Introduction to Manufacturing Processesmyweb.astate.edu/sharan/Intro to Manufacturing/Lecture Notes 2006... · 3 ME 4563 Dr. S. Haran 5 Extrusion is a process that forces metal to

1

1ME 4563 Dr. S. Haran

College of EngineeringArkansas State University

College of EngineeringCollege of EngineeringArkansas State UniversityArkansas State University

Introduction to Manufacturing Processes

Introduction to Manufacturing Introduction to Manufacturing ProcessesProcesses

ME 4563ME 4563ME 4563


Bulk DeformationBulk Deformation

2


ExtrusionExtrusion


Production of long lengths of solid or hollow Production of long lengths of solid or hollow products with constant crossproducts with constant cross--sectionsectionUsually performed at elevated temperaturesUsually performed at elevated temperaturesProduct can be cut to desired lengthsProduct can be cut to desired lengthsCan be competitive to roll formingCan be competitive to roll formingCold extrusion has similarities to forging and is Cold extrusion has similarities to forging and is used to make discrete partsused to make discrete partsModerate to high equipment and die costsModerate to high equipment and die costsLow to moderate labor costsLow to moderate labor costsLow to moderate operator skillsLow to moderate operator skills

As a Process As a Process ……

ExtrusionExtrusion

3


Extrusion is a process that forces metal to flow Extrusion is a process that forces metal to flow through a shapethrough a shape--forming dieforming die

The metal is plastically deformed under compression The metal is plastically deformed under compression in the die cavityin the die cavity

Compression is achieved mechanically or hydraulicallyCompression is achieved mechanically or hydraulically

Extrusion processes can be carried on Extrusion processes can be carried on hot or coldhot or cold

Extrusion differs from drawing in that the metal is Extrusion differs from drawing in that the metal is pushed, rather than pulled under tensionpushed, rather than pulled under tension

The Process The Process ……

The crossThe cross--sections that can be produced vary from solid sections that can be produced vary from solid round, rectangular, to L shapes, T shapes. Tubes round, rectangular, to L shapes, T shapes. Tubes and many other different types. and many other different types.

ExtrusionExtrusion


Schematic illustration of the direct extrusion process.Schematic illustration of the direct extrusion process.

ExtrusionExtrusion

4


Extrusion produces compressive and shear forces in Extrusion produces compressive and shear forces in the stockthe stock

No tensile force is produced; this makes high No tensile force is produced; this makes high deformation possible without tearing the metaldeformation possible without tearing the metal

The cavity in which the raw material is contained is The cavity in which the raw material is contained is lined with a wear resistant materiallined with a wear resistant material

This can withstand the high radial loads that are This can withstand the high radial loads that are created when the material is pushed the die created when the material is pushed the die

Extrusions, often minimize the need for secondary Extrusions, often minimize the need for secondary machining, but are not of the same machining, but are not of the same dimensional accuracy or surface finish as dimensional accuracy or surface finish as machined partsmachined parts

ExtrusionExtrusion

8ME 4563 Dr. S. HaranJet Plastics, Los Angeles, CA

ExtrusionExtrusion

5


ExtrusionExtrusion

The tooling cost is low, as well as the loss due to The tooling cost is low, as well as the loss due to material waste (it has high material utilization) material waste (it has high material utilization)

Intricate cross sectional shapes, hollows and with Intricate cross sectional shapes, hollows and with undercuts can be produced undercuts can be produced

The hardness and the yield strength of the material are The hardness and the yield strength of the material are increased increased

In most applications, no further machining is necessary In most applications, no further machining is necessary

AdvantagesAdvantages


High tolerances are difficult to achieve. High tolerances are difficult to achieve. The process is limited to ductile materials. The process is limited to ductile materials. Extruded products might suffer from surface cracking. Extruded products might suffer from surface cracking.

It might occur when the surface temperature rise It might occur when the surface temperature rise significantly due to high extrusion temperature, significantly due to high extrusion temperature, friction, or extrusion speed. friction, or extrusion speed.

Surface cracking might also occur at low speeds due Surface cracking might also occur at low speeds due to periodic sticking of the extruded product to periodic sticking of the extruded product along the die land. along the die land.

Internal cracking might also occur. These cracks are Internal cracking might also occur. These cracks are attributed to a state of secondary tensile attributed to a state of secondary tensile stresses at the centerline of the deformation stresses at the centerline of the deformation zone in the die. zone in the die.

DisadvantagesDisadvantages

ExtrusionExtrusion

6


Types of Extrusion ProcessTypes of Extrusion Process

There are four basic types of extrusion as follows:There are four basic types of extrusion as follows:

Forward or Direct ExtrusionForward or Direct Extrusion

Reverse or Indirect Extrusion Reverse or Indirect Extrusion (or inverted or backward)(or inverted or backward)

Hydrostatic ExtrusionHydrostatic Extrusion

Impact ExtrusionImpact Extrusion


Direct or Forward Extrusion ProcessDirect or Forward Extrusion Process

7


Types of extrusion: Types of extrusion:

(a) indirect; (b) hydrostatic; (c) lateral.(a) indirect; (b) hydrostatic; (c) lateral.

ExtrusionExtrusion


Forward extrusionForward extrusion is also known as is also known as Direct ExtrusionDirect Extrusion(sometimes known as the Hooker process)(sometimes known as the Hooker process)

In this process the confined metal is forced to flow in In this process the confined metal is forced to flow in the direction of the punch travelthe direction of the punch travel

The process is generally used to produce thinThe process is generally used to produce thin--walled walled tubular parts with heavy flanges, straight tubular parts with heavy flanges, straight tubular shapes, and extrusion of stepped; tubular shapes, and extrusion of stepped; multiple diameters. Production of rods and multiple diameters. Production of rods and other solids shapes, for example other solids shapes, for example

Best applied to parts having an outer diameter of Best applied to parts having an outer diameter of 25.4 mm (1 in) or more. 25.4 mm (1 in) or more.

Direct or Forward Extrusion ProcessDirect or Forward Extrusion Process

8


In practice, the work piece is placed in a closeIn practice, the work piece is placed in a close--fitting die. fitting die.

