Evaluation of milli-scale cylindrical cup in two-stage deep drawing process

In this study, to enhance the accuracy of products in metal forming, the product accuracy in two-stage cylindrical cup deep drawings was investigated. To consider the local and global forming factors simultaneously, we focused on milli-scale order, which is classified as the intermediate region between micro- and macro-scales. For evaluation of the drawn cups, the cup wall geometry, thickness distribution and surface roughness were precisely investigated using both experimental and finite element (FE) analyses. Milli-scale deep drawing experiments were performed with mirror-polished and unpolished tool sets to investigate the effect of tool roughness. The validity of the modeling of surface roughness as well as the effect of tool roughness on drawn cup surface accuracy was investigated via FE simulation. Some evaluated characteristics in the experiment were in good agreement with FE simulation results. It was also shown that tool roughness is strongly related to frictional behavior, but does not affect the cup surface accuracy under the condition of less than 0.1 μm tool roughness.