Hi all. After our successful registration to ISO 9001:2000, my next major task is to work on FMEA review and RPN reduction. This will be the first time my company has actually reviewed FMEA's under circumstances other than a corrective action that requires it. Many control plans will also be updated as a result of the across the board review. The goal, as stated by the QM, is to reduce RPN's. He started looking at the broad picture last week, and ran into this question. "How do we identify that a particular RPN is too high?" The question is subjective of course, and depends on what we could do to improve detection, or reduce occurence. The root of his question, I think, is how do we label a particular RPN for an element of our process as excessive? We manufacture bearing accessories - sleeves, spacers, bearing races, thrust races, etc. We supply to industries of every description, mostly automotive of course, but also marine, aerospace, and manufacturing. No particular customer is pressing for FMEA review or RPN reduction - we are doing it so it doesn't become an issue. Typical severity for us is a 4, occurrence is 3-5, and detection is 6-9. RPN's range from 72-192 with 128-144 being typical. We do a sample plan of product verification at the production cell, checking most features every 15 minutes. Some less critical features are checked a couple of times per shift, or at set-up only. Some critical features are checked 100%. We use a few quality gates, and some machines use an error proofing feature we call "fixed configuration". This is an air detection mechanism built into the work-holding that verfies the part is loaded flush to the locating face of the work holding to reduce parts being turned out of parallel.
My question, to answer the QM's question, is: Is there any "rule of thumb" as to what makes an RPN too high? Is it preferable to be under 100? Obviously, in some cases that won't be possible, but is there a desirable RPN in general?
My question, to answer the QM's question, is: Is there any "rule of thumb" as to what makes an RPN too high? Is it preferable to be under 100? Obviously, in some cases that won't be possible, but is there a desirable RPN in general?