Question

What are the "FACTORS" that affect/control the maximum drawing ratio per pass in the drawing process? Can you please focus on only the "FACTORS" in your answer and explain how they affect it.

Answer 1

Drawing ration is the ratio of blank diameter to the cup diameter. As the blank size increases there is an increase in the total force ( force required for deformation + frictional force + ironing force ) and if the total force exceeds beyond a certain value, fracture occurs in the cup wall. This puts a limit on the blank size that can be successfully drawn into a cup without failure. Another factor affecting Drawing ratio is formability of the material, more is the formability more will be the drawing ratio. To increase Drawing ratio we will have to increase the applied forces as well as blank holding forces, when these forces are more than the required fracture occurs.

So factors affecting Drawing ratio are -

a.) Formability of material

b.) Limit on total forces to avoid fracture

c.) Limit on blank holding force to avoid fracture.

d.) Limit on blank size so that total forces remain under limit.