The non-hydrostatic response of polymer melts as a pressure medium in sheet metal forming

The polymer injection forming process is a recent invention for producing plastic–metal hybrids. It is a combination of injection molding and sheet metal hydroforming process in which polymer melt serves as a pressure medium. This paper presents the experimental investigations on the non-Newtonian nature of thermoplastic melt as pressure medium. The objective of this work is to identify the presence of non-hydrostatic pressure distribution within the cavity and its influence on the final shape of the formed sheet metal component. Experiments are conducted with center-gated injection mold under varying processing conditions. The development of localized cavity pressure during the process is recorded and evaluated against the final shape of formed sheet metal. It has been observed that higher injection rate, higher injection temperature, and higher melt flow index of the processed polymer is necessary for the uniform pressure distribution and subsequently uniform forming of the sheet metal.