Lecture 15 Extrusion die designLecture 15 Extrusion die design

Course Hour: 2Course Hour: 2Basic requirements: Grasping the Basic requirements: Grasping the principles of die design, principles of die design, acquainting with die materialsacquainting with die materialsEmphasis: Die design principlesEmphasis: Die design principlesDifficulties: Die design principlesDifficulties: Die design principles

Hot Extrusion — Die DesignHot Extrusion — Die Design

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 zones around ) give rise to dead metal zones around

the diethe die Dead metal zones give bright finishes to aluminum alloys (no surface Dead metal zones give bright finishes to aluminum alloys (no surface

exposed to air)exposed to air) Spider dies produce hollow shapes How is the cross section Spider dies produce hollow shapes How is the cross section

completed?completed?

Extrusion-Die Extrusion-Die ConfigurationsConfigurations

Typical extrusion-die Typical extrusion-die configurations: (a) die for configurations: (a) die for nonferrous metals; (b) die nonferrous metals; (b) die for ferrous metals; (c) die for ferrous metals; (c) die for T-shaped extrusion, for T-shaped extrusion, made of hot-work die steel made of hot-work die steel and used with molten and used with molten glass as a lubricantglass as a lubricant

Components for Extruding Hollow Components for Extruding Hollow ShapesShapes

(a) An extruded 6063-T6 aluminum ladder lock for aluminu(a) An extruded 6063-T6 aluminum ladder lock for aluminum extension ladders. This part is 8 mm (5/16 in.) thick and im extension ladders. This part is 8 mm (5/16 in.) thick and is sawed from the extrusion (see Fig. 15.2). (b)-(d) Compones sawed from the extrusion (see Fig. 15.2). (b)-(d) Components of various dies for extruding intricate hollow shapes.nts of various dies for extruding intricate hollow shapes.

Cross-Sections to be ExtrudedCross-Sections to be Extruded

Poor and good Poor and good examples of examples of cross-sections to cross-sections to be extruded. be extruded. Note the Note the importance of importance of eliminating sharp eliminating sharp corners and of corners and of keeping section keeping section thicknesses thicknesses uniformuniform

Lecture 16 Cold extrusionLecture 16 Cold extrusion

Course Hour: 2Course Hour: 2Basic requirements: Acquainting with Basic requirements: Acquainting with cold extrusion practice; Grasping diffecold extrusion practice; Grasping different types of extrusion defects and theirent types of extrusion defects and their causes and preventionr causes and preventionEmphasis: Extrusion defectsEmphasis: Extrusion defectsDifficulties: Formation extrusion defeDifficulties: Formation extrusion defectscts

Cold ExtrusionCold Extrusion More recent development (1940's)More recent development (1940's) Includes some operations similar to forgingIncludes some operations similar to forging AdvantagesAdvantages – – Improved mechanical propertiesImproved mechanical properties – – Work hardeningWork hardening – – Good control of tolerancesGood control of tolerances – – Improved surface finishImproved surface finish – – Elimination of heating costsElimination of heating costs – – High production ratesHigh production rates DisadvantagesDisadvantages – – Higher stresses require more expensivetooling and die materialHigher stresses require more expensivetooling and die material – – Difficult die design essential to successDifficult die design essential to success – – Lubrication criticalLubrication critical

Cold ExtrusionCold Extrusion

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

Further Examples of Cold Further Examples of Cold ExtrusionExtrusion

Production steps for a cold extruded spark plug.Production steps for a cold extruded spark plug.

A cross-section of the metal part A cross-section of the metal part showing the grain flow pattern.showing the grain flow pattern.

Product Quality IssuesProduct Quality Issues Surface cracking (tearing, fir-tree Surface cracking (tearing, fir-tree

cracking, speed cracking, bamboo cracking, speed cracking, bamboo defects)defects)

– – Caused byCaused by • • high temperaturehigh temperature • • high speedhigh speed • • high frictionhigh friction • • Surface appearanceSurface appearance – – Oxides, scratches, discolorationsOxides, scratches, discolorations

Pipes (tailpipe, fishtailing)Pipes (tailpipe, fishtailing) – – Caused by surface oxides and defects being piped Caused by surface oxides and defects being piped to the middle by the flow patternto the middle by the flow pattern – – Results in significant lengths being scrappedResults in significant lengths being scrapped – – Can be minimized by machining billet surface first, Can be minimized by machining billet surface first, making the flow pattern more uniformmaking the flow pattern more uniform

Product Quality IssuesProduct Quality Issues Internal CrackingInternal Cracking – – Caused by a state of hydrostatic stress at the Caused by a state of hydrostatic stress at the center of the extrusion which results from poor center of the extrusion which results from poor

die die designdesign

Chevron CrackingChevron Cracking

(a) Chevron cracking (central burst) in extruded round steel bars. Unless (a) Chevron cracking (central burst) in extruded round steel bars. Unless the products are inspected, such internal defects may remain undetectethe products are inspected, such internal defects may remain undetected, and later cause failure of the part in service. This defect can also deved, and later cause failure of the part in service. This defect can also develop in the drawing of rod, of wire, and of tubes. lop in the drawing of rod, of wire, and of tubes.

(b) Schematic illustration of rigid and plastic zones in extrusion. The te(b) Schematic illustration of rigid and plastic zones in extrusion. The tendency toward chevron cracking increases if the two plastic zones do nondency toward chevron cracking increases if the two plastic zones do not meet. Note that hte plastic zone can be made larger either by decreasint meet. Note that hte plastic zone can be made larger either by decreasing the die angel or by increasing the reduction in cross-section (or both).g the die angel or by increasing the reduction in cross-section (or both).

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)