The punch is forced downward, displacing the metal through a The punch is forced downward, displacing the metal through a restricted opening in the bottom of the die restricted opening in the bottom of the die

The metal is forced to flow The metal is forced to flow considerable distance beyond considerable distance beyond the end of the punch the end of the punch

Cupped or tubular parts of the Cupped or tubular parts of the punch extension serve as a punch extension serve as a mandrel. This controls the wall mandrel. This controls the wall thickness and inner contour of thickness and inner contour of the extruded parts.the extruded parts.

Forward Extrusion ProcessForward Extrusion Process


•• AdvantagesAdvantages–– high dimensional accuracyhigh dimensional accuracy–– complex shapes (from complex shapes (from

poor ductile materials)poor ductile materials)

•• DisadvantagesDisadvantages–– low productivitylow productivity–– short tool lifeshort tool life–– expensive toolingexpensive tooling


9




Backward extrusion is a process that forces the metal Backward extrusion is a process that forces the metal confined in the cavity to flow in a direction confined in the cavity to flow in a direction oppositeopposite to to that of the punch travel. that of the punch travel.

Backward or Indirect Extrusion ProcessBackward or Indirect Extrusion Process

The slug (work piece) is The slug (work piece) is contained in a closed die. contained in a closed die.

The descending punch The descending punch enters the slug. enters the slug.

The pressure displaces the The pressure displaces the metal upward through the metal upward through the opening between the punch opening between the punch and die. and die.

This is generally used for This is generally used for extruding symmetrically extruding symmetrically shaped parts having a closed shaped parts having a closed end.end.

10


The frictional forces are lower and the power The frictional forces are lower and the power required for extrusion is less than for direct required for extrusion is less than for direct extrusion. extrusion.

In practice, a hollow ram carries a die, while the In practice, a hollow ram carries a die, while the other end of the container is closed with a plate. other end of the container is closed with a plate.

Frequently, for indirect extrusion, the ram Frequently, for indirect extrusion, the ram containing the die is kept stationary, and the containing the die is kept stationary, and the container with the billet is made to move.container with the billet is made to move.

Backward Extrusion ProcessBackward Extrusion Process


Extrusion pressureExtrusion pressure30% lower than direct method30% lower than direct method

WasteWasteonly 5%only 5%

ToolingToolingexpensiveexpensivecomplexcomplex

Backward Extrusion ProcessBackward Extrusion Process

11


Combined extrusion uses a combination of Combined extrusion uses a combination of forward extrusion and backward extrusion. forward extrusion and backward extrusion.

The metal is confined inside a matrix between The metal is confined inside a matrix between the lower and upper punches. the lower and upper punches.

This forces the metal to flow both up and This forces the metal to flow both up and down. down.

The extruded part is lifted from the die on the The extruded part is lifted from the die on the upward stroke of the slide by a lift out on upward stroke of the slide by a lift out on the bed of the press. the bed of the press.

Combination Extrusion ProcessCombination Extrusion Process


Some aspects of combined extrusion are: Some aspects of combined extrusion are:

it is fast it is fast it can complete parts in few steps it can complete parts in few steps it can produce large quantities with low unit it can produce large quantities with low unit

costs costs it wastes little material it wastes little material it can make parts with small radii it can make parts with small radii it requires mirror tooling it requires mirror tooling

Combination Extrusion ProcessCombination Extrusion Process

12


Hot ExtrusionHot Extrusion

Hot extrusion is done at fairly high temperatures, Hot extrusion is done at fairly high temperatures, approximately 50 to 75 % of the melting point of the approximately 50 to 75 % of the melting point of the metal. The pressures can range from 35metal. The pressures can range from 35--700 700 MPaMPa (5076 (5076 -- 101,525 101,525 psipsi). ).

Due to the high temperatures and pressures and its detrimentalDue to the high temperatures and pressures and its detrimentaleffect on the die life as well as other components, good effect on the die life as well as other components, good lubrication is necessary. lubrication is necessary.

Oil and graphite work at lower temperatures, whereas at higherOil and graphite work at lower temperatures, whereas at highertemperatures glass powder is used. temperatures glass powder is used.

Typical parts produced by extrusions are trim parts used in Typical parts produced by extrusions are trim parts used in automotive and construction applications, window frame automotive and construction applications, window frame members, railings, aircraft structural partsmembers, railings, aircraft structural parts



•• At elevated temperaturesAt elevated temperatures–– For metals and alloys that donFor metals and alloys that don’’t have t have

sufficient ductilitysufficient ductility–– Lower force requiredLower force required

•• ProblemsProblems–– Cooling: unacceptable metal flowsCooling: unacceptable metal flows–– Oxide film formed: abrasiveOxide film formed: abrasive–– Not good surface qualityNot good surface quality

•• Dummy blockDummy block–– Forms Skull of oxide layerForms Skull of oxide layer

13



•• AdvantagesAdvantages–– Lower stressesLower stresses–– Sometimes the only way to extrude Sometimes the only way to extrude

certain metalscertain metals•• e.g. Titanium, refractory alloys, high e.g. Titanium, refractory alloys, high

strength alloysstrength alloys

•• DisadvantagesDisadvantages–– Higher die wearHigher die wear–– Oxide film buildup results in nonOxide film buildup results in non--

uniform flow, inclusions and poor uniform flow, inclusions and poor surface finishsurface finish

–– Cooling of billet in container results in Cooling of billet in container results in nonnon--uniform flowuniform flow

–– Distorted partsDistorted parts


Process temperature rangesMaterial Temp

Range (oC)Lead 200-250Aluminum and alloys 375-475Copper and alloys 650-975Steels 875-1300Refractory alloys 975-2200


14


•• Difficult and requires a lot of experienceDifficult and requires a lot of experience•• Square dies (die angle = 90Square dies (die angle = 90oo) give rise to dead metal ) give rise to dead metal

zones around the diezones around the die•• Dead metal zones give bright finishes to aluminum alloys Dead metal zones give bright finishes to aluminum alloys

(no surface exposed to air)(no surface exposed to air)•• Spider dies produce hollow shapes Spider dies produce hollow shapes

Die Angle

Dead Metal Zone

Die

Hot Extrusion Hot Extrusion –– Die DesignDie Design


Comparatively recent development (1940's)Comparatively recent development (1940's)Cold extrusion is the process done at room Cold extrusion is the process done at room

temperature temperature or slightly elevated temperaturesor slightly elevated temperaturesThis process can be used for most materialsThis process can be used for most materials--subject to subject to

designing robust enough tooling that can withstand designing robust enough tooling that can withstand the stresses created by extrusion the stresses created by extrusion

Examples of the metals that can be extruded: lead, Examples of the metals that can be extruded: lead, tin, aluminum alloys, copper, titanium, tin, aluminum alloys, copper, titanium, molybdenum, vanadium, steel molybdenum, vanadium, steel

Examples of parts that are cold extruded: Examples of parts that are cold extruded: collapsible tubes, aluminum cans, gear blanks collapsible tubes, aluminum cans, gear blanks

Cold ExtrusionCold Extrusion

15


Two examples of Two examples of cold extrusion. cold extrusion. Thin arrows Thin arrows indicate the indicate the direction of metal direction of metal flow during flow during extrusion.extrusion.



