ANALYSIS OF FILLING, PACKING, AND COOLING STAGES IN INJECTION-MOLDING OF DISK CAVITIES

This research tried to simulate three stages of injection molding cycles (filling, packing, and cooling) for polypropylene. The cavity used was a center-grated disk-shaped mold. During the filling stage, we assumed the polymer fluid obeyed the CEF equation and flowed nonisothermally. The packing stage was represented by isothermal flow of Newtonian fluid, and, during cooling stage, we took into account the effect of pressure drop on the energy balance. By finite difference method, we could solve the partial differential equations numerically. The results showed: (1) Elastic effect was not significant at the filling stage. (2) Pressure buildup in the cavity was very quick at the packing stage. (3) At the cooling stage, temperatures predicted by taking into account pressure drop were lower than those without considering pressure drop. In addition, the influences of mold temperature, flow rate, and inlet melt temperature on the three stages of injection molding process were discussed.