Question

In wire drawing, is there a difference and if so how much is the force required to draw a wire from cross sectional area of A₀ down to A₁ in one operation as compared to drawing it through two dies in tandem. Assume that there is friction but no redundant work

Answer 1

Ans. In wire drawing a circular cross section billet is reduced in diameter and increased in length by pulling through a conical die of semi angle.

Expression for drawing force under frictionless condition is given by

Where Sigma average is the average true stress of material.

Ao= original cross section area

Af= final cross section area

Because more work has to be done to overcome friction , the force increases with increasing Friction.

As reduction increases the drawing force increases.

There is a limit to force due to tensile stress reaches yield stress of metal so our billet will simply yield and eventually breaks.

Maximum reduction in the cross section area per pass is limited to 63%.

Drawing through two dies in tandem will not matter ideally for drawing force if we assume frictionless condition. But in real application force required depends on strength of the billet material , friction between billet and chamber of dies surface and process variables such as temperature and speed of drawing.