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Bulk Deformation Processes in

Metal Forming

Chapter 19

part 3- Extrusion

Manufacturing Processes, MET1311

Dr Simin Nasseri

Southern Polytechnic State University


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Manufacturing ProcessesProf Simin Nasseri

BULK DEFORMATION PROE!!E!

IN METAL"ORKIN#

1. Rolling

2. Other Deformation Processes Related to Rolling

3. orging

!. Other Deformation Processes Related to orging

". Extrusion#. $ire and %ar Dra&ing

http://wiki.spsu.edu/index.php/Image:HighRes-Horny.gif


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Extrusion

Compression forming process in &hich &or'metal is forced to flo& through a die openingto produce a desired cross sectional shape‑

Process is similar to s(uee)ing toothpaste out of a

toothpaste tu*e

+n general, extrusion is used to produce longparts of uniform cross sections

&o *asic tpes/ Direct extrusion 0or&ard extrusion etal flo&s

in direction of Ram moement4

+ndirect extrusion 0%ac'&ard extrusion etalflo&s in opposite direction of Ram moement4



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5dantages of Extrusion

6ariet of shapes possi*le, especiall in hotextrusion

7imitation/ part cross section must *e uniform

throughout length

8rain structure and strength enhanced in coldand &arm extrusion

Close tolerances possi*le, especiall in cold

extrusion

+n some operations, little or no &aste of material

Examples/ Door&indo& frames, sliding door railings, doorhandles, *rac'ets, gears, etc



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:ot s. Cold Extrusion

:ot extrusion - prior heating of *illet to a*oe itsrecrstalli)ation temperature Reduces strength and increases ductilit of the

metal,

permitting more si)e reductions and

more complex shapes

Cold extrusion - generall used to produce

discrete parts he term impact extrusion is used to indicate high

speed cold extrusion



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Common extrusion shapes



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igure 19.3; Directextrusion.

Direct Extrusion

5lso called forward etrusion 5s ram approaches die opening, a small portion of *illet

remains that cannot *e forced through die opening

his extra portion, called the !utt , must *e separated from

etrudate * cutting it


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Example

:ae ou plaed &ith a dough plunger to *efore>?



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igure 19.31 0a4 Direct extrusion to produce a hollo& or semi hollo&‑cross sections@ 0*4 hollo& and 0c4 semi hollo& cross sections.‑

:ollo& and =emi-:ollo& =hapes



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igure 19.32 +ndirect extrusion to produce 0a4 a solid crosssection and 0*4 a hollo& cross section.

+ndirect Extrusion

Ram forces the &or' *illet in a closed container,causing the &or' metal to flo& against the

direction of the ram.

Final shape= a solid rod

Final shape= a hollow rod



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Comments on +ndirect Extrusion

5lso called !ac"ward etrusion and reverse etrusion

7imitations of indirect extrusion are imposed *

7o&er rigidit of hollo& ram

Difficult in supporting extruded product

as it exits die



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Extrusion Ratio

5lso called the reduction ratio, it is defined as

&here r extrusion ratio@ #o cross-sectional area of

the starting *illet@ and #f final cross-sectional area of

the extruded section

5pplies to *oth direct and indirect extrusion

f

o

#

#r =



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Orifice =hape of Extrusion Die

=implest cross section shape is circular die orifice =hape of die orifice affects ram pressure

5s cross section *ecomes more complex, higher

pressure and greater force are re(uired



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igure 19.3# 5 complex extruded cross section for a heat sin'0photo courtes of 5luminum Compan of 5merica4

Complex Cross =ection



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Extrusion Presses

Either hori)ontal or ertical

:ori)ontal more common

Extrusion presses - usuall hdraulicall drien,&hich is especiall suited to semi continuous direct

‑

extrusion of long sections

echanical dries - often used for cold extrusion

of indiidual parts