Blank holder force optimisation strategy in deep drawing process

Abstract

This paper develops an efficient and fast optimisation procedure for the cup drawing process in order to produce a defect free deep drawn cup. The finite difference technique is used as the solution engine for the deep drawing problem in the optimisation procedure. A procedure that minimises the Blank Holder Force (BHF) scheme is proposed, which searches for a linearly varying BHF scheme that minimises the maximum punch force while avoiding tearing and wrinkling. The optimised linear BHF scheme resulted in an improved cup forming when compared to that produced by the constant BHF scheme. The BHF scheme is optimised for different cases of drawing ratios and die coefficients of friction. It was found that the slope and the intercept of the linear BHF scheme increase in a nearly linear manner with the increase of the drawing ratio. A general equation is deduced for the optimum BHF at any drawing ratio for the cup under study. The proposed optimisation strategy can be applied to BHF schemes other than the linear one and with different objectives. [Received 3 March 2006, Accepted 10 January 2007]