A Study on Initial Blank Design to Minimize Earing in Multi-Stage Deep Drawing Process for Rectangular Cup Using High Strength Steel Material

Multi-stage deep drawing process for rectangular cups with extreme aspect ratio using finite element analysis is performed. The process is mainly consists of four forming stages including blanking, drawing, ironing and trimming. However, main deformation of the rectangular cup is completed during the drawing-ironing procedure. Tool design and blank modification for the multi-stage deep drawing process are presented. To consider the deep drawing and the ironing operations, the multi-stage deep drawing process is applied to obtain the rectangular cup by using each numerical simulation models from first to fifth drawing. Based on the design results of the initial blank, the multi-stage deep drawing process is performed, but it is shown that severe earing phenomenon is occurred at the upper flange part. To solve the severe deformation at the upper flange due to normal anisotropy of the used sheet material, initial blank modification is carried out. The simulation results for the rectangular cup are compared with the final configuration before and after the modification of the blank shape. The predicted result is confirmed that the modified blank shape not only improve the quality of a deep-drawn product but also reduce the cost of production.