Production steps for a cold extruded Production steps for a cold extruded spark plug. spark plug. SourceSource: National : National Machinery Company.Machinery Company.

A crossA cross--section of the metal part section of the metal part from figure above, showing the from figure above, showing the grain flow pattern. grain flow pattern. SourceSource: : National Machinery Company.National Machinery Company.


16


•• AdvantagesAdvantages–– Improved mechanical propertiesImproved mechanical properties–– Work hardeningWork hardening–– Good control of tolerancesGood control of tolerances–– Improved surface finish (with use of lubricant)Improved surface finish (with use of lubricant)–– Elimination of heating costsElimination of heating costs–– High production ratesHigh production rates

•• DisadvantagesDisadvantages–– Higher stresses require more expensive tooling Higher stresses require more expensive tooling

and die materialand die material–– Difficult die design essential to successDifficult die design essential to success–– Lubrication criticalLubrication critical



•• Comparison to Hot ExtrusionComparison to Hot Extrusion–– Improved mechanical propertiesImproved mechanical properties–– Good dimensional toleranceGood dimensional tolerance–– Elimination of billet heatingElimination of billet heating–– Production rates and costs Production rates and costs competetivecompetetive

•• 2000 parts/hour2000 parts/hour–– However, High stresses involvedHowever, High stresses involved

•• Tool and die materials crucialTool and die materials crucial–– Sufficient strengthSufficient strength–– Sufficient toughnessSufficient toughness–– Good Wear and fatigue resistanceGood Wear and fatigue resistance


17



Developed 1950sDeveloped 1950sThe chamber is filled with a fluid that transmits the pressureThe chamber is filled with a fluid that transmits the pressure to the to the

billet, which is then extruded through the die. billet, which is then extruded through the die. NO friction along the walls of the container. NO friction along the walls of the container.


Because of the pressurized fluid, lubrication is very Because of the pressurized fluid, lubrication is very effective, and the extruded product has good surface effective, and the extruded product has good surface finish and dimensional accuracy. finish and dimensional accuracy.

Since friction is nearly absent, it is possible to use Since friction is nearly absent, it is possible to use dies with very low semidies with very low semi--cone angle which greatly cone angle which greatly minimizes the redundant deformation. minimizes the redundant deformation.

The only limitation with this process is the practical The only limitation with this process is the practical limit of fluid pressure that may be used because of the limit of fluid pressure that may be used because of the constraint involving the strength of the container and constraint involving the strength of the container and the requirement that the fluid not solidify at high the requirement that the fluid not solidify at high pressurepressure


18


•• Suitable for extruding metals of average Suitable for extruding metals of average ductility at high extension ratios.ductility at high extension ratios.

•• ProductsProducts–– helical gearshelical gears–– copper wirecopper wire

•• Improved process controlImproved process control–– augmented hydrostatic extrusionaugmented hydrostatic extrusion

•• MaterialsMaterials–– brittle materialsbrittle materials–– cast ironcast iron




•• AdvantagesAdvantages–– No friction at wallsNo friction at walls–– Can successful extrude brittle materialsCan successful extrude brittle materials–– Yield stress reduced by hydrostatic pressureYield stress reduced by hydrostatic pressure–– Room temperature operationRoom temperature operation

•• DisadvantagesDisadvantages–– Limited industrial applicationsLimited industrial applications–– Complex toolingComplex tooling–– ??

19




Form of indirect extrusionForm of indirect extrusion

Particularly suitable for hollow shapes. Particularly suitable for hollow shapes.

Usually performed on highUsually performed on high--speed mechanical press. speed mechanical press.

The punch descends at a high speed and strikes The punch descends at a high speed and strikes the blank, extruding it upwards. the blank, extruding it upwards.

The thickness of the extruded tubular section is a The thickness of the extruded tubular section is a function of the clearance between the punch and function of the clearance between the punch and the die cavity. the die cavity.

Although performed cold, considerable heating results Although performed cold, considerable heating results from the highfrom the high--speed deformation. speed deformation.

Restricted to softer metals: lead, tin, Al & Cu Restricted to softer metals: lead, tin, Al & Cu

Impact ExtrusionImpact Extrusion

20


Impact Extrusion Impact Extrusion -- ForwardForward

•• Cold slug held in a die cavityCold slug held in a die cavity–– usually aluminumusually aluminum

•• Hit by a rapidly moving punchHit by a rapidly moving punch•• Metal flowsMetal flows

–– around the puncharound the punch–– Into the die openingInto the die opening


Schematic Schematic illustration of the illustration of the impactimpact--extrusion extrusion process. The process. The extruded parts are extruded parts are stripped by the use stripped by the use of a stripper plate, of a stripper plate, because they tend because they tend to stick to the to stick to the punch.punch.

Impact Extrusion Impact Extrusion -- BackwardBackward

21


(a) Two examples of products made by impact extrusion. These parts may also be made by casting, by forging, or by machining; the choice of process depends on the dimensions and the materials involved and on the properties desired. Economic considerations are also important in final process selection. (b) and (c) Impact extrusion of a collapsible tube

Tube for toothpaste

Impact Extrusion Impact Extrusion -- ExamplesExamples


Impact Extrusion Impact Extrusion -- CombinationCombination

Forward and Backward in one shot !Forward and Backward in one shot !

