Fact Sheet : METAL REMOVAL/CUTTING

8/9/2019 Fact Sheet : METAL REMOVAL/CUTTING

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FACT SHEET

Created on 21/10/04 10:31

CATEGORY: 3.1 MANUFACTURING

PROCESSES

METAL REMOVAL/CUTTING

INTRODUCTION

A broad range of metal removal and cutting methods are available to meet the differingneeds of manufacturers. Metal removal techniques and metal cutting processes arediscussed within the factsheet.

METAL REMOVAL PROCESSES

Milling

Milling is the process of machining flats, slots, grooves, etc in material by means of a rotatingcutter with multiple cutting edges. Two main types of milling machine exist: horizontal millingmachine and the vertical milling machine. Milling cutters usually have teeth cut on theperiphery and/or on the end of a disc or cylinder. Alternatively, inserted tooth cutters withreplaceable teeth may be employed. In horizontal milling, up-cutting is common practice,but down-cutting can also be performed. There are many types of cutter designed for manydifferent milling applications.

Drilling and Reaming

Drilling is the process of cutting holes in a component. A twist drill is a manually or machinerotated tool with cutting edges to produce circular holes in a variety of materials (metals,

woods and plastics). It is manufactured from hardened steel bar with usually two helicalgrooves, called flutes, terminating in two angled cutting edges. The flutes permit regrindingof the drill bit, to retain its sharpness and hence accuracy and ability to cut, and assist inswarf removal during drilling operations. Core drills have three or four flutes and are used toopen out existing holes. Drills vary in size from a fraction of a millimetre to over 100mm.Drill bit grinding is best undertaken upon a special drill-grinding machine.

A reamer is used to finish a hole accurately with a high quality surface finish. It is aperiphery cutting tool, unlike the drill which is end cutting. Flutes may be straight or helical(usually left handed). A hand reamer requires a long slow taper, but machine reamers havea short 45o lead. The hole is drilled slightly smaller than the reamer diameter bearing inmind that the allowance is about 0.015mm per millimetre, but this also depends on the

material. Taper reamers are used for finishing hole for taper pins.

Turning

Turning is the process of producing cylindrical shaped components on a lathe. Theworkpiece is mounted in a chuck and rotated. A stationary cutting tool is employed toremove material either from the face or side of the workpiece. Metal removal rate willdepend on the speed of rotation of the workpiece and the linear speed of the cutting toolrelative to the workpiece. Both these speeds are heavily dependent on the workpiecematerial and the surface finish required. Screwcutting can be accurately performed on thelathe using a set of gears to control the spindle and cutting tool speeds respectively.


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Shaping

Shaping is the process of producing flat surfaces and slots on a component. A shapingmachine consists of a reciprocating ram that carries a tool horizontally in guides or verticallyin a clapper box and is driven by a quick return mechanism. There are different types of

shaping machine including profilers - machines that follow a template to cut into blanks, andpantographs - machines that use a plug (sample board) to trace the tool paths for thecutting head to shape the blank.

Surface Grinding

Surface Grinding is the process of applying a high gloss finish to a metal component byusing an abrasive wheel. Grinding machines can produce flat, cylindrical and other surfacesby means of a high-speed rotating abrasive wheel. Grinding is a means of giving a moreaccurate surface finish to a pre-machined component but is also a machining process in itsown right as material is removed during the operation.

The main types of grinding machine are the surface grinding machine for flat surfaces andthe cylindrical grinding machine for cylindrical surfaces. More complex shapes may beground using shaped abrasive wheels called contour grinding wheels.

Grinding wheels use bonded abrasive powders typically based on the following materials:Aluminium oxide (Al2O3), silicon carbide (SiC) and diamond dust.

Thread Cutting Machines

Thread cutting machines may be used as an alternative to thread rolling machines wherebythe thread is formed by plastically deforming the metal component. Internal (tapped) thread

or external thread cutting machines may be employed for thread cutting operations.

Electro Chemical Machining (ECM)

Electro-Chemical Machining (ECM) is based on the phenomenon of electrolysis. Thismachining method does not involve actual cutting of the workpiece. ECM shapes theworkpiece by dissolving the metal into metallic ions. Because an actual cutting tool is notneeded, the shaping tool does not have to be harder than the workpiece that makes thismethod particularly suitable for hard metals.

