Fabrication of Deep Cup with Flange by In-Plane Stretch Forming Applying Compressive Force in Thickness Direction

Abstract

This paper presents a new stretch forming method that applies compressive force for forming a deep cup with a flange. In this method, a punch and a die having a hole are used, and the main parameters are the depth of the die hole, ddh, and the clearance between the punch and the die, c. The effect of ddh and c was investigated by using an aluminum blank of thickness 2 mm in an experiment and a finite element analysis (FEA). When ddh was too small, the material flow could not be controlled appropriately, and when ddh was too large, a local thinning occurred during initial stretching into the die hole. When c was set at large, the side wall thickness of the formed cup was uneven, but a deep cup could be obtained by setting c below a half of the blank thickness. As a result, a deep cup of height 8.3 mm and with a flange was formed successfully under the condition that ddh was 1.5 mm and c was 0.5 mm.