Effect of microstructures on the shrinkage of injection molding product

Abstract

Shrinkage of injection molding product is a well-known phenomenon which is determined by many factors such as material property, processing condition, mold design, and product design. This study aims to investigate the effect of microscopic structures on the shrinkage of macroscopic product. Flat specimens with and without microstructures were injection molded and the distribution of in-plane shrinkage was measured using an optical method. In the case without microstructures, anisotropic shrinkage is observed and the shrinkage magnitude increases with the distance from the gate. By applying the microstructures, the shrinkage could be reduced significantly, and the effect is especially noticeable when lower packing pressure was applied in the injection molding process. The numerical simulation result is also presented which suggests the importance of material data and lateral motion modeling for accurate prediction of the shrinkage.