FMEA Explained: Failure Mode and Effects Analysis Fundamentals
Quick answer: FMEA is a structured method for finding the ways a product or process could fail, judging how serious each failure would be, and fixing the highest-risk ones before they happen. Each potential failure is scored on Severity, Occurrence, and Detection (1–10 each); multiplying them gives a Risk Priority Number (RPN) that tells you what to tackle first.
Design FMEA vs. Process FMEA
- Design FMEA (DFMEA) examines how a product's design could fail — a weak part, a tolerance, a material choice.
- Process FMEA (PFMEA) examines how a manufacturing or assembly process could fail — a missed step, a machine setting, a handling error.
Most plants spend the majority of their time on PFMEA, often as part of the APQP/PPAP quality core tools.
How the Risk Priority Number Works
Each factor is rated 1–10 against agreed scales:
- Severity — how serious the effect is if the failure reaches the customer.
- Occurrence — how likely the cause is to happen.
- Detection — how likely your current controls are to catch it first (10 = almost never caught).
RPN ranges from 1 to 1000. There is no universal "pass" threshold — use RPN to rank and always act on high-severity items regardless of their RPN.
How to Run an FMEA, Step by Step
- Define the scope — the product or process and its boundaries.
- Break it into functions or process steps.
- For each, list the potential failure modes and their effects.
- Identify the likely causes and the current controls.
- Rate Severity, Occurrence, and Detection; calculate RPN.
- Prioritize and assign corrective actions to the biggest risks.
- Implement actions, then re-score to confirm the risk dropped.
Common Pitfalls
- Treating the FMEA as a one-time document instead of a living tool.
- Chasing RPN while ignoring high-severity, low-RPN failures.
- Doing it in a silo — FMEA works best as a cross-functional team exercise.
Frequently Asked Questions
What's a good RPN threshold?
There isn't a standard one. Modern guidance favors using RPN to prioritize and acting on severity first, rather than relying on a fixed cutoff.
Who should be in an FMEA?
A cross-functional team — quality, engineering, production, and maintenance — so the failure modes and controls reflect reality.
Build Quality Core-Tools Skills with Vetted Safe
Vetted Safe's Quality library covers FMEA, control plans, MSA, and the other core tools — assignable by role, tracked, and documented for audits and customer requirements.