Gas-assisted Injection Molding: Case Study on Process Optimization of CD-Rom Tray Manufacturing

Gas-assisted injection molding involves the injection of a short shot of resin into the mold cavity and followed by injection of nitrogen gas under high pressure through the nozzle or mold wall. Gas-assisted injection molding is a relatively new process with good compatibility with the conventional injection molding process. It offers a lot of benefits to the manufacturing of polymer products, such as reduced molded-in part stress, less warpage, reduced or no sink, and greater design freedom. The product chosen as a case study for this work is CD-Rom tray, which is a thin plastic disc holder that allows a disc to be inserted into the optics reader. The material that is being used to manufacture CD-Rom tray is acrylonitrile butadiene styrene (ABS). The gas-assisted injection molding was simulated using a commercial computer aided engineering software dedicated for injection molding. This study intends to obtain the optimum parameters when five processing parameters were varied, which are melt injection time, gas delay time, melt temperature, mold temperature, and gas injection pressure. The quality characteristics concerned in this study are volumetric shrinkage, warpage, and weld line. Based on the study, the optimum parameters setting for the CD-Rom tray manufacturing is low level in melt injection time, melt temperature and mold temperature while high level in gas delay time and gas injection pressure. By using the optimum parameters setting, the production time and cost can be greatly reduced.