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). Circumscribing-Circle Diameter (shape factor). Length (butt end). Temperature (billet and Die). Speed. Lubricants

Extrusion Operations Direct Extrusion Indirect 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.

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

Extrusion Operations Impact Extrusion Hot 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.

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).

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

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.

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).

Drawing Lubrication Wet drawing Dry 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.

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

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

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