Make a list of the independent variables that influence the punch force in deep drawing of a cylindrical cup, and explain why and how these variables influence the force.

The independent variables are listed at the beginning of Section 7.6.2. The student should be

able to explain why each variable influences the punch force, based upon a careful reading of the

materials presented. The following are sample answers, but should not be considered the only acceptable ones.

(a) The blank diameter affects the force because the larger the diameter, the

greater the circumference, and therefore the greater the volume of material to be deformed.

(b) The clearance, c, between the punch and die directly affects the force; the smaller

the clearance the greater the thickness reduction and hence the work involved.

(c) The workpiece properties of yield strength and strain-hardening exponent affect the

force because as these increase, greater forces will be required to cause deformation

beyond yielding. (d) Blank thickness also increases the volume deformed, and therefore increases the force.

(e) The blankholder force and friction affect the punch force because they restrict the

flow of the material into the die, hence additional energy has to be supplied to overcome

these forces.