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ENGR 241 – Introduction To Manufacturing

ENGR 241 – Introduction To Manufacturing. Chapter 15 Extrusion & Drawing. Extrusion. Process that consists in forcing material through a die (aluminum, copper, magnesium, lead, steel). Extrusion Process Variables. Die Angle (dead metal zones). Extrusion Ratio (reduction in area).

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ENGR 241 – Introduction To Manufacturing

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  1. ENGR 241 – Introduction To Manufacturing Chapter 15 Extrusion & Drawing

  2. Extrusion • Process that consists in forcing material through a die (aluminum, copper, magnesium, lead, steel).

  3. Extrusion Process Variables • Die Angle (dead metal zones). • Extrusion Ratio (reduction in area). • Circumscribing-Circle Diameter (shape factor). • Length (butt end). • Temperature (billet and Die). • Speed. • Lubricants

  4. Extrusion Operations • Direct Extrusion • forward extrusion. • billet is placed in a chamber and forced through a die (actuator, ram). • Indirect Extrusion • reverse or backward extrusion. • die moves toward billet.

  5. Extrusion Operations • Hydrostatic extrusion • billet immersed in fluid to prevent (reduce) friction. • Coaxial extrusion • Cladding. • two different metals extruded together. • Stepped extrusion • more than one die.

  6. Extrusion Operations • Impact Extrusion • punch and die techniques. • similar to indirect extrusion. • Hot Extrusion • for materials that do not have sufficient ductility at room temperature. • reduce extrusion forces. • die wear, cooling/non-uniform deformation.

  7. Hot Extrusion vs. Cold Extrusion • Advantages of Cold Extrusion (over Hot Extrusion) • improved mechanical properties (work-hardening). • good control of tolerances (little machining required). • improved surface finish (lubrication used). • elimination of billet heating processes. • production rates/costs are competitive with other methods (same part).

  8. Hot Extrusion vs. Cold Extrusion • Disadvantages of Cold Extrusion (over Hot Extrusion) • lubrication is critical • higher stresses on tool and workpiece

  9. Extrusion Defects • Generally related to excessive speeds, friction, and temperature. • surface cracking: bamboo effect. • pipe (tailpipe, fishtailing ): funneling. • internal cracking • center. • center-burst. • arrowhead or chevron cracking.

  10. Drawing • Operation where the cross-section of a solid wire or tubing is reduced or changed by pulling it through a die (tension instead of compression).

  11. Drawing • Lubrication • Wet drawing • dies and rod completely immersed in a lubricant. • Dry drawing • surfaces of rod to be drawn are coated with lubricant by passing through a box containing lubricant.

  12. Drawing • Lubrication • Coating • soft metal (copper or tin) used as a solid lubricant. • Ultrasonic vibration • dies and mandrels are vibrated to reduce friction.

  13. Drawing Defects • Generally similar to extrusion • seams (longitudinal scratches or folds).

  14. Deep Drawing • A punch forces a flat sheet-metal blank into a die cavity. • typical products • beverage cans • pots and pans • containers • automobile panels

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