Dimensional Accuracy Optimization of the Micro-plastic Injection Molding Process Using the Taguchi Design Method

Plastic injection molding is an important field in manufacturing industry because there are many plastic products that are produced by injection molding. However, the time and cost required for producing a precision mold are the most troublesome problems that limit the application at the development stage of a new product in precision machinery industry. This study presents an approach of manufacturing a hard mold with microfeatures for micro-plastic injection molding. This study also focuses on Taguchi design method for investigating the effect of injection parameters on the dimensional accuracy of Fresnel lens during plastic injection molding. It was found that the dominant factor affecting the microgroove depth of Fresnel lens is packing pressure. The optimum processing parameters are packing pressure of 80 MPa, melt temperature of 240 degrees C, mold temperature of 90 degrees C and injection speed of 50 m/s. The dimensional accuracy of Fresnel lens can be controlled within +/- 3 mu m using the optimum level of process parameters through the confirmation test. The research results of this study have industrial application values because electro-optical industries are able to significantly reduce a new optical element development cycle time.