Experimental verification of a deep drawing tool system for adaptive blank holder pressure distribution

In deep drawing, the strain path in the blank during the forming process can be significantly affected by application of temporal and spatial variation of the blank holder force. In this study, an active tool system capable of controlling the distribution of the blank holder force is presented which can be integrated into existing stacked deep drawing tools without need for modification of the press. A working system is presented consisting of a controller, designated volume displacement cavity pressure supply units and a shimming plate. It is applied to the deep drawing of a rectangular geometry using a conventional stacked tool design. The shimming plate is used to support the blank holder plate, and has four integrated hydraulic cavities in which the pressure can be controlled individually whereby a controlled deflection of the blank holder plate is achieved analogous to the conventional shimming method using paper or metal shims between the tool plates. The tool systemʹs ability to influence the material flow is investigated by performing a series of deep drawing experiments. Eight different cavity pressure schemes are applied during the punch stroke and the schemeʹs effects are documented by means of process data and 3D-coordinate measurements of the formed parts demonstrating that both the geometric shape and the thickness distribution in the formed parts can be affected by the shimming system.