Steps
1. Open the FMEA Document in Risksheet
Navigate to the Risks space and open your FMEA document (System FMEA, Design FMEA, or Process FMEA) using the ** Open in Risksheet** button.
2. Locate the Rating Columns
Scroll to the ratings section of the risksheet. You’ll see three assessment columns:
- Severity — Impact of the failure effect on the customer/system
- Occurrence — Likelihood of the failure cause happening
- Detection — Probability that current controls will detect the failure before it reaches the customer
If using progressive workflow views, the ratings columns appear in the “Risk Assessment” view (typically View 4-5 in the workflow). See Use Progressive Workflow Views for navigation guidance. 3. Assess Severity
Click the Severity cell for the failure mode and select a rating from 1 to 10:
| Rating | Impact | Examples |
|---|
| 10 | Hazard without warning | Loss of vehicle control, no warning to driver |
| 9 | Hazard with warning | Loss of braking, ABS warning lamp active |
| 7-8 | Very high disruption | Vehicle inoperable, towed to dealer |
| 5-6 | Moderate disruption | Partial feature loss, service visit required |
| 3-4 | Minor inconvenience | Cosmetic defect, reduced performance |
| 1-2 | No noticeable effect | Undetectable by customer |
If the failure mode relates to a hazard with ASIL classification (from HARA), ensure the severity rating aligns with the hazard severity. ASIL D hazards should typically have severity 9-10, ASIL C: 7-8, ASIL B: 5-6, ASIL A: 3-4.
4. Assess Occurrence
Click the Occurrence cell and select a rating from 1 to 10 based on failure probability:
Rating Probability Cpk Prevention Effectiveness
------ ----------------- ------- ---------------------------
10 Very High (1/2) < 0.33 No proven prevention
9 High (1/8) 0.33 No proven prevention
8 High (1/20) 0.51 No proven prevention
7 Moderate (1/80) 0.67 Low prevention
6 Moderate (1/400) 0.83 Low prevention
5 Low (1/2000) 1.00 Moderate prevention
4 Low (1/15k) 1.17 Moderate prevention
3 Very Low (1/150k) 1.33 High prevention
2 Remote (1/1.5M) 1.50 Proven effective prevention
1 Almost Never > 1.67 Prevention near-perfect
For Process FMEA (PFMEA), use historical defect rates from production data or Cpk values from Statistical Process Control (SPC) charts. If Cpk ≥ 1.33, occurrence should be rated 3 or lower.
5. Assess Detection
Click the Detection cell and select a rating from 1 to 10. Note the inverted scale: lower numbers = better detection.
| Rating | Detection Likelihood | Control Method |
|---|
| 1 | Almost Certain | Error-proof design (poka-yoke) |
| 2 | Very High | Automated detection prevents defect progression |
| 3 | High | In-process gauging with automated alerts |
| 4 | Moderately High | Variable gauging after processing |
| 5 | Moderate | 100% manual attribute gauging |
| 6 | Low | SPC charting or post-process gauging |
| 7 | Very Low | Double visual inspection |
| 8 | Remote | Single visual inspection |
| 9 | Very Remote | Random or sporadic checks |
| 10 | Almost Impossible | No detection controls |
Detection ratings work opposite to Severity and Occurrence. Detection 10 = worst case (no controls), Detection 1 = best case (error-proof design). Many users accidentally reverse this scale when first learning FMEA.
6. Review Calculated RPN or Action Priority
After entering all three ratings, the risksheet automatically calculates:
- RPN (Risk Priority Number) = Severity × Occurrence × Detection (range: 1-1000)
- Action Priority = H/M/L classification per AIAG-VDA 2019 methodology
The Action Priority logic uses decision matrices combining S/O/D ratings rather than simple RPN thresholds. High Action Priority (H) triggers mandatory corrective action.
AIAG-VDA 2019 deprecated pure RPN-based prioritization. A failure mode with S=9, O=2, D=2 has RPN=36 (low), but the high severity should trigger Action Priority H. The Action Priority methodology prevents severity-9/10 failure modes from being ignored due to low occurