G S S S G G G
Chemical G G G S P P G G G G
Mass Finishing VG G VG VG G S S G VG S S
Spindle VG G G G G G G G G P
Turbo-Abrasive VG G G G G S S G G P
Orbital Beam G G G S P P S G G S
Orbital G G G G S S G G S S
Magnetic G G G S G
Explanation of letter symbols
VG Very good
G Good
S Some
P Poor
Left Blank not recommended for application or classification
* Rating based upon material removal, not surface finish.
I alluded to size as a determining factor in equipment classification earlier; however, I
did not go into any details. Part size is a very important factor for determining equipment and
processes, not only for determining or maintaining production rates, but also for controlling
accountability of the parts. In most industrial applications, assembled parts are relatively large
in comparison to electronic, medical, and jewelry type parts. Why I mention that is because
almost every material removal system discussed so far has alternative smaller systems which
have different specifications and cost factors.
Finishing equipment is built to reflect different size parts and volume. Small parts can get
lost in large capacity machines and never found again and large parts in small machines may
not be processed properly or achieve a uniform surface finish. Selection of a finishing system is
mostly determined by capacity which in turn is determined a lot of times by a mixture of parts
that must be processed as well as volume. Why choose a 10 ton press when a hammer will do?
In addition to size of the equipment, part size is another major determining factor, which
is especially evident in mass finishing equipment. Generally speaking, there are about 4 sizes or
ranges of parts in most metal processing systems. To make it simple, I’ll just say that if a part
Chapter 10 – Technology & Equipment Summary 201
can be held in the palm of one hand and can’t be seen, then that is one size. If a part can be held
in one hand and weights less than about 2 pounds, that is another size range. If a part exceeds
the two hand or the 2 pound range, then that is the third size of parts. Any parts that need
mechanical loading help would be a fourth size group of parts.
This part size analogy creates another classification system and equipment chart. As in
drafting that has drawing sizes, our hand-held part now equates to what we will call” A” size
parts, or parts under a half inch in size. Parts capable of being held in one hand are “B” size
parts and will be over a half inch in size to approximately 8 to12 inches in length, or about a 8
inch cube. Parts capable of being handled by a single operator using two hands unassisted are C
size parts and are somewhere over 12 inches in length or over the 8 inch cube size. D size parts
are any parts that are difficult for one person to handle and/or control and are more subject to
weight limitations than size limitations. In short, D size parts need material handling devices.
Each one of these part sizes constitutes a specific range of recommended equipment.
Classification of Part Sizes
Letter Measurement Description
A ½” or smaller parts Can’t be seen in closed hand
B ½” up to 12” length Can be held in one hand
C weight Need 2 hands, or over 2 lbs.
D weight Need material handling assistance
Finishing equipment systems are built to reflect different size parts and/or volume. That
means, one size does not fit all. The only except to that rule are the chemical deburring systems
that depend primarily on size and capacity of the liquid tanks, but even here, the electric
generating equipment are sized to a certain mass or volume of parts. Therefore you can shop for
equipment size and function as well as price in a lot of instances. So, not only do you have
alternative material removal processes and equipment, you also have different size systems to
accommodate the part sizes A through D mentioned above.
Also mentioned is the problem of accountability, which is a very important factor for
some parts. Even though the size of a part maybe smaller, the cost of producing them may not
be; therefore, greater care is required for the overall quantity of the parts as well as the quality
of the surface finish produced or required. Below is another generalized chart indicating
equipment classification and the part size range these systems normally handle.
Chapter 10 – Technology & Equipment Summary 202
Fig. 85. Equipment Classification by Part Size
System A B C D
Wheel & Belt S VG G
Abrasive Blasting S VG G G
Cryogenic Blasting G G P
Wheel Blasting S VG VG
Wet Blasting S VG S
Water Jet S G G
Ultrasonic S G
Abrasive Extrusion S G G S
Thermal G G S
Chemical G G S
Mass Finishing VG VG G G
Spindle G G
Turbo-Abrasive G S
Orbital Beam G VG S
Orbital VG G S
Magnetic VG S
Explanation of letter symbols
VG Very Good
G Good
S Some
P Poor
Left Blank not recommended for application
Chapter 10 – Technology & Equipment Summary 203
Now, we have talked about part size to some extent and have made some
recommendations. Sometimes size is not a good quick reference guide in the selection of mass
finishing equipment. In addition to part size and equipment size, we have also talked about
capacity in cubic feet as a way to measure equipment. All these previously mentioned guides
normally require some calculations in order to come up with what volume of parts can be
processed in what system. In my opinion, the quickest way to come up with capacity figures is
by weight of parts in a machine system.
As another quick reference capacity guide for mass finishing equipment, I’d like to give
you some rough guidelines in terms of weight of parts in a machine system that also takes into
account a media capacity of 50 to 60% which is good for deburring. Do not use this guide for
dry media or processing. As a side note, as machine systems become smaller, so too do the
energy forces; therefore, the smaller the system the longer the time cycle to produce the same
results.
Fig. 86. Weight Capacity of Parts
Pounds of Parts Cubic Foot Capacity
10 ¼ Cu. Ft.
100 1 Cu. Ft.
250 5 Cu. Ft.
500 10 Cu. Ft.
Part size is an important factor for determining equipment and processes. In most
industrial applications, assembly parts are relatively large in comparison to electronic, medical,
and jewelry type parts. Why I mention that is because almost every material removal system
discussed so far has an alternative smaller systems, which has different specifications and cost
factors. Equipment is built to reflect different size parts and/or volume. So, not only do you
have alternative material removal processes and equipment, you also have different size
systems. Each system has a range or limiting factors to consider.
There you have it. These are the primary options for deburring and polishing. We have
covered the most popular processing methods and machinery for deburring and polishing. This
explanation of equipment basically serves as a guideline to advise you of advantages and
limitations of different systems. All systems will work or do something to some extent. How
material removal systems work and the efficiency of their operation are the determining factors
that should guide you. Of the mechanical energy force options, mass finishing systems and their
relationship to abrasives and/or media as well as parts being processed are probably the most
aggressive and popular. The following chart is a summary of the systems we have reviewed.
Chapter 10 – Technology & Equipment Summary 204
Deburring Equipment Classification Chart
System Range
Wheel and Belt Systems 100 – 151
Abrasive Blasting 250 - 253
Cryogenic Blasting 5200 - 5233
Wheel Blasting 250 - 251
Wet Blasting 4200 - 4233
Water Jet 4200 - 4231
Ultrasonic 4200 - 4211
Abrasive Extrusion 4200 - 4243
Thermal 500 - 533
Chemical 400 - 433
Mass Finishing Systems 300 - 351
Spindle/Drag Finishing 300 - 351
Turbo-Abrasive 300 - 351
Orbital/Sonic Beam 300 - 323
Orbital 300 - 331
Magnetic 300 - 321
We can now go into the explanation of media, liquid systems, and the processing of
materials, specifically designed to be used with and control mass finishing processes. But before
we do that, perhaps we should explain a little about the ways and means for determining
surface finishes. If we do not set up any ground rules of what you are trying to achieve and
what type of ruler we are using to try to maintain standards of performance or uniformity, we
are not going to achieve apples and apples.
205
Chapter 11 – Surface Finishing Standards
Surface Finish Quality Control:
An acceptable finished part is normally concerned with three things. They are fit, form,
and function. If a finished part does not conform to at least one of these criteria, it is not an
acceptable part. It is a reject. The main reasons for part rejection are burrs or surface variations
that affect how a part fits, its overall dimensions or form, and how it functions in relationship to
other mating parts. If we are talking about a part that can be seen, we may also be talking about
a surface appearance.
What is an acceptable part is determined by engineering. They in turn determine the
parts final dimensions. They do not necessarily determine the most appropriate method of
making the part, just how it is to operate and its final dimensions. Other people or engineers
decide how a part is to be made and what is an acceptable surface finish based upon its
function, use, and its operating environment.
Now, the measurement of a part seems to be pretty straight forward and simple, but it is
not. That is, a parts basic outside and inside dimensional shapes are somewhat simple to
measure, because we are talking about mainly the separation or measurement of two points.
However, the flatter surfaces or planes in between these dimension is just one or a multitude of
points that also need a certain amount of uniform conformity which can also be measured.
To determine the acceptability of a part is to a large extent determined when that part is
designed. That is, the materials are specified to conform to its function. Then specific
dimensions are machined or formed into the part and the surface finish is determined by the
environment in which that part is to work. To protect that part, increase its life, and to function
in that environment requires a secondary process which is either a chemical treatment or
coating, or the absence of any secondary operation. The secondary protective coating is only as
good as the materials surface preparation.
Because of manufacturing options and cost factors of raw materials, forming, and/or
machining, every part can be somewhat different from one another. That also means that edges,
surface finish, and burrs can also vary slightly from one part to that of another and from batch
to batch and from machine to machine. There are a lot of different ways in which a part can be
made and this somewhat effects the final results, in good or bad ways. That also goes for
whatever processing method, equipment, and media is used to correct material or machining
irregularities. In mass finishing systems, surface preparation or finish is determined by the type
of energy forces exerted on the part by an abrasive or media and particle size.
Again, external dimensions are relative easy to determine, but how a parts surface finish
is measured is determined by the way in which it is made and what is acceptable. The way it is
measured or inspected to conform to predetermined specifications or critical dimensions is also
another factor to consider. The most common means for determining a surface finish and/or
surface irregularities besides visual appearance and feel, is an instrument called a profilometer.
Chapter 11 – Surface Finishing Standards 206
The profilometer is device that measures the peaks and valleys of the surface of an object
by moving a stylus ball type probe over a pre-set measurable surface. The read out
measurement of this device is related to a calculation of the average surface variations of the
peaks and valleys of a given measurable surface and is called RMS or Rq. RMS stands for the
mathematical term root mean square determined in micro inches or micrometers. A micro inch
or micro meter is one millionth of an inch or meter which is equal to .000001 of which ever scale
you are using. Depending upon the part, usually 5 readings or measurements are taken over
different center lines of the part and should be approximately the same length.
RA (Roughness Average)
Rq/RMS (Root Mean Square)
These terms are derived from mathematics to indicate a relationship of overall flatness of any surface
material. In the US, this surface is measured in millionths of an inch or microinch, 1 microinch = .000001. The
illustration shows a surface profile of a part with shaded peaks and valleys in relationship to a centerline average.
A number of terms are used interchangeably to describe certain aspects of a surface profile. The more common
term used to measure flatness is RA. This is the arithmetic average roughness profile measurement of the surface
profile of the material from the centerline to the maximum height of the profile. The RMS is the geometric average
of the roughness profile and is derived by taking the square root of the squares of the average vertical distances. Rq
is the more current terminology being used in place of RMS. Although these two terms and measurements are
related, they are not compatible. In most cases, the relationship is 1.11RMS to 1 RA when in fact is a variable that
can go from 1.11 to 2.10:1.
Fig. 87. Surface peaks and valleys: centerline average
Chapter 11 – Surface Finishing Standards 207
Other Terms and Measurement
From the centerline or mean average, other forms of measurements can be established.
Each of these terms or measurements serves a purpose, but the bottom line is to establish a
dialog of universal or a standard form of measurement. The following show some of the more
common terms used.
Rv is the maximum valley depth in a profile below the mean line of the measured area.
Rp is the maximum peak height of the profile above the mean line of the measured area.
Rt is the sum of Rv & Rp or the maximum peak to valley height or total roughness of the
profile of the measured area.
Rsk is the measurement of asymmetry (skewness) of the profile of the measure area.
As stated earlier, when a part is designed, a lot of the pre-determined qualities of a part
are specified and those critical qualities that are more important than others may be checked or
determined for acceptability. For surface finishing, there are measurement parameters or
standards for amplitude or surface variations in height as well as spacing and/or a combination
of both. A measurement tolerance or a range of acceptable surface variations is normal for
determining this acceptability. Most finishing processes can only control amplitude parameters.
As a general rule, normal mill steel or sheet metal after processing averages about 35 RMS or
Rq. As the number becomes less or down to zero, the surface finish becomes finer or smoother.
Chapter 11 – Surface Finishing Standards 208
Fig. 88. Components of Surface Finish
Measurement parameters are basically designed to identify roughness (height), waviness (spacing0, and
form (hybrid). Each standard serves a special purpose. With the advent of a world community, European ISO
standards are being integrated and updated to reflect more universal measurements. The following are some
examples of working standards.
RsK – Skewness – is the measure of the symmetry of the profile
about the mean line. It will distinguish between asymmetrical
profiles of the same Ra or Rq
Rz - Also known as ISO 10 point height parameter, is measured on the
unfiltered profile only and is numerically the average height
difference between the five highest peaks and five lowest valleys
within the traverse length.
S - is the mean spacing of adjacent local peaks, measured over the
assessment length (A local peak is the highest part of the profile
measured between two adjacent minima, and is only included if the
distance between the peak and it’s preceding minima is at least 1%
of the P + V of the profile.
HSC – The high spot count is the number of complete profile peaks
(within assessment length) projecting above the mean line, or a line
parallel with the mean line. This line can be set at a selected depth
below the highest peak or a selected distance above or below the mean
line.
Sm - is the mean spacing between profile peaks at the mean line,
measured over the assessment length. (A profile peak is the highest
point of the profile between an upwards and downwards crossing of
the mean line
Pc – The peak count is the number of local peaks which project
through a selectable band centered about the mean line. The count is
determined only over the assessment length though the results are
given in peaks per cm (or per inch) The peak count obtained from the
assessment lengths of less than 1 cm (or 1 inch) is obtained by using a
multiplication factor. The parameter should therefore be measured
over the greatest assessment length possible.
Chapter 11 – Surface Finishing Standards 209
To achieve a good surface finish acceptable to a secondary chemical treatment or anodize
finish coating, usually a measurement of 16 to 18 RMS is required. Paint coatings can be rougher
than 20 RMS; however, if a good flat paint appearance is required, then the finish should not
exceed 22 RMS. In mass finishing systems, a mirror finish parts can be achieved at almost any
RMS using steel media; however, most engineering people think in terms of smoothness and
brightness. That is, even though bright finishes can be achieved with rough surface finishes,
once they get dirty, they are hard to restore to brightness because of the roughness of the
surface finish. Therefore, mirror finishes and/or acceptability is normally around 8 to 12 RMS.
Lastly, perhaps the best surface finish that can be achieved, without lapping, is probably about a
2 to 4 RMS using mass finishing systems, and step processing.
Another common terminology used to measure surface finishes is Ra, which stands for
roughness average. This is the most commonly specified standard for machine shops in the
USA. This measurement standard would seem similar to RMS, because it is a measurement of
only the peaks of the roughness profile from the center line average. Therefore, as a general
rule, most shops have been using a conversion factor or RMS of 4 times greater than of an Ra.
That means that a normal mill finish on materials of 30 to 35 RMS would be equivalent to an Ra
of 120 to 140.
Now, what I just said is about the conversion factor may be true, but it is not correct. In
reality, this is a variable ratio that depends upon the process used to create or manufacture the
surface profile. This ratio is actually a minimum of 1.11 RMS, Rq to 1 Ra up to 2.10 to 1. See the
following conversion table.
Ratio of RMS to Ra
Actual ratios of RMS, Rq to Ra for various processes:
Turning 1.17 to 1.26
Milling 1.16 to 1.40
Surface grinding 1.22 to 1.27
Plunge grinding 1.26 to 1.28
Soft honing 1.29 to 1.48
Hard honing 1.50 to 2.10
Electrical Discharge Machining 1.24 to 1.27
Shot peening 1.24 to 1.28
For most processes 1.25 to 1
For honing 1.45 to 1
In addition to the terms RMS and Ra are a number of different other measuring
parameters. The following are a few popular examples. The term Rp is used to determine the
average peak height profile from the centerline. This information is sometimes more helpful for
Chapter 11 – Surface Finishing Standards 210
determining how well the surface profile may wear. Rv is the average valley depth of the profile
below the centerline. This information is helpful for determining how well that surface may
retain lubricant. Rt is the maximum peak to valley height profile and high lights the extreme
surface features. The term Rsk is a measurement of asymmetry or skewness of the surface
profile in relationship to the centerline. This information tells you the direction of the profile to
positive, neutral, or negative, which is desirable for a good bearing surface.
As stated, there are probably countless numbers of measurement scales, plus both new
and old terminology, which complicates things. Other scales which may affect burrs, but are not
covered in any detail here are those which are used to measure hardness, waviness, sharpness,
lay, texture, slope, etc.
This book was written and/or expresses all measurements in RMS; however, this term
may become obsolete shortly and replaced with Rq. I mentioned Ra which measures a surface
profile, but this too may become obsolete, in order to be more specific or limiting. This is a new
scale developed for Europe and is a ISO 10 point height parameter, or a 10 point Ra. That is, it is
an average measurement, which specifically covers readings over 5 peaks and 5 valleys within a
traverse length.
The function or performance environment of a part may require special considerations or
quality control standards that are more important than just surface smoothness. Therefore, there
are other scales that may be necessary for checking the parts acceptable performance, but not
necessarily a condition that can be controlled by mass finishing systems.
Other technical information or standards may be necessary to meet contract obligations
or performance requirements. That means being on the same page of the play book as everyone
else to meet the working conditions of the part, but again, these standards may not be
requirements of surface finishes which we are concerned with. Mass finishing can effect a lot
surface and edge conditions, but it cannot correct a badly made or machined part. Again, this
information is for reference only and cannot be effected by mass finishing systems. For
simplification, our references will all relate to RMS in inches for the rest of this book.
The following media selection information is directed at how to accomplish the best
surface finish results using abrasives and mass finishing equipment and media. We will start off
with media selection and or guidelines for processing certain type of materials and/or parts.
Then we will cover the liquid chemical side of this processing as a separate segment issue,
which it is.
Equipment will only provide the energy forces for the media and liquid to do their work.
Chapter 11 – Surface Finishing Standards 211
Surface Finishing Standards
The following chart is a good reference guide for a number of standards used for surface
profile measurements and their relationship to one another, if any.
Surface Profile Parameters
Parameter Name Standards Related
Height Parameters
Ra Roughness Average (Ra) 1,2,3,4 Pa, Wa
Rq Root Mean Square (RMS) Roughness 1,3,4 Pq, Wq
Rt Maximum Height of the Profile 1,3 Pt, Wt
Rv, Rm Maximum Profile Valley Depth 1,3,4 Pv, Wv
Rp Maximum Profile Peak Height 1,3,4 Pp, Wp
Rpm Average Maximum Profile Peak Height 1
Rz Average Maximum Height of the Profile 1,3 Pz, Wz, Rtm
Rmax Maximum Roughness Depth 1 Ry, Rymax, Rti, Rz
Rc Mean Height of Profile Irregularities 3,4 Pc, Wc
Rz (ISO) Ten Point Height 4
Ry Maximum Height of the Profile 4
Wt, W Waviness Height 1,2,3 Rt, Pt
Spacing Parameters
S Mean Spacing of Local Peaks of the Profile 4
Sm, RSm Mean Spacing of Profile Irregularities 1,3,4 PSm, WSm,
D Profile Peak Density 4 Sm
Pc Peak Count (Peak Density) 1
HSC High Spot Count
a Average Wavelength of the Profile 4
q Root Mean Square (RMS) Wavelength of the
Profile
4
Hybrid Parameters
a Average Absolute Slope 1,3 Pa, Wa
q Root Mean Square (RMS) Slope 1,3 Pq, Wq
Lo Developed Profile Length 4 Ir
Ir Profile Length Ratio 4 Lo
ADF and BAC Parameters
Rsk, Sk Skewness 1,3,4 Psk, Wsk
Rku Kurtosis 1,3 Pku, Wku
Tp, Rmr(c) Profile Bearing Length Ratio (Material Ratio of the
Profile)
1,3,4 Pmr(c), Wmr(c), Pmr,
Rmr, Wmr
Htp, Rc Profile Section Height Difference 1,3
H Swedish Height Htp, Rt
Rk Core Roughness Depth 5
Rpk Reduced Peak Height 5 Rpk*
Rvk Reduced Valley Depth 5 Rvk*
Mr1 Material Portion 5 Rmr(c), tp
Mr2 Material Portion 5 Rmr(c), tp
Vo “Oil-Retention” Volume
Rpq, Rvq, Rmq Material Probability Curve Parameters
212
Chapter 12 – Media Media Supplies
The word media is a very generic catch all word. It is a proper noun that acts more like a
descriptive verb. It can mean virtually anything that is used to convey or transfer some kind of
result, be it good, bad, or indifferent. Early on in this book we talked exclusively of abrasives
and this is a form of media, because an abrasive transmits energy from one source to another
and in the process, it causes mechanical movement and friction. When this movement is
controlled in a uniform way with uniform abrasive materials, this produces predictable results.
In addition to being an energy transfer system or process, this can also be considered a
destructive system or process. That is because whatever media or parts are placed into these
energy systems there is an expected modification result to the media and parts.
Within the text of describing all mechanical deburring equipment, we eventually added
and changed the word abrasives to media or used the words inter changeably. However, in
mass finishing systems, media is the most common term used to describe any material that is
used to produce a modified or altered appearance to a part. This usually refers to an abrasive,
but it can still be anything that will abrade, polish, clean, or separate parts. Media can be
random stone or mineral aggregate, preformed shaped ceramics, plastics, steel, or alloy metals
and all forms of organic materials. In other non-mechanical material removal processes it can
also be a liquid, or extreme heat. Most of the media talked about in mass finishing systems are
inorganic materials used in what are called wet processing operations; however, there are also
dry organic materials that do light material removal and polishing.
Given one specific part, run in different media compositions of the same size in the same
machine, or similar technology machines, you will get different results over the same period of
time. That is because each media system has different abrasive qualities, wear rates, and surface
finishing characteristics, but the surface profile of a part is also effected by liquids, chemical
compounds, and machine adjustments. Therefore, that means that the selection of a media
requires some knowledge of both the equipment being used and the abrasive media and that
discourages a lot of people from using mass finishing equipment.