22


Commonly used to make collapsible tubes such as toothpaste tubes, cans usually using soft materials such as aluminum, lead, tin




23




Extrusion of TubingExtrusion of Tubing

•• Tubing extrusionTubing extrusion–– Forward extrusion processForward extrusion process

–– Use of a Mandrel to pierce a Use of a Mandrel to pierce a hole in billetshole in billets

–– Use of hollow billetsUse of hollow billets

24


Extrusion of Hollow ShapesExtrusion of Hollow Shapes

Figure 15.9

•• WeldingWelding--chamber methodchamber method•• Metal divides and flows aroundMetal divides and flows around•• Then Then reweldedrewelded under high pressure in welding chamberunder high pressure in welding chamber

•• Aluminum and its alloysAluminum and its alloys•• No lubrication usedNo lubrication used


Metals and alloys: Metals and alloys: Brass, copper, lead, aluminum, steel, Brass, copper, lead, aluminum, steel, magnesium, magnesium, tin, titanium, and zinctin, titanium, and zinc

Thermoplastics: Thermoplastics: ABS, Acrylic, Butyrate, Flexible Vinyl, PETG ABS, Acrylic, Butyrate, Flexible Vinyl, PETG CoCo--Polyester, Polycarbonate, PolyethylenePolyester, Polycarbonate, Polyethylene--High & Low Densities, Polypropylene, High & Low Densities, Polypropylene, Polystyrene, Polyurethane, Rigid Vinyl,Polystyrene, Polyurethane, Rigid Vinyl,Thermoplastic Thermoplastic ElastomersElastomers, etc., etc.

Materials used in ExtrusionMaterials used in Extrusion

(just a list (just a list ……))

25


•• F = AF = A00 k k lnln (A(A00/A/Aff))–– k: Extrusion constantk: Extrusion constant, a billet material related , a billet material related

properties properties •• gives good estimation of forcegives good estimation of force•• important in analysisimportant in analysis

Extrusion ForceExtrusion Force


Extrusion constant Extrusion constant kk for various metals at different for various metals at different temperatures. temperatures. SourceSource: P. : P. LoewensteinLoewenstein

Extrusion Constant Extrusion Constant ‘‘kk’’ for various metalsfor various metals

26


Process Variables in Direct ExtrusionProcess Variables in Direct Extrusion

•• Extrusion variablesExtrusion variables–– Geometry VariablesGeometry Variables

•• Die angle Die angle αα•• Extrusion ratio (E.R.)Extrusion ratio (E.R.)

–– Process VariablesProcess Variables•• Extrusion speed, v, (power = Extrusion speed, v, (power =

Force x velocity)Force x velocity)–– Lower for Al, Mg, CuLower for Al, Mg, Cu–– Higher for steels, Ti, BeHigher for steels, Ti, Be

•• TemperatureTemperature•• Lubrication, Lubrication, µµ

–– Material variablesMaterial variables•• Extrusion Constant, kExtrusion Constant, k

Process variables in direct Process variables in direct extrusion: extrusion:

die angle, reduction in crossdie angle, reduction in cross--section, extrusion speed, billet section, extrusion speed, billet temperature, and lubrication temperature, and lubrication

all affect the extrusion process.all affect the extrusion process.


•• Extrusion Ratio, Extrusion Ratio, ER = AER = A00 / / AAff–– AA00: Original Area: Original Area–– AAff: Final Area: Final Area

•• E.R. varies typically from 10 to 100E.R. varies typically from 10 to 100•• Must be Must be atleastatleast 4.0 to deform the material (as high as 400)4.0 to deform the material (as high as 400)•• E.R. is a function of the material ductilityE.R. is a function of the material ductility•• ExampleExample

–– dd00 = 100 mm, = 100 mm, –– ddff = 20 mm, = 20 mm, –– ER = ?ER = ?

•• ER = [ER = [ππ.(100/2).(100/2)22] / ] / [[ππ.(20/2).(20/2)22]]•• ER = 25 ER = 25

Extrusion RatioExtrusion Ratio

27


•• CCDCCD = = CCircumscribing ircumscribing CCircle ircle DDiameteriameter•• Diameter of the smallest circle into which an extruded Diameter of the smallest circle into which an extruded

crosscross--section will fitsection will fit

Method of determining the circumscribingMethod of determining the circumscribing--circle diameter circle diameter (CCD) of an extruded cross(CCD) of an extruded cross--section.section.

Circumscribing Circle DiameterCircumscribing Circle Diameter

–– Typically 6 mm Typically 6 mm to 250 mmto 250 mm

–– Can be as high Can be as high as 1000 mmas 1000 mm

–– Steel usually Steel usually restricted to restricted to <150 mm<150 mm


•• Shape Factor = Shape Factor = Perimeter / Cross Section AreaPerimeter / Cross Section Area–– Perimeter: including Perimeter: including innerinner geometry and geometry and outsideoutside geometrygeometry

Important becauseImportant because it relates to the complexity (i.e. cost) it relates to the complexity (i.e. cost) of the productof the product

Extrusion Extrusion –– Shape factorShape factor

products made by products made by sectioning off extrusionssectioning off extrusions

28


•• Ram speedsRam speeds–– Up to 0.5 m/sUp to 0.5 m/s–– Slower for aluminum, magnesium and copperSlower for aluminum, magnesium and copper–– Higher for steels, titanium and refractory alloysHigher for steels, titanium and refractory alloys

•• LengthLength–– Typically less than 7.5 m (heat treat ovens limiting)Typically less than 7.5 m (heat treat ovens limiting)

•• Straightening by stretching or rolling (simple crossStraightening by stretching or rolling (simple cross--sections)sections)

•• Coaxial extrusionCoaxial extrusion–– Two metals with similar properties can be coTwo metals with similar properties can be co--extrudedextruded

•• Stepped extrusionStepped extrusion–– Start with small dieStart with small die–– Switch to larger XSwitch to larger X--section diesection die–– Use in Aerospace industry to minimize machining scrapUse in Aerospace industry to minimize machining scrap

Extrusion PracticeExtrusion Practice


Extrusion Extrusion –– Cross Section DesignCross Section Design

PoorPoor

GoodGood

Poor and good examples of Poor and good examples of crosscross--sections to be sections to be extruded. extruded.

Note the importance of Note the importance of eliminating sharp corners and eliminating sharp corners and of keeping section of keeping section thicknesses uniform. thicknesses uniform.

SourceSource: J. G. : J. G. BrallaBralla (ed.); (ed.); Handbook of Product Design Handbook of Product Design for Manufacturingfor Manufacturing. New . New York: McGrawYork: McGraw--Hill Publishing Hill Publishing Company, 1986. Used with Company, 1986. Used with permission.permission.

