What Is FMEA?
Failure Mode and Effects Analysis is a structured method for identifying what could go wrong in a process or product design, assessing the risk of each potential failure, and prioritizing actions to prevent the highest-risk failures. It is proactive problem solving — finding and fixing problems before they happen, not after.
FMEA was developed by the U.S. military in the 1940s, adopted by NASA, and became a standard requirement in automotive (AIAG) and aerospace manufacturing. Today it is used across every industry where failure has consequences.
Two Types of FMEA
| Type | Focus | When | Who Leads |
|---|---|---|---|
| Design FMEA (DFMEA) | What could go wrong with the product design? | During product development, before release to production | Design / product engineering |
| Process FMEA (PFMEA) | What could go wrong in the manufacturing process? | Before production launch, updated throughout production life | Manufacturing / process engineering |
This guide focuses on Process FMEA, which is what most manufacturing teams work with daily. The methodology is the same for both types.
The FMEA Structure
For each process step, the team identifies:
RPN Scoring
Each failure mode is scored on three dimensions, each rated 1-10:
| Rating | Severity (S) | Occurrence (O) | Detection (D) |
|---|---|---|---|
| 1 | No effect | Extremely unlikely (<1 in 1M) | Almost certain to detect |
| 2-3 | Minor annoyance / cosmetic | Very low (1 in 100K) | High probability of detection |
| 4-6 | Moderate — customer dissatisfied, partial function loss | Moderate (1 in 1,000) | Moderate detection capability |
| 7-8 | High — major function loss, customer very dissatisfied | High (1 in 100) | Low detection — likely to escape |
| 9-10 | Safety/regulatory — hazard without warning | Very high (1 in 10+) | No detection — will reach customer |
RPN Formula
RPN = Severity × Occurrence × Detection
Range: 1 to 1,000. Higher RPN = higher risk = higher priority for action. But do not use RPN blindly — a failure with Severity 10 (safety) and low occurrence still needs attention regardless of the total RPN.
FMEA Example
| Step | Failure Mode | Effect | Cause | S | O | D | RPN |
|---|---|---|---|---|---|---|---|
| Install gasket | Gasket missing | Oil leak in field, warranty claim | No poka-yoke, operator skips step | 8 | 4 | 7 | 224 |
| Torque bolt | Under-torqued | Joint loosens, noise, potential safety | Torque wrench not calibrated | 9 | 3 | 5 | 135 |
| Apply label | Wrong label | Customer confusion, recall risk | Multiple labels at station, no verification | 7 | 5 | 6 | 210 |
Taking Action
The FMEA is useless without actions. For high-RPN items, the team assigns:
| Action Type | Target | Example |
|---|---|---|
| Reduce Severity | Change design to make failure less impactful | Add redundant seal so single gasket failure does not cause leak |
| Reduce Occurrence | Prevent the cause from happening | Install poka-yoke fixture that will not close without gasket |
| Reduce Detection | Make the failure easier to catch before it leaves | Add vision system to verify label after application |
Prioritize Occurrence Over Detection
The best FMEA actions reduce occurrence (prevent the failure) rather than improve detection (catch it after it happens). Installing a poka-yoke (O drops from 4 to 1) is always better than adding an inspection step (D drops from 7 to 3). Prevention beats detection. See jidoka.
Running an FMEA Session
✅ FMEA That Drives Improvement
- Cross-functional team with operator input
- Done at the gemba, not in a conference room
- Honest scoring — high RPNs are opportunities
- Actions prioritize prevention over detection
- Living document updated with process changes
❌ FMEA Theater
- Done by one engineer alone at a desk
- Scores kept low to avoid creating work
- Actions = "train operator" for everything
- Completed once for PPAP and never updated
- Sits in a binder for the auditor, not used by the team
🎯 Key Takeaway
FMEA is your crystal ball — it lets you see and prevent failures before they reach the customer. Build it with a cross-functional team at the gemba, score honestly, prioritize prevention over detection, and keep it alive as a working document. The best time to do an FMEA is before production launch. The second best time is today. Pair it with poka-yoke for the highest-RPN items and SPC for ongoing monitoring.
Interactive Demo
Adjust the Severity, Occurrence, and Detection ratings for each failure mode. Watch the RPN scores update and the priority ranking shift in real time.
Stop reading, start modeling
Model your process flow, run simulations, optimize staffing with TOC math, and test your knowledge with 107 interactive checks — all in one platform.