| Gas-Assisted Injection Molding (GAIM) has been developed for production of hollow plastic parts and for parts with separate internal spaces or channels. It offers a cost effective means of producing large, smooth surface, rigid parts requiring little or no finishing. The present study involved investigating the effect of various processing variables on the part weight reduction, gas bubble length penetration and the residual wall thickness (RWT). The materials which were used for the study included Polycarbonate (Lexan{dollar}spcircler{dollar}121 and Lexan{dollar}spcircler{dollar}141), PBT (Valox{dollar}spcircler{dollar}325 and Valox{dollar}spcircler{dollar}414) and PC/PBT (Xenoy{dollar}spcircler{dollar}NBX 097). Developing a "Gas injection mold" and a microprocessor controlled gas control system were the preliminary phases of the study. Two different "rod shaped" cavity geometries were used in the study. The experimental study was carried out using a Taguchi L8 design on a CAMAC 250T (32 oz.) injection molding machine. Results of the study show shot size is the dominating variable in the part weight and gas bubble length analysis. Melt Temperature, Delay Time, and Gas Pressure play important roles in the residual wall thickness formation. Using a variety of materials showed that the gas bubble length and residual wall thickness (RWT) are sensitive to material rheology and glass fiber content. |
