Blame it on supplier

The normal practice of manufacturing/assembly plant would categorize quality issues into the process, supplier parts, design, workmanship etc. 

Very often if a product quality performance was unstable with many customer issues, the first focus would be supplier parts especially those only assemble parts.   There are even some organization will just conduct a very surface failure analysis which isolates to which part is contributing to the failure and concluded it is a supplier problem. No doubt supplier part quality does contribute to the majority of quality issues, it will be a bit exaggerating to fault supplier contribute almost 100% of the problem.

Just imagine if the defect pie chart show >90% of the problem are supplier part when the fact supplier only contributes to less than 40%, no matter how many supplier improvement project will not get to 90% improvement. The best part is the actual quality issue never get resolve as the real root cause was not surface up.

Therefore an organization quality engineering function must have the capability to drive for deep-dive analysis to the real root cause which leads to correct categorization of the problem. Only through accurate root cause lead to an accurate solution. This is also important for supplier quality engineer to take note if they found supplier data show >90% of quality issues are contributed from the sub-tier supplier. This data might not give a true picture which means you will have a lot of fun driving the supplier's organization as you do not want to end up barking up the wrong tree!!!