隨著塑膠基礎原料成本不斷的攀升，射出成型產業已進入微利的時代，儘管 S 公司在日本有著堅強的材料研發團隊與卓越的產品設計能力，但若無法做好製程系統化與標準化的管控，過多生產中的損耗與不良將會蠶食掉此優勢更甚者造成虧損，因此著手於提高原料使用效率進而降低射出成型製程中的不良率已經是該產業刻不容緩的課題。 本研究的目的係以 S 公司之射出成型不良之歷史資料為基礎，運用六標準差步驟將不良模式中最嚴重的冷料不良，逐步進行量測、分析、改善與對策擬定及執行改善，並搭配 PFMEA 防範於未然的特性將造成冷料不良的要因納入評估、管控與標準化以遏止異常的再發。 藉由分析的結果，本研究也擬出一套有效的改善流程有效地降低塑膠射出成型的冷料不良率。另外，PFMEA 表的實施與建立更能替公司留下改善的軌跡，做好製程改善的知識管理，此對於製程人員的教育訓練亦是一套實用的教材。未來更可以依照此流程對其他不良模式進行改善。Along with the continuously increasing cost of plastic raw materials, the injection molding industry has got into the Low-profit times. In spite of there are strong raw material R&D team and the outstanding product design ability. However, if it is no well control of process systematically and standardized, this strength will be nibbled away or even resulted of loss by producing too many waste and nonconforming products. Therefore, it is an urgent issue to enhance the material efficiency then reduce the defect rate in injection molding process. The purpose of this thesis is based on the S company’s historical defect data of injection molding to apply Six Sigma approach to implement measurement, Analysis, improvement, action drawing up and execution, and to use PFMEA to evaluate, control and standardize to avoid the reoccurrence of cold slug defect with its preventive characteristics.As the results of the analysis, it is defined an efficient improvement process to significantly reduce the cold slug defect of injection molding through this research. Furthermore, the improvement tracks can be left for company to implement and build up the PFMEA then do the knowledge management well of process improvement, it is also a practical training material for process members. We can further follow this improvement pattern to implement improvement for the other defect modes.