Proses bulk deformasi

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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 Processes Prof Simin Nasseri

    BULK DEFORMATION PROE!!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

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    Extrusion

    Compression forming process in &hich &or' metal is forced to flo& through a die opening to 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 long parts of uniform cross sections

     &o *asic tpes/  Direct extrusion 0or&ard extrusion  etal flo&s

    in direction of Ram moement4

     +ndirect extrusion 0%ac'&ard extrusion  etal flo&s in opposite direction of Ram moement4

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     5dantages of Extrusion

     6ariet of shapes possi*le, especiall in hot extrusion

     7imitation/ part cross section must *e uniform

    throughout length 

     8rain structure and strength enhanced in cold and &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, door handles, *rac'ets, gears, etc

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    :ot s. Cold Extrusion

     :ot extrusion - prior heating of *illet to a*oe its recrstalli)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; Direct extrusion.

    Direct Extrusion

     5lso called forward etrusion    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

    etrudate * cutting it

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    Example

     :ae ou plaed &ith a dough plunger to *efore>?

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    igure 19.31 0a4 Direct extrusion to produce a hollo& or semi hollo&‑ cross [email protected] 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 cross section 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 etrusion and reverse etrusion

     

     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 [email protected] #o   cross-sectional area of

    the starting *[email protected] and #f    final cross-sectional area of

    the extruded section

      5pplies to *oth direct and indirect extrusion

    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 hdraulicall drien, &hich is especiall suited to semi continuous direct

    extrusion of long sections

     echanical dries - often used for cold extrusion

    of indiidual parts 

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