A Study on the Part Shrinkage in Injection Molded Annular Shaped Product for Glass Reinforced Polycarbonate

摘要

Part shrinkage in injection molding is inevitable phenomenon. Thus, it is necessary not only study on the reducing part shrinkage but characterization of part shrinkage. In this study, part shrinkage in injection molded 2.5 dimensional annular shaped specimens has been studied using glass fiber reinforced PC. Annular shaped specimens were designed with various sizes of outer diameter and thickness. Injection temperature, packing time and packing pressure were selected for operational conditions. Profile variations of outer and inner diameters of molded specimens for various operational conditions were investigated. Sizes of outer and inner diameters of injection molded specimens were smaller than the sizes of mold. Part shrinkage decreased as outer diameter and thickness increased. Part shrinkage showed anisotropic behavior and it depended upon gate location Subsequently, molded specimens were not circular but oval in shape, and showed the largest shrinkage in the direction of gate. It was realized that the mold design such as gate design is important to control the shape of molded products.