In-situ monitoring of deformation in rapid prototyped injection molds

Abstract

The ever growing demand for reducing costs and decreasing the time to market in today’s plastics industry makes rapid tooling and rapid prototyping a highly researched area. 3D printed injection mold inserts make it possible to produce prototype parts in small series fast and cost-effectively. The mechanical strength and therefore the life expectancy of 3D printed polymeric injection mold inserts are low compared to their traditional steel counterparts. In order to increase the reliability and life expectancy of polymeric mold inserts, in-situ state monitoring during injection molding is essential. In this paper, we analyse the effect of thermal and mechanical loads on the resulting strains of the mold inserts. Three series of rectangular plate products were injection molded with a different type of insert in each series. The pressure inside the cavity and the strain of the 3D printed inserts were measured during injection molding. We correlated maximal cavity pressures and changes in strain with each other in order to set up the deformation characteristic of the inserts. The results indicate a satisfactory correlation between the maximal cavity pressures and the strain change of the inserts. The second important result was that strain gauges can be applied to in-situ monitor the state of the inserts during injection molding.