An analogy of abrasive media here is that it behaves like the numerical controls of a
computerized machine system. However, instead of pushing buttons or numbers to control
movements and tools, the operator physically puts in or installs the proper size, shape, and
composition of media and this determines the parameters of the final surface profile and the
rate of material removal.
Depending upon the parts to be worked, almost anything can serve as deburring media.
In a pinch or in an extreme need, you can go outside and dig up some gravel and put it into a
mass finishing machine and it will achieve some kind of results. The trick is to find and use that
same consistent media to produce the same predictable results you are looking for, in the
shortest period of time, and hopefully produce acceptable uniform results over and over again.
Chapter 12 – Media 213
As mentioned, not only do you have to worry about selecting the right media, you have
to be concerned with its size, shape, and composition. Other factors to be concerned about are
the life or wear of the media, and what kind of end results or surface finish that has to be
achieved. There is no single cure all media that will work on all parts or materials and having
and storing of a lot of different abrasive media is sometimes not practical. There are tradeoffs.
The following are some general rules or patterns that can help you select the right media for the
right part. Here then are some rough guidelines to help your selection process.
Random Media
First of all, let's narrow down some basics. Long ago, most abrasives used in any kind of
material removal process were random aggregate of mixed stone materials. It was soon found
out that without controlling the type of mineral aggregate used, different results would be
achieved using different batches from even the same material or source. Therefore, the
aggregate was identified to a specific mineral content. If the mineral was a mixture of different
particle sizes of the same material, non-uniform results were also possible due to the inability of
the random mix to achieve good uniform surface contact on the part or material being
processed. That difference of particle sizes also effected the processing time and surface finish of
the part; therefore, abrasive suppliers began to be classifying minerals into a particle size range.
The random shape or nature of crushed aggregate makes it almost impossible to come up
with a singular specific uniform size or weight per particle; however, it is possible to come up
with a size range. Classification even within a size range still does not exactly end up with a
100% uniform particle size. That is because over 90% of the particle size falls within the x and y
or length and width dimensions of the screen size, but that it does not control the z or height of
the particle size. However, the parameters of the classification and the remaining materials are
normally within 5 to 10% of that size range and that is close enough to produce good uniform or
predictable results within limits. Just as a note, random aggregate generally has a spherical or
elongated shape to it and that limits its access to certain part recesses, inside dimensions, and
corner angles.
Depending upon the abrasive material, approximately 90% of the aggregate particles will
conform to a screen size hole opening. The screen serves as the classification method and is used
as the standard to measure crushed random aggregate particles. Any material that passes
through a specific size screen is classified as being that size, but it also has a lower screen upon
which and from which that media is taken. A secondary screen, below the first screen
somewhat controls the lower minimum size of the particle or aggregate classification. That also
means, the finer the screen, the better the conformity of the particle size.
In the manufacturing process of making abrasives products, rock mineral is crushed and
allowed to fall through a series of wire mesh screens stacked one on top of another. Wire is used
because of the efficiency of open area to solid wire; therefore, the hole size is not exactly a true
indicator of particle size. The proper classification of abrasive particle size is separated by a
series of screens which block out larger materials from passing through a screen and catching
Chapter 12 – Media 214
the size range which is allowed to pass through the upper screen and retained on the next
smaller size screen.
As stated before, perforated holes or screens are better for more uniform media
classification, but it has too much solid mass to be efficiently used in separation systems. Square
holes are better, but although they have fixed X and Y dimensions, they also have a larger
diagonal dimension. In most cases, the classification of aggregate usually comes off of a group
of screens, especially on small sizes, giving a range or a two number type grade or classification,
but it can be a single screen size or number.
In addition to a size range, there is normally an abrasive mineral range. Minerals have a
molecular crystal bonding structure that affects the cohesive nature or hardness of the particles
within the material description. If a mineral product is consistent, or produces consistent
results, one does not normally question the purity of the abrasive mineral, provided it achieves
the final surface finishing results.
Unless one absolutely needs a pure form of a specific mineral, which is not likely, there is
also a range of mineral product and this is determined by natural availability. Particle size is
controllable by man, but mineral conformity or content can vary from different sources. There
are mineral variations and because of this, there are products sold as a blend rather than a
straight mineral. These blends may have a specific name, but they are still composites of a
group of minerals. The main advantage to blends is a reduced cost factor rather than a
performance factor.
Because of all these variables the abrasives industry was established to control more
uniform standards of classification for sizes, mineral grades, and blends. Today, not a lot of
people question the size and/or content of the abrasive product they use, because most of the
variable characteristics of the abrasive are known, or the limits or range of the product is
known. In some extreme cases letters or certificates of quality can be obtained to conform to the
product purchased. Generally any product sold must conform to specific quality standards set
by the industry.
Besides quality, if the cost of a product changes drastically, and/or new safety hazards
are discovered, such as the problems associated with silica or gypsum, this may require a
person or company to consider a new alternative product with similar performance capabilities
and the industry should have ready alternatives. Then again, alternatives are readily available
because of stocking. That is, unless a company is buying from a manufacturing source, it is
buying from a warehouse that stocks a number of items from different manufacturers. If the
product is not available, or costs have changed, normally one can select another particle size, or
another product with similar material characteristics.
Loose random abrasive materials of different sizes or a size range has certain application
limits. That is, for cost purposes, this industry makes a mix or blend of sizes of a specific
product in order to accommodate specific applications. If this standard size range is not
acceptable to the end user, then additional screening operations can take place to control the
size of the particle needed; however, that also means additional handling and costs.
Chapter 12 – Media 215
The economics of supply and demand, plus the sorting operation and the manufacturing
or quality control of screens determine the accuracy of these sizes and their cost. The next
biggest cost factor is freight and maintenance or storage costs. The availability of mineral
sources and the law of supply and demand really controls what is produced and sold. That law
may also be superseded by technical knowledge of availability versus costs. I suppose that both
cost and usage of a mineral product are shared or determined by the distributor and the user.
A company that uses abrasives is basically dependent upon a supply source for
information. Therefore, if they do not have the information or it is unknown, then they or you
are locked into what you can get or have knowledge of. That means that what is sold comes
back to the statement that the more commonly used abrasive materials and size ranges that are
stocked by the manufacturing source and their distributors.
What abrasive is common or sold is or should be what works best. However, on the other
hand, if a manufacturing source doesn’t have high labor and maintenance cost to produce a
product then the cost factor becomes very important and they can pass on the savings to the end
user. If a company doesn't have to make many processing changes and has a good source for
the raw material, and it doesn't present a safety hazard when used, then it is cheaper to process
that single abrasive product than it is to process several different sizes or products. Even though
I just used the word products, most mineral sources are geographic in nature and there is only
one product mined and processed.
Media Size
Why is abrasive particle size so important? Because all parts are designed to function to
accomplish some desired end and their design is dictated to certain pre-determined dimensions
and/or shape plus function. Part shapes must maintain certain dimensions that when machined
can be quite complicated. That is, they must have fixed equal distant points or angles. That
means that abrasive materials have to pass freely around or through these points to deburr the
part properly without effect the critical dimensions of the part. Simple right? Not exactly!
Unfortunately, most parts are engineered and designed to perform a function with little
thought about the manufacturing or surface finishing problems associated with the finished
product. Parts can and should be made to take into account both machining and finishing
limitations. That means that parts should be designed to avoid as many recesses, pockets, holes,
or sharp angles as possible or within reason. Again, there are tradeoffs.
The design engineer does not normally take into account the material finishing
requirements. He usually leaves that up to a mechanical engineer who tries to work with
existing equipment systems. It is usually only after the ME determines that the company does
not have the proper machine or enough machine capacity to work the part does he look at new
or alternative equipment. When it comes to the surface finish profile of the part, most engineers
leave that decision up to a process engineer or worker on the floor. Normally, a finishing system
is the last consideration of any manufacturing operation and is not considered an important
issue.
Chapter 12 – Media 216
I purposely spent some time here to show you some of the steps prior to surface finishing
to emphasize the problems and/or delegating of responsibilities here. What I hope you see is a
trend to shrug off responsibility to normally lesser and lesser qualified or trained people. Then
again, the operator using the equipment may ultimately be way more knowledgeable of the
equipment limitations and finishing capabilities than the engineer responsible for the final
product. Finishing problems are determined by use and conveying the importance of what is
critical or important to the finished part. For instance, why polish a part, if it will never be seen.
From the stand point of processing only, the following is just good sense. For
simplification, efficiency, and ease of separation, one usually selects a media that is smaller than
the part, because it is easier to let the media pass through a separation screen than the part. At
the same time, you do not want to select a media that will get stuck or lodge itself within the
part. Also remember that multiple pieces of media can get jammed or get stuck as easily as one
piece. A good rule of thumb is to select a media that is larger than the smallest hole or
dimension that has to be deburred. If inner dimensions have to be worked or deburred, select a
media size that is not too close to a half size of those dimensions because of the multiple pieces
jamming problem.
Abrasives or media breaks down and becomes smaller with use. Therefore, another
guideline or the best rule to follow is that the larger the size or the heavier the media, the faster
it will work because the specific gravity or weight of the media will apply more pressure to the
work the part. Why media larger than the part is not commonly used is because it cannot
contact the part uniformly. Media size must be selected that is able to reach into all areas of the
part that must be worked to produce uniform results.
If the media selected to work the part is larger than the part the deburring process works
faster because there is more bulk, weight, and pressure in the process; however, it is also more
difficult to separate the parts from the media. The larger the media the faster the material
removal and normally the rougher the surface finish. That also means that thin or soft parts may
be susceptible to damage or marks caused by heavier and larger media. As for separation, that
normally means that the media will have to be handled at least twice, or at least differently,
because the media itself may become smaller or fracture causing a wide range of sizes both
larger and smaller than the part.
The process of removing parts from larger media is called reverse separation. There is no
standard machine built that I know of that can automatically remove smaller parts from larger
media, unless the parts are magnetic. Fully automated systems can and have been built with
multiple screen systems for this purpose, but they are not common. The cost to build such
automated equipment does not seem to warrant the extra benefits of using larger media than
the part.
If reverse separation is needed, it is normally cheaper to dump both the parts and the
media onto an inclined secondary screen device to allow the parts to fall through and be
captured by one container while the media goes into another container off to the side. Because
of media breakdown, you may still not end up with 100% parts after this type of double
screening, especially if the media and parts are nearly the same size. Also, this practice is
inefficient because the machine from which everything came must be refilled.
Chapter 12 – Media 217
For inorganic random media to be effective deburring parts over 1 inch in size in mass
finishing systems, its minimum size should be over 1/2 to maybe 3/4 inches in over all
dimensions or grit sizes 3 to 2. Media can be up to 2 inches or 00 grit size, provided there is a
good way to separate parts from media. A good size range between media and parts is
desirable for part separation rather than abrasive characteristics. Media smaller than a 1/2 inch
or under a 3 grit size for this application example will not be efficient economically because of
time; however, given the same media composition, the surface finish will be smoother. The
same basic rules apply for parts smaller than 1 inch down to about .030 in size or approximately
24 grit. At this small size, mechanical systems are not very effective.
Standard Inorganic Grit Sizes
Grit Size # Mesh Microns Inches
USS** (Average) (Average)
4 3.5 5600-4750 0.187 (nom)
5 4 4750-4000 0.157
6 5 4000-3350 0.132
7 6 3350-2800 0.111
8 7 2210 0.087 (av.)
10 8 1845 0.073
12 10 1600 0.063
14 12 1346 0.053
16 14 1092 0.043
20 16 940 0.037
24 20 686 0.027
30 25 559 0.022
36 30 483 0.020
46 40 356 0.014
54 45 305 0.012
60 50 254 0.010
70 60 203 0.008
80 70 165 0.0065
90 80 145 0.0057
100 100 122 0.0048
120 120 102 0.0040
150 140 89 0.0035
180 170 76 0.0030
220 200 63 0.0025
Micro Grit Mesh Microns Inches
240 200 50-53.5 0.00200
280 40.5-44.0 0.00154
320 32.5-36.0 0.00122
360 25.8-28.8
NOTE: As grit size becomes smaller the size range becomes more in line with the screen
size hole openings used to separate and classify the mineral.
Chapter 12 – Media 218
Because of dimensional irregularities of larger inorganic random media shape, there are
multiple dimensional factors, which may vary substantially. Therefore, the larger the size of
random media the larger the possibility of random size media to get stuck. Any random media
size over a 1/4-inch may not pass freely around a machined part without getting stuck or lodge
in specific locations within a part design. Most random media used for deburring is in a size
range of .120 to .030. There are just too many variables that cannot be controlled by using
random media. Therefore, greater control of media dimensions is desirable and accomplished
by preformed shaped media.
Loose random abrasive media is commonly used in all composite abrasives, belts, and
rigid wheels. It can be found in a lot of re-formulated compounds or hard coatings. By its self, it
is used mostly in abrasive blast systems, but is not that common in mass finishing systems. The
main reason for its usage has to do with how the energy is applied. That is, in abrasive blast
systems, energy is transferred to air born particles of a specific size of random media in an
indirect application of energy and that impacts the part. Upon impact, energy is diffused
rapidly to both the abrasive and the part or materials surface, resulting in a spot or contact
point. In mass finishing systems, there is a direct application of energy in the form of pressure
and friction that causes material removal in a line of force rather than a particle spot.
Again, how energy is applied is the reason for the different forms of deburring and
surface finishing systems and equipment technologies. Abrasives are the most popular media
form used in mechanical processes to transfer energy and remove materials. However, there are
new developments in manmade synthetics that improve the abrasive characteristics and
longevity of transfer devices even though they may cost more. Normally, manmade media is
normally a more pure mineral form or variation of a naturally occurring abrasives, but have
better control over abrasion, size, and wear life.
Preformed Shaped Media
Because of the problems of random media dimensions and/or its tendency to get stuck in
parts, manmade preformed shapes were developed that specifically control outside dimensions
of the abrasive media shape. The preformed media shape is also designed to control the rate of
material removal, media wear, and performance. It is the advent of the preformed shape that
made material removal and surface profiling an exact science and for the popularity of mass
finishing processing equipment.
Technically speaking, a preformed shape is a part, but because its purpose is to work
other parts, it is never referred to as a part, but it does have fit, form, and function just as the
part being worked. Instead of being called a part or a proper noun, it is referred to how this man
made material is used, that being media or abrasive. In the trade, the manufactured abrasive
media is just referred to as a preform or the shape that the preform is made into.
Composition
A preformed abrasive is a rigid molded shape or cut extrusion shaped part usually made
with either a ceramic or plastic based bonding agent somewhat like cement or an epoxy blend.
Chapter 12 – Media 219
Besides the bonding agent, which is designed to break down or deteriorate at a fixed rate of
usage, the shape contains a specific size of random abrasive particles. The size of the abrasive
normally determines the amount of material removal from the part and the bonding agent
determines the rate of material removal. That means that there can be a lot of formulations for a
specific size and shape of that preformed media.
Although mineral particle sizes can vary to some extent in a preformed shape, but it is
the bonding formulations that vary the most and control the rate of media and part breakdown.
The shape contains a uniform matrix of smaller abrasive mineral particles, rigidly held in place
by the bonding agent to do the material removal work. The abrasive particles in the preform
shape behave like a series of small chisels or the teeth on a hacksaw that abrade the material
being worked. As mentioned, the abrasive particles that go into these preformed shapes are a
specific size of loose random abrasive particles. However, unlike random shape media, the
abrasive particles in these compositions don’t exceed .060 in particle size.
As the media shape is used, the smaller abrasive particles in the preformed shape lose
their roughness or ability to cut or do material removal to the parts due to either rounding off or
fracturing of their exposed abrasive particles within the preformed shape. One of the
advantages of preformed media is that the bonding compound is formulated to continuously
recede and expose new or more abrasive particles that are more pristine or sharp. These shapes
are capable of maintaining a relatively consistent efficient material removal rate over at least
half the life or size of the preformed media shape. Actually, the media retains its cutting ability
until it is used up; however, because of the weight factor being reduced, the media shape loses
its effectiveness and shape characteristics around it half life.
A quick word about the terminology, “life.” Media can be used up to the point it
completely disappears by itself down the drain. However, prior to this point, there may be
additional problems. Therefore, I like to talk in terms of half life. You know that radioactive
materials have half lives, well so too does everything else. Half life, in my opinion, is about the
best mileage or usage you can get out of a preformed shape. In most cases, based upon a 40
machine hours week, the half life of a fast cut preformed shape is about 3 or 4 months. This time
frame can change depending upon the bond or composition of the preformed shape. A fine cut
media is probably closer to 4 or 6 months life and ceramic porcelain media is measured in years.
Getting back to half-life. Why I chose this point is because at this size the preformed
shape looses significant weight and energy mass to do the same amount of work as it did when
it was new. Therefore, as media gets smaller, it takes longer and longer to do the same amount
of work. Also, at half-life, the media shape is virtually gone. That means that the media is
subject to getting stuck a lot easier and holes become a major problem for lodging. At this half
life point, if you want to continue to use this media for other smaller parts, you should re-sort,
separate, or classify the media to know what new size part it can work without getting stuck.
A preformed shape does not guarantee that the media will not get stuck in a part, but it
does minimizes the potential for such a problem, if one sizes the media to the part properly. The
human factor still plays a big part in this potential lodging problem. That is, the media selected
Chapter 12 – Media 220
must still meet certain criteria of compatibility before it should be used. Also, as I indicated
earlier, there is no one shape for all media that will or can do the job on all parts. On top of that,
it is nearly impossible to maintain a stock or inventory of all of the different media sizes and
shapes needed or necessary to work all of the parts that most companies have to process. All of
this means that somewhere down the line tradeoffs or compromises have to be made on what to
stock and use in your mass finishing equipment.
The two main problems for media selection that should be address first are: 1, What
composition media to use for the application? 2. What size and/or shape to use for the
application? For deburring, there are two main selections and these are determined or involve
the nature of the part to be worked. Are the parts to be deburred ferrous or non-ferrous
materials? Ferrous materials almost always use ceramic preformed shapes. Non-ferrous parts
normally use plastic or synthetic preformed shapes. Non-metals can normally use either
depending upon the results one wants to achieve.
Part size is an important factor that effects media selection. For processing small parts
under a 1/2-inch in size, dry organic materials are normally recommended and can be used that
have a fine abrasive in them. There is also a new organic shape media that is also used dry.
Some inorganic media shapes can be used in some cases, without a liquid, but are not normally
recommended. When inorganic materials are used dry by themselves there is a relatively fast
breakdown of the preform shape and contamination has no place to go and it can become a
problem.
Preformed ceramic media is made and available down to 2 millimeters in size for wet
processing and 1 millimeter porcelain balls are available for burnishing. However, water and
small lightweight parts do not work properly in the recommended proportions of normal mass
finishing guidelines. This is especially true of any size of heavier flat parts as well. The next
problem is basically you do not want the media to get stuck in the part configuration, recesses,
or holes and at the same time it has to get into the problem areas to deburr or surface finish all
areas of the part.
Ceramic Media:
The most common abrasive performed shaped media is made with ceramic based
materials and is capable of working harder carbon steel materials than plastic bonded shapes.
Because of its hard rigidity and composition, it is more abrasive than plastics and therefore
transfers its energy and weight more directly to the parts in question. Also, ceramic media
normally has greater weight than plastic, at around 80 to 120 pounds per cubic foot of media,
and is capable of working materials relatively fast. The preformed media shape size, particle
size within the shape, and the mineral composition of the preformed shape determines the
surface finish. Normally, the larger the particle size, the faster the material removal.
Plastic and synthetically formulated based preformed shaped media weights around 55
to 90 pounds per cubic foot and is softer, lighter, and more flexible than ceramic. Some newer
formulations exceed 100 lbs. per cubic foot of material. A fast cut ceramic with .060 particles,
will generally leave processed ferrous metal parts with a dull galvanized texture appearance
Chapter 12 – Media 221
and so does a coarse plastic on non-ferrous materials. Plastic media shapes on ferrous parts will
take an extremely long time cycle and may not properly deburr the part no matter how long
your process time.
If you do try to use plastic media on carbon steel, what you will get are parts with a
glossy uniform finish, but not necessarily smoother. On the other hand, ceramic media on non-
ferrous materials will chew up your parts in a short period of time, maybe in 5 or 10 minutes.
Also most ceramic compositions will probably leave your non-ferrous parts with a rougher
surface finish than what you started out with and that may not be suitable for a secondary thin
coating or anodizing.
Earlier, we talked about abrasive particles and their relationship to specific gravity or
weight. We said generally the larger the size and weight of the particle, the faster it works. This
same principal applies to preformed media shapes, except you have a number of other factors to
consider and all of these effect the characteristics of preformed media and its ability to remove
or abrade other materials, how fast it works, and what kind of surface finish it will produce. The
following criteria are used to determine a good preformed media shape.
Preformed Shape Media Factors
1. First is the hardness and weight of the abrasive particles. This is the same as
characteristics for random media.
2. Second is the bonding agent, which controls the rate of breakdown of the media wear,
amount of abrasive particles, porosity, and general hardness of the media.
3. Third is the size of the abrasive mineral particle within the compound matrix and
media shape.
4. Fourth is the actual manufacturing process and/or how the media is made.
5. Five is the temperature at which the media is cured.
We have talked about specific gravity and weight of random media before; therefore, we
will start out with the second factor, which are the inorganic bonding materials used in the
manufacturing process. These ingredients are all trade secrets, but nearly 100% of a man made
preform is naturally occurring inorganic clay type materials which are designed to lock up or
bind everything together and therefore control the rate of breakdown or wear rate and/or
hardness of the preformed media shape. These bonding additives have certain characteristics
that control the amount or percentage of abrasive particles and their size in the matrix and
control the porosity and/or absorption rate of these bonding materials.
