【正文】 o prevent or detect. See FMEA Checklists and Forms for an example PFMEA Detection Ranking Scale. Taking a lead from AIAG, consider three different forms of Custom Detection Ranking options. Custom examples for MistakeProofing, Gauging, and Manual Inspection controls can be helpful to PFMEA teams. See FMEA Checklists and Forms for examples of Custom PFMEA Ranking Scales. (Examples of custom scales for severity, occurrence, and detection rankings are included in this Appendix.) Return to topStep 7: Calculate the RPNThe RPN is the Risk Priority Number. The RPN gives us a relative risk ranking. The higher the RPN, the higher the potential risk. The RPN is calculated by multiplying the three rankings together. Multiply the Severity ranking times the Occurrence ranking times the Detection ranking. Calculate the RPN for each failure mode and effect. Editorial Note: The current FMEA Manual from AIAG suggests only calculating the RPN for the highest effect ranking for each failure mode. We do not agree with this suggestion。 we believe that if this suggestion is followed, it will be too easy to miss the need for further improvement on a specific failure mode. Since each of the three relative ranking scales ranges from 1 to 10, the RPN will always be between 1 and 1000. The higher the RPN, the higher the relative risk. The RPN gives us an excellent tool to prioritize focused improvement efforts. Return to topStep 8: Develop the Action PlanTaking action means reducing the RPN. The RPN can be reduced by lowering any of the three rankings (severity, occurrence, or detection) individually or in bination with one another. A reduction in the Severity ranking for a PFMEA is often the most difficult. It usually requires a physical modification to the process equipment or layout. Reduction in the Occurrence ranking is acplished by removing or controlling the potential causes. Mistakeproofing tools are often used to reduce the frequency of occurrence. A reduction in the Detection ranking can be acplished by improving the process controls in place. Adding process failsafe shutdowns, alarm signals (sensors or SPC), and validation practices including work instructions, setup procedures, calibration programs, and preventative maintenance are all detection ranking improvement approaches. What is considered an acceptable RPN? The answer to that question depends on the organization. For example, an organization may decide any RPN above a maximum target of 200 presents an unacceptable risk and must be reduced. If so, then an action plan identif