Electro Discharge Machining (EDM)

Spark Discharge machining or Electrical Discharge machining (EDM) is material removalmethod suitable for any material which is a reasonable conductor of electricity. Instead ofcutting the material, EDM removes material with electrical discharges or sparks. EDM can beemployed for use on very hard or brittle materials that could not be machined usingconventional milling machines or lathes. EDM is particularly suitable for hardened tool steeland is used frequently in the tooling industry.


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METAL CUTTING PROCESSES

Flame cutting, water jet cutting, laser cutting and plasma cutting are presented hereon.

Flame Cutting

Flame cutting is the process of cutting metal with an oxy-acetylene or oxy-hydrogen flame.Oxy-fuel cutting applications are limited to carbon and low alloys steel. These materials canbe cut economically, and setup is simple and quick. For manual oxy-fuel gas cutting there isno electric power requirement and equipment costs are low.

Water jet Cutting

Water jet cutting is the process of cutting materials using a high-pressure (60 000 psi) water jet with the addition of abrasive particles. This enables any geometry to be cut from anymaterial to be cut cleanly to close tolerances, squarely and with a good edge finish. Waterjet cutting creates super-smooth cut surfaces that have no heat affected zone, no burrs orslag and can eliminate secondary finishing and hence reduce machining costs.

Laser Cutting

Laser cutting is the process of using a laser to make high quality cuts in a wide variety ofmaterials. All metals (excluding highly reflective metals), all plastics, glass, and wood can becut. Computer controlled laser cutting provides a fast, accurate and precisely repeatablemethod of creating components of all shapes and sizes in small, medium or large batchesfrom flat sheet or tubular materials. Components that have been laser cut require a minimalamount of finishing work.

Plasma (arc) Cutting

Plasma (arc) cutting was developed in the 1950s for cutting of metals that could not be flamecut, such as stainless steel, aluminium and copper. The plasma arc cutting process useselectrically conductive gas to transfer energy from an electrical power source through aplasma-cutting torch to the material being cut. The plasma gases include argon, hydrogen,nitrogen and mixtures, plus air and oxygen.

Reference: Tesko Laser Division.

METAL CUTTING & REMOVAL INTERNET RESOURCES

For additional information contact the Manufacturing Technologies Association (MTA)www.mta.org.uk

Lathes provides detailed information relating to lathes and milling machines.http://www.lathes.co.uk/

The Cutting Edge provides Laser, Flame and Water cutting services in the UK.http://www.thecuttingedge.co.uk/ the website provides some basic details and benefits ofeach of the processes

Chris Heapy details drilling and reaming on the lathe.http://easyweb.easynet.co.uk/~chrish/t-drill.htm
http://www.mta.org.uk/http://www.mta.org.uk/http://www.lathes.co.uk/http://www.thecuttingedge.co.uk/http://easyweb.easynet.co.uk/~chrish/t-drill.htmhttp://easyweb.easynet.co.uk/~chrish/t-drill.htmhttp://www.thecuttingedge.co.uk/http://www.lathes.co.uk/http://www.mta.org.uk/http://www.mta.org.uk/


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Hypertherm provides the history of plasma cutting.http://www.hypertherm.com/technology/plasma_history.htm

Tesko Laser Division discusses the merits of laser, flame and plasma cutting.

http://www.teskolaser.com/laser_cutting2.htmlhttp://www.teskolaser.com/flame_cutting.htmlhttp://www.teskolaser.com/waterjet_cutting.html

The Modern Machine Shop Online (MMS Online) provides a number of articles on ElectroDischarge Machining.

The University of Edinburgh AMP Laboratory conduct Electrochemical Machining using theirAnodic Machining facilities. Their webpage provides background information on ECM.
http://www.hypertherm.com/technology/plasma_history.htmhttp://www.teskolaser.com/laser_cutting2.htmlhttp://www.teskolaser.com/flame_cutting.htmlhttp://www.teskolaser.com/waterjet_cutting.htmlhttp://www.mmsonline.com/dp/zones/index.cfm?cat=EDM01&zone=EDMhttp://www.mech.ed.ac.uk/research/ECM/ECMContents.htmlhttp://www.mech.ed.ac.uk/research/ECM/ECMContents.htmlhttp://www.mmsonline.com/dp/zones/index.cfm?cat=EDM01&zone=EDMhttp://www.teskolaser.com/waterjet_cutting.htmlhttp://www.teskolaser.com/flame_cutting.htmlhttp://www.teskolaser.com/laser_cutting2.htmlhttp://www.hypertherm.com/technology/plasma_history.htm

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Fact Sheet : METAL REMOVAL/CUTTING