Design optimization of initial blank shape and segmented variable blank holder force trajectories in deep drawing

Abstract

Blank shape minimizing earing, which is trimmed off after forming, is an important issue in sheet metal forming. In addition, blank holder force (BHF) have an influence on the product quality. Recently, variable BHF (VBHF) that the BHF varies through punch stroke is recognized as one of the advanced forming technologies. Furthermore, segmented VBHF will be valid to complex shapes for successful sheet metal forming. However, the optimal segmented VBHF trajectories and the optimal blank shape minimizing the earing are unknown in advance, and consequently the trial and error method is widely used to determine them. To resolve above issues, in this paper, a simultaneous design optimization of the blank shape and the segmented VBHF trajectories is performed. Numerical simulation in sheet metal forming is so intensive that a sequential approximate optimization using a radial basis function network is adopted to determine them. Based on the numerical result, the experiment using AC servo press is carried out. It is confirmed from the numerical and experimental result that the proposed approach is valid.