The use of stereolithography rapid tools in the manufacturing of metal powder injection molding parts

Abstract

The utilization of stereolithography molds in the manufacture pre-series for injection molded plastic parts aims to reduce costs throughout the product life-time, but mainly during design and manufacturing phases. The use of this Rapid Tooling technique in powder metal injection molding is evaluated in this work. One of the greatest differences between traditional and stereolithography tools is related to the heat conductivity of the materials employed. For example, steel molds have a heat conductivity coefficient 300 times higher than molds made with the photosensitive resin used in the stereolithography process. The discrepancy regarding the cooling rate of the molded parts during the injection cycle must be compensated with adjustments in the injection molding parameters, such as temperature, pressure and speed. The optimization of these parameters made it possible to eject green parts from the mold without causing defects which would become evident in debinding and sintering stages. The dimensional analysis performed at the end of each case study showed that the shrinking factor of the component after the sintering had the same value obtained for components using traditional metallic molds. Moreover, the dimensional error remains under 2% which can be considered low for a pre-series of components (or prototype series).