The number of inorganic bonding ingredients or compositions are normally limited to
about seven different standard blended formulations of materials per manufacturer and are
designed to perform in a certain manner on specific materials or parts and have certain expected
abrasion characteristics and/or surface finishes. The number of formulations is only governed
by the ability of the manufacturer and/or customer on a supply and demand bases. That is, any
number of formulations is possible, but the cost goes up if it is not a standard stock formulation.
Chapter 12 – Media 222
Dramatic deburring finishes can be achieved that involve the bonding agent only. That is,
given the same abrasive particle size in a different bonding composition, the rate of cut can be
significantly greater or faster using a different bonding agent that breaks down faster. At the
same time, the overall surface finish will normally be rougher than a slower rate of cut or break
down. Preformed media shapes must break down in order to do material removal properly and
in a reasonable period of time.
If the media shape does not break down, it will lap or burnish a part rather than deburr it
and/or the cycle time will be greatly increased to accomplish nearly the same end results. In this
case, the result of burnishing is more the deforming of the parts surface profile. Burnishing
basically flattens or moves surface features rather than removes them. Ceramic porcelain media
is nothing more than a very hard formulated bonding agent made into a preformed shape.
Preformed media shapes made with a soft or loose bonding agent normally produces a
fast cut rate on parts. Again, particle size is also important in the amount of material removal,
but generally the bond is very important. The faster the breakdown of the media the greater the
costs and economics of the material and maintenance of the process. Again, there are tradeoffs
of speed versus costs, or the cut rate of the abrasive versus the wear rate of the media. No
deburring media will last forever. All this means that the economics of media usage may not be
as important as the economics to produce a good acceptable end product.
We talked about half-life before, but it deserves mentioning again. A typical wear rate for
media is somewhere around 3 or 4 months, based upon a 40 hours per week, before half life sets
in (see application section for specific attrition rates.) and/or where the media becomes too
small, in most cases, to be effective on the parts for which this media was originally selected.
There is the inherent problem of the media becoming smaller and smaller and eventually small
enough to cause lodging within the parts being worked and this maybe way before the half life
time cycle sets in; therefore, other factors need to be considered other than direct labor or
material costs.
The third factor of size was explained earlier. The larger the size the more aggressive. The
smaller the particle size, the finer the surface finish. Rough finish versus smooth finish. Fast,
short time cycles versus long time cycles. The fourth factor that controls a preformed media
shape is the actual manufacturing process. The amount of pressure and/or how it is applied to
the preformed shape affects the density and weight of the media. In the manufacturing of
preformed shapes, pressures of 7,000 PSI to 20,000 PSI can be applied by extruding or pressing
the preform into a shape. Naturally, the greater the pressure, the harder and denser the
preformed media shape and this normally relates to wear resistance or longevity of the media.
Some preformed media shapes are made from what are called sintered materials. This
manufacturing process causes materials to react or bond under pressure to create a preformed
shape, without liquid additives. These preformed shapes have very high wear rates or longevity
and are used mostly for burnishing because they are so hard, but they are also capable of some
light deburring. On the negative side, because of porosity of sintered media, leaching of finer
Chapter 12 – Media 223
microscopic abrasive particles occurs and this may tend to discolor or darken the materials
during processing.
The fifth factor that effects preformed media performance is the curing of the media. That
is, all media begins as a slurry mix, except sintered materials, of ingredients with just enough
moisture to hold a shape or configuration. Then this green or uncured media is baked in ovens
at temperatures between 2,000 degrees to 3,100 degrees Fahrenheit. All of these inorganic
materials are heated to reach a point short of absolute melt down were fusion or the binding of
the matrix compounds takes place. The way in which the heat is applied and/or cooled also
plays a part in the media wear rate and hardness. Media cured at higher temperatures normally
are harder porcelains and are used for burnishing. By the way, all ceramic media is gray or
brownish in color. The harder and/or a finer the abrasive compound preformed, normally the
lighter the color. A porcelain or burnishing media is normally pure white and a very abrasive
media is usually a dark gray or dark brown in color.
Before choosing a preformed media shape there are other factors to consider. Besides all
of this technical background on the media and selection, one’s choice may still not be a one shot
deal. That is, one size, shape, and media composition may not achieve the end results you are
looking for on a specific part. If you have multiple parts, multiple materials, or your part
requires a very low RMS and/or polished finish, then you may not achieve the results you are
looking for using one size, shape, or media composition alone. This is especially true if you are
trying to achieve very low surface finishes. In the latter case, you will need to change media
compositions before you achieve the results you are looking for, if you want to do the
processing in the shortest quickest most efficient time. This is true of any and all abrasive media
deburring systems.
There are surface finish limitations designated by the characteristics of the abrasive
particle size within the preformed media shape. That means that you may need to use more
than one media in a series of steps or operations to achieve the end results you are looking for.
You cannot combine media of different compositions within the same work chamber or process
and achieve the desired end results.
To achieve a surface improvement of over 8 to 10 RMS or get to a certain point or surface
finish under 12 RMS, it is normally faster to achieve that surface improvement by using more
than one media composition in a series of operating steps. For economical reasons these
operational steps are usually limited to 3 steps, but 5 or 7 are possible. This is what is called or
referred to in the industry as step processing. More detail will be said about this latter. This
multiple processing is part of that black art we talked about at the beginning of this book. But, it
is also the same criteria used to produce fine finishes using buffing wheels.
The most common abrasive used in a ceramic and plastic preformed shapes is aluminum
oxide, it is very hard and therefore effective for fast deburring. Also, as you learned earlier,
there are different grades or hardness depending on the type of aluminum oxide that you use to
make the preformed shape. Silicon carbide is sometimes preferred over aluminum oxide for
faster cutting action, especially on hard materials or ferrous parts that become weldments.
Chapter 12 – Media 224
Another abrasive that is popular for fast deburring is zirconia, but it is more expensive. Less
abrasive is straight silica sand and quartz which also cost less. Other special abrasive mineral
formulations can also be made to order but need minimum weight production runs.
Another media selection factor to consider is based on contamination. The bulk of the
bonding agent of the media breaks down and is heavy enough to settle out of solution. Some of
the media waste breaks down and becomes so fine that it can become microscopic in particle
size. This particle solution can penetrate and get trapped in the porosity of the materials being
abraded; therefore, some quality control requirements will not allow the use of aluminum oxide
or silicon carbide abrasives on some metals for other technical reasons.
Other processing factors to consider besides media formulations are the problems of
using the same media, or re-circulating the same liquid for both ferrous and non-ferrous parts.
Mixing metals, media, or liquid are not recommended because they are all good transfer devices
for contaminating dissimilar metals or parts and producing potentially undesirable end results.
Earlier, I mentioned that manufacturers usually make about seven formulations of media
in different sizes and shapes. In most cases, users of media want to deburr a part in the fastest
shortest period of time possible to keep costs low. That means that the customer wants the
largest size media possible with the largest abrasive particle in the preformed shape. What
limits or prevents the use of the largest media is the size of the part and all of the areas of the
part that have to be worked. You should consider limiting your selection to a media that will
not get stuck or jam in the part and will not bend or distort the part and yet work all the areas
that have to be worked.
For simplification and/or classification I will arbitrarily say that there are only coarse,
medium , and fine grades of ceramic media. That is not true, but it is a simple example. Starting
with a normal mill finish carbon steel formed part with about a 35 RMS, a fast cut coarse media
will, in about a 5 cubic foot capacity vibratory machine system, takes 5 to 20 minutes to deburr
most metal parts. This variance in time depends on the hardness of the material, the severity of
the burr, and the configuration of the parts. The finished part from this media should have a
surface finish or profile of around 24 to 32 RMS. Multiple this time factor by about 10 for older
barrel systems and divide by 10 for high-energy mass finishing systems. Again, this is not
exactly true, but it is close. The visual appearance of this part will look very dull and have a
galvanized textured appearance. Stainless steel, machined parts, metal castings, and some
flexible synthetics may take longer than our carbon steel example.
To accomplish a finer finish, suitable for most paint coatings, a medium grade abrasive
media is normally required after the abrasive fast cut media. The normal range of this media,
after the coarse media, will achieve a surface finish of around 22 to 28 RMS. The end results will
have a finer appearance or a dull satin type finish with no major noticeable abrasion pattern.
These results can be accomplished in about 15 to 45 minutes when used as a second step process
and using the same parameters mentioned above. If this media is used as a first step, starting at
35 RMS, the finer finish will probably take more than twice as long and may take as much as 2
to 4 hours to accomplish in a vibratory machine system.
Chapter 12 – Media 225
Normally, any part that needs to be plated requires a fine finish of around 16 to 22 RMS.
To achieve these results, a third step may be required using a fine cut media. Parts with a
surface finish of 22 to 24 RMS processed with this media, after the second step mentioned
above, will take 20 minutes to 1 hour to achieve at least an 8 RMS improvement or result using
the vibratory equipment. The visual finish on the part will be a bright looking luster, but far
short of a mirror finish. Naturally, if you start out with this media, instead of the steps indicated
above, the processing time will take well over 4 hours. Maybe triple that time or more.
The above three-step process is typical for parts requiring a fine finish prior to plate. It is
not absolute. There are variables that may affect time cycles and surface finish. That is why
there are so many variations and/or varieties of abrasive media. It may not be a simple and or
choice for media. Future technology and abrasive compositions may change, but for now that is
how fine surface finishes are accomplished using mass finishing systems and that is one of the
areas that few engineers or management understands. Excluding material handling of parts and
the cost of replacement media, liquid compound, and water, that is the fastest most cost efficient
deburring way to process parts requiring a fine surface finish of around 8 to 12 RMS.
Before I move on to plastic media, I will say that there are new formulations being
produced all the time. A lot of these new products are designed or formulated to try to find a
good media that will work both ferrous and non-ferrous parts equally well. One company has
come close, but again there are tradeoffs. There is a good new hybrid product that does work
both ferrous and non-ferrous materials, but it does not work either one very well. But it does
come close to being a universal acceptable media for both materials and it is very helpful for
companies that use and process a lot of mixed metals or just non-ferrous producers who are not
concerned with a fine RMS finish.
The term used to describe this hybrid media is called light weight ceramic. This media
weights around 61 to 65 pounds per cubic foot rather than the normal 90 to 100 pounds for most
other ceramic deburring media. Because of this lighter weight and low density or porosity of
this new media it can maintain good cutting ability to the part and it maintains relatively good
wear characteristic to the media. This material still has some problems such as ferrous parts take
longer to achieve good results, and non-ferrous parts normally result in rougher finishes. When
this product was first introduced, the wear or attrition rate was so fast that that the media
replacement cost made this media questionable to recommend. However, improvements to this
product now make this a very competitive product which I would now recommend, providing
one can live with the problems indicated earlier. Again there are tradeoffs.
Chapter 12 – Media 226
Preformed Shaped Media
Fig. 89. Ceramic Media
Ceramic preformed shaped media bonds are extruded and more rigid than plastic.
Ceramic shapes are used for deburring and/or surface removal of hard ferrous metals or where
a lot of material needs to be removed. Ceramic shaped media comes different angles of the same
shape and in compositions or shades of gray or brown, the lighter the color the finer the cut.
Some of the more common shapes are shown below. The more the geometric straight lines of
the media, the more resistance or force is needed to move the mass. The rounder the lines, the
more mobile the mass.
Mobility Resistance
Plastic
Plastic preformed shaped media bonds are molded and used to deburr mostly on non-
ferrous metals. The bond is softer and more flexible than ceramic and therefore produces
normally smoother RMS surface profiles. The plastic bond compositions can be made with
either polyester or urea plastic resin formulations, which are usually distinguished by bright
colors.
Fig. 90. Plastic Media
Mobility Resistance
Chapter 12 – Media 227
Plastic media:
For a good number of years, random media and later ceramic preform media shapes
were the only choices available to most people using mass finishing equipment. In the 1940's
plastic preform media was developed to produce better surface finishes on non-ferrous
aluminum and brass parts. Even though ceramic media deburrs non-ferrous parts, the surface
finish was not fine enough to produce a good surface finish capable of accepting a uniform
chemical alodined or anodized sealing coat to protect against oxidation.
It was found that by changing the hard bonding agent of ceramic media to plastic, better
or smoother surface finishes could be achieved on non-ferrous parts because of the softer more
flexible characteristics of plastic. Because of this less rigid quality and significantly greater
processing time, this media is not recommended for deburring ferrous materials. Hard materials
and soft media are not normally a good combination. Usually the media gets worn out and
produces questionable results versus costs. However, plastic media has also become the choice
for processing precious metals and jewelry because of its finer surface finishing characteristics.
Except for the bonding agent used in the manufacturing of plastic media, almost
everything that was said about ceramic media above can be said about plastic media. Just as
there are five steps that effect the manufacturing and final product of ceramic preformed
shapes, so too are these same steps a factor with plastic media. However, preformed plastic
media has a bonding agent made from synthetic chemical compound variations, which deserve
maybe some additional information.
First of all, most common plastic media is made with a polyester plastic based bonding
agent. Polyester has a tendency to break down and produce a white milky residue which has a
greater tendency to go into solution as microscopic particles finer and lighter than ceramic
residue and more difficult to settle or filter out. Also, that residue can cause foam to form and
harden in the discharge waste of a holding container if it traps air. This harden foam residue is
flammable under some normal disposal conditions; therefore, appropriate safety precautions
are required especially where people smoke. It is not exactly highly flammable, but it does burn
rapidly and may be difficult to put out because of its lightweight feather like qualities.
Unlike ceramic media, which uses basically one inorganic type of formulation, plastic
comes in two basic formulations. We talked about polyester based performs, the other
formulation for plastic media in use today is a formulation that uses a urea plastic bonding
compound. This media is made with formaldehyde and in its raw state before manufacturing
can be very hazardous. However, after this manufacturing process is complete there is virtually
no hazard of formaldehyde in its use or problem for its disposal.
The advantage of this urea formulation is that it is softer, more flexible, and will not foam
as much as polyester based plastics. That means that it is less likely to leave marks on finer,
softer materials, or precious metals. Also, urea is less likely to work as fast as polyester. All of
these differences are minimal; therefore, there is relatively little difference in performance
characteristics. Cost wise, urea is less expensive than polyester and therefore it is gaining
greater popularity and usage.
Application information for plastic media is basically the same as you find for ferrous
and ceramic media; however, as stated, non-ferrous materials usually require finer surface
Chapter 12 – Media 228
finishes. Step processing using plastic media is also commonly used in processing non-ferrous
parts. In fact, it is probably used more than ceramic step processing. That is because normally
non-ferrous products require finer finishes so that secondary operations can be preformed to
improve their surface hardness or put a protective coating on the parts. If we compare plastic
step processing to ceramic, a wider range of surface finishes are possible than with similar
ceramics equivalents.
Using the same criteria as the ceramic example, the following results can be obtained
using plastic media. A fast cut abrasive polyester plastic media can probably result in a 26 RMS
or an 9 point improvement from the normal 35 RMS in 15 to 20 minutes in a five cubic foot
capacity vibratory machine. The appearance of the part will have a fine dull galvanized pattern.
The medium plastic used after the fast cut, will produce a 16 to 18 RMS in about 30 minutes and
will have a uniform luster to the part. To start out with the medium cut media first would take 2
to 3 hours to accomplish the same RMS finish. Using the finest grade of plastic media available
after the medium cut, probably an 8 to 12 RMS may be achievable in about one hour or more
and will appear to have a bright luster. To achieve a 12 RMS using fine media only might take 6
to 8 hours or more of processing time.
Another advantage of plastic media versus ceramics is that the media is available in more
shapes and sizes and as stated before, more bonding compositions. The reason why more plastic
preformed shapes are available than ceramic shapes is because they are made from molds and
most ceramics are cut extrusions. An explanation about shapes will be covered in a separate
section or heading.
One of the disadvantages of plastic media is the aging factor. That is, all media shapes
continue to dry out after manufacturing and that effects its moisture content. If plastic media is
not used routinely, it is more susceptible to cracking or drying out with age. Therefore, shelf life
for storage is limited or less than that of ceramic under more dry conditions, but we are still
talking about years rather than months. If plastic media is stored in humid or damp conditions,
its shelf life maybe over 10 years or exceed the life of ceramic media.
The use of colors makes plastic media more easy to identify the different abrasive
compositions than that of ceramic media; however, each manufacturer has their own color code.
There are no standard uniform color codes in this industry. Therefore, in most cases, you need
to know who the manufacturer is before you can identify the abrasive composition and/or wear
qualities of the media by color. However, even color is not an absolute within a manufacturer
because they will produce whatever color a customer requests. The only sure way to identify
composition is by seeing or reading the part number on the box from which the media came in.
Once it is in the machine, there is no way to be sure what composition it is; therefore,
identification after use is also important.
Generally speaking the darker the color of the preform plastic shape, the more abrasive
the media. A red color use to indicate a more aggressive media than say a blue. A green was
normally used to indicate a medium cut, but this is not necessarily true now. Reds and greens
seem to be inter changeable by different manufacturers. Any color can be added to any abrasive
formulation and therefore, color should not be used to identify media compositions alone. If this
Chapter 12 – Media 229
trend continues, perhaps, besides ordering plastic media by composition, you will also be able
to select your own color as well.
About the only thing the manufacturers seem to agree on is the description of the size
and shape of the preform media. Every manufacturer of preform media shapes have their own
description for their make of preform shape, abrasive, and composition. Some companies
designate their part number description to denote the size of the abrasive particles in the
composition. In this case, the lower the number, the larger the abrasive particle and the higher
the number the finer the particle size. A number of manufacturers use letter designations to
identify their media compositions. Outside of the letter P for porcelain which seems to be
common usage for this item, there is no other discernable patterns in use. Again, there are no
industrial standards. See comparison charts.
Ceramic Media Comparison Chart
Manufacturer Abrasive Media Composition Equivalents
Abrasive Finishing
(Fortune) PV-25
AX-
44& 90 AX-65 AH-41 C-46 SP-3 F-33
Ceratech 1 2 3 4 5 6
Rosemont Ceratech RC 100 RC 200 RC 300 RC 400 RC 500 RC 600
Tumblex N L J K &G C
U.M.Abrasive P LL MC FC
Vibra Finish P M F XF SF XXF UC SC DM DF C60
Washington Mills 10 20 30 40 50 HE
Wisconsin Porcelain FB/F C XC SC H HE
NOTE: Chart reads from left to right in the degree of abrasion or coarseness. Exception is C60, which is a special fine hard
burnishing media.
Plastic Media Comparison Chart
Manufacturer Abrasive Media Polyester Composition Equivalents
Almco 100 200 X XX
Ill.Electro 5000 4000 3271 2000 1500 3104 1000 H-10 H-20 H-30 H-40
Polyflow D70 D10 D30 D50 D165 D155 D154 D150
Rosemont R500 R600 R650 R700 R800 R900 R1250 R3600 R3700 R3800
Superfine LD1 LD2 LD3 LD4 LD5 LD6 LD7 HD1 HD2 HD3 HD4
Ultramatic PS 400 PFQ PJQ PAO
U.M. Abrasives XFF3 FF1 FC1
Vibra Finish VF-V VF-B VF-X VF-XV VF-AO VFXX3
0 VF-Z1 VF-Z2 VF-Z3
NOTE: The cross reference comparison charts used to compile the above come from a number of manufacturers and may not or
do not match up exactly, except for the last 4 vertical columns to the right. Also, the above are the most common products
produced; there are a number of formulations still not shown. Lastly, there is no comparison chart available to compare urea
formulations with the polyester resins shown above. Chart reads from left to right in the degree of abrasion or coarseness.
Chapter 12 – Media 230
As shown and stated, these charts are for reference only, they are not a 100% match up,
but a close relationship. I would have also liked to have included a third chart to show attrition
rates of the media breakdown with usage; however, there is additional difficulty in presenting
such information in chart form. I have included an attrition chart in the back of the book under
the sub-heading category call applications. However, this information is not very accurate for
comparing one product against or with one another; rather it is for use in determining costs of
operating equipment. It is not a good indication of comparisons or really media wears, because
of questionable testing procedures, but it is a start.
Because abrasive deburring preformed shaped media is the most commonly used
abrasive in all mass finishing processes, that is the reason for the comparisons charts. They are
close proximity's. The charts do not show any burnishing media or dry organic materials,
because these are not normally abrasive products and/or there is little wear or difference from
one make or supply source of media to another.
Let me explain a little more about the difficulties in providing detailed comparisons. First
of all, as stated, there is no one central organization like the abrasives industry to regulate or
enact standards. Therefore, almost all information derived for publication is from the actual
manufacturing source. That means that the information is biased or shown to indicate the
positive attributes of their product in the most optimistic terms. Therefore, in conducting tests
no one company is about to devote a great deal of time and resources for impartial testing. To
do so is or can become quite costly. Therefore, with no immediate positive monetary results no
or few companies want or are willing to undertake such testing.
Although mass-finishing systems is somewhat an exact science, it can also be used or
considered as smoke stack type industry. That is, it gets results based upon trends that can be
used to manipulate results. You are already aware of at least three factors governing mass
finishing as that of the equipment, the media, and the liquids. Each one of these factors can be
affected or can control the end results to some degree. In addition to these factors are a lot of
other variables that can be controlled to make this an exact science.
To do proper testing for scientific results of a consistent nature, one must first determine
the equipment to be tested or the media composition or shape to be tested. If one is comparing
equipment, then the same media must be used in each of the machines using the same amount,
size, shape, composition, liquid control, and the parts to be processed. If you vary any one of
these factors, the results may change drastically.
In determining attrition or wear rate of a media in use, one machine system capacity size
and machined part must be selected for use in all tests. However, the results will only be
applicable for that type of equipment and part used. Technically each machine system will have
a different result from one another and the work chamber size or weight factor of the work load
effects the results a great deal. Since no two competing systems has exactly the same capacity
size, comparisons are still somewhat difficult to come by, but there are indicating trends.
