ON THE ACCEPTABLE BLANK-HOLDER FORCE RANGE IN THE DEEP-DRAWING PROCESS

In the current study, a system for computer control of the variable blank-holder force (BHF) was implemented for a deep-drawing process, using a multi-action, computer-controlled press. The press was developed at the Engineering Research Center for Net Shape Manufacturing for simulation research in the cold forming of complex parts and for sheet-metal forming. The controlled blank-holder forces (BHF) system was programmed and tested. It was found that the system has a quick response and enables the user to preset the desired BHF path over the entire punch stroke. An acceptable BHF range was predicted experimentally by performing a series of deep-drawing tests with different constant BHF. The acceptable BHF range obtained is bounded by two critical loci, the rupture locus and the wrinkling locus. Various experiments were performed with different constant BHFs located within an acceptable zone. Higher punch forces were recorded and a thinner product was obtained for the higher BHF test. From the experimental results, it is expected that the minimum acceptable BHF locus (slightly above the wrinkling locus) is the optimal path of BHF variation during the drawing stroke.