Development of a new process for producing deep square cups through conical dies

In this article, a new process for increasing the drawability of square cups has been developed. A circular blank is pushed by a flat-headed square punch through a conical die with a square aperture. The deformed blank conforms to the square shape of the die throat and finally a square cup is obtained. The developed technique has a simple tooling set in which the drawing process can be efficiently preformed in a single-acting stroke without using draw beads or blankholder. A commercial finite element simulation package, DYNAFORM, is used to investigate the developed setup in order to determine the optimum die cone angle. An experimental setup is built accordingly with a half cone angle of 18°. Brass alloy (67/33 Cu–Zn) and commercially pure aluminum (Al99.5w) sheets are used in the experimentations. The effects of the original blank thickness (to=1, 1.5, 2, 2.5, and 3 mm) and the orientation of the blank rolling direction (0°, 22.5°, 45°, and 67.5°) to the punch side on the limiting drawing ratio (LDR) and punch load are experimentally investigated. The present process successfully produces square cups with drawing ratios of 2.92 for brass and 2.74 for aluminum. The new process has shown superiority over the conventional methods through achieving high drawing ratio especially for thick sheets (2–3 mm). Comparison between experimental results and the available published work showed that the required punch force in the new process is significantly reduced while the LDR is increased.