Elimination of Earing Defects in Square Cup Deep Drawing Using an Inverted Die Design for Different Materials

Abstract

The deep-drawing process for square cups is primarily used in sheet metal production, but it is associated with several defects, such as tearing, earing, and wrinkling. This research intends to optimize the square deep drawing process to minimize or eliminate earing defects using an inverted deep drawing die design and to produce an optimal cup (without defects). Thus, the design and manufacture of the inverted deep-drawing die for the production of square cups are carried out experimentally and by the finite element method using the ANSYS program. The investigation is carried out by conducting several experiments using three metals (low carbon steel st1008, brass CuZn30, and aluminum A1100). The metal thickness is 0.7mm, and the materials are characterized by tensile testing and mechanical properties, including Young's modulus and yield stress. Experimental tests have been carried out under various load conditions for the empty holder. A three-dimensional square-cup model (43mm by 43mm) with a (0.7mm) thickness is built. Given the sample's symmetrical geometry, only one-fourth of the model needed to be analyzed. The minimum Blank Holding Force (BHF) for steel and brass sheets is higher than that required for aluminum sheets. The percentage difference between the experimental punch force and ANSYS test results is 7.4% for steel, 9% for brass, and 6.5% for aluminum. An important thing to note during the formation of square cups is that the deformation conditions in the die's hollow change. In fact, the corners of the cup are subject to greater deformation than the sides, because during distortion the metal on the sides of the cup moves more uniformly and more easily than in the corners.