29


Material FlowMaterial Flow

•• Easy to extrude metals and alloysEasy to extrude metals and alloys–– AluminumAluminum–– CopperCopper–– MagnesiumMagnesium–– SteelsSteels–– Stainless steelsStainless steels

•• Difficult to extrude metals and alloysDifficult to extrude metals and alloys–– TitaniumTitanium–– Refractory metalsRefractory metals


Flow of metal in an Al extrusion processFlow of metal in an Al extrusion process

The core flows more rapidly then the peripheryThe core flows more rapidly then the periphery

The periphery left behind as a residue is recycledThe periphery left behind as a residue is recycled

ExtrusionExtrusion

Flow of metal during the process of extrusionFlow of metal during the process of extrusion

30


•• Because the billet is forced through a die, with a substantial Because the billet is forced through a die, with a substantial reduction in its crossreduction in its cross--sectional area, the metal flow pattern in sectional area, the metal flow pattern in extrusion is important. extrusion is important.

•• Typically, three different metal flow patterns have been Typically, three different metal flow patterns have been observed during the process of extrusion depending upon the observed during the process of extrusion depending upon the prevailing conditions. prevailing conditions.

•• The conditions under which the different flow patterns are The conditions under which the different flow patterns are obtained are as followsobtained are as follows

ExtrusionExtrusion



Flow of metal during the process of Flow of metal during the process of extrusion with square diesextrusion with square dies

Types of metal flow in extruding with square dies. (a) Flow patTypes of metal flow in extruding with square dies. (a) Flow pattern obtained at low tern obtained at low friction, or in indirect extrusion. (b) Pattern obtained with hfriction, or in indirect extrusion. (b) Pattern obtained with high friction at the billetigh friction at the billet--chamber interfaces. (c) Pattern obtained at high friction, or wchamber interfaces. (c) Pattern obtained at high friction, or with cooling of the outer ith cooling of the outer regions of the billet in the chamber. This type of pattern, obsregions of the billet in the chamber. This type of pattern, observed in metals whose erved in metals whose strength increases rapidly with decreasing temperature, leads tostrength increases rapidly with decreasing temperature, leads to a defect known as a defect known as pipe, or extrusion defect.pipe, or extrusion defect.

31


(a)(a) The most homogeneous flow pattern is obtained when The most homogeneous flow pattern is obtained when there is little or no friction at the billetthere is little or no friction at the billet--containercontainer--die interfacesdie interfaces. . This type of flow occurs when the This type of flow occurs when the lubricant is very effectivelubricant is very effective or or with indirect extrusionwith indirect extrusion

(b)(b) When friction along all interfaces is highWhen friction along all interfaces is high, , a deada dead--metal metal zone developszone develops. As a result a high. As a result a high--shear area appears as the shear area appears as the material flows into the die exit, somewhat like a funnel. This material flows into the die exit, somewhat like a funnel. This configuration may indicate that the billet surfaces could enter configuration may indicate that the billet surfaces could enter the high shear zone and be extruded, causing defects in the the high shear zone and be extruded, causing defects in the extruded productextruded product

ExtrusionExtrusion



(c)(c) The high shear zone extends further back. This extension can The high shear zone extends further back. This extension can result from high container wall friction, which retards the flowresult from high container wall friction, which retards the flow of the of the billet or materials in which the flow stress drops rapidly with billet or materials in which the flow stress drops rapidly with increasing temperature. increasing temperature.

In hot working, the material near the container walls cools In hot working, the material near the container walls cools rapidly & hence increases the strength. Thus, the material in thrapidly & hence increases the strength. Thus, the material in the e central regions flows toward the die more easily than that at thcentral regions flows toward the die more easily than that at the e outer regions. outer regions.

As a result, a As a result, a large large dead metal zonedead metal zone formsforms and the flow is and the flow is inhomogeneous. This flow pattern leads to a defect known as a inhomogeneous. This flow pattern leads to a defect known as a pipe or extrusion defectpipe or extrusion defect

ExtrusionExtrusion


32


°CLead 200–250Aluminum and its alloys 375–475Copper and its alloys 650–975Steels 875–1300Refractory alloys 975–2200

ExtrusionExtrusion

Extrusion Temperature Ranges for Various MetalsExtrusion Temperature Ranges for Various Metals


Deformation is greater in the outer zones of a bar than it is Deformation is greater in the outer zones of a bar than it is at the center, particularly when the extrusion ratio is low. at the center, particularly when the extrusion ratio is low.

The center receives only light deformation.The center receives only light deformation.The improvement in tensile strength of Al 1100 resulting The improvement in tensile strength of Al 1100 resulting

from extrusion with 3:1 ratio is 5000 from extrusion with 3:1 ratio is 5000 psipsi (before extrusion) to (before extrusion) to 19000 19000 psipsi (after extrusion). In general, the (after extrusion). In general, the yield strength is yield strength is increasedincreased about four times the initial strength.about four times the initial strength.

In general, the In general, the inside surfaces of backward extrudedinside surfaces of backward extruded parts parts are 5 to 25 Rockwellare 5 to 25 Rockwell--B Hardness B Hardness harder than the outside harder than the outside surfaces. surfaces.

The hardness of material alloys which undergo this The hardness of material alloys which undergo this backward extrusion process is decreased by 20 to 10 backward extrusion process is decreased by 20 to 10 RockwellRockwell--B Hardness. However in B Hardness. However in forward extrusion the outer forward extrusion the outer surfacessurfaces are harder than the inner surfaces.are harder than the inner surfaces.

