Studies on Draw and Thin Redraw Forming : Experimental Investigation of Optimum Working Conditions for multi-Stage Stretch Draw Forming Using Laminated Sheet

Abstract

By repeating the stretch draw forming, the side wall thickness of a cup which is made of steel laminated with polyester film on both sides can be reduced significantly and this method has lead to the development of a container having a higher H/D (cup high/cup dia.) ratio. The purpose of this paper is clarifty the effect of die radius conditions on thickness reduction of the multi-stage stretch draw forming. From experimental results, higher side wall reduction can be obtained by using two-stage stretch draw forming. The available range of 2nd redraw expands by making the side wall thickness in the prior redraw stage as thin as possible. The optimal conditions for the highest conditions are to set the 1st redraw to have a Rd₁/to in the range of 1.4∼1.6 and the 2nd redraw a Rd₂/to of 1.1∼1.6. The stretch draw method is different from the conventional redraw method in terms of properties of plastic strain. The maximum wall thickness rate obtained in two-stage stretch draw forming is approximately 35% using high strength steel.