Numerical Study on Flow Length in Injection Molding Process with High-Speed Injection Molding

Abstract

In thin-wall injection molding, due to the very fast polymer melt heat transfer to the mold wall, the freeze layer appears quickly during the filling stage. In this study, high-speed injection molding (up to 1400 mm/s injection speed) was studied. A mold of spiral shape, 0.4 mm thick, is used to verify the ability of melt filling under different injection speeds. Simulation by Moldflow software was also performed for verification. The result shows that when injection speeds vary for 100 mm/s, 500 mm/s, 1000 mm/s, and 1400 mm/s, the flow length to thickness ratio was increased with the value of 335, 467.5, 605, and 640, respectively. The simulation results also show that the heat transfer coefficient between hot melt and mold wall has a strong influence on the flow length, especially with the high-speed injection molding. In general, slower injection speed requires a higher heat transfer coefficient, whereas higher injection speed require only a lower heat transfer coefficient.