Properties of extruded materialsProperties of extruded materials

33


•• Important to extrusionImportant to extrusion–– harder materialsharder materials

•• Reducing friction Reducing friction –– Reducing extrusion Reducing extrusion

forcesforces–– Reduces sticking to wallsReduces sticking to walls–– increased tool lifeincreased tool life–– reduced powerreduced power–– Prevents contaminationPrevents contamination

LubricationLubricationImportant in Hot ExtrusionImportant in Hot Extrusion

•• Choices Choices –– soapssoaps–– lubricating oilslubricating oils–– graphitegraphite

•• Steel & Hi Temp Steel & Hi Temp MaterialsMaterials–– GlassGlass

•• Billet also enclosed in a Billet also enclosed in a jacketjacket of softer material of softer material such as Cu (when metal such as Cu (when metal sticks to wall) sticks to wall) ––jacketing or canningjacketing or canning

ExtrusionExtrusion


Extrusion MachinesExtrusion Machines

34


Most extrusions are made with hydraulic presses. Hydraulic Most extrusions are made with hydraulic presses. Hydraulic extrusion presses are classified into horizontal and vertical extrusion presses are classified into horizontal and vertical presses, depending upon the direction of travel of the rampresses, depending upon the direction of travel of the ram

Extrusion Extrusion -- MachinesMachines


generally built with capacities of 300 to 2000 tons forcegenerally built with capacities of 300 to 2000 tons forceadvantage of easier alignment between the press ram and advantage of easier alignment between the press ram and

the toolsthe toolshigher rate of productionhigher rate of productionthe need of less floor space than horizontal presses the need of less floor space than horizontal presses

However, they need considerable headroom, and to make However, they need considerable headroom, and to make extrusions of appreciable length, a floor pit is extrusions of appreciable length, a floor pit is frequently necessary. frequently necessary.

Vertical extrusionVertical extrusion pressespresses


35


Vertical presses produce uniform cooling of the billet Vertical presses produce uniform cooling of the billet in the container, and thus symmetrically uniform in the container, and thus symmetrically uniform deformation will resultdeformation will result

In commercial operations the chief use of vertical presses In commercial operations the chief use of vertical presses is in the production of thinis in the production of thin--wall tubing, where wall tubing, where uniform wall thickness and concentricity are most uniform wall thickness and concentricity are most important important

Vertical extrusionVertical extrusion pressespresses



Horizontal extrusionHorizontal extrusion pressespresses

Used for most commercial extrusion of bars and shapesUsed for most commercial extrusion of bars and shapesPresses with a capacity of 1500 to 5000 tons are in regular Presses with a capacity of 1500 to 5000 tons are in regular

operation, while a few presses of 14000 tons capacity operation, while a few presses of 14000 tons capacity have been constructedhave been constructed

The bottom of the billet which lies in contact with the The bottom of the billet which lies in contact with the container will cool more rapidly than the top of the container will cool more rapidly than the top of the surface, unless the extrusion container is internally surface, unless the extrusion container is internally heated, and therefore the deformation will be nonheated, and therefore the deformation will be non--uniformuniform

Warping of bars will result, and nonWarping of bars will result, and non--uniform wall thickness uniform wall thickness will occur in tubeswill occur in tubes


36


Horizontal extrusionHorizontal extrusion presspress



HydraulicHydraulic--Extrusion PressExtrusion Press

General view of a 1000General view of a 1000--ton hydraulicton hydraulic--extrusion pressextrusion press

37


Horizontal extrusion press

These two pictures show the profile just emerging These two pictures show the profile just emerging (left) and production in progress (right)(left) and production in progress (right)



““Twin screwTwin screw”” extruders extruders

Wood profiles Wood profiles


38


Extrusion DiesExtrusion Dies


The Die AssemblyThe Die Assembly

ExtrusionExtrusion

39


Solid DieSolid Die

SemiSemi--Hollow DieHollow DieThe DieThe Die

Hollow DieHollow Die

ExtrusionExtrusion


The Die Assembly on the MachineThe Die Assembly on the Machine

ExtrusionExtrusion

40


Die angle Die angle -- effect on extrusion forceeffect on extrusion force

•• (a) total force(a) total force•• (b) ideal force(b) ideal force•• (c) force required to overcome friction (c) force required to overcome friction •• (d) force required for redundant work (d) force required for redundant work

a

b

d

c


Types of Metal Flow in Extruding With Square DiesTypes of Metal Flow in Extruding With Square Dies

Types of metal flow in extruding with square dies. (a) Flow patTypes of metal flow in extruding with square dies. (a) Flow pattern tern obtained at low friction, or in indirect extrusion. (b) Patternobtained at low friction, or in indirect extrusion. (b) Pattern obtained with obtained with high friction at the billethigh friction at the billet--chamber interfaces. (c) Pattern obtained at high chamber interfaces. (c) Pattern obtained at high friction, or with cooling of the outer regions of the billet in friction, or with cooling of the outer regions of the billet in the chamber. the chamber. This type of pattern, observed in metals whose strength increaseThis type of pattern, observed in metals whose strength increases s rapidly with decreasing temperature, leads to a defect known as rapidly with decreasing temperature, leads to a defect known as pipe, or pipe, or extrusion defect.extrusion defect.

41


ExtrusionExtrusion--Die ConfigurationsDie Configurations(a)

(b)

(a) die for nonferrous metals

(b) die for ferrous metals

(c)(c)

(c)(c) die for Tdie for T--shaped extrusion, shaped extrusion, made of made of hothot--work die steel and used with work die steel and used with molten glass as a lubricantmolten glass as a lubricant


(a)

(b)

(c)

Typical extrusionTypical extrusion--die configurations: (a) die configurations: (a) die for nonferrous metals; (b) die for die for nonferrous metals; (b) die for ferrous metals; (c) die for Tferrous metals; (c) die for T--shaped shaped extrusion, made of hotextrusion, made of hot--work die steel and work die steel and used with molten glass as a lubricant. used with molten glass as a lubricant. SourceSource for (c): Courtesy of LTV Steel for (c): Courtesy of LTV Steel Company.Company.

ExtrusionExtrusion--Die ConfigurationsDie Configurations

42


The DieThe Die

CoCo--extrusion extrusion ––two profilestwo profiles

ExtrusionExtrusion


Extrusion DefectsExtrusion Defects

43


•• Surface appearance/crackingSurface appearance/cracking–– Often along grain boundariesOften along grain boundaries–– Due to high temperatures, high friction Due to high temperatures, high friction

and high velocitiesand high velocities–– Or due to sticking of the product to the Or due to sticking of the product to the

die surfacedie surface–– Tearing, FirTearing, Fir--tree effect, Bamboo defecttree effect, Bamboo defect

•• Piping (tailPiping (tail--piping / fishpiping / fish--pipe)pipe)–– Drawing surface oxides and impurities Drawing surface oxides and impurities

toward the center of the billetstoward the center of the billets–– Results in significant length lostResults in significant length lost–– Minimized by machining the billets first Minimized by machining the billets first

to make flow more uniformto make flow more uniform

v1

v2

V1> V2

Extrusion Extrusion -- DefectsDefects


(a)(b)

•• Chevron cracking (internal) Chevron cracking (internal) –– Increases with increasing impurities, Increases with increasing impurities,

die angledie angle–– Decrease with increasing E.R. and Decrease with increasing E.R. and

frictionfriction


44


Surface defectSurface defect If the extrusion temperature, friction, or extrusion If the extrusion temperature, friction, or extrusion speeds are too high, surface temperatures rise significantly andspeeds are too high, surface temperatures rise significantly and can can lead to surface cracking and tearinglead to surface cracking and tearing

These cracks are interThese cracks are inter--granular and are a result of hot shortness. granular and are a result of hot shortness.