The ideal test parts should be a round bar or object about half the work chamber channel
in width and maybe anywhere from a half inch to two inches in thickness to get good
Chapter 12 – Media 231
movement or rotation within the work mass. Its weight should not allow it to sink to the bottom
or float to the top during processing. That means that the part should not be effected
substantially by the media shape or configuration. Unfortunately, there are no universal type
parts; therefore, test results can vary from part shape or material to some degree. Parts too can
have a dramatic result on the processing and wear rate, because they can to some degree,
control the flow and movement of the media. Again, there is a relationship of variables.
The media used in each test must be new and weighted. If the media where to be used
over again on another test, there will have been some wear rate and that means that the media
has to some extent begun to change its configuration and/or become smaller. As media becomes
smaller, its actual surface contact with the part increases. For impartial test results, the media
should be new each time a test is begun.
Perhaps the biggest problem with accurate test results for media is moisture content. To
get a good wear rate the media must be weighted before and after each test. Also the liquid
used during the test must be consistent and be monitored for the same volume per test. Upon
competition of the test period, the media must be dried to the same conditions that existed
before the tests were performed or some exact cut off time period point so noted. Because it is
difficult to duplicate the moisture content of the media before the test and to restore it to that
same condition after the test is nearly impossible. Maybe a better way to proceed with such a
test is to soak the media in a predetermined amount of water and/or include the weight of the
water before and after the tests. Once all of these variables have been monitored and regulated,
then, and only then will you begin to see consistent repetitive and/or similar test results that can
be translated into wear rates or attrition.
So you see, it is not that easy to come up with comparison or attrition rate charts. Also,
you can’t blame the manufacturers for their presentation of the information that they supply. A
lot of factors are know within limits. A lot of factors are too costly to determine accurately. But,
in determining comparisons, you, in effect, have just learned a little more about a number of
other factors that can and do effect mass finishing processes, preform media, and the ideal part
size.
Steel media:
In addition to abrasive media, there is non-abrasive burnishing media. We have already
talked about ceramic non-abrasive porcelain media and a sintered aluminum oxide material
called XM. Besides inorganic ceramics, inorganic metals of carbon steel and stainless steel are
also made into preform shapes for the specific purpose of burnishing or brightening parts.
Again, it does not polish per se, but does roll or lap the materials being worked almost like how
sheet metal is made or finished between two rollers. At about 300 lbs. per cubic foot, steel media
movement does modify or shine all materials in a relatively short period of time. Porcelain can
produce the same results but it weights anywhere from 100 to 150 lbs. per cubic foot and takes 3
to 4 times as long to do the same job.
Because of this weight factor for steel, certain precautions must be taken to properly
adjust the energy transfer of mass finishing equipment to use this media. First of all, not a lot of
Chapter 12 – Media 232
equipment is capable or properly designed to handle or work this heavy weight media. Again,
we are talking about a lot of force and energy required to start things moving, keep them
moving, and then the extremely violent movement associated with the start up and shut down.
If not properly reinforced, machine systems not specifically designed to run steel will either not
move the media properly or will incur pre-mature break downs.
Systems that are capable of running steel media have to be adjusted properly. That is, too
high an energy transfer action to the media may result in the parts being impacted too violently
and thus leaving a pocked mark or orange peel appearance commonly associated with shot
peening equipment. In some cases this may be acceptable, but the more gentle or uniform the
rolling action, the smoother the surface finish.
As an interesting statement only, it is said by some manufactures of burnishing media,
that in order for steel preform media to move or roll properly, there must be a little oxidation or
rust on the media. Without oxidation, the media will continuously slip and not create a rolling
movement or action, which is desirable for the performance of this media. I suspect that this
statement may be true; however, I also believe that such oxidation is not noticeable to the eye.
But if this statement were true, there is still the question of stainless steel media. That is, I
suppose oxidation has to take place on stainless steel, the same as carbon steel, but again there
would not be any noticeable oxidation.
A little while ago I mentioned a condition causing a shot peening surface condition. In
addition to this problem, we should also say something about the other effects of steel media on
the finished part. While steel media is often used to produce bright shinny parts, it also does a
good job of work hardening and stress relieving parts, either intentionally or unintentionally.
That means, that because of the weight factor, there may be some distortion to the physical
shape, surface profile, or dimensions of thin, lightweight, or soft metal parts.
The surface finish of a work-hardened part is almost equal to a plated part in hardness;
therefore, if precision is critical to the performance of a part, the use of this media must be
monitored closely. Once a part has been work hardened, it is difficult to correct or remove burrs
that have been distorted by weight. By the way, this work hardened coating is a very thin
microscopic layer of denser parent metal, almost like the case hardened coating on the media
itself.
As mentioned, the weight factor of steel media is so great in relationship to other media
that most manufacturers of mass finishing equipment specifically design or make a special
heavy duty version of their machines to handle this media. They also advertise the fact that
their equipment can run steel media. That is because the amount of energy required and the
construction and suspension of the work chamber are critical to the performance of any mass
finishing equipment using this media. That also means that not all machines can run or hold up
to the effects of steel media. This is the acid test for all good mass finishing equipment. If a
machine cannot run steel media, it normally does not have a good life span, is under powered,
or is poorly designed, or all of the above.
Chapter 12 – Media 233
In describing media up to this point, we have been talking about grades or the abrasive
quality of different formulations of preform media. With steel media, we drop the classification
or grades of coarse, medium, or fine for primarily size and shape as the controlling factor for
governing performance. We can use the term grades to denote different formulations of steel
and stainless steel which are used to make preform shapes for burnishing; however, the
characteristic of metal grades are not significantly different from one another. That is, their
performance and wear rate are nearly identical to one another. There is a difference of cost and
maintenance of steel versus stainless steel, but generally the term grades is not used to
distinguish differences of steel media. In addition to these metal grades are the less common
non-ferrous media products.
As the size of steel media becomes larger, it also works faster, because of this increased
volume and weight factor. As stated before, size and weight are also factors with abrasive
media, but with steel we are talking about a surface treatment of primarily performing a rolling
or burnishing operation to aesthetically brighten parts, not to remove any material. Any actual
material removal is a result of metal fatigue than abrasion. In fact, burrs may still be present, but
in a modified or distorted form. Therefore, if critical dimensions are required, care must be
taken using this media.
I mentioned earlier that steel media is available in a preformed shape. Most people think
in terms of steel shot or the ball shape as the most commonly used shape for achieving a bright
uniform finish. But it also should be noted that better or greater mobility is achieved with a
mixture of balls of different sizes. The ball shape does lend itself to great mobility, but it is not a
good shape for getting into corners and it really has a small point of contact with which to do
surface modification. When uniform ball media is used, surprisingly, they do not roll as well as
a mixture of different sizes. The reason for this is due its limited uniform point of contact with
the part and other balls. When a mass of identical shapes are used, there are a lot of equal stress
points that require a lot of energy to make them move, versus unequal points cause faster,
greater movement in a shorter period of time and less energy.
In addition to the standard ball shape are the oval balls and the eclipses which are balls
with flats, both of which have more surface contact than the ball. For getting into tight spots are,
ballcones and cone shapes, both of these look like the planet Saturn, but the ballcone is not
symmetrical and is more pointed at one end. The diagonal shape is an angle cut cylinder that is
used to get into corners and angles. The pin shape has both ends that come to a point and is
used to work detail. A mixture of primarily pins plus other small shapes are used a lot by
jewelers and is for working detail designs in jewelry parts; there it is called a jewelers mix.
Earlier, under the heading of equipment, we talked about magnetic tumblers. The media
used in this equipment is made from extruded stainless steel wire cut to length. It is similar to
pin media, but not as thick. That is, it is stainless steel wire made from .02 to .05 diameter to 2 or
3 times that in length. That makes it very thin, light weight, and relatively expensive. Probably
because this is new technology type equipment requiring special media and it is in demand and
the supply is limited, the cost is very high. Normal stainless steel media is not magnetic, but
when any non-magnetic material is drawn thin, it re-aligns its molecules to become susceptible
Chapter 12 – Media 234
to magnetism. Most of these magnetic machines use less than a pound of steel media in their
operating capacity, but the cost of this new media can exceed $300 a pound.
Normally, we think of steel media for burnishing only; as mentioned, any material
removal or true deburring is only through metal fatigue or the flexing of the burr until it cracks
and/or falls off. There is however, one manufacturer who produces a form of steel cylinder
media made with a high nickel content that is formed with serrated or knurled edges that is
specifically designed to cut or deburr parts to a limited extent and for a limited time period. The
life expectancy of this configuration is said to be about 2000 hours with proper maintenance.
In some cases any burnishing media can be used with fine inorganic abrasive particles to
accomplish some deburring; however, it is not recommended because carbon steel media is in a
condition called case hardened. This case harden condition is a thin dense hardened layer of
metal with a Rockwell rating of about 55 on the C scale for 1045 steel or C 60 for 1018 steel;
therefore, if this layer is removed or damaged, the media wears very quickly.
If abrasives are added to steel media, they will deburr, but the weight of the media still
has a tendency to flatten the burr, rather than to remove it. Most people and companies take the
easy way out by deburring with either ceramic or plastic media first, then burnishing with steel
as a secondary operation. If this media is used with abrasive particles, it must be run by itself to
smooth itself before it can be used to burnish again, provided the case hardening is not affected.
Normally all burnishing media requires a break in period or reconditioning cycle so that
it is smooth and will perform polishing. Not only is this necessary after the use with abrasives,
but also any length of time where this media is allowed to sit idle, especially if no precautions
are taken to protect against oxidation.
Perhaps the biggest problem of steel media, beside its expensive cost is the amount of
maintenance required to keep the media in prime working condition. That is, carbon steel
media not properly dried and protected after every use will rust, pit, and eventually begin to
stick or adhere to one another. If properly cared for, steel media will last almost forever;
however, because of handling, more media is lost through poor handling practices than for any
other reason. If not properly maintained, some carbon steel media may only have a life span of
500 hours. Also, any operation using steel media taking longer than 4 hours does or should
require a purging and replenishing of the liquid compound in the process to avoid chemical
reactions that darken parts and effect the media itself.
Lastly, this heading refers to steel media for the purpose of describing the most common
burnishing media used to brighten parts. However, it should be known that other metals, such
as brass and aluminum can be made from cut wire, shaped into ball form or other shapes and
used to perform the same task as steel media. Whatever these metal based materials of these
other media shapes, they are normally used to process parts of the same basic alloy so that no
metal contamination takes place. Cut wire of any alloy can be used but rarely is any other alloy
formed into shapes for burnishing.
Chapter 12 – Media 235
There seems to be an interest in aluminum for both deburring and burnishing. There is
an aluminum cylinder or heavy cut wire shape as well as a star shaped media that weighs 65
pounds per cubic foot. The star is used primarily for deflashing and working aluminum die cast
parts, but it can be used for burnishing after it is well worn. Another interesting feature of this
aluminum media is that it has no problems for disposal like other metal waste by-products and
processes. The only waste problem that might occur is from the parts being worked.
It should also be mentioned here that steel or stainless steel media shapes are the most
expensive of all the preform media shapes. Stainless steel prices can be more than double the
cost of carbon steel media and both steels can be up to 3 or 5 times the cost of ceramic or plastic
media. This is the initial purchase price only. You should consider this price or cost as an
investment, because the media normally never has to be replaced over one's life time with
proper maintenance procedures.
Another interesting benefit feature of using stainless steel media instead of carbon steel is
that you can use a magnet on ferrous parts to remove them from this media after processing is
complete and you don't have to remove the media from the machine. A combination of steel
parts and media does require a screen separation system; therefore, another factor must be
considered.
As mentioned, but not emphasized, perhaps the main reason for most media replacement
is due to poor material practices than any other reason. Steel media, especially ball shapes,
behave like a super ball when dropped or spilled. They will scatter to the 4 winds as quickly as
you blink your eye. Therefore, designated barriers should be considered when handling this
media in or around the mass finishing equipment. Even with good maintenance and handling
practices this media can deteriorate and lose some of its mass over a period of about 10 years
plus or minus.
A special note should be added here also to advise you that there are a number of
applications where parts are sometimes used as media to work, or massed together to work
each other. That is, formed parts are run en mass to deburr and to some extent brighten each
other as well without the use of media. This is sometimes done to eliminate the problems
caused by lodging or the need to separate parts from media. This method of part processing is
not considered deburring, because it is a metal on metal operation which should fall under this
category of burnishing, but it does deburr. Not many parts are good candidates for this type of
processing. Most parts get stuck or tangled with each other, or don’t get all the areas that need
to be worked because of part configuration, but sometimes such problems are better than the
alternative problems. Another factor to consider is that the surface finish may not be improved
or may in fact become rougher using part on part deburring processing.
Chapter 12 – Media 236
Steel Media Shapes
All steel and stainless steel media is derived from cut wire stock, formed, deflashed, heat
treated, ground, and finished. Other raw materials are available in ball form and molded
aluminum mill star shapes are also available. The following constitute nearly all media shapes:
Fig. 91. Steel Media Shapes
1) Balls – Round balls without flats for more critical finishing requirements.
2) Balls, Eclipse – Round Balls with slight flattening at the poles (Precise roundness is not required for most
steel media finishing operations) Pole flattened balls are less expensive to manufacture and purchase.
3) Oval Ball – This shape introduces an oscillating motion to the finishing mass and provides more surface-
to-surface contact than balls
4) Diagonals - Beveled edges of diagonally cut ends provide effective finishing action in corners. Cylindrical
body offers wide area contact.
5) Pins, Slim (S) – Tapering to pointed ends, pins reach into recesses and grooves, deflash through holes and
clean threaded areas.
6) Pins, Taper (T) – See 5
7) Cones – Center flange and tapered crowns provide contact in angles and on curved surfaces. Small sizes
are ideal for ornamental designs.
8) Ballcones – This design combines the burnishing abilities of balls and cones into one scientifically
proportioned shape.
9) Abcut Cylinder or Rod - Patented abrasive surface puts teeth into finishing for fast heavy deburring,
burnishing and material removal
10) Aluminum Mill Star – Molded aluminum alloy media shapes are designed to punch trough and deburr
thin sections of molded parts.
Chapter 12 – Media 237
Organic media:
The last major category of deburring and polishing media is organic. It was interesting to
find out that the earliest barrel tumbling operations of the 1900’s did not use water or liquids to
deburr parts. However, it was soon discovered that inorganic and water did improve the speed
of cutting and improve the appearance of parts. Prior to water based systems, sand was used as
a lubricant with larger abrasives to improve material removal and that also improved the
surface appearance of the part by carrying away dirt. However, sand or solid materials are not
very absorbent and organic materials began to be used with fine abrasives particles. These
organic materials proved to better at cleaning and polishing than the inorganic materials;
however, because of their lightweight, they also proved to require greater processing time.
Again, the trade-off factor.
Organic materials are the least expensive of all media, because they do not involve a
forming process or a lot of labor prior to distribution and use. Organic materials are naturally
occurring materials that are easier to process than the solid inorganic materials. Organic
materials are basically hollow cellular structures of former living vegetation which don't have a
lot of weight or mass and because of its weight or bulk by volume it tends to be the least
expensive per cubic foot of material.
A rough guide line average for all loose granular dry organic media is 21 to 35 pounds
equals about one cubic foot of material; whereas, plastic is about 55-90 lbs. and ceramic weights
around 100-120 lbs. The most common organic materials used as media are corncob, wood, and
nutshells. Until just recently, materials derived from naturally occurring cellular organic
materials could not be made into preformed shapes.
Organic Shapes
Dry organic hard wood is a special exception to the generalized statement that organic
materials cannot be made into shapes needs clarification immediately. Fine grain hard wood is
commonly cut into preform shapes; however, instead of being formed as all the previous
preformed materials. Wood is first cut to thickness and then cut into specific length and width
sizes and shapes for bulk and/or to serve the same function as a manufactured preform ceramic
or plastic shape media form. The basic shapes that wood is cut into is a cube, a diamond, and
either a one sided pointed peg or a two sided wedge type peg.
The residue of this same fine grain wood shape or sawdust is also used, but not as a
preformed shape. With the exception of the cut wood shape, nearly all organic materials are
ground up and sifted into size classifications similar to random media and abrasive particles
and used in that form. There are at least three different sizes or classifications of the saw dust
form of wood; however, there can be more variations than this. Normally fine organic materials
like wood saw dust is not sold as a finished product as it is classified; rather, it is treated with
either an abrasive or polishing additive and then sold as a treated compound to be used with
the wood shape or by itself.
Chapter 12 – Media 238
Fig. 92. Organic Media Shapes
Up to relatively recent times, all organic shapes were basically 2 dimensional wood
shapes cut to thickness. Media shapes that have a shaped point are formed before they are
cut. See below silhouettes. About 1996, a new process was developed that takes fine gain
loose or random size organic materials and combines them in a viscous resin bond to form
shapes similar to how plastic media is made. The new media formulations can actually have
more organic abrasives than organic materials and are very abrasive, but they are still used
dry without water. There are no visuals of the three media shapes, which come in triangles,
squares, cylinders of different sizes and compositions.
Media, Actual Size
Dry shapes
Now, there have been some rather recent developments in dry organic finishing that a lot
of people do not know about that should be of interest to everyone. Around 1996, a company
developed a patented method for making dry organic preformed media shapes with abrasives
materials found in ceramic and plastic media shapes. These preformed shapes look and behave
just like ceramic and plastic deburring media shapes, but it is used dry. The key to this product
is the resin bond that holds both organic and inorganic materials together. In fact, because of
this bond, it is possible to have more inorganic abrasive materials than organic materials in its
composition; therefore, it is hard to classify. Because the shape contains organic materials and is
only run in a dry process, it falls under our dry organic category.
Chapter 12 – Media 239
Formulations of these preformed shapes weight between 65 to 85 pounds per cubic foot.
In addition to improving the cutting or material removal speed of organic media, it can work or
modify a greater range or surface profile than can most other ceramic or plastic media
formulations. That also means that parts usually achieve a smoother surface finish in less time.
The biggest advantage of this new preformed shape is that the media lasts 5 to 20 times longer
than that of most wet preformed inorganic media. Along with the weight factor, this media
gives you more bang for your buck.
Like any new product on the market, there are pluses and minuses. Presently, there is
only one source for this preformed shape and therefore it is somewhat expensive at about $12
per pound. However, at the same time, it has a lot of advantages that make this media very
attractive. If you take into consideration the cost of attrition, water, waste treatment, chemical,
maintenance, and labor relating to wet processing, the cost of this new product is very
competitive. Some other indirect tangible savings are: there are no water marks on parts, no
rusting, no sticking together of flat or light weight parts, and basically smoother, brighter, dry,
clean parts ready for their next operation.
Random Organic Materials
With the exception of the above dry shapes, organic materials are extremely light weight
in comparison to both random and preformed inorganic shape media. Because of this weight
factor, random organic materials do not have a lot of energy mass that can be transferred onto
the parts being worked. It is for this reason that this media is normally used as a last step
polishing operation.
For random media to be effective, parts should first be reduced to about 18 to 20 RMS
surface finish by other processes or media, the finer the surface finish the better. Organic media
can achieve surface finishes as smooth as 2 RMS, but 4 to 8 RMS is more easily achievable. In the
opposite direction, additives can make organic materials very abrasive to do relatively faster
material removal work, or create an antique look, or can be used to help shorten the time period
of the final polish. Polish here refers to the material being flat or smooth, rather than a bright
mirror finish.
Because we are talking about natural occurring materials and relatively small or fine
particles that are very absorbent. That means that this category of materials is normally run dry.
In some instances organic wood shapes can be used as a filler material in a wet processes to
soften the action of abrasive preform plastic or ceramic media, or for obtaining smoother
finishes. However, it is not normally recommended and is not good practice because the media
will deteriorate quickly and the small organic particles will clog the drain system.
All of the other preformed and random media materials prior to this category or group of
abrasives are normally run in a water and chemical solution. Most mass finishing systems are
designed and built to run wet processing. Therefore, to run a dry media may require some
changes to existing equipment before these materials can be used properly. Specifically, we are
talking about the drain system and the open top of the machine. The drain must be taped or
sealed before usage to prevent clogging of the drains with the fine small breakdown particles
Chapter 12 – Media 240
that eventually behaves like cement. However, eccentric weight systems may also have to be
changed or adjusted to accommodate the lighter weight load.
In a wet deburring equipment system you have the waste byproducts of the deburring
operation plus the ceramic or plastics, plus metals and miscellaneous dirts and oils. With dry
materials you do not get that much amount of waste byproducts, but you do get dust problems.
That is, as one runs a dry process, the organic particles break down and become finer and finer
and a lot of it can becomes airborne. Therefore, precautions must be taken to either vent the air
or cover the machine or both.
Another less serious problem is the disposal of used organic media. Normally 90% or
greater of the original sawdust like compound media behaves in a self cleaning or self destruct
mode. That is, it breaks down, becomes finer, and dusts to the atmosphere. A good portion of
the organic material clings to the parts being processed and/or is therefore called drag out. That
means that you normally never have to remove any organic media or waste. In fact, it is
common practice to always add new dry media to the existing machine operation every time a
new batch process is started to replace the loss from break down of the previous materials and
replacement of the spent compound or additives. Replacement material should be a small cup
per cubic foot of the machine capacity being used, per batch. Naturally cross contaminates of
metals and soils is always a problem.
Most manufacturers of treated organic products recommend changing this type of media
as soon as it becomes dark or black. To them, this is an indication that this material has used up
its ability to perform its task of either polishing or deburring. Where quality is an issue, this is
probably a very good practice. Another good practice is to try to maintain a separate batch of
organic material per type of material being processed. You don’t normally want to polish brass
after stainless steel or aluminum. Cross contamination of metals is probably a more common
problem than achieving a fine surface finish.
