Deep drawing characteristics of square cups through conical dies

This paper studies the deformation characteristics of a newly developed process for increasing the drawability of square cups. The process has a simple tooling set in which a circular blank can be easily deformed by a flat headed square punch through a conical die with a square aperture. Finite element analysis (FEA) was used to study the influences of the geometric parameters on the formability of square cup in order to find out the optimum setup dimensions of the present process. The effects of die fillet radius, die corner radius, die throat length, punch profile radius; punch corner radius, punch shape factor, relative die clearance and blank thickness on the drawability of square cup were mainly investigated. Cup drawability was also studied with the change of material strain hardening exponent, n, strength coefficient, K, average anisotropy, R, and friction coefficients between die-sheet-punch to find the best operating conditions. The limiting drawing ratio (LDR) was used to evaluate the effects of all these parameters on the square cup drawability. The LDR's, maximum drawing loads, cup thickness, cup height and modes of failure were predicted. The analysis reveals that the determination of the optimum setup dimensions of our developed process has increased the drawing ratio up to 3.1 for brass alloy (67/33 Cu-Zn) and 3.15 for aluminum (Al99.5w) in a single-drawing stroke. Experiments have been also done in order to compare and verify the FE-predictions. Successful square cups with drawing ratio of 3.07 for brass and 2.93 for aluminum were produced. These LDR's are significantly higher than that of the improved conventional methods with blank holder. (C) 2014 Published by Elsevier Ltd.