An Experimental Study of a Plasto-Hydrodynamic Strip Drawing Process

Abstract

Experimental results are presented for a new dieless strip drawing process in which conventional wedge-shaped dies have been replaced by a reduction unit having a stepped rectangular cavity. The smallest cavity dimensions are larger than those of the incoming strip, thus eliminating the problem of die friction and consequential tool wear. In this novel process, the strip is passed through a chamber filled with polymer melt and then pulled through the reduction unit. The strip material is deformed due to the combined effects of shear drag and the hydrodynamic pressure generated by the converging flow of the polymer melt. Experiments were carried out in which the process parameters such as the unit geometry, speed and polymer melt temperature and hence viscosity were varied and the hydrodynamic pressure, reduction in strip size and drawing load were measured. Initial experiments were carried out by using copper strip and low-density polyethylene at two different melt temperatures. Results from experiments showed that a reduction in area of strip of more than 10 per cent could be achieved in a single pass. The Newtonian analysis presented by the authors in reference (9) is modified to incorporate the critical shear stress limit of the polymer melt and the non-linear strain-hardening property of the strip material.