Effect of lap-sheets on deep drawing of metallic foil cups

In order to improve the deep drawability of stainless-steel foil cups, foil-lap blanks in which thin sheet metals (lap-sheets) were lapped over the foils were used in the deep-drawing operations. In the deep-drawing process, aluminum sheets were used as lap-sheets. The following three foil-lap blanks were used. B-sheet type: a two-ply foil-lap blank in which an aluminum sheet is on the blank holder side. D-sheet type: a two-ply foil-lap blank in which an aluminum sheet is on the die side. Sandwich type: a three-ply foil-lap blank in which a stainless-steel foil blank is sandwiched between two aluminum lap-sheets. In the D-sheet type, cracks on the foil cups were prevented by the lap-sheet on the die side. In the B-sheet type, wrinkles on the foil cups were prevented by the lap-sheet on the blank holder side. The deep drawability of stainless-steel foil cups was improved effectively when using lap-sheets. The thickness and the strain-hardening characteristics of aluminum lap-sheets influenced the deep drawability of foil cups.