Measurement of Gas-vent Clogging Ratio Using Evaluation Mold of Gas-vent Performance

摘要

In injection molding, when gas generated from molten resin becomes deposited in the gas-vents of molds, burns and short-shot are formed on products. In this study, we developed a mold for evaluating gas-vent performance, and proposed a quantitative evaluation method of gas-vent performance by supplying a known gas to gas-vent grooves where mold deposits increase during continuous molding. We applied this method for gas-vent grooves with three kinds of gaps and quantitatively inspected the effective cross-sections of the gas-vent grooves by flow rate Q and time T when gas pressure was reduced by half. Furthermore, we applied this method to the continuous molding process and detected the changes in Q and T with shots, calculated the clogging ratio of the effective cross-sectional area of the gas-vent groove, and confirmed that changes in the gas-vent performance can be evaluated quantitatively.