In a recent course I was asked to explain ‘what feeds what’ and ‘how this all fits together’. This sounds simpler than is is as while some relationships are quite clear, such as the control plan deriving its contents from the product and process FMEAs, other aspects are less clear. It is one thing to say that one phase feeds another. It is another thing to attempt to show each and every ‘this leads to that’. In part this is because many times there is nothing quantifiable or there is a lack of an equivalent. An example would be customer questionnaires and surveys as a part of Market Research. From the laundry list in 1.1.1 Market Research, your company has to have a methodology of taking the items and translating them into some type of measurables.
The above diagram is meant to illustrate the sequence of the required documentation. This is one way of looking at the relationships. Here we see the sequence of a sub-set of required documents. It is evident that the Design FMEA precedes the Process FMEA. But here we must pause to consider reality. More often than not these documents are actually being developed concurrently. Knowing this we can only say that the sequence above, as in the APQP manual, is ‘preferred’. In truth, the Design FMEA should, for example, be completed prior to the completion of the Process FMEA and the Control Plan because it is a possible input to each.