Pressure generated in the hydraulic-pressure augmented deep-drawing process

Abstract A recently developed hydraulic-pressure augmented deep drawing process to draw cups at large draw ratios is introduced briefly. A hydraulic pressure proportional to the punch force is generated in this process, the blank-holding force also being provided by this hydraulic pressure. In addition, the hydraulic pressure is applied on the periphery of the flange of the cup, the drawing being performed in a simultaneous push–pull manner making it possible to achieve higher draw ratios than those possible in the conventional deep-drawing process. The process has other advantages such as the automatic coordination of the punch force and the blank-holding force, low friction between the blank and the tooling as the high-pressure liquid lubricates these interfaces, and the elimination of the need for a complicated control system. The deep-drawing process can be easily carried out on a single-action press without the need for a cushion. The principle of the process is introduced in this paper. Experiments were conducted in the drawing of cups of 36 mm diameter at draw ratios of up to 3.11 using annealed aluminum blanks. Using a process model, a finite-element analysis of the process was carried out. The hydraulic pressures measured in the experiments are compared with those calculated using a simple analytical method and those from the finite-element analysis.