Direct redrawing of cups using an annular urethane pad

A recently introduced redrawing process enables the redrawing of cups at a redraw ratio of 3. In this process, a cup drawn by the conventional deep drawing process is directly redrawn by repeatedly squeezing an annular urethane pad held inside (at the bottom of) the cup. The cup itself is held inside a cylindrical container. The redrawing action is similar to that of Maslennikov’s technique for drawing cups from flat sheet metal; the difference being that the present process makes use of a cup instead of the flat blank. Redrawing experiments conducted with annealed aluminium cups indicate that with sufficient friction at the urethane–cup interface and proper lubrication of the die, very deep cups can be produced by this process. Results from these experiments are reported in this paper.