When the quality of the end product is not an important issue or a specific finish is not
specified, this organic media can be used for a long period of time. I have been using a batch of
dry organic polishing mix for over 10 years. I better qualify that statement. I am using a special
organic blended mix that I keep adding new replacement material per batch of parts. As far as I
can remember, I have never disposed of any dry mix that I have started with; however, as
stated, when quality is an issue, I always start out with a new blend or mix.
Any disposal of organic media is because it becomes so contaminated with the debris
from parts being worked that it turns black and gummy and interferes with the movement of
the media or work mass. If too much moisture or liquid additives are used to improve the
performance of the mix, parts may come out with white dimples, or it may result in the media
creating balls or deposits on the side walls of the work chamber. All of these problems are a
result of too much compound additive treatment creating a saturation point either on the part,
work chamber, or within the media itself.
This saturation or loading condition does not hurt the part, but it does not help it either.
Unless the media and part can maintain good surface contact in a non-sticking mode, the
Chapter 12 – Media 241
process will not improve the surface finish. Instead of improving the surface the compound will
behave and act like a magnet, creating conditions center around the excess compound. If this
condition occurs the disposal of this excess or contaminated waste is recommended over the
adding of new dry material. The waste can normally be disposed of in paper trash; however, if
it contains concentrations of metals and oils then care should be taken to conform with local
disposal procedures.
Loose Random Dry Organic Media
Most loose random shaped dry organic materials are made from the cellular structures of
former living plants; therefore, their shape and size are determined by what part and/or size of
the plant was. That means that the most materials used are of relatively small size so they can
flow freely when they are made into uniform particles. Shell particles are normally larger and
harder than fibrous wood products, but both can be made into very small almost powder like
sizes. In their natural state, the weight of these products do not vary much except when liquid
and/or solid additive compounds are added to the products to assist the materials in either
polishing or to increase their abrasive qualities. Visuals show actual size of some common
materials.
Fig. 93. Common Organic Media
Corn Cob
Of these organic materials, corn cob is the lightest grain or cellular structure size particle
at about 23 to 33 pounds per cubic foot and is normally the softest of the dry media. Ground up
cob has been used for a long time as a drying agent for spills because of its absorption qualities
and is used in vibratory and the older barrel systems for that same purpose. In fact, there are
special designed inline drying machines that use corn cob to follow parts washers. These are
usually more efficient than hot air blow off dryers, or centrifugal systems, because they are still
a solid mass in relationship to the part being processed.
Because corncob media makes contact with the part it also has the ability to do light
cleaning and brightening of surface features, which technically is deburring to some extent and
that's also why a cob drier is more efficient than hot air type system alone. This light cleaning or
abrasive characteristic of the media is important because all tap water retains minerals in
solution and consequentially it does leave spots when it dries or even if it sits for any short
period of time without being wiped dry. Water stains are a common problem with polished
metals; therefore, the soft organic nature of corn cob media makes it ideal as a drier and cleaner
for most parts processing.
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Because of the lightweight of corncob, it is often used on non-ferrous soft metals such as
aluminum and/or delicate and detailed parts. As stated, the media does have some minor
abrasion qualities by itself. Where it really is superior to most wet media is when it is blended
with other additives of inorganic abrasives or chemically treated to perform certain tasks. The
absorption qualities make it an ideal candidate to soak in, retain, and transfer polishing
compounds.
Organic materials can also be pretreated to retain, hold, or suspend some fine abrasive
particles provided another bonding agent is used to enhance its ability to stabilize the mixture.
In some cases, where the materials are nearly the same specific gravity weight of the particle
size to create a homogeneous blended mix, additives may not be necessary. Lastly, dry organic
materials can be pre-soaked with waxes, lacquers, and dyes to transfer these products evenly
and uniformly to other parts or products in barrel tumbling systems.
When either a liquid or polishing paste is added to corn cob, the processing results are
nearly equal to a hand buffed finish. Unlike burnishing media that is used to get bright but
rough finishes, organic media does remove microscopic amounts of material and does polish
and smooth parts to a very low RMS finish. This can be as low as a 2 RMS or better provided
other operations are preformed first and this also depends upon this and previous processing
steps and time cycles.
In most mass finishing systems, polishing results take a long time. In fact, normally the
longer you run a part in this media the finer the finish. Also, the greater the percentage of media
to parts the better the end results. To polish parts, the proper mix is about 80% media to 20%
parts by volume. This mix can be changed to more media to parts, but at some point the
quantity of parts per batch and the time cycle does effect costs adversely.
To get good mirror surface finishes using dry media, parts normally have to be run in a
step process. Dry media should only be considered for polishing after the parts being worked
have a surface finish of 18 RMS or finer. Starting from this 18 RMS and soft non-ferrous metals
in a centrifugal high energy barrel systems, a mirror finish of about 8 RMS can be accomplished
in about a half hour to one hour and a 4 RMS in about two hours. In vibratory systems good
results of 12 RMS can be achieve in 2 to 4 hours with good mirror finish of 8 RMS in 8 to 12
hours and about 24 hours for a nearly hand buffed type finish of 2 to 4 RMS. Old barrel systems
may take 24 hours for a 12 RMS and about 48 hours for an 8 RMS and maybe 120 hours for a 4
RMS result.
Another common organic polishing media are nutshells with walnut being the dominant
choice of most users because it is about the hardest and heaviest of all organic materials. Again,
when mixed with polishing additives, the results are spectacular. This media is commonly used
in the jewelry industry because of its excellent results when treated with polishing additives.
However, because of its hardness, some care must be taken to regulate the amount of energy or
amplitude, vibration, or RPM's of the equipment to prevent what is called an orange peel effect
of the media impacting the metal surface. This effect is similar to what can occur using steel
media, but it is not nearly as bad.
Chapter 12 – Media 243
Wood
In addition to the granular organics of cob and nut products is wood. There are some
unique qualities to wood that have both positive and negative benefits. The most common
wood used to make up this media is beech and birch. These woods have dense fine grain
structures and are therefore considered hard woods. Wood in saw dust form is fibrous and/or
occurs in long strands of short cellular fibers. In that state, given the same volume, it is actually
lighter than corn cob and weights between 20 and 25 pounds per cubic foot of material and also
depends upon the moisture content of the product.
The long cellular fiber quality of wood means that this material behaves or produces
results more like that of cloth buffing wheel. It has more of a wiping action than do the granular
organic particles. It cannot create the dimple patterns or orange peel effect of grain type
particles. On the negative side, the fiber is somewhat elongated and that causes it to adhere or
stick to most materials being worked either assisted by moisture from the air or from the
additives. This adhesion problem is also caused in part by static electricity.
Wood shapes in cut form behaves similar to extremely fine plastic media when used with
non-ferrous metals. It does not abrade alone by itself, as does plastic, without some additives. In
fact it has a tendency to polish or clean a little by itself. If some of the saw dust particle form of
wood were to be added to the cut wood shapes, the results, without additives would be
somewhat abrasive in nature, until the materials break in or becomes smooth through usage.
This break in period is actually a process of the closure of microscopic pores of the material.
With polishing additives and with or without the fine particle saw dust form, and properly
broken in, wood shapes do an excellent job of polishing almost all materials.
Most dry organic polishing mixes are a combination of the dry organic particles plus a
polishing additive, which is blended into the mix, but is still dry and free flowing. This additive
is usually a paste type product that requires additional time to mix and be dispersed within the
organic materials; however it can also be a liquid or a powder. The blending process produces
what is called impregnated or a treated product. As mentioned earlier, these products can and
do work the same as buffing compounds in almost the same way except no manual labor is
involved using mass finishing equipment. The resulting surface appearance is almost equal to a
hand buffed finished appearance.
As parts are processed in any dry organic media blended mix, the temperature does rise
and this helps the additive to coat the parts and the organic materials wipe and smooth them.
Usually after each batch of processed parts, new materials or additive must be added to the
process due to loss and break down of both the organic material and the additive. In some cases
when the mixes become too dusty, water can be added sparingly. Too much water will
drastically shorten the life or organic materials. That also means that care and storage of dry
blended materials is of some importance and concern.
Moisture Content
Perhaps another interesting thing should be mentioned here about moisture content of
dry organic materials and machine systems. Some blended formulations or dry organic mixes
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can have more moisture content and while that sounds good, it causes them to adhere or cling
to everything. This moisture content is especially not good for centrifugal type systems because
this equipment amplifies the adhesion properties that cause the particles to cling together more
than they would in barrels and vibratory equipment; therefore, newer formulations of treated
organic materials are blended with dry forms of polishing additives.
Moisture content also seems to have an indirect effect on plastic parts. The combination
of wood saw dust and wood shapes plus a proper polishing additives is commonly used to
polish and restore clarity to clear plastic parts that have either been saw cut or sanded to shape.
However, because of the light weight of these materials, we are again talking about a long time
cycle of may 24 or 48 hours in a vibratory system and almost twice that long for barrel systems.
However, given enough time the appearance from a barrel system will be superior to a
vibratory machine, because of the longer slide motion of the media.
Moisture adds weight to dry organic materials and this can have a beneficial effect;
however, weight can better be accomplished with bulky wood shapes added to any fine grain
organic particle to provide more mass. Bulk and volume increases any mass finishing process or
shortens processing times greater than treated dry organic media alone. At the same time, wood
shapes can also create impact deformity on plastic parts if the equipment is not properly
adjusted. In addition to bulky wood shapes, other preformed shapes of plastic and porcelain
can also be added to dry organic mixes and achieve good results in shorter periods of time;
however, adjustments must be made to compensate for this increased weight factor.
Blended or mixed media
Up to this point, we have talked about adding polish to organic materials and I have
described some of the results. Fine inorganic abrasives can also be added to organic materials to
do deburring and material removal and/or create a surface texture. In all cases, the random
organic particles provide the bulk of the mechanical energy requirements; however, because of
the weight differential, sometimes a glue like binder must also be added to the mix to properly
suspend the inorganic abrasives. This deburring process is more commonly done with the wood
products, because the fibrous form of wood plus a sticky additive of wax or oil creates a type of
filament matrix that behaves similar to sand paper or a metal file. Organic particles materials
are more rounded and don't have the same good results as do the wood fibers.
Pumice
The most common abrasive additive used to work with organic materials is pumice
because of its lighter weight than the organic particles. Other materials can be used; however, if
their weight or size is significantly different than the organic media particles the inorganic
abrasives will not stick or stay bonded to the organic materials. Sometimes, without the use of
special bonding agents, separation can take place within the work mass. That means that you
may get a situation where the media mix can be in two distinct levels rotating in the same work
chamber and that may not work parts uniformly. Sometimes this condition can be good for
processing parts, but it is a tricky situation and is normally avoided.
Chapter 12 – Media 245
Because of the lightweight, porosity, and hardness of pumice it is the primary abrasive
used with organic materials. However, it also has the fastest breakdown rate of any inorganic
material in use. Pumice will out cut aluminum oxide, silicon carbide, or zirconia in a dry
process operation. The reason for this is that it is a very friable and porous material which
breaks down into smaller long slivers that cling to both parts and other materials equally. This
break down characteristic makes it ideal for relatively fast surface refinement in a relative short
period of time especially on soft non-ferrous materials. On the negative side, a batch of parts
gets modified as well as the media mix itself. The constant replacement of replenishment of
pumice makes it difficult to properly control. It is for that reason why pumice alone is not
commonly used.
In special cases, pumice can be used by itself to perform deburring and surface
modifications both in an all dry process or when used with liquids. That means that a wider
RMS range is possible using pumice with other preform shapes. By itself in a dry state, it is a
slow process that works well on soft non-ferrous metals, especially small parts under a half inch
in size. When used wet by itself, it is very effective in working plastic materials, because it
produces a rough finish very fast and then it begins to produce finer and finer surface finishes
without adding or changing the liquid. However, to get a superb finish, you should change to a
burnishing chemical compound.
Other inorganic additives
Other abrasive materials and particles sizes can be added with varying results to dry
organic materials. Probably the heaviest weight abrasive used with dry organic media is
zirconia. On ferrous metals this works well up to a point, then it has a tendency to start
polishing. The abrasive particles are so hard they begin to round off and become smooth; rather
than break down and stay as an abrasive. Therefore, new zirconia material must be added or
blended with bulk shapes or pumice to maintain its abrasive quality.
Other small size inorganic materials have the same problem as zirconia. That is, without
the use of water to aid in their decomposition, the materials themselves round off their edges
and/or load up and begin to polish. The parts being worked may also have some influence over
the inorganic abrasive media by glazing or sealing up whatever porosity the abrasive might
have had before it was used. Therefore, although inorganic materials can be small enough to do
the same work as organics, they do not have the same polishing or abrasive qualities as treated
organic materials.
Antique Appearance
The appearance of parts processed with abrasive organic blended mixes is similar to the
results produced by sand blasting systems, but without the fine dimple pattern. It can also be
compared to that of a wire brushed or satin finish. A lot of new antique looking parts are done
in this way. Antique looks can be accomplished by blackening the metal first and then
processing the parts in a dry abrasive organic mix or inorganic blend.
Chapter 12 – Media 246
With abrasives added to dry organic materials, normally a wider range of surface
finishes and textures can be accomplished with the preform shapes used in wet processing. Dry
abrasive organic media blends seem to produce good results between 22 to 12 RMS starting
from 35 RMS. That means that in most instances, everything that wet preform shapes can do, so
too can dry organic materials with abrasives. Besides the lack of water, chemicals, and debris,
the only difference between wet and dry processing is the increased amount of processing time
and the finer surface finish that organic particles will produce.
Felt and Miscellaneous
Besides the more common uses of organic media described above, there are also some
more infrequently used media materials that can be used. One of these is felt. A very hard felt,
cut into square shapes, is used in some instances to perform polishing tasks that require extreme
delicacy and/or smooth surface finishes. Most felt materials tend to break down and become one
big ball of cotton felt; therefore, be careful to get the hardest grade or density of this material.
Like most organic materials, felt does take and hold polishing additive chemicals very well.
However, felt is not normally sold for use as a media and can be difficult to find and expensive
to buy.
In addition to felt are a class of weird materials of which I will just mention one. A
number of years ago, I saw a barrel process using big gummy type rubber based erasers being
used to clean up plastic parts and small light weight aluminum parts. I mentioned earlier that
almost anything can be used as a media and have some effect on whatever it is you are trying to
do or accomplish in the way of mass finishing. This is one of those way out applications.
Today it is not impossible to run with completely dry mass finishing processes only. In
fact, this seems to be a trend that high energy equipment is taking. In addition to improvements
in mass finishing equipment performance, there are improvements in new CNC machine
centers and equipment. That means that parts are being worked to finer surface finishes and
tolerances due to better tool control. That also means that these parts need less deburring and
better more refined surface finishes. These factors plus the concern of water pollution, and other
controlling rules, regulations, and the restrictions being placed on chemicals all add up to the
popularity and trend toward dry organic media.
Temperature
Lastly, while we are talking about dry organic media and blends, we should also mention
the fact that when this media is run, it does not behave as wet systems do. What I mean by that
is the fact that water, besides being a lubricant and conveyor for chemicals, also acts as a
coolant. On the other hand, dry organic materials run considerably warmer. This elevated
temperature aids in the performance of the polishing additives similar to how a buffing wheel
works. That is, as the temperature increases, so too does the efficiency of the buffing
compounds within the mix. In fact, the same buffing compound used on wheels, can also be
used with dry organic materials; however, the bar form must be changed to either a powder
form or liquefied some way to add and or be disperse within the media.
Chapter 12 – Media 247
The greater the temperature within the work chamber of the mass finishing system,
normally the better the polishing results up to the range or point limitation of the additive
compounds. There are also relatively low flash points to organic materials; therefore, too high a
temperature may be undesirable. This is especially true when heated corn cob is used for drying
parts. Normal temperature range of long processing cycles of 24 hours using dry media can get
up to maybe 100 degrees Fahrenheit in closed barrel type systems, to 120 degrees in vibratory
equipment, and up to about 150 degrees in high energy type systems.
While dry organic media is not harmful or hazardous to the environment or for use
around people, what you put into the media may be. To clarify that statement, the media is not
the problem. The problem is either the parts being worked or the additives being used to
impregnated the dry organic media. Because of EPA and OSHA requirements, abrasive or
polishing compounds are not normally a problem. That leaves the process itself or the materials
being worked as a potential problem; however, even this situation is a very remote possibility.
The process problem is nothing more than a good housekeeping problem of airborne particles
and good maintenance. Any form of dust can become a problem if it is not properly controlled
and any waste disposal from dry processing can normally be placed into the paper trash.
However, like any trash disposal, you should check with whoever regulates such things in or
out of your company.
Media Shapes:
I choose not to include the physical description and dynamics of media shapes earlier in
the descriptions of media because we were talking mostly about abrasion characteristics. I did
provide visual information; however, I decided that shapes needed a category all by themselves.
Media shapes do play a part in the amount of material removal, but it is not the determining
factor like abrasive particles are in determining the end results. That is, you know now that
weight is a very important factor in mass finishing and the fastest way to alter weight in a
preformed shape is through increase size and/or shape as well as media composition.
Shape is more a determining factor that controls mobility and accessibility, or how and
where a part is worked. Mobility maybe somewhat easy to understand, but accessibility needs
clarification. The term access is just that. Unless a preformed media shape can get into all of the
areas of a part that have to be worked, it cannot perform its function of deburring and/or
surface modification. Even if the area doesn’t have to be worked, it basically needs surface
conditioning to produce uniform results. That is, if say a media is selected that cannot get into
corners of a part and it later gets anodizes in a secondary operation, there may be a definite
noticeable appearance to the part due to different surface profile finishes.
Shape determines access to the work area and the ability of the preformed shape to work
without getting stuck. That last word stuck is a very important word in the mass finishing
industry. Probably the most single important factor in mass finishing is the ability to select a
preformed media shape that is the most universal in size, shape, and composition, that will
work as many different parts as possible without getting stuck. Such an ideal selection is next to
impossible.
Chapter 12 – Media 248
Just the sheer size or scope of part configurations makes it extremely rare that one can get
away with one media size and shape size fits all. Consequently, most companies select a
number of different sizes and shapes of media to perform different tasks and/or produce
different finishes. Even though the proper practice is to maintain some diversity of media size
and shape, this is still not very common until you get into larger companies or companies that
do a lot of deburring and surface finishing. As mentioned, the cost of storage and maintenance
maybe traded off in the name of some additional material handling or cost effectiveness.
In selecting media shapes, there are usually compromises that have to be made to live
with a certain amount of potential lodging in parts, but time is money; therefore, selection must
be based on part configuration first and/or the volume of that part versus other parts. That is,
common sense tells you to select the media that will work your most numerous parts first, but if
critical dimension parts are less numerous but cost a whole lot more to make, you don’t want to
trade off volume for cost considerations. On the negative side, if you have a certain number of
parts that require a lot of hand work to remove media that gets stuck, then you may want to
consider another size and shape just to eliminate this problem.
Basic shapes
The following are some rough guidelines to follow for media shape selection. As a
general statement only, there are really only two choices or shapes from which to make a
selection. My own slang terminology for these shapes are steamrollers and bulldozers, or just
rollers and pushers. The basic media shapes roll and crush the burr or scrape and push the burr.
One selects either mobility or pressure. The greater the diameter or roundness of the media
shape the easier it rolls and moves both the media and the parts. The greater the geometric
straight lines a media has, the greater the pressure, force, or resistance the media and parts
encounter. All shapes work and perform the task of material removal almost equally well.
The more symmetrical and/or uniform the shape of the media, normally the greater the
mobility of the media. In this category are: cylinders, spheres/balls, and cones. In mass finishing
equipment, these shapes behave something like both a fixed wheel and a mobile wheel. That is,
as these shapes move, they rotate en mass and by themselves. These shapes work extremely
well where you have a lot of holes and the shape can poke itself slightly into the hole and rotate
a little before it moves on. Because these shapes are so mobile en mass, they do not hold,
support, or restrict parts from reaching the bottom of the work chamber. That characteristic
means that the full weight of the media mass is utilized on the parts. The only negative of this
shape is that you cannot work inside corners or inside angles very well and that can develop a
shadow appearance.
Given the same mass finishing equipment, the more geometric the shape, such as
triangles, pyramids, tetrahedrons, and the straight wedge, the slower and noisier they rotate.
The reason for this behavior is because there are more points of surface contact with the parts
and other media. Sharp edge media movement is restricted due to the alignment of edges and
that resistance causes the mass to push and scrape along. Instead of using weight and mobility,
these shapes tend to transmit this resistance into greater pressure to the parts being worked.
Chapter 12 – Media 249
Because of this resistance factor, parts in the media mass maintain relatively good separation,
maintain their position, and they do not sink to the bottom of the mass.
In addition to these two basic shapes, there are combination shapes that try to
incorporate the best attributes of both configurations. Probably the most common geometric
characteristic shape used in both configurations is the angle cut. Naturally, ball media has no
angles; however, cylinder ends are cut on an angle and a cone incorporates an angle into its
shape. Most geometric shapes have sharp edges and can easily incorporate an angle into their
shapes.
Because ceramic media came first and were extruded, it was discovered that instead of
cutting the shape straight up and down or perpendicular to the extrusion, the finished product
shaped worked better and reached more areas if it was cut on an angle. Hence the term and
popularity of the angle cut shapes. Most plastic media is molded and instead of cutting the
media on an angle, the media shape incorporates the angle into its design.
The angle cut can vary from shape to shape and within the same shape, but it is normally
cut at 22 degrees. A lot of the angle shapes depend upon who the manufacturer of the media is.
The same shape made by a different manufacturer can be anywhere from 20, 22, 25, or a 30
degree angle cut. For special applications and deeper penetration, there are also 45 and 60
degree angle cuts. Naturally the more angle, the thinner the shape at the point. That also means,
the sharper the angle, the thinner and the weaker the material is at that point. There are trade-
offs.
