Determining the optimal processing parameter is routinely performed in the plastic injection moulding industry as it has a direct and dramatic influence on product quality and costs. In this volatile and fiercely competitive market, traditional trial-and-error is no longer sufficient to meet the challenges of globalization. This paper aims to review the research of the practical use of Taguchi method in the optimization of processing parameters for injection moulding. Taguchi method has been employed with great success in experimental designs for problems with multiple parameters due to its practicality and robustness. However, it is realized that there is no single technique that appears to be superior in solving different kinds of problem. Improvements are to be expected by integrating the practical use of the Taguchi method into other optimization approaches to enhance the efficiency of the optimization process. The review will shed light on the standalone Taguchi method and integration of Taguchi method with various approaches including numerical simulation, grey relational analysis (GRA), principal component analysis (PCA), artificial neural network (ANN), and genetic algorithm (GA). All the features, advantages, and connection of the Taguchi-based optimization approaches are discussed.

Additives are costly and can have negative environmental effects. Thus, searching for other alternatives to improve recycling plastics without using additives is necessary. This study aims to improve the hoop tensile strength, elongation at break, and shrinkage of the ring stopper made from an acrylonitrile butadiene styrene blend comprising 40% recyclates through the optimization of processing parameters using the Taguchi method. By adopting the 9 Taguchi orthogonal array, four controllable factors each at three levels are tested to determine the optimal combination of factors and levels in the injection moulding process. Considering the multiple quality characteristics involved in this study, we investigate the effects of processing parameters on hoop tensile strength, elongation at break, and shrinkage of the ring stopper both separately and simultaneously because changing a parameter can result in the improvement or deterioration of each quality response and of the overall product performance. The results revealed that the performance of an injection-moulded ring stopper under the optimal process conditions is equivalent or slightly better than that of the part produced from virgin resin. The performance of recycled plastics can be effectively enhanced to levels comparable with virgin resins using the Taguchi optimization approach.