SC QUALITY GUILDFMEA worksheet
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Failure modes, effects and causes scored for severity, occurrence and detection, with the RPN calculated, the rows ranked and the high-severity ones flagged.
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What an FMEA is
Failure mode and effects analysis is a structured way of asking, step by step, how could this go wrong, what would happen, and why would it happen? before it does. A process FMEA works through the steps of a process; a design FMEA works through the functions of a product. The output is a ranked list of risks and the actions taken to reduce them.
Reading the columns
- Failure mode: how the step fails to do its job (seal nicked, seal missing).
- Effect: what the customer, the next step or the user experiences as a result.
- Severity (S): how serious that effect is, 1 to 10.
- Cause: why the failure mode happens. One row per cause.
- Occurrence (O): how often the cause is expected to happen, 1 to 10.
- Current controls and detection (D): how likely the failure is to get past today's controls undetected, 1 to 10, where 10 means it will almost certainly not be caught.
The risk priority number is RPN = S × O × D, from 1 to 1000.
The trouble with RPN
RPN is easy to calculate and easy to misread. The same number can describe very different risks: 9 × 2 × 5 and 3 × 6 × 5 are both 90, but the first is a severe effect and the second a nuisance. That is why the worksheet shades every row with severity 9 or 10, and flags equal RPNs with different severities. A high-severity failure needs attention however low its RPN.
This is also why the 2019 AIAG and VDA FMEA handbook replaced RPN with an action priority rating that weighs severity first. Many companies, and the Yellow Belt exam, still use RPN, so it is used here; if your customer requires action priority, use their table for the ranking.
After the action
An FMEA is not finished when the actions are assigned. Re-score each row after its action is in place. Severity normally stays the same, because an action rarely changes how bad the effect would be; occurrence or detection should fall. If neither does, the action did not reach the cause.
On the Yellow Belt exam
FMEA is topic IV.A.2 of the 2022 CSSYB Body of Knowledge. Expect to calculate an RPN, to say which of several rows to act on first, and to know which of the three ratings an action is likely to change.