A note on fluid-pressure-assisted deep drawing processes

Hydraulic pressure can enhance the capabilities of the basic deep drawing process for making metal cups. Amongst the advantages of the hydraulic pressure assisted deep drawing techniques, increased depth-to-diameter ratios and reduced thickness variations of the cups formed are notable. Hydraulic pressure contributes positively in several ways to the deep drawing process. Different combinations of these positive effects of hydraulic pressure on deep drawing are found in the existing hydraulic pressure assisted deep drawing processes. Two important effects focused on in this paper are: (a) hydraulic pressure pushing on the periphery of the flange of the cup, thereby contributing to the externally supplied work for deformation and (b) hydraulic pressure in the die cavity helping to generate frictional support of the cup wall so as to enable the work-hardened metal at the die throat to carry a larger draw stress. It is hoped to stir further interest in developing novel fluid-assisted deep drawing processes capable of producing even larger draw ratios than the present limit of about 3.5 realized with the existing processes.