Design and modification of tool to manufacture rectangular cup of Ni-MH battery for hybrid cars

The shape of rectangular cup of Ni-MH battery which is one of the electric power supplying parts of hybrid cars looks quite simple, but process and tool designs to product the rectangular cup are a little too hard to achieve. Some researches for sheet metal deep drawing process have been performed on the formability of a rectangular Li-Ion battery container for mobile phone. However, there are few concrete reports on the rectangular container as part of vehicles. In this study, tool design for rectangular cup in multi-stage deep drawing process is carried out using the result of FE analysis. This study identified such unfavorable mechanism in deep drawing for rectangular section with ironing and proposed a new tool design of the process through numerical simulation of drawing and ironing process with the thickness control of each wall of the deep drawn cup. Numerical simulation incorporated brick elements for a rigid-plastic FEM with an explicit time integration scheme. The results of FE analysis with the improved tool design confirmed not only reducing thinning of that wall and possibilities of failure but also improving the quality of drawing product through the modification of tools.