塑膠射出成型技術已經被廣泛應用於工業產品中，但由於射出成形製程常欠缺系統性之方法以維持品質之穩定，而發生產品品質之不一致性或變異的情形。若能解決此一問題，則產品品質水準必能有所提升，進而提高企業競爭力。本研究結合田口方法與主成分分析法（principal
component analysis, PCA）來最佳化生產製程參數以改善化妝盒產品品質，研究結果顯示品質特性之平均值均移至規格界線內，標準差也減少約6% 及10%：同時PCA 可以取得多品質特性之整體最佳解以有效解決多品質特性問題；又，射出成型之保壓壓力可為製程平均值之調整子；材料溫度、保壓壓力、射出位置對於完成品品質之尺寸大小有顯著之影響。

Plastics injection molding technology is widely used in industrial products. However, the product quality is inconsistent and variance is significant in the conventional plastic injection molding process. This phenomena occurs due to the absence of a systematic method for maintaining stable processes. If this issue can be resolved, product quality can increase to higher levels and further reinforce industry competitiveness. This study uses a combination of the Taguchi method and
principal component analysis (PCA) to improve the real product quality of cosmetic containers produced by conventional plastics injection molding processes through optimizing the parameters.This study determined that when all the values of the three quality characters were moved to the
intervals of specification, the standard deviation reduced by approximately 6 % to 10 %. Additionally,PCA can be effectively applied to problems with multiple quality characteristics to establish an
integral solution. Furthermore, the holding pressure can be considered as an adjustment factor to the process mean. Through analysis of variance, this study determined that the material melting temperature, holding pressure, and injection location significantly affected the size of the finished product.