RPN’s can be evil
What do I mean by this statement? Using RPN thresholds to take actions is not the intent of the FMEA tool. This is according to AIAG, SAE and other authorities. There are three paths that one takes when developing an FMEA:
- Severity first when 9 or 10
- Take action to error proof to eliminate the Failure Mode
- High Occurrence (4 or higher) when linked to higher severity 5 or more
- Take action to error proof the cause or make it more capable
- Detection number too high greater than 3 when a Cause and Failure Mode combination indicates testing or inspection for a probable cause is not adequate.
- Take action to improve testing (DFMEA) or Inspection methods (PFMEA)
RPN’s are then assigned to the Actions from the three above action drivers. The new RPN calculated after the action is compared to the RPN assigned to the action to see what the delta or difference is. Improvement is expected in the category that the action was developed.
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