An Experimental Investigation into the Redrawing of Cylindrical Shells

Abstract

Cups having a height/diameter ratio greater than unity cannot as a rule be produced from flat, circular blanks in a single stage, and redrawing in one or more operations has to be carried out until the desired shape of the shell is attained. In this paper an account is given of an experimental investigation into the forces, work, and strains involved in the first redrawing process. The work was carried out in an experimental crank press (Seed and Swift 1950)‡ of 50 tons nominal capacity, and was based on a first-stage cup diameter of 4 inches. Brass, mild steel, and aluminium (in two tempers) were used. The conditions examined include the direct and reverse methods of redrawing, first-stage drawing ratio, inter-stage heat-treatment, punch profile radius, first-stage punch-die clearance, redrawing ratio, blank thickness, material, and temper. It is thought that the results are sufficiently accurate and detailed to give a reasonably complete insight into the redrawing process, and conclusions have been drawn to assist press-tool engineers in the design of drawing tools.