The document discusses common mistakes in design failure mode and effects analysis (DFMEA). It recommends (1) not wasting time arguing over ratings, (2) rating the occurrence of failure causes rather than just occurrence, (3) considering preventability rather than just detection, (4) updating the DFMEA often as the design evolves, and (5) evolving the DFMEA from an initial conceptual analysis to a bottom-up analysis of the final design.

1. Arguing over the rating A waste of time, save the energy for finding potential failure modes. If the team can not agree on a rating within a few minutes, use the highest (worst case) number proposed. Use of a 1-10 scale – it’s not worth the effort trying to split hairs this fine? Common Design FMEA Mistakes

2. Don’t rate Occurrence of a failure mode until you have defined its cause Each failure mode has one or more causes, and it is the occurrence due to the cause that is rated. Note: if there are multiple causes, analyze each individually. Don’t lump them together. Common Design FMEA Mistakes

3. Detection Detection traditionally means detecting the defect before it reaches the customer. If there is any chance of the defect reaching the customer the DFMEA has already failed. For DFMEA, think preventability when rating Detection. That is, how preventable is the cause of the potential failure mode? Common Design FMEA Mistakes

4. Update the DFMEA often Many teams only create a preliminary DFMEA early in the design cycle, and a final one during verification testing. But as the design is evolving, so should the DFMEA. A late update of the DFMEA can lead to surprise discoveries of design problems once it is finally updated. Common Design FMEA Mistakes

5. Conceptual vs. Bottom-Up Teams sometimes create a preliminary FMEA based on the concept of the product as known at the time, and only update this conceptual DFMEA as the design is evolving. By not performing a bottom-up analysis of the final design, the analysis can have many undiscovered design-specific potential failure modes. Common Design FMEA Mistakes

6. Summary Don’t waste time arguing over ratings Rate the occurrence of the cause, not just the Occurrence Think preventability when evaluating Detection Keep the DFMEA up to date with the state of the design As the design evolves, the DFMEA should evolve - from an initial concept to a bottom-up analysis Common Design FMEA Mistakes