Dimpling Suppression by Chamfered Rotatable Cubic Punch in Reconfigurable Die Forming

The dimpling defects caused by conventional hemispherical punch in doubly curved sheet metal reconfigurable die forming process were considered. The rotatable cubic punch (RCP) was developed to suppress the dimpling defects more effectively and conveniently. The former punch contacts with the work-piece through a point-surface contact and the latter punch contacts with the work-piece through a surface-surface contact. A series of stamping experiments were carried out using three different punches (hemispherical punch, RCP, chamfered-RCP) with three different loads. Some finite element simulations about the stamping experiments were carried out. The dimple scales were evaluated through the dimple depths. The corresponding data were obtained by 3-D scanning and FE result analysis respectively. A 3-D plate forming machine was developed, in which chamfered-RCP was adopted. Plate forming experiments were carried out on this machine. The stamped samples show a clear basis for the performance of chamfered-RCP. The study provided a means to guide the design of punches for dimpling suppression used in reconfigurable die.