Forming work deep drawing

Mean factors — Fig. 1
Determination of the drawing work: area integral and averaging factor
Punch force F U Maximum punch force F max
Mean value factor m U Drawn part height h Z

Eqn. 1

Both the blankholderforce F_nh and the forming force F_U must be applied. The deep-drawing and hold-down work is obtained from the integral below the respective force-displacement curve.

A simplified determination of the forming work can be achieved by using the mean value theorem of the integral calculus.

To determine the drawing work, the maximum occurring drawing force F_max is multiplied by the mean value factor m_U and the drawing height h_Z. This results in the punch or forming work. Typical mean factors in deep drawing are:

Mean value factor of punch force in the predraw m_U = 0.66

Mean value factor punch force in the drawing m_U = 0.55

Average factor blankholderforce m_nh = 0.95

If the blankholderforce is set to be constant, the mean factor is significantly higher than the mean factor of the punch force. Even if the blank holder force is less than the maximum punch force, the hold-down work is often higher than the punch work due to the higher averaging factor.

The mean factors of different stamping processes vary. See table Mean Factors.