Angles are actually commonly found on all media shapes and help perform special
functions. Angular shapes have the ability to penetrate into holes, and work corners, and sharp
recesses very well. The angle works or behaves similar to a knife blade or a triangular file. The
sharper the angle, the deeper the penetration and the tighter the area or detail it can work. Even
though I mentioned the weakness of the point area, there is not too much fear of the media
shape breaking because of its hardness, even with 60 degree angle cut media. Angle cuts are
recommended for whatever media shape you do select.
There is another interesting problem associated with angle cuts and that is how the shape
is measured. All preformed media is measured and specified by length, width, and height. The
basic shape of media is really in two dimensions; therefore, because of the angles, the media
dimensions normally exceed that of the shape. This can be confusing and sometimes needs
clarification, especially before you buy a 3/8 inch 60 degree angle cut triangle. When you receive
that shape, you will find out that it has an actually length of about 3/4 of an inch that extends
from point to point.
Now, the angle cut is a very effective shape for deep penetration and the cylinder is very
effective shape for mobility. When these two attributes are combined with a different type of
angle cut or cut to a point instead of parallel, you come up with another very interesting hybrid
shape described as a V cut cylinder, a cylinder wedge, or a tricyl. What is so special or unique
about this shape is how it behaves and where its center of gravity is.
Chapter 12 – Media 250
Perhaps the cylinder wedge shape is the best of both worlds or a good media for most
general purpose deburring applications. The cone shape is also a good mobile media, but it has
limited surface contact. The cylinder wedge shaped media seems to be the best of both worlds,
because it is cut to a point like a piece of pie when looked at from one side and is completely
round from the other 90 degree side. That means that this shape has great mobility and has a lot
of contact with broad flat areas. The cylinder wedge and the cones are popular choices and are
the only media shapes that come in both ceramic and plastic compositions.
Balls and cylinders and especially cone shapes have great mobility, but the cylinder
wedge shape seems to be the most mobile and it still maintains a sharp angle with two broad
flats which are good for surface profiles, heavy material removal, and deep penetration abilities.
Unlike all of the other shapes mentioned so far, all of the other media shapes have their center
of gravity right in the center of the shape. As mentioned, the center of gravity controls the
movement of the mass and/or media shape. All other shapes are very stable and don't move too
far away from the energy source and they do work their way into tight spots and can get stuck.
The cylinder wedge shape is the only shape that actually has its center of gravity of the
outside edge of the shape. That means that the cylinder wedge is very unstable and moves a lot.
This unstable mobility can best be proven by placing a piece of media on its rounded edge a
move it slightly. This shape is the only shape that will continue to rock back and forth for some
time after being energized. That mobility also means that it is less likely to work itself into tight
spots and stay there. Like Murphy's Law, if media can get stuck, it will get stuck because of the
mobility factor. The lodging problem is less likely in the case of the cylinder wedge, because
that shape has a lot of material that extends to one side beyond the geographical center of the
shape. See chart
Operating Characteristics Preform Plastic and Ceramic Media Shapes
Media
Shape * Lodging Mobility Surface
Contact
Area
Retain
Shape
Surface
Finish
Process
Time
Total
Score
Rating
Sphere 1 4b 1P 5 5 1 16
Cylinder
Wedge
1.2 4 5F 5 5 5 24
Cylinder 2.5 4C 2L 4 5 3 18
Cone 3 5 2L 5 5 3 20
Pyramid 3.5 3 5F 2d 4 4 18
Elliptical 3.5 4 3FL 4 5 3 19
Triangle 5 3a 5F 4 4 5e 21
Diamond 5 3a 4F 4 4 4e 19
Tetrahedro
ns
5 1b 4FL 2 4 4 15
Tri-Star 5 3a 3FL 3 4 4 17
NOTE 1: * Lodging column is not added or part of overall score, but the lower this
number the less likely this media is to get stuck. The Total Score Rating is the sum total of all
other columns and which is based upon a numerical score where the lower the number the less
Chapter 12 – Media 251
versatile the media is, and the higher the number, the more versatile it is in processing
applications.
NOTE 2: Sub letter designations and explanations are as follows:
(a) Mobility factor works best when the media dimensions are closer to a square, bulky,
or equal X Y rather than elongated or thin dimensions.
(b) These shapes display peculiar qualities when used in bulk. That is, when used in
uniform sizes, this media shape absorbs energy offering greater resistance and
decreases its mobility significantly.
(c) Shape looses mobility when the length to width ratio exceeds 2 : 3.
(d) The edges wear down and become a tapered elliptical shape.
(e) A thin flat shapes work more aggressively than bulky shapes.
P Point contact, or extremely small surface contact.
F Primarily Flat broad surface contact.
L Primarily Line surface contact
FL Primarily Flat broad surface contact but also Line contact.
Based upon a chart developed by Sam Thompson.
In the selection of a media shape, some general rules to remember are that geometric
shapes that have a lot of bulk, straight lines, and/or angular edges to them also have a tendency
to work faster on outside surface areas. These are relatively sharp shapes that encounter more
resistance between themselves and the parts being worked. The broad flat ceramic shapes of
triangles, tri-stars, pyramids, tetrahedrons, and straight wedges are all good selections for this
type of work.
Geometric shaped media movement is not very smooth flowing or mobile because the
energy force is somewhat locked up in short burst of energy that behave similar to an ice flow
breaking up on a river. In fact, this can be noticed by just listening to the noise emitted during
the deburring process. This media will run very noisy because of the resistance factor, but it will
also do an excellent job of removing a lot of material from outside edges and flat surface areas
more than most rounded shapes.
For deburring I.D. and O.D. holes in parts, cylinders seem to be the shape of choice. They
offer greater mobility than flat configurations, but give way to heavy parts en mass allowing
them to sink to the bottom. In some cases this is good for obtaining the greatest weight of the
media mass or energy to deburr, but it is bad if you want to retrieve small parts by hand after
the processing is complete. One more feature of this shape is the amount of surface contact can
be actually greater with this shape if the part has a lot of contours than a straight geometric
shaped configuration. Because this shape has basically a broad line or point on point contact
that rotates, the material removal process maybe less than the flat configurations.
Chapter 12 – Media 252
As mentioned, cylinders can be selected either to pass through holes and recesses or
penetrate deep enough into a hole to do edge removal or work a problem area. This is similar to
how a larger drill bit is used to chamfer smaller I.D. holes. To do this deep deburring, most
cylinders are cut on either a 22 or 25-degree angle, but as mentioned, they also can be gotten in
45 and 60-degree angles for this problem of penetration. These angles are normally cut parallel
to one another to give them uniform balance and performance.
Getting back to holes. Holes present an interesting problem. If you want the media to
pass through the hole, select a cylinder media, if possible, that is about 1/8 of an inch smaller
than the smallest hole being worked. However, be careful that you don't have some holes
exactly twice the size of the media, because two pieces or more of cylinder media can jam as
easy as one. The safe procedure is to select a media larger than the hole sizes and work the burr
from outside or above the surface of the hole.
Even though we have talked about the more common shapes and various configurations,
perhaps I should say more about plastic media. The reason for this is that there are many more
shapes made from plastic than there are from ceramics. The reason for this is that more plastic
media is made with molds. One exception to this is a special formulated plastic composition
and machine that works like a Hershey kiss candy-making machine that produces the curly top.
Besides the kiss shape, they also make a four-sided pyramid kiss shape with the same top.
Most ceramic media is normally extruded and cut to thickness. Molded shapes tend to
have more points or protrusions that can get into tight spots. Besides the plastic cone and
cylinder wedge shapes mentioned above are flat wedges, pyramids, tetrahedrons, triangles,
tristars, arrowheads, coniforms, and tetraforms and some minor variations to these
configurations.
Because molded media shapes normally have more angles in their configuration, some
thought must be given to the wear of all of these shapes. That is, as a shape wears down, it loses
some of its sharpness or cutting edges. That also means that it cannot reach into angles or recess
areas as well as it did when it was new or had an sharp edge. Angle cut media does help
preserve a shapes configuration during this wear rate; however, most angular molded media
becomes more of an irregular oval shape mass with use. Therefore, when a media reaches or
wears to half its original size, its shape cannot normally be determined readily. That means that
the life of the media may be a lot less than its actual half life or functional life. This situation
occurs in about 3 or 4 months based upon use of 40 hours per week in an average vibratory
machine system.
With all of that in mind, the following are some guidelines to use in selecting deburring
and polishing media for mass finishing equipment:
Chapter 12 – Media 253
Media Guidelines
1. For rapid or large amounts of material removal from parts in the shortest period of time,
you need the largest preformed shape available, which will get into and work all the areas
that have to be modified. It should also be the coarsest abrasive particle size with a fastest
break down bonding agent.
2. The preformed shape you select depends upon the configuration of your part and/or what
burr or surface finish is required. Mobility, resistance, size, and abrasion characteristic are
the determining factors for media selection.
3. For the smoothest surface finish, you want either a fine abrasive preform shape in a small
size and a good hard bonding agent, or you may want to do a step down process of more
than one media preform operation. Which way you go depends on where you start. That is,
the optimum abrasive range for deburring or surface modification using media shapes is
somewhere around a 10 to 15 RMS improvement. That is about the limit of all preformed
shapes except the new dry organic shapes.
4. Ferrous metals should be run in ceramic preformed media. Plastic parts should also be run
in ceramic media for speedy short time cycles and when appearance is not a factor.
5. Non-ferrous parts can be run in ceramic if surface appearance is not important and where
short time cycles are desirable. If a part is to be anodized or plated, medium to fine grades
of plastic or synthetics should be used. Normally all non-ferrous parts are run in plastic
based media.
6. Do not mix metal parts or materials of different compositions in the same media without
thoroughly rinsing or cleaning the work chamber, especially after batch type processing.
Microscopic debris may contaminate, react, or discolor the next batch of materials. You
don't want aluminum parts with iron rust spots on them.
7. For bright finishes on all surfaces or materials, without regard to roughness, steel or
porcelain preformed shaped balls is the preferred shape in most applications with a good
liquid compound.
8. For the brightest smoothest surface finish possible, dry organic media impregnated with a
polishing additive is recommended.
9. Flat parts and parts under a 1/2 inch in size should be run with dry organics for both
deburring or polishing for uniform finishes. The surface tension of water tends to glue flat
parts together and small parts to the work chamber walls.
10. For the best, shortest time cycles in all machines fill your machines work chamber to its
maximum working capacity and to the proper proportion of media to parts ratio. Weight
and pressure are the two most important elements for deburring using mass finishing
equipment.
254
Chapter 13 - Liquid Systems
Chemical Compounds
As mentioned earlier, mass finishing systems are like a three-legged stool. It takes three
elements to properly deburr or polish parts. We have talked about two of these elements of
equipment, and media. The third element is chemical compounds or solutions. To achieve the
best results in mass finishing systems, water and chemicals must be added, properly monitored,
and/or regulated to produce good clean acceptable parts, or for dry processes there are dry
organic compounds. For simplification, the remainder of this section will deal only with wet
processing chemicals.
Of the three principles governing mass finishing processing results, chemical compounds
are probably the most difficult to nail down or control. Why chemicals are so important and yet
so difficult to recommend or be specific about is because of all the variables prior to the parts
getting to the deburring stage. All manufacturing companies do things differently. That means
they use different production equipment, supplies, and processing methods. That also means
that they normally all require the use of chemical lubricants in making of their parts. Not only
do companies make parts out of more than one material, they may use more than one chemical
lubricant or oil in the production of a single part. Some companies may even go as far to change
lubricants due to cost factors. To complicate matters even more, these companies may also buy
parts from someone else that has other lubricants different from their own. Knowing what has
to be cleaned helps a great deal in selecting the right chemical cleaning or deburring compound
for wet processing.
Again, if the lubricants and oils are known, the chemical base is relatively easy to
determine and that means that a cleaning product can also be properly selected. Without the
knowledge of the contaminates, all of this adds up to a lot of possible unknowns and guess
work and that sometimes makes it difficult to find a chemical cleaning compound that will
clean, deburr, and protect the finished part in a fast economical way.
For consistent accurate finishing results a simple answer for the processing problem or
chemical selection of a deburring compound is to wash all parts prior to them entering the mass
finishing equipment, but rarely is this ever done. A mechanical cleaning process is actually
better at removing all contaminates either known or unknown. The pressure and surface contact
exerted by media, chemicals, and water is a very efficient method of cleaning; therefore, most
companies do not clean parts prior to mass finishing.
The purpose of a chemical deburring compound is to maintain lubrication and the
suspension of contaminated debris and soils off the parts being worked and the media itself.
Without this liquid purging action, cutting oils and debris will stick to the parts and glaze up
the surface of both the part and the media. If the porosity of either the part or media gets coated
with contaminates it makes it more difficult to deburr because it reduces the abrasive
relationship and thereby significantly increasing the processing time. On the up side, perhaps a
Chapter 13 - Liquid Systems 255
side benefit of this media glazing over is that the parts will come out brighter, shinny, and
maybe smoother, but they will still be dirty.
Media which has become glazed requires a significant amount of time to be
reconditioned or restored to its original abrasion qualities once this glazing has occurred. The
actual restoration requires the use of a good strong degreasing chemical and/or cleaning cycle.
In this process, the media can lose as much as 20 or 30% of its mass and require a significant
amount of time; therefore, this is not a recommended or desired procedure. Normally it is more
cost effective to just replace the media. The best way to correct the problem is not to create the
problem.
Water alone will not prevent media from loading up with contaminates. Chemical
additives must be used to clean the parts and the media. Generally speaking cleaning involves
the dissolving of contaminates and their suspension in a soluble solution; however, because of
molecular attraction, surface contaminates may require some additional help to remove these
materials. To do that, chemicals are chosen that react with the metal parts to help purge the
surface contaminates. This cleaning action is best accomplished by controlling the pH of the
solution or the chemical additive.
The pH of a liquid substance is considered either acidic or basic. The pH scale is the
logarithm of the effective hydrogen-ion concentration or hydrogen-ion activity in gram
equivalents per liter. The pH scale measures from 1 to 14 with water as neutral, but has a rating
of 7. Anything above this number is considered basic or a soap and anything below this number
is considered acidic. Again, generally speaking, acidic solutions seem to work well with non-
ferrous materials and basic solution work well with ferrous materials. This is not a hard and fast
rule and there are a lot of exceptions with liquids depending upon what you trying to achieve.
Besides the compound affecting the solution, water itself is a major factor in mass
finishing. That is, water is not a constant everywhere in the world, or for that matter, within a
mile of each source. Water contains minerals, which are leached out of the soil from which it
comes and then stays in the solution. This mineral content, called hardness, effects the
performance of media, but even more so the chemical additives. That means that given the
same chemical additive for processing to a company in one part of the country may not work as
well as that same product for another company somewhere else. All of the above factors
concerning liquids makes a simple problem more difficult. That also means that most
companies will have to do some experimenting on their own with chemicals even though there
are guideline recommendations.
Another factor complicating the proper mixing of solutions is that there are a lot of
chemicals to choose from and each has their own formulations, recommended dosage, or
dilution rate. Probably the first thing one should look at after the pH or the product and before
selecting a chemical additive is the concentration or dilution rate of the chemical compound. A
quart of chemical solution with a dilution rate of 640:1 is actually better than a 55 gallon drum
of user strength chemical, unless you are not prepared to monitor, mix, or regulate the solution
properly.
Chapter 13 - Liquid Systems 256
In a concentrated form, a chemical is normally a better deal for storage and probably
price, but the inconvenience of mixing and adding the chemical may cause addition problems
and/or costs. Most chemicals are now designed to be biodegradable and that means that if you
do nothing with them over a period of time they will cease to be of any use. The best chemical
compound in the world will not work if the solution is not properly maintained. Also, too much
dilution will change the pH of the product and it may not work properly.
Besides pH and dilution rate as criteria for selecting a cleaning compound is the question
of another additive within the chemical itself. Because mass finishing systems are mechanical
abrasion processes, they do remove materials from whatever is being worked or abraded. That
also means that in effect, this material removal process is recreating new raw surface features
that have never been exposed to oxygen and/or the oxidation process found in nature. All of
this means that another additive is usually incorporated into a chemical cleaner that does help
seal or protect new exposed metals and material against oxidation. This product is often
referred to as an inhibitor.
An inhibitor is not a cure all protective coating, but is more of a retardant against
oxidation. Too much inhibitor or too heavy of a coating will also affect the performance of the
media just like glazing will; therefore, a diluted solution of an inhibitor is recommended to
prevent flash rusting of parts prior to follow up coatings. Flash rusting is a more noticeable
problem as either outside temperatures increase or parts are heated to dry faster. If parts sit for
any length of time prior to their next operation, too little inhibitor will not protect the parts long
enough. Dilution rates or secondary coatings may have to be adjusted periodically because of
environmental and storage factors.
Liquid Flow Systems:
Besides the chemical, another controlling aspect of liquid solutions is the proper rate of
flow into the mass finishing systems. Without the proper amount of liquid to lubricate and carry
away cutting residue and debris, parts will become dark or black and may develop imbedded
abrasives and scratches. The flow rate or liquid volume is a variable factor governed by the size
of the machine, the media, and the drain system. In addition to these factors is the way in which
a process is run.
In smaller equipment systems under 1 cubic foot in size and any barrel system, the liquid
and chemical are normally a one shot deal where you add the chemical solution to a batch or
work, close up the system, and then empty it when the process is over. If a close loop or batch
system is used, then a secondary rinse is suggested for the parts and/or media to clean off any
debris or residue on both the parts and the media and to stop any chemical reactions.
A second type of closed loop system is a re-circulating system. This system is the same as
a batch process, but it re-circulates more volume of the solution. Usually these are relatively
small systems of 30 to 50 gallon capacity where the solution is constantly used over and over
again until it becomes ineffective because of the chemicals reacting with materials being
worked, oils, other contaminates and the deburring debris. Even though these closed loop
Chapter 13 - Liquid Systems 257
systems can become contaminated, the volume of the liquid solution is very effective for a
longer period of time than batch type operations.
A large, closed loop single chamber holding tank with a capacity of 20 to 50 gallons will
normally provide 5 to 10 days of good reusable solution based upon 40 hours of processing
time. Longer life is possible up to one month; however, most biodegradable chemical solutions
begin to lose their effectiveness at about 10 days in solution.
More common closed loop tank systems used to re-circulate the liquid are usually
separated into two or three partition segments called weirs that stagnate or slow the liquid
allowing the heavier particles to settle out. The tank can also have some kind of oil capturing
device that screens, transfers, or collects the oils and other light weight materials so that the
solution will have a longer life and the contaminates will not get re-used or screw up the
process. A pump is used to collect the least contaminated solution in the last weir and returns it
to the mass finishing system.
The third system is called a flow through, which is not considered a closed loop system.
This system constantly provides a new supply of solution and it drains to an outside source.
Some of these outside sources are still much larger version of the closed loop system mentioned
above; however, they do not re-circulate the spent or used liquids without purifying them. This
third system still requires the use of chemicals to be added to the mass finishing equipment and
this addition can be done in a couple of ways.
One way to control chemical input is to manually pre-mix a large container of a user
strength solution either by using a concentrate of liquid or powder form and use it as a reservoir
until it is complete used up and start all over again. The capacity of the tank or solution can be
determined by a flow rate of about a gallon per hour per cubic foot. On large equipment, over 5
cu. ft., this is not recommended.
Another automatic form of the same tank system uses an orifice to regulate and control
incoming liquid or the chemical compound additives to water in a pre-mixing tank with a
control float to monitor liquid level. This is a relatively inexpensive system for medium size
machine systems. Once an orifice size is selected and a chemical or liquid supply is hooked up,
this system requires no maintenance provided the liquid flows do not change. Lastly, there are
the more expensive metering pumps that do the same thing as the orifice system can but these
are not dependent on flow. They regulate liquid chemical compounds and water flowing into a
machine system. These are more expensive systems, but they are the simplest input systems that
take the guesswork out of liquid control.
With the exception of the batch type closed system, the re-circulating and flow through
systems still need to maintain a proper flow through the mass finishing equipment and process.
In new start up operations where the media has never been used or has drier out, the initial
flow requirement may be greater in the first 5 to 10 minutes of processing than the normal
amount of solution while in operation. After the moisture content of the media is reached, a
good liquid flow should be about 1 to 2 gallons of liquid per hour per cubic foot of media or
Chapter 13 - Liquid Systems 258
machine capacity. So, even with fixed liquid controls in place, the intervention of the machine
operator may still be necessary
The flow into a machine should nearly match the flow out of the machine. Because of
debris from the deburring operation, there are inherent problems of clogged drains. Therefore,
long processing cycles should be checked periodically to make sure the drain systems are
working properly. Most manufacturers account for this potential problem by putting in
normally 2 or more drains with a 2 to 1 output drain capacity than the liquid input. An obvious
sign of a clogged drain is the noise or sound level of the process system itself which decreases
and it may be possible to observe water splashing up into the air and/or around the machine.
When chemical compounds were first introduce into mass finishing equipment, a good
rule of thumb for chemical usage was, the more suds, the better the product and/or end result.
This is no longer true. Most chemicals used in these operations no longer have high suds rates.
In closed barrel type systems, suds are still acceptable and can be used effectively; however, as
indicated, formulations have changed primarily because in most other equipment foam or suds
is not desirable. What is visually looked for now in a good chemical compound is a slight
temporary bubble observed between the media as it moves. Too much suds as well as too much
water in a mass finishing process will slow down the action of the equipment and process. Suds
may produce nicer looking parts in some cases and may lessen the chance of part on part
impingement, but it will also take a lot longer time to process the parts.
