Impact of drawing ratio and shape on thickness distribution along the walls of deep drawn cups

Abstract

Deep drawing is the process of converting a flat blank into cup shaped articles. In this process a punch forces the blank to take the shape of die cavity. Different shapes and sizes of products for automotive bodies, structural parts, utensils and beverage cans are manufactured by this process. Using bimetallic strip in preparing the various products by deep drawing has become the recent trend in manufacturing process. The main reason to carry out such a process is taking the advantages of different materials such as high strength, low density and corrosion resistibility, at the same time and in a single component. The cost of the component gets reduced too. In the deep drawn cups the thickness of the sheet metal varies throughout the walls of cup. This is undesirable as non uniform thickness leads to defects like cracks or failures. As thickness variation depends upon several parameters like limit drawing ratio, drawing force, sheet material, geometry of blank etc. it can be minimized by selecting optimum process parameters.

This work is related to deep drawing of cups which are made using bimetallic strip. The objective of this work is to study the variation in thickness along the side walls of deep drawn cups which are made using bimetallic material i.e. Cu-Al and also to determine the optimum drawing ratio for producing a cup of specific size. The study was carried out in Amba Bhavani tool crafts and Metal Forming lab of CBIT. In this work the variation in thickness along the walls of cup for three different shapes, i.e: circular, square, heart. were investigated. The studies reveal that the variation in thickness is different for different shaped cups and also the variation in sheet thickness is different when Copper and Aluminium are in turn made as inside surfaces of bimetallic cups.