The optimal process conditions of an injection-molded thermoplastic part with a thin shell feature using grey-fuzzy logic: A case study on machining the PC/ABS cell phone shell

This paper presents a fast and effective methodology for the optimal process conditions of an injection-molded thermoplastic part with a thin shell feature based on the orthogonal array with the grey relational analysis and fuzzy logic. The proposed optimal procedure in solving the optimal multi-responses problem applies the grey relational coefficient for each machining response and converts a grey-fuzzy reasoning grade to evaluate the multiple machining responses. One real case study in the injection molding process of Polycarbonate/Acrylonitrile Butadiene Styrene (PC/ABS) cell phone shell has been performed to substantiate the proposed optimal procedure in order to indicate its feasibility and effectiveness. Through the grey-fuzzy logic analysis, the principle injection molding parameters, namely the opening mold cavity time, mold temperature, melt temperature, filling time, filling pressure, packing time, packing pressure and cooling time, are optimized with considerations of multiple machining responses including the strength of welding line, shrinkage and difference of forming distributive temperature. The results of confirmation test with the optimal levels of process parameters have obviously shown that the above machining responses in the injection molding process can be improved effectively together through this procedure. In addition, the analysis of variance (ANOVA) is utilized to find the effect of machining parameters on the multiple machining responses problem of the injection molding process.