FMEA RPN Calculator
FMEA (Failure Mode and Effects Analysis) quantifies risk with RPN = Severity × Occurrence × Detection. RPN ≥ 200 requires immediate action.
| Failure Mode | Effect | Severity S | Cause | Occurrence O | Control | Detection D | |
|---|---|---|---|---|---|---|---|
S/O/D: 1 = Least severe / Lowest / Easiest to detect, 10 = Most severe / Most frequent / Hardest to detect
Once a new product design is finalized, engineers use FMEA to systematically identify potential failure modes for each process step or component, rate Severity (S), Occurrence (O), and Detection (D), and compute the Risk Priority Number RPN = S×O×D. High-RPN items get corrective actions first, preventing problems before they occur. FMEA is a core document in APQP and PPAP approval. IATF 16949 requires manufacturers to maintain an up-to-date PFMEA for all production parts and update it promptly after design or process changes.
FMEA example (SMT reflow process): Step: solder paste printing Failure mode: paste printing offset Failure effect: solder bridging, opens → customer complaints Severity S = 8 (affects function, no safety risk) Potential cause: stencil wear Occurrence O = 5 (occasional, 1-5 per thousand) Current control: first-article visual check Detection D = 7 (hard to catch early) RPN = 8 × 5 × 7 = 280 (high risk) Recommended action: add AOI inspection, lowering D to 3 Post-improvement RPN = 8 × 5 × 3 = 120
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FMEA identifies high-risk failure modes; the Control Plan defines concrete controls for those risks — the two are tightly linked in the APQP process.
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