This can be avoided by using lower temperatures and speeds. This can be avoided by using lower temperatures and speeds.

However, surface cracking may also occur at low temperatures aHowever, surface cracking may also occur at low temperatures and nd has been attributed to periodic sticking of the extruded producthas been attributed to periodic sticking of the extruded product along along the die land. Because of this sticking, the extrusion pressure the die land. Because of this sticking, the extrusion pressure increases rapidly increases rapidly

ExtrusionExtrusion



Extrusion defectExtrusion defect Some types of metal flow tend to draw Some types of metal flow tend to draw surface oxides and impurities toward the center of the billet. Tsurface oxides and impurities toward the center of the billet. This his defect is known as defect is known as extrusion defectextrusion defect, , pipepipe, , tailpipetailpipe or or fishtailingfishtailing. .

A considerable portion of the metal can be rendered useless A considerable portion of the metal can be rendered useless as an extruded product because of this. as an extruded product because of this.

This defect can be reduced by modifying the flow pattern to a This defect can be reduced by modifying the flow pattern to a less inhomogeneous one, such as by controlling friction and less inhomogeneous one, such as by controlling friction and minimizing temperature gradients. minimizing temperature gradients.

Another method is to machine the surface of the billet prior tAnother method is to machine the surface of the billet prior to o extrusion to eliminate scale and impuritiesextrusion to eliminate scale and impurities

ExtrusionExtrusion


45



Internal crackingInternal cracking The center of an extruded product can The center of an extruded product can develop cracks (also known as develop cracks (also known as centerburstcenterburst, , centercenter crackingcracking,,arrowhead fracturearrowhead fracture or or chevron crackingchevron cracking) due to a state of ) due to a state of hydrostatic tensile stress at the centerline of the deformation hydrostatic tensile stress at the centerline of the deformation zone in the die. zone in the die.

This situation is similar to the necked region in an This situation is similar to the necked region in an uniuni--axial axial tensile test specimen. tensile test specimen.

The major variables influencing this are the die angle, The major variables influencing this are the die angle, extrusion ratio and friction. extrusion ratio and friction.

ExtrusionExtrusion


ExtrusionExtrusion

46


ExtrusionExtrusion

Plastic ExtrusionPlastic Extrusion


The most common variation on straight extrusion is The most common variation on straight extrusion is dual dual durometerdurometer extrusion.extrusion. Here, a "side machine" (about 1/4 or less Here, a "side machine" (about 1/4 or less the size of the main machine) runs in tandem with the primary the size of the main machine) runs in tandem with the primary machine, feeding a different material (flexible vinyl with rigidmachine, feeding a different material (flexible vinyl with rigidPVC, for example) to the die, where the the streams merge into PVC, for example) to the die, where the the streams merge into one extrusion made of two bonded profiles that are often "two one extrusion made of two bonded profiles that are often "two hardnesseshardnesses", or dual ", or dual durometersdurometers. .

ExtrusionExtrusion


47


Another common variation is Another common variation is crosscross--head extrusionhead extrusion.. In this process In this process the flow of plastic is altered to allow solid material, such as the flow of plastic is altered to allow solid material, such as copper copper wire or fiberglass strands to feed into the melt flow, and becomwire or fiberglass strands to feed into the melt flow, and become part e part of the extrusion.of the extrusion. Cross head extrusion is used when such Cross head extrusion is used when such reinforcements cannot pass through the machine's screw and reinforcements cannot pass through the machine's screw and barrel.barrel.


ExtrusionExtrusion


Most thermoplastics can be extruded, including LDPE, Most thermoplastics can be extruded, including LDPE, HDPE, ABS, polystyrene, polypropylene, acetates, HDPE, ABS, polystyrene, polypropylene, acetates, butyratesbutyrates, nylons, , nylons, polyphenylenepolyphenylene sulfides, sulfides, acetalsacetals, , polycarbonates and thermoplastic rubbers and polycarbonates and thermoplastic rubbers and polyesters, among otherspolyesters, among others

Materials:Materials:


ExtrusionExtrusion

48


Include cutting and drilling, mitering of corners (for Include cutting and drilling, mitering of corners (for gaskets or frames), belling (increasing the diameter at the gaskets or frames), belling (increasing the diameter at the end), taping (typically done during extrusion), and cutting to end), taping (typically done during extrusion), and cutting to length.length.

This can be done during extrusion (onThis can be done during extrusion (on--line), or after line), or after extrusion (offextrusion (off--line).line). OffOff--line cutting is more laborious and line cutting is more laborious and expensive, but can hold tighter tolerances.expensive, but can hold tighter tolerances.

Secondary punching can be done onSecondary punching can be done on--line or offline or off--line, but is line, but is cheaper oncheaper on--line.line. This setup actually has a miniThis setup actually has a mini--punch press punch press as part of the extrusion line.as part of the extrusion line.

Secondary OperationsSecondary Operations


ExtrusionExtrusion


Basic eBasic extrusion tooling typically consists of a xtrusion tooling typically consists of a flat plate flat plate diedie, (see "A") , (see "A") or a round steel plate with a cut opening to the or a round steel plate with a cut opening to the profile shape.profile shape.

Streamlined diesStreamlined dies (see "B"and "C") (see "B"and "C") are longer, and have a are longer, and have a gradual transformation from round (at the machine end) to gradual transformation from round (at the machine end) to the profile shape at the exiting end.the profile shape at the exiting end.

ToolingTooling

A B

C


ExtrusionExtrusion

49


Plastic Extrusion Plastic Extrusion -- CalibratorCalibrator

A A CalibratorCalibrator is a long assembly, being either a continuous is a long assembly, being either a continuous piece, or many pieces, through which the profile passes.piece, or many pieces, through which the profile passes.

