Investigation of Cavity Pressure and Thickness Precision in Injection Compression Molding Transparency

In injection molding transparency, cavity pressure determines the evolution of the polymer inside the mold cavity. The profile of cavity pressure and its repeatability have very strong influence on the quality of the molded transparency, particularly, the dimensional accuracy. To understand the cavity pressure behavior of the melt in injection compression molding, three pressure sensors are equipped in an injection compression mold and polycarbonate plates were molded by injection compression molding at different process variables. In addition, the thickness of PC plates and the cavity pressure of melt were compared. The results show that the variables of compression stage make the plates thickness and cavity pressure exhibit different behavior with respect to injection velocity. High injection velocity and high melt temperature is beneficial to both of the uniformity of thickness and cavity pressure.