Optimising the variables when deep-drawing C.R.1 cups

One of the most important, yet simplest deep-drawing operations on a flat blank of sheet metal is the production of a cylindrical cup. The mechanics of forming are quite complicated and there are many different factors affecting the successful drawing of a blank. In order to further investigate the process of deep-drawing an instrumented tool was designed for operation on a Norton, 20 t, double-acting hydraulic press. Previous work carried out on this experimental tool yielded relatively good results [Effects of punch and die geometry, blank-holding and deformation velocity on deep-drawing, IMC-15, 1998, p. 135]. This paper investigates the variation and effects of punch and die geometry, blank-holding pressure, top-ram pressure, lubrication, and drawing speed in the deep-drawing of C.R.1 steel cups of 0.9 mm thickness. These effects were investigated by drawing a series of cups using DOE, where a screening experiment was conducted and the desired factors were varied at different levels. The chosen responses were punch load and wall thickness variation. This paper deals with the experimental work being carried out in order to investigate these effects and provides the optimum levels for each of the factors.