The openings are cut to the profile shape, graduated from The openings are cut to the profile shape, graduated from oversized at first to the final profile shape.oversized at first to the final profile shape.

As the profile passes through, any tendency for it to move or sAs the profile passes through, any tendency for it to move or sag ag is counteris counter--acted, and it is pushed back (repeatedly) to it's correct acted, and it is pushed back (repeatedly) to it's correct shape.shape.

While these devices are expensive, (2,000 to $20,000 or more), While these devices are expensive, (2,000 to $20,000 or more), they help the profile to be run at maximum speed, for the best they help the profile to be run at maximum speed, for the best piece price.piece price.

Give a better defined shape, and thus, a tighter set of Give a better defined shape, and thus, a tighter set of tolerances.tolerances.

ExtrusionExtrusion



This simplified underwater CALIBRATOR may consist of 4 to 40 This simplified underwater CALIBRATOR may consist of 4 to 40 plates, at intervals along a steel rod frameplates, at intervals along a steel rod frame

More plates at closer intervals mean much tighter tolerancesMore plates at closer intervals mean much tighter tolerances

Profile opening starts oversized, and reduces to the final shaProfile opening starts oversized, and reduces to the final shapepeCalibrators maximize running speed and accuracyCalibrators maximize running speed and accuracy

ExtrusionExtrusion

50



ExtrusionExtrusion


Typical uses of extrusionsTypical uses of extrusions

•• Windows and doors (aluminum)Windows and doors (aluminum)•• Aircraft componentsAircraft components

–– stringers, ribsstringers, ribs•• TubingTubing

–– copper and plastic for plumbing, copper and plastic for plumbing, –– aluminum, steel for lawn furniturealuminum, steel for lawn furniture

•• Discrete parts (sawn off)Discrete parts (sawn off)

51


DrawingDrawing


Drawing ProcessDrawing Process•• Like extrusion but material Like extrusion but material pulledpulled out the orifice of out the orifice of

the required shape instead of being pushed in.the required shape instead of being pushed in.•• Resulting shape variety is more limited than extrusionResulting shape variety is more limited than extrusion

–– Rod (larger cross sections)Rod (larger cross sections)–– Wire (smaller cross sections)Wire (smaller cross sections)

52


Process variables in wire drawing. The die angle, the Process variables in wire drawing. The die angle, the reduction in crossreduction in cross--sectional area per pass, the speed of sectional area per pass, the speed of drawing, the temperature, and the lubrication all affect drawing, the temperature, and the lubrication all affect the drawing force, the drawing force, FF..

Process Variables in Wire DrawingProcess Variables in Wire Drawing


•• AdvantagesAdvantages–– Very long product with nonVery long product with non--flat crossflat cross--section than section than

extrusion extrusion -- wire, rod (total length can exceed wire, rod (total length can exceed miles)miles)

–– Non circular cross sections can be producedNon circular cross sections can be produced•• DisadvantagesDisadvantages

–– Higher forces requiredHigher forces required–– If exceed tensile strength further deformation can If exceed tensile strength further deformation can

be nonbe non--uniformuniform–– Limited size reduction per pass (Maximum 63%)Limited size reduction per pass (Maximum 63%)–– Need multiple dies and take up rollsNeed multiple dies and take up rolls

Drawing ProcessDrawing Process

53


Die for Round DrawingDie for Round Drawing

Terminology of a Terminology of a typical die used for typical die used for drawing round rod drawing round rod or wire.or wire.

TungstenTungsten-- carbide die carbide die insert in a steel casing. insert in a steel casing. Diamond dies, used in Diamond dies, used in drawing thin wire, are drawing thin wire, are encased in a similar encased in a similar manner.manner.


Roll StraighteningRoll Straightening

Schematic illustration of roll straightening of Schematic illustration of roll straightening of a drawn round roda drawn round rod

54


Multistage wire drawing machineMultistage wire drawing machine


Drawing is a plastic deformation in which a flat sheet or Drawing is a plastic deformation in which a flat sheet or plate is formed into a recessed, threeplate is formed into a recessed, three--dimensional dimensional part with a depth several times the thickness of part with a depth several times the thickness of the the metalmetal

As a punch descends into a die or the die moves As a punch descends into a die or the die moves upward over a punch, the metal assumes the upward over a punch, the metal assumes the configuration of the mating punch and die tooling configuration of the mating punch and die tooling

We distinguish between We distinguish between hot drawinghot drawing and and cold drawingcold drawing

Variations Variations –– Drawing of Sheets and PlatesDrawing of Sheets and Plates

55


Hot drawingHot drawing is used for forming relatively thickis used for forming relatively thick--walled walled parts parts of simple geometry, usually cylindrical of simple geometry, usually cylindrical

The thickness of the material reduces considerably as it The thickness of the material reduces considerably as it moves through the dies moves through the dies

This process is used in forming components such as This process is used in forming components such as oxygen tanks and large artillery shells oxygen tanks and large artillery shells

Cold drawingCold drawing uses relatively thin metal, changes the uses relatively thin metal, changes the thickness very little or not at all, and produces parts in thickness very little or not at all, and produces parts in various shapes various shapes

ExtrusionExtrusion




ExtrusionExtrusion

56


Examples of TubeExamples of Tube--Drawing OperationsDrawing Operations

Examples of tubeExamples of tube--drawing operations, with and without an internal drawing operations, with and without an internal mandrel. Note that a variety of diameters and wall thicknesses mandrel. Note that a variety of diameters and wall thicknesses can be can be produced from the same initial tube stock (which has been made bproduced from the same initial tube stock (which has been made by other y other processes).processes).


Summary of Metal Forming ProcessesSummary of Metal Forming Processes

•• They rely on plastic flow of the bulk of the They rely on plastic flow of the bulk of the materialmaterial

•• Forces causing the plastic flow are the result Forces causing the plastic flow are the result of different kinds of machinesof different kinds of machines

•• Result in products which typically require Result in products which typically require subsequent processing to make useful subsequent processing to make useful productsproducts

•• Products from these processes are ubiquitousProducts from these processes are ubiquitous

Documents

Introduction to Manufacturing Processesmyweb.astate.edu/sharan/Intro to Manufacturing/Lecture Notes 2006... · 3 ME 4563 Dr. S. Haran 5 Extrusion is a process that forces metal to