Additives:
Most chemical compounds in use today are liquid; however, at one time, powders where
the preferred choice of the end user. The main reason was and is cost. Chemicals in the form of
powder are normally easier to store and are more concentrated. Other than cost, dry powders
still have some advantages in products that contain fine abrasive and organic materials used in
polishing. In the case of dry organic compound additives, one advantage is that these products
can usually be used in both wet and dry applications. Most liquids too can be used in wet and
some dry applications, but their formulations are not the same and they may not be effective for
dry organic materials.
Normally, polishing additives used in dry processes contain waxes or oils that do not dry
out and work well in dry processes. Most liquids cannot suspend these same ingredients
properly and they would probably cause a glazing situation to occur with a preformed shaped
media. For liquids to work properly, they must be able to be uniformly soluble. If liquids
contained or retained organic materials in suspension a biological reaction would take place
which would make the compound or organic materials in the solution deteriorate quickly and
would create other problems.
The popularity of liquids are also due in part because of the ease of handling, dispensing,
and/or metering by pump to achieve proper dilution rates. Liquids contain and hold inhibitors
better than powders and are a lot easier to control and dispense into equipment than powders.
Most equipment systems are not capable of handling powders and they must be premix by
Chapter 13 - Liquid Systems 259
hand and due to the safety factor and handling procedures, powders are not used much
anymore.
Deburring and burnishing compounds contain a number of surfactants to improve the
performance of water. The word surfactant is a very generic word used a lot in the chemical
industry to mean almost anything they want it to mean. I used the word, but by itself, it means
nothing. A surfactant is nothing more than another additive to water that effects the waters
behavior or performance. It can be anything organic or inorganic.
By itself, water alone does not have or allow for good surface contact or penetration of
the materials porosity. If the water cannot get into the pores of the material, it cannot dissolve or
clean the part. Surfactants are basically ingredients that work on the surface tension of water
and they react or interface between the media, metals, the solution, and air. For safety reasons,
products are formulated in such a way as to have a minimum concentration level below which
the product becomes ineffective. Most deburring products are alkaline in nature and contain an
inhibitor that re-deposits a protective coating on parts after cleaning them.
Surfactants can be almost anything added to water to make it work better. Therefore, the
solubility of a chemical and water solution is very important. Equally important is the nature of
dirt and or debris. The longer contaminates stay on a part the more difficult it is to clean. Some
contaminates can interact with a metals porosity and bond to it. To remove bonded
contaminates one needs a product with a good surfactant ingredient or good wetting agent.
That is, it should have a chemical that makes the water wetter so that it can penetrate and
displace the contaminated soils on the parts being cleaned. In a sense, a wetting agent breaks up
the attraction process of the soil and the parts substrate.
In some cases, an emulsion surfactant is more desirable where you have thick, grease
like, insoluble soils. This type of chemical product produces a milky solution that causes the
dispersion of the contaminates and holds them in suspension. A saponifier is another type of
product similar to the emulsion process chemical, but is better for use on the cleaning of animal
fatty acids. The latter products usually contain a significant amount of sodium or potassium
hydroxide. Naturally, the higher the temperature of any chemical solution the better and faster
it will work. Even pure water, at a high enough temperature will dissolve most contaminated
soil.
Getting back to mass finishing compounds, the difference between a burnishing
compound and a deburring compound is that the burnishing product contains a significant
amount of microscopic chelating agents which seeks out metal ions, encapsulates them and
suspends them in solution for easy disposal. The problem of chelating agents is in the disposal
and treatment of the waste water. The bonding qualities of chelating products makes it
extremely difficult to break up; therefore, the use of this agent may increase the problems of the
waste disposal with possible long term effects of the debris or costly recycling treatment.
Another important ingredient of a burnishing compound, and to some extent deburring
products, are ingredients that provide lubricity. Lubricity is very important in steel ball
burnishing. Not only does lubricity additives help the mechanical action of media, it also creates
Chapter 13 - Liquid Systems 260
or encapsulates the media with a charge that allows the compound to cling to the media. In
effect, it seals, glazes, or buffers any possible abrasive action to a limited extent. In effect, it
provides a buffer zone that is extremely thin and does not allow any abrasive particles to work.
Lubricity ingredients also provide a little more mobility to the contact shape and mass.
A single, one chemical fits all does not exist. Most chemical compounds used in mass
finishing systems are low foaming alkaline. Acid based products are still popular for working
non-ferrous materials of stainless steel, some aluminum, copper, and brass alloys. An ideal
chemical deburring product would be free of chromates, phosphates, silicate, fluorides,
chelators, nitrites, and cyanide. Also, it should be non-caustic, solvent free, emulsifier free, low
foaming, non-carcinogenic, biodegradable, environmentally safe, and have a pH of around 7.0
to 9.0. Also, the product selected besides cleaning the material being worked must not attack
that material and cause it to deteriorate. Other than these few desirable qualities, selection of a
chemical cleaning compound is easy.
In mass finishing systems sometimes there are instances were chemical reactions are
desirable to speed up deburring operations. A lot of strong alkaline or caustics are used to
create a surface condition called embrittlement which affects burrs very quickly and causes
them to become stiff and break off relatively fast. Acidic compounds can also be used to assist
deburring operations in a similar way and are usually desirable for processing aluminum parts.
The negative side, strong concentrates of chemicals require care and special handling or
disposal of waste by-products. Also, concentrated chemical solutions tend to turn parts dark or
black if left in batch or closed loop systems too long. If a mass finishing process takes over four
hours, or the chemical is used over a period of four hours, both the parts and chemical should
be monitored in some way to check the effectiveness of the process. Flow through systems that
do not use the liquid over again but dispense chemical on a proportioning bases are about the
safest way to process strong chemicals over a long period of time.
Chemical Accelerators:
We have just talked about the use of strong concentrates of chemical compounds in mass
finishing equipment and how they affect parts and the potential problems associated with them.
There is another category of chemical deburring and polishing compounds called accelerators
which are similar to the chemical concentrates mentioned above, but these products are
specifically designed to react with parts and produce fast metal removal and low RMS surface
finishes, without major harmful chemical effects or waste treatment problems.
Accelerator chemicals are formulated to produce different results on different materials
in a fast and efficient manner. The companies who are making these accelerator products claim
to be able to remove 150 to 80 grit sanding belt lines in 3 to 7 hours and produce 2 to 6 RMS
surface finishes. Typically, these chemical products are formulated and used on heavy metal
removal, especially hard materials such as Inconel, titanium, Waspalloy, and some stainless
steels, but there are also formulations for aluminum, brass, and zinc.
Chapter 13 - Liquid Systems 261
These accelerators are chemical concentrates, which require care in handling but are
diluted when in use and are recommended to be used with non-abrasive high-density porcelain
preformed media shapes. The products are designed to produce chemical reactions with the
metal, which in turn produce an inert soft surface metal coating or salt film, which is called
blackmode. The name is derived from the metals appearance before the part is processed.
Unlike other strong chemicals, chemical accelerators do not etch the metal and the salt
that is produced is not an oxide. When in use, the media is constantly removing this reactive
surface coating without having or producing the normal abrasive slurry debris of the media. If
the media cannot get into or contact this soft salt like film, no surface refinement can take place
and the remaining salt will retain its parent metal hardness.
As the chemical accelerator works, it removes a lot of surface roughness in a relatively
short period of time, and then it slows as the surface becomes smoother. It will always continue
to work to some extent, but at some point it does not become cost effective to continue. Normal
time cycles are about four hours in vibratory equipment to achieve extremely fine surface
finishes. It is interesting to note that when this surface finish is achieved by the first chemical, a
second burnishing chemical accelerator can be successfully added or used to achieve brightness,
without the machine being shut down or cleaned between these processing steps.
Besides the increased speed of metal removal the chemical accelerator process also has
the additional side benefit of using media with long life or wear than the normal deburring
media used in vibratory processes producing the same results. In addition to the media life is
the cost savings of not having to use more than one step and having to change the composition
of the preform media shape.
Chemical accelerators can have a pH as low as 2 on the acidic deburring side to about a 9
pH on the burnishing compound side. That means that these products are stronger concentrates
than normal deburring compounds and that some precautions must be taken by employees
who work around these products constantly. It is mandatory that all personnel who work about
chemicals wear impervious boots, gloves, clothing and protective eyewear. Also like all
processing fluids and waste products they must eventually wind up being treated before being
disposed of; therefore, safety and treatment cost must be weighted with the increase processing
speed or time element. Again, there are tradeoffs.
Chemical Control/Monitoring:
As stated earlier, all manufactured parts can vary from one batch to another; therefore,
one should always monitor the process and results and, if necessary, adjust the chemical
additive accordingly. Again, the black art or witch craft returns. Perhaps the simplest way to
work with and select a chemical compound for mass finishing is to try it. Take a recommended
product and use it as directed. If the product works, stay with it and use it. It is also a good
suggestion, once a chemical is selected, to cut the dilution rate in half and see if it continues to
work well. If a chemical product does not work well initially, try doubling the concentration
and then cut back. This cutting in half or doubling is probably the only sure way to get the
proper solution based upon your water hardness.
Chapter 13 - Liquid Systems 262
The dispensing of chemical compounds by metering pump systems make the process of
dialing dilution rates a whole lot easier than it used to be. Without the use of metering pumps,
there are pumps that can siphon chemicals in proportion to water usage that can be controlled
by orifice fittings designed to proportion the chemical in a direct relationship to the water input.
Lastly, there is still the pre-mixing of chemical by hand in batches and either dispensed with
pumps or gravity feed into the equipment being used using the proper solution flow. However,
any premixed or pre-measured tank still requires monitoring over a given period of time.
Talking about monitoring, once a chemical or chemicals have been selected, their use or
consistency must be monitored periodically. Some products deteriorate faster than others and
concentration has a lot to do with actual performance of the product. Omitting all the selection
criteria for the chemical compound product, there is still a need for the proper maintenance
controls of the solution while in use or storage. That is, like preform deburring or polishing
media that deteriorates with use, so to do liquids lose their characteristic properties to lubricate
and clean the media, the part, and to some extent the equipment.
As mentioned, there are metering systems to regulate a proper constant flow of chemical
and water mix through processing equipment and you can say that these systems are in a sense
already being monitored, controlled, and/or being maintained based upon the process of
selection. These flow through systems are normally concerned with an input only. However,
batch systems that re-circulate liquids over and over again must be concerned with an ever
changing solution that must be monitored and maintained periodically. If the processing
chemicals do not change per batch of parts, then the chemical should still be checked every four
hours of operation for their pH value. Although pH is the most important measure of a
chemicals strength and life, it is not the only factor.
Without going into elaborate testing equipment, most chemical solutions can be tested
with hand-held electronic digital read out measuring meters. Some of these devices are not as
accurate as others; therefore, some care must be taken for selecting a meter. Before selecting a
meter know what are its parameters or sampling criteria and/or in what are the units or
increments being read. Also check to see if there is a way to re-balance or zero out the meter or
is there a pre dip solution to get a proper base line correction. Lastly, there is care and
maintenance of the meter to consider.
The simplest way to monitor a solution is with litmus paper. However, most of these
products are not very accurate and are not precise enough to use as a monitoring device. There
is one company who makes a good quality, narrow range, of pH papers. This company makes a
number of products that measure from 0 to 14 pH. Each paper strip measures a chemical
solution range of 1.5 pH in step increments of 0.2 or 0.3, by using visual color code matching.
Using this observation method, it is possible to be accurate to within .05 pH. Another tricolor
product measures a wider range of pH values from 1 to 11 in whole pH units to the nearest .25
pH unit using this color code method.
Chapter 13 - Liquid Systems 263
Fig. 94. Liquid Monitoring Devices
The least expensive method for testing chemical solutions is by a variety of treated pH
or litmus paper products. Sticks of paper can measure a pH range of 1.5 units in steps of .2
and .3 pH for accurate readings to within .05 pH of the chemical solution. Tricolor rolls can
measure a range of 1 to 11 in whole units for readings to within .25 pH. For ion detection,
liquid chemical reaction kits also use the color change or visual color principle against chart
standards to determine the existing current test range of a chemical solution. There are also
now a number of more costly small fountain pen size mechanical devices with either visual
or digital read outs to perform these same tests.
Filtration and degreasing or oil skimmers are also important in re-circulating systems.
Filtration itself is a very complex science. Rather than go into a lot of detail on this subject, I will
only say that we are primarily dealing with waste water that has a lot of large size heavy
particulate and it will setting out of solution very quickly. That also means that for re-
circulating purpose, we do not need a great deal of high or fine quality water purification. In
fact, such quality is uneconomical and a waste of money, unless we are talking about large
volumes of liquid. Therefore, the biggest concern of a filter system is not to allow the re-
circulation pumping system to get jammed up with an accumulation of waste. Most mass
finishing systems do not need pure, clear water for clean parts.
Oils are another problem. In most cases, lubricants and oils float to the surface of the
waste water. Although it spreads across the top surface of the waste water, it can be confined,
directed, and controlled. If it is allowed to pass through most filtering systems, it will eventually
screw up the filter system and stop it from working properly. The confinement of oils can be
accomplished by a containment tank weir and then removed by a continuous wheel or belt that
picks up and deposits the oil into a separate container. Other systems allow the confinement of
the oils in a closed off area or spill area. All of these methods and/or removal devices require
monitoring of proper liquid levels periodically.
Anything in the solution that is not water will react or change a chemical product over a
given period of time. The more debris or foreign particles in a solution the faster it will
deteriorate. All of these factors or particulate weakens the strength of chemicals and are
constantly inter reacting with one another. Therefore, the more contaminates that can be
Chapter 13 - Liquid Systems 264
removed from a system while it is in use or in process, the better and longer the chemical
compound will work.
Alternative Processing Methods:
As mentioned, beside wet processing there are dry organic mass finishing systems. Fine
dry organic materials, or any fine grain material acts and behaves similar to water up to a point;
however, the very nature and cellular form of organic material particles give them a rather
interesting characteristics that allow them to clean by a slightly abrasive method. Their small
size or upper limit size range allows it to flow just like water and as stated earlier, chemicals can
be added in the same manner, but not proportionate, to organic materials as it can be added to
water. The only thing that fine organic materials cannot do is dilute or dissolve materials;
otherwise it behaves the same as water in mass finishing systems.
Organic materials can get extremely small and they do become ineffective at a particle
size range of under .010 to .020 in size unless used with other bulky materials. Certain inorganic
materials around .010 to .050 can also be run as a dry process operation; however, dust can be a
problem. A pretreatment can be added to some inorganic materials to control dusting, but it is
still difficult to control both the cutting, glazing, and the dusting problem. Normally dry organic
operating procedures are almost mandatory on parts smaller than a half inch diameter or
square, because of the problems that water adhesion creates.
Getting back to liquid systems, we talked about batching systems, closed loop re-
circulating systems, and flow through systems for controlling abrasion and cleaning of parts in
mass finishing systems. Each of these systems have advantages and disadvantages and a lot
depends on the machinery involved. However, because of government regulations, nearly all
systems, even flow through are no longer flow through systems as they were known before.
That is, nearly all systems are closed loop systems either dedicated to this specific equipment or
product line or to the manufacturing plant as a whole.
Even though most of the waste and by-products of mass finishing operations are
harmless they do contain metals in solid and solution form which must be treated. If nothing
else, the waste solids do behave like cement and they will eventually clog a drain system;
therefore, proper maintenance is required and drain access should be considered during
installation.
A couple of thoughts might be appropriate here regarding how to improve the
performance of liquids in special cases. Normally cost prohibits the implementations of these
ideas, but you should be aware of them. It is possible to improve or speed up processing time
and/or chemical reactions by using hot water instead of normal ambient tap water into mass
finishing equipment. In closed systems, this occurs naturally to a point; however, in bigger open
systems this does not occur. Also, deionized and distilled water has greater cleaning and
penetrating abilities than tap water and can also be used to improve the cleanliness of the end
product substantially.
265
Chapter 14 – Selection Guidelines & Cost Factors
Waste Treatment:
Let’s get back to the disposal of wastewater from mass finishing equipment operations. It
is suggested that all liquid waste materials first enter a settling tank with baffles like all
standard close loop systems. Because we are dealing mostly with inorganic materials,
approximately 80 to 90% of the waste is heavy enough to settle out. Suspended solids in
solution eventually accumulate at the bottom of the collection tank and these solids must be
removed and disposed of in some fashion. When dealing with primarily precious metals this
solid waste can be quite profitable.
Most of the remaining liquid waste and contaminates must be filter or treated to comply
with local, state, and federal regulations, before allowing it to be disposed of as run off to the
environment or public sewer system. To help you comply with new rules and regulations, the
following is a checklist for your review to seek approval for discharging effluent wastewater
from mass finishing systems directly into a sewer system:
Before contacting your local municipality, you should have the following information
available for review.
Waste Treatment Guidelines
1. Estimated number of gallons, both the minimum and maximum, to be discharged
every 24 hours.
2. Estimated cost of the water for that discharge.
3. Determine water hardness level, if possible.
4. Get a copy of standard municipal limits from sewer department.
5. Get copy of municipal guidelines and/or submission form.
6. If submission form does not list following, obtain information for:
i. COD - Chemical Oxygen Demand
ii. BOD - Biological Oxygen Demand
iii. FOG - Fats, Oils, and Grease
iv. SS Mg/L - Suspended Solids in milligrams per liter.
7. OSHA approved MSDS sheet for media being used.
8. OSHA approved MSDS sheet for chemical compound.
9. OSHA approved MSDS sheet for materials being worked in mass finishing machine. 10. All of the above should be reviewed for compliance to standards plus any local regulations.
11. Obtain or create typical wastewater sample.
12. Submit sample to municipal sewer department.
It is suggested that you may want to have an outside testing laboratory review
sample first, before submitting to sewer department. This may eliminate any undo
concerns or scrutiny by regulators.
Chapter 14 – Selection Guidelines & Cost Factors 266
13. Install mass finishing equipment upon acceptance of effluent disposal by sewer
authority. Set up and adjust water flow through settling tanks or filtration system.
Check SS Mg/L. Adjust PH and chemical usage to help ensure bio-degradable
breakdown of all waste products.
14. Establish a monitoring schedule for cleaning the system and disposal of the solid and
liquid waste.
Applications
I have discussed guidelines for media selection earlier; however, I would like to cover
some of the more common generalized guidelines concerning all mass finishing systems. They
are as follows:
Quick Guideline Briefs For Mass Finishing System Processing
Rule #1. There are no hard and fast rules for achieving immediate good surface finishing
results every time, unless a lot of information is known about the parts and the operations prior
to mass finishing.
Rule #2. All mass finishing equipment will work faster, more aggressively when the
equipment is filled to its maximum working capacity or capacity so designated. Weight and
pressure are the major factors for fast material removal. Note: Barrel systems cannot operate
properly with a full barrel, there must be room for proper movement.
Rule #3. To achieve the fastest, shortest time cycles, use the coarsest media possible that
will get into all the areas that have to be worked without getting stuck or distorting the part.
Rule #4. Normal procedure for media selection is as follows:
Ceramic media is used for ferrous metals.
Plastic media is used for non-ferrous metals.
Steel or porcelain media is used to achieve a bright shinny burnished finishes on all
materials.
Dry treated organic media is used for smooth, polished mirror finishes on all
materials.
Rule #5. Extremely small or flat parts tend to stick together in a wet processes; therefore,
they are better processed with dry abrasive mix products.
Rule #6. Multiple step processing is recommended to remove the most amount of
material in the shortest amount of time.
Rule #7. The higher or lower the pH of the liquid chemical compound from 7.0 (neutral),
the cleaner the parts and media; therefore the faster the deburring process will work. Also the
more concentrated the chemical compound, the faster it will work up to a point where excessive
foam will slow down or retard movement of the process.
Rule #8. To achieve good clean looking parts, use an ample flow of liquid through the
work chamber liquid system or use a filtered close loop system rather than to close loop batch
Chapter 14 – Selection Guidelines & Cost Factors 267
parts. If a batch system is used, drain and rinse the parts and media the last 5 or 10 minutes of
the processing cycle.
Rule #9. Too much liquid and/or chemical will slow down deburring action, but maybe
useful to reduce or cushion part on part contact or for burnishing operations where the chemical
is very important.
Rule #10. To achieve a fast bright finish on part, use a heavy non-abrasive burnishing
media after deburring.
Rule #11. To achieve the finest, smoothest, mirror finish and lowest RMS use a dry
organic polishing media after deburring. Most chemical compound additives contain inhibitors
that will protect parts for a short period of time, maybe 24 hours, but some parts need
additional protection.
Rule #12. All parts should be cleaned and protected as soon as possible after processing
to prevent oxidation.
I have tried to emphasize in rule #1 the importance of knowing as much as possible about
the part or parts prior to the finishing process. Maybe we should create a check list of things
that should be known that can effect part finishes and determine which finishing method is best
to use. The following is such a list, but is not the total list, because there are other factors which
in turn are dependent upon the finished product itself. Some of the information required here is
the same as that above; however, the above information relates more to equipment than the
actual processing of that equipment.
Required Part Information for Proper Processing
1. What is the part made out of?
A. Ferrous metal
B. Non-ferrous metal
C. Plastic
D. Composite
E. Organic
F. Other
2. What is the hardness of the material?
3. How was it made?
A. Cast or molded
B. Forged
C. Machined
D. Sheet
4. What is the weight of the part or cubic foot of parts?
5. How big or small is the part?
6. What quantity of parts have to be processed?
Chapter 14 – Selection Guidelines & Cost Factors 268
7. What time cycle is required?
8. What is the configuration or part volume?
9. Are there any interior dimension or recesses?
A. What is the smallest I.D. Dimension?
B. Does the part have any thin material areas under .020?
10. What is the desired finish?
A. Part needs to be deburred only
B. Part has to be chemically treated
C. Part has to be painted
D. Part has to be polished
E. Part has to be protected against oxidation only
11. What is the existing surface finish?
12. Are there any tight measurement tolerance requirements?
13. Are there any cost restraints?
14. What equipment , if any, is available?
15. Were there any chemical coolants or lubricants used to manufacture part?
16. How long have parts sat idle before required surface finishing?
17. Has oxidation of part started to occur?
18. Were parts subject to any gases or dust?
19. Can or have parts been subject to extreme temperatures?
20. Will temperature effect part?
21. Are there any problems using chemicals to process part?
22. Is contamination a problem in processing?
In addition to these mass finishing guidelines for processing and part information, there
is still another list needed for equipment requirements for the end customer. This list takes
production needs into account more than the part or the process. The first thing one needs to do
is analyze the needs of customer or end user for mass finishing equipment. That is, let’s take a
look at what is normally needed to make a logical and reasonable decision as to what is needed
in the way of equipment, media, and compound necessary to accomplish a specific task of mass
finishing. Again, there may be some repeated items from the above lists here. The following are
some guidelines for determining equipment needs:
Chapter 14 – Selection Guidelines & Cost Factors 269
Equipment Requirements
1. What is the size of the part to be worked?
Length, width, and height?
2. What is the weight of the part?
3. What material is the part made from?
Metal, plastic, composite, other?
4. What quantity has to be processed?
Per year, per month, per lot, per shift, per day, per hour, other?
5. What is the basic part function?
6. Burr requirement:
Slight edge break, remove sharpness, remove burr completely, burr
removal plus edge break, other?
7. Finishing requirement:
Smooth only, specific RMS, bright, mirror finish, other?
8. Will part be painted or plated?
9. Critical tolerance considerations:
None, corner and edges, holes, diameter or thickness, other?
10. Other parts considered for this processing?
11. Mixed metals?
12. Current needs?
13. Future needs?
14. Cost limitations?
15. Electrical power requirements?
Once these questions have been answered an intelligent engineer maybe able to make a
proper recommendation on equipment, media supplies, and compound to do mass finishing.
However, if there are monetary limitations or there is a need for future planning to acquire new
or additional equipment and supplies, then an operating cost estimate might have to be
prepared. The following are some guidelines for determining estimated costs:
Chapter 14 – Selection Guidelines & Cost Factors 270
OPERATION COST ESTIMATE*
Parts: Produced Required
DATE per shift ______________________
Company per hour ______________________
Part # per month ___________________
per ____________________
________________________________________________________________________
Part Length Actual Displacement______Cu. Inches
Part Width Indicate # of parts________Cu. Feet
Part Height Working # of parts* _______Cu. Feet
Part Weight Cu. Ft. pts. in machine______Cu. Feet
Number of parts in batch________Qty
*80%of Indicated # of parts.
Ratio of media to parts
Machine Used:______________________________ Capacity________Cu. Feet
Machine hourly cost(See Table Below) Machine cost /hour
Power Cost__________Horsepower at $.065† per HP hour
Compound cost at __________ per ounce per cu. ft.
Media Used:_________________________________________________________
Media in machine__________ Cu. Ft. Weight per Cu. Ft.__________
Pounds in machine_________ Lbs. Cost per pound__________
Cost media in machine___________ Attrition rate per hr.__________%
MEDIA COST / HR.____________________
TOTAL MACHINE HOURLY COST _______
Load Cost:
Load Process Time_____Hours______ minutes __________
Labor Rate___________Per Hour X Labor Rate_____ minutes __________
TOTAL COST / LOAD __________
TOTAL COST / PART __________
TOTAL COST / 1,000 PARTS. __________
NOTE 1: The information contained on this page are also available on a Windows 95 computer program available
upon request from author’s company. All numbers appearing to the right after the solid line under the part
description are automatically calculated by the program. For those who do not have the program, the following
description explains in better detail what these figures mean.
†Based on Michigan job shop data in Michigan in 2000. Results will vary, depending on local electric power rates.
Chapter 14 – Selection Guidelines & Cost Factors 271
After part length, width, and height are multiplied, the total is divided by 1728 to get the
actual displacement in cubic inches. In the program, parts per cubic inch are rounded off to one
tenth. On the computer program, it is a 5 digit number. The figure from this calculation is then
divided into 1728 to get the indicated number of parts per cubic foot. Now, parts do not and
should not fit or stack neatly into a mass finishing work chamber system; therefore, an 80%
figure of the indicated number of parts is used to get a good, free flowing working number of
parts.
The ratio of media to parts is an arbitrary number based upon what kind of finishing
requirements you want to achieve. I usually use a percentage of media to parts; however, most
large machine systems use a ratio to determine volume displacement. So, for abrasive deburring
instead of 60% media to 40% parts, this equates to about a 3.5 : 1 ratio of media to parts. To
convert percentage to ratio or vice–versa add the total number of both halves of a ratio and
divide into 100. For polishing this 90% media to 10% parts becomes about 9 : 1 ratio.
Based upon the arbitrary ratio you need, this number is divided into the size of the
machine system you have, need to have, or expect to have for future needs. So, if you have a 25
cubic foot machine and you have a 4 : 1 ratio of media to parts, the function of this ratio is 5 and
you divide that into 25 to get the cubic foot of parts in the machine. (As an added note here,
most of this book talks about percentages rather than ratio. Therefore, to covert either
percentage to ratio or vice-versa, take the function number and divide it into 100 to find out
what the number one equals.). To get the total number of parts in the batch or load capacity per
processing cycle, you multiple the number, in this case 5 times the working number of parts per
cubic foot.
NOTE 2: Machine hourly cost figures below are based upon averages computed over
2,500 hours of machine operation per year and include: rent, heat, light, insurance, supervision,
and general overhead. A depreciation rate of five years and an average maintenance costs were
also used. To be more accurate, you may use the following estimate sheet to compute actual
costs.
All Vibratory Equipment: Machine hourly cost rate*
1 cu. ft. includes screen and reloading accessories…………………….. $ 0.50
2 cu. ft……………………………………………………………………… $ 0.58
3 cu. ft……………………………………………………………………… $0 .93
5 cu. ft……………………………………………………………………… $ 1.40
10 cu. ft……………………………………………………………………… $ 2.23
15 cu. ft……………………………………………………………………… $ 3.36
20 cu. ft……………………………………………………………………… $ 4.45
25 cu. ft……………………………………………………………………… $ 5.57
35 cu. ft……………………………………………………………………… $ 6.36
*Based on Michigan job shop data in Michigan in 2000. Results will vary, depending on local electric power rates.
Chapter 14 – Selection Guidelines & Cost Factors 272
To determine the hourly machine cost, you can use the figures provided under NOTE 2,
or calculate them on the following spreadsheet. To use the later requires yearly cost figures and
accounting numbers for depreciation. To arrive at the final cost figure is a simple straight
forward calculation. Enter this number under machine coast per hour.
Power cost is based upon the horsepower of the machine system selected. Again, this
number can be calculated from your existing records, or it can be gotten from your local power
supplier, or you can use the figure which is provided above of $.065 per horsepower per hour.
The compound cost figure is based upon the following information. For this figure, a
common compound use rate for processing is one ounce per gallon of water. The displacement
or size of the machine. Example: 20 cu. ft.= 20 gallons per hour. Divide the cost of the compound
by 128 ounces to get the cost of compound per ounce per cubic foot, then multiply this figure to
get the machine cost per hour.
Media selection is important as mentioned in another section of this book. Your selection
of a composition, size and shape, pretty well locks you into a lot of the following information.
The pound in 50-pound boxes, which is standard packaging, normally sells media and
sometimes this equates to about 1 cubic foot of media. The latter information is only a rough
estimate and should not be used in these calculations.
Media capacity may be slightly difficult to determine because of variable standards also
mentioned elsewhere in this book. That means that the size of the machine is not the media
capacity of the machine; therefore, get that capacity information from the equipment
manufacturer. Example: A 20 cu. ft. machine at a normal 3 : 1 ratio of deburring media to parts
equals 15 cubic feet of media in the machine. Multiple this capacity figure times the weight of
the media per cubic foot, which is normally given by the supplier or manufacturer, to get
pounds in the machine. Multiply the pounds in the machine by the cost per pound to get the
cost of media in the machine.
The Attrition rate per hour percentage is based upon a series of tables enclosed, see
NOTE 3, supplied by the manufacturers of the media. These are figures from the most common
suppliers of media. However, this does not have all of the suppliers.
NOTE 3: The following comparison chart is a composite of information provided by
manufacturers as to the wear characteristic of their media. Most of the figures were derived
from tests from a high energy Harperizer machine system; however, some tests were also
conducted in vibratory equipment. Unfortunately, that means that the results may not be 100%
comparable because we are not comparing apples and apples. Also the equivalent compositions
are just that, they are approximately the same , not exactly the same. However, this is the best
we can do to arrive at reasonable figures. Again, there is no one standard or central organization
which can make these determinations.
Chapter 14 – Selection Guidelines & Cost Factors 273
Attrition Rate Chart for Media
Abrasive Finishing
(Fortune)
Ultramatic Washington Mills Wisconsin Porcelain
Composition Rate Composition Rate Composition Rate Composition Rate
AX – 90 .3 LL .2 D – 20 .3 .3
AX - 65 .4 MC .4 D – 30 .4 XC .4
AH - 41 1.0 FC .6 D - 40 1.3 H 1.3
AX – 44 .1 D - 10 .1 F .1
CS - 46 .6 GC .7
C .3 SC .4 D - 50 .44
N .001 HD .1 I 40 .02
XB .005 XM .003
UL .5 LW .6
H – 33 .2
F – 33 .3
SP – 3 .4
F – 36 .5
Once the machine operating costs are known, one can calculate the hourly machine costs
or general administrative costs of operating this equipment. Most of this costs are not
specifically related to the equipment, but the overall costs of one’s business and labor. That
means that even though the equipment or machine system costs the same for everyone buying
that same system, it will have different hourly operating costs because of the company itself.
Chapter 14 – Selection Guidelines & Cost Factors 274
Determination of Machine Hourly Cost Rate
A. Floor Space Costs
Add costs per year for floor area where machine is located
Cost per year
Rent $__________
Heat $__________
Light $__________
Insurance $__________
General Overhead $__________
Supervision $__________
Total Cost of Department Floor Space
Total $_____ X Sq. Ft. needed for operation = Floor Space Cost Per Year
Sq. Ft. in department
B. Depreciation and Maintenance
Total Cost of Equipment $__________
Divided by _____ Years of Depreciation $__________
Maintenance Cost Per Year $__________
MACHINE HOURLY COST RATE
Total of A & B above = $_________ Hours Used Per Year________= $ ________ Per Hour
Well, that concludes deburring and mass finishing systems to a great degree. I will not
say that this finalizes future possibilities. There are a lot of relatively new systems discussed
earlier in this book and just as mass finishing systems have evolved into basically 3 generations
of equipment, so it is possible that these other technologies may also.
The simplest system for deburring would be the best, because generally speaking no one
likes to do deburring or polishing work, especially by hand. Most companies or supervision
think and practice a negative bias toward deburring systems. That is, they put their least skilled
workers on this task or equipment because it is generally dirty work supposedly requiring no
special talent. As you can see from the amount of material we have covered in this book, this is
not a true statement, nor is it far from being idiot proof!
You would think that the time and money spent to achieve the making of precision parts
should deserve some attention and expense for a good and proper finish. That is, some parts
cost literally hundreds or thousands of dollars and yet they can be relegated to the most
unskilled people and tools to do the final surface finishing. I think that is a potential for disaster.
Hopefully, this book might help to shed some light on this profession and clean it up.
Bibliography and Credits 275
Bibliography and Credits
Book
Metal Finishing
Guidebook and Directory Issue 98 & 99
January 1998 Volume 95, Number 1 &
January 1999, Volume 97, Number 1
Articles:
Polishing and Buffing by Al Dickman and Bill Millman
Buffing Wheels and Equipment by Stanley P Sa
xSurface Conditioning Abrasives by Jan Reyers
Belt polishing by George J. Anselment
Filament Brushing Tools for Surface Finishing Applications by Robert J. Stango
Blast Finishing by Daniel Herbert
Impact Blasting with Glass Beads by Robert C. Mulhall and Nicholas D. Nedas
Mass Finishing Processes by David A. Davidson
Seminar
5th International Conference on Deburring and Surface Finishing
Copyright 1998 Deburring Technology International, Inc.
San Francisco, CA. Sept. 1998
Turboabrasive Machining-Automated Technology for Finishing of Part
Prof. Zinoviy I. Kremmen, St. Petersburg, Russia
Advanced Abrasive Flow Technology
Ralph Resnick, Extrudehone, Irwin, PA.
Electropolish Deburring
Peter Marcilese and John Stackhouse, Dynetics, Woburn, MA.
Developments in High-Pressure Water Jet Deburring
Klaus Berger, Daimler Benz, Stuttgart, Germany
Bibliography and Credits 276
Contributors:
Michael, Mark, & Scott Cantwell
Finishing Associates Inc.
320 Constance Drive, Unit 2
Warminster, PA. 18974
David A. Davidson
Pegco Process Labs
Bartlett, NH 03812
James Randal , retired
Jenex Corp.
Chelsea, MI 48118
Bob Kramer
47 Chestnut Hill Rd.
Roslyn, N.Y. 11576
George Bull
Electrohone Technologies, Inc.
P.O. Box 317
Crystal Lake, IL. 60039
Sam R. Thompson
Retired, Ultramatic Equipment Corp.
Wallingford, CT 06492
Stanley A. Mayer
SMC Systems Inc.
San Diego, CA 92117
Dave Arber
Omni Finishing Systems Inc.
163 Railroad Drive
Ivyland, PA. 18974
Dave Koster & Robert Schaeffer
ThermoBurr
6310 Wall St.
Sterling Heights, MI. 48312
Bill Neibiolo
REM Chemicals, Inc.
325 West Queen St.
Southington, CT. 06489
Mark Singer
P.O. Box. 434
Morristown, NJ 08057
Vibrodyne
2853 Springboro West
Dayton, Ohio 45439
Photo and Image Credits
3M Industrial Abrasives Div.
3M Center
223-6NW-01
St. Paul, MN 55144-1000
Fig. 16, Fig. 17, Fig. 28, Fig. 29, Fig. 30,
Fig. 34
Abbott Ball Co.
Illinois Railroad Ave.
West Hartford, CT. 06133-0100
Fig. 91
Almco Inc.
902 E. Main St.
Albert Lea, MN. 56007
Fig. 73, Fig. 80, Fig. 81
C & M Topline Manufacturing
5945 Daley St.
Goleta, CA. 93117
Fig. 58 (bottom)
CAE Ultrasonics
PO Box 220
Jamestown, NY 14702
Fig. 46
Bibliography and Credits 277
Cryogenic Systems & Parts
3595 Cadillac Ave.
Costa Mesa, CA 92626
Fig. 41
DEWALT Industrial Tool Co.
701 E. Joppa Road
Baltimore, MD 21286
Fig. 3
Diston Corp
87 John Dretsch Sq.
North Attleboro, MA 02760
Fig. 7, Fig. 54
Dreher Corp.
57 George Leven Dr.
N. Attleboro, MA 02760
Fig. 93
Empire Abrasive Equipment Corp.
2101 West Cabot Blvd.
Langhorne, PA. 19047
Fig. 4, Fig. 35, Fig. 36
Extrudehone
8075 Pennsylvania Ave.
Irwin, PA. 15642
Fig. 47, Fig. 48, Fig. 49
Farr Mfg.& Engineering Co
Williamstown
WV. 21687
Fig. 14
Fill-Chem Inc.
PO Box 90833
Raleigh, NC 27675
Fig. 94
Finishing Associates Inc.
1610 Republic Rd.
Huntingdon Valley, PA. 19006
Fig. 6 (center and bottom), Fig. 64, Fig. 76,
Fig. 77, Fig. 78, Fig. 79
Glen Mills Inc
395 Allwood Rd.
Clifton, NJ 07012-1794
Fig. 74
Grav-l-Flo Corp.
400 Norwood Ave.
Sturgis, MI 49091
Fig. 68, Fig. 69, Fig. 80, Fig. 81
Guyson Corp. of USA
E.J. Grande Ind. Park
Saratoga Springs, NY 12866-9044
Fig. 38
ICM Inc.
10630 S. Garfield Ave.
South Gate, CA 90280
Fig. 44
Illinois Electro-Deburring
9393 Seymour
Schiller Park, IL. 60176
Fig. 90
Jackson Lea
75 Progress Lane
Waterbury, CT 06720-0071
Tables on page 67 and 68
Jenex Corporation
13550 Luick Drive
Chelsea, MI 48118
Fig. 66, Fig. 90
Kersarge Peg Co.,Inc.
P.O.Box 158
Bartlett, N.H. 03812
Fig. 92
Bibliography and Credits 278
Kmeech Corp.
1 Oak Hill Rd.
Fitchburg, MA 01420
Fig. 53
Kramer Ind., Inc.
1189 Sunrise Highway
Copiague, N.Y. 11726
Fig. 5, Fig. 58 (top), Fig. 10, Fig. 37, Fig. 55-
Fig. 57, Fig. 59, 0
L.A. Abrasive Products
400 Sibley Blvd.
Harvey, IL 48209
Fig. 27
Metal Improvement Co. Inc.
10 Forest Ave.
Paramus, NJ 07652
Fig. 43
MSC Industrial Supply Co.
75 Maxess Road
Melville, New York 11747
Fig. 3 (top)
Noga Engineering Ltd.
PO Box 55
Schlomi, Israel 22832
Fig. 9
Norton Corp.
Worcester, MA 01615-0008
Fig. 31, Fig. 32
Nova Finishing Systems, Inc.
1610 Republic Rd.
Huntingdon Valley, PA 19006
Fig. 1, Fig. 6 (top left, side view drawing),
Fig. 75
Osborn Brush
5401 Hamilton Ave.
Cleveland, OH 44144-3997
Fig. 2, Fig. 11, Fig. 18, Fig. 19. Fig. 20, Fig. 21,
Fig. 22
Rampart Finishing Equipment Co.
632 E. 152nd St.
Cleveland, OH 44110
Fig. 58
Rose Training Systems Inc.
6161 Cochran Rd., Ste. 0
Solon, OH 44139
Roto-Finish
1600 Douglas Ave.
Kalamazoo, MI. 49007
Fig. 6 (top right), Fig. 67, Fig. 72, Fig. 74
S.S. White Ind.Products Pennwalt
151 Old Brunswick Rd.
Piscataway, N.J. 08854
Fig. 39, Fig. 40
Sommer & Maca Ind., Inc.
5501 West Ogden Ave.
Cicero, IL 60806-3507
Fig. 2, Fig. 11, Fig. 12
Stanley P. Sax Corp.
101 South Waterman
Detroit, MI 48209
Fig. 23, Fig. 24, Fig. 25, Fig. 26
Sugino Corp
1700 Penny Lane
Schaumburg, IL 60173
Fig. 45
Surftran Bosch Group
30250 Strephenson Highway
Madison Heights, MI. 48071
Fig. 8, Fig. 50 - Fig. 52
Bibliography and Credits 279
Sweco, Inc.
8029 US Hwy. 25
Florence, KY. 41022-1509
Fig. 6 (top left), Fig. 60, Fig. 65, Fig. 74
The Wheelabrator Corp.
27 Amlajack Blvd.
Shenandoah, GA. 30265
Fig. 42
Timesavers Mass Finishing Div.
5270 Hanson Court
Minneapolis, MN. 55429-3111
Fig. 3 (bottom), Fig. 15
Tipton US Corp.
8411 Seward Rd.
Hamilton, Ohio 45011
Fig. 12, Fig. 13, Fig. 70, Fig. 71
Turbo-Finish Corp.
25 Williamsville Rd.
Barre, MA 01005
Fig. 82, Fig. 84
Ultramatic Equipment Corp.
8502 E. Via De Ventura #210
Scottsdale, AZ. 85258
Fig. 62, Fig. 63
USF Surface Preparation Group
1605 E. Hwy 34, Ste. A
Newman, GA
Fig. 4
Vapormatt Ltd.
Rue a Chiens
St. Sampson’s, Guernsey
Channel Islands GY24AG
Fig. 12, Fig. 44
Vibra Finish Co.
8491 Seward Rd.
Hamilton, Ohio 45011
Fig. 90
VSM Abrasives Corp.
1012 E. Wabash St.
O’Fallon, MO 63366-2774
Fig. 33
Washington Mills Ceramic Corp.
20 North Main St.
North Grafton, MA. 01536
Fig. 89
About the Author 280
About the Author
Anthony (Tony) Kenton went to college at Indiana University, Bloomington, Indiana, and Temple University Philadelphia, PA. He worked for a number of manufacturing companies in engineering capacities before he entered sales. In the 1980’s he had a lot of hands on knowledge and experience in the finishing and abrasives industry. So, in 1988, with a lot of help from friends and business partners, he started his own company now called Nova Finishing Systems Inc.
Originally this company made vibratory deburring machines he designed for small surface finishing applications. He has expanded this to include one registered separation patent and has acquired and now builds centrifugal deburring systems formally manufactured by R.N. Hutson Co.
Mr. Kenton takes pride in the fact that he is constantly improving his products and designing new systems. In addition to being a leading innovator, he is a well published technical writer on abrasive and processing systems for the industry and has been featured in nearly all US trade publications. he is also an author, and respected consultant for the finishing industry.
In this book, Evaluating Material Removal and Surface Modification Systems, he wants the reader to know as much as possible about options and alternatives on how to accomplish their desired end result. Mr Kenton not only designs equipment, but he has designed a classification system similar to the Dewey Decimal system for surface finishing. His book and system employs the KISS principle by reducing all processing methods into a total of six classifications based upon how energy is applied. A simplified equation of this principle is found on the front cover of his book, “The application of energy + pressure + hardness of media and material = the rate, amount, and time of material removal and surface modification.”
ISBN - 978-0-615-85574-5
Evaluating Material Removal and Surface Modification Systems, by A.F. Kenton
Recommended