Shape Imperfection in Cylindrical Cups Formed by Processes of Deep- and Stretch-Drawing with Ironing

Focusing our attention mainly on the shape quality of formed cups, the conventional cylindrical cup-drawing and the stretch-drawing processes with or without ironing are carried out. Four materials including titanium are tested. The shape quality of the products is represented by the uniformity of the wall thickness and the roundness of the cup cross-section. A new index, the distortion index, is introduced to evaluate the lack of roundness. Comparing with the cups formed by the conventional deep-drawing, the effects of the stretching and ironing on the shape quality are investigated in detail. As a rule, the stretching as well as the ironing makes the wall thickness to distribute more uniformly. Broadly speaking, the roundness of the cup is improved by the accompanied ironing with the reduction in thickness. This is not necessarily true for the stretching. However, the complete ironing does not improve the roundness of the copper cup. Typical shapes of the distorted cup cross-section are demonstrated, such as are oval, square, cross and others. For the deep- and stretch-drawing, the cup distortion pattern is related to the planar anisotropy of the tensile material properties. This is not the case for the ironing.