DEVELOPMENT OF DEEP DRAWING WITHOUT BLANK-HOLDER FOR PRODUCING ELLIPTIC BRASS CUPS THROUGH CONICAL DIES

Abstract

This paper introduces a new technique for deep drawing of elliptic cups through a conical die without blank holder or draw beads. In this technique an elliptical-cup is produced by pushing a circular blank using a flat-headed elliptic punch through a conical die with an elliptic aperture in a single stroke. A 3D parametric finite element (FE) model was built using the commercial FE-package ANSYS/APDL. Effects of die and punch geometry including, half-cone angle, die fillet radius, die aperture length and punch fillet radius on limiting drawing ratio (LDR), drawing load and thickness strain of the cup have been investigated. A die with half cone angle of 18° has shown the best drawability for the new technique. Finite element model results showed good agreement with experimental results. A die with an aspect ratio of 2 has been used with punches having aspect ratios ranging from 2 to 2.25. Tensile tests were carried out to obtain the stress-strain behavior for the used material. A total of seven punches were used for forming sheet metal of brass (CuZn33) with initial thicknesses of 1.5, 1.9, 2.4 and 3.2 mm at different clearance ratios (c/t). The effects of blank thickness and clearance ratio on limiting drawing ratio, drawing load and thickness strain were experimentally investigated. An elliptic cup with a limiting drawing ratio (LDR) of 2.26 has been successfully achieved.