Pressure Distributions in Deep Drawing with a Passive Cardanic Blank Holder

Abstract

Deep drawing processes are strongly influenced by the blank holder forces, as well as their local distribution. In current deep drawing tools, this pressure distribution is dominated by the compliance of the specific machine the tool is mounted on. Therefore, each tool must be manually polished to enable the desired distribution of the blank holder pressure. This regularly causes problems when transferring tools from one machine to another, for example from a try-out press to a regular press line. As both machines have unique compliances, the pressure distribution on the flange of the drawn part changes. Additional manual spot grinding is needed to achieve the desired pressure distribution on the flange. To counteract this problem, the use of a passive cardanic blank holder is proposed in this paper. The cardanic blank holder can freely tilt around two axes, which leads to an auto-leveling effect of the blank holder on the sheet, resulting in a more uniform blank holder pressure. This effect is demonstrated experimentally using pressure sensitive film on the same tool with two different blank holders, one equipped with a conventional blank holder, the other with a cardanic blank holder. To demonstrate transferability, the experiments are repeated on multiple single acting presses. The contribution will present and discuss the resulting pressure distributions.