Mutual effects of defective components in assemblies

The focus of this study is a known and disturbing actual problem. The industry will soon celebrate a century of quality awareness and efforts. Still, according to field data, many new products exit the manufacturing systems defective. This study proposes mutual effects among assembly's components as an explanation to this phenomenon - many defective new products. While each item in a serial manufacturing process moves individually, items are joined to others in assemblies. There, a single defective component suffices to disqualify a whole assembled unit! Surprisingly, few studies have focused on the repercussions of defective items on production. Particularly, there appears to be no study that quantifies these mutual effects of components which arrive from different sources with different defect rates. Thus, this study is also a first attempt to analyze and quantify these mutual effects. Apparently, the mutual effects of their components amplify the defect rates of assemblies dramatically, to the extent that defects due to common or random causes become significant.