Extrusion and Drawing

Question 1

typical extruded parts

Answer 1

• Long pieces with a variety of cross sections
• Cross-section must be constant along length of the part
• May be cut into shorter lengths

Question 2

Process of extrusion

Answer 2

• cylindrical billet is forced through a die

- Large deformations take place without fracture due to high triaxial compression

Question 3

Characteristics of Extrusion

Answer 3

• is economical for large and small productions as tooling costs are low
• hot and cold extrusion

Question 4

Advantages & Disadvantegs Hot & Cold extrusion

Answer 4

• same as other manufacturing processes

higher accuracy, higher energy cost, shorter tool life,

Question 5

Forward (Direct) Extrusion

Answer 5

• Die is not moving, but workbillet is (by the ram)

- more force than indirect extrusion

Question 6

Backward (Indirect) Extrusion

Answer 6

• Die is moving, but workbillet is not (by the ram)

Question 7

Hydrostatic Extrusion

Answer 7

• The billet is smaller in diameter than the chamber (which is filled with fluid), and the pressure is transmitted to the fluid by a ram.
• better pressure control on material
• extrusion of very sensitive materials

Question 8

fluids for hydrostatic extrusion

Answer 8

• oil

- molten glass

Question 9

Poor design extrusion parts

Answer 9

• knife edges
• sharp outside corners
• unbalanced section walls
• unbalanced voids

Question 10

Drawing

Answer 10

• An operation where the cross section of solid rod, wire or tube is reduced or changed in shape by pulling it through a die

Question 11

Drawing variations

Answer 11

bar drawing:
- larger diameter bar, typically just one die
Wire drawing:
- smaller diameter stocks
- typically done with a series of dies (multiple wire drawing machines)

Question 12

Wire drawing

Answer 12

- ca. 30 % of reducement of wire per die
 why many steps?
- not so hard on material
- faster than make the total diameter change at once
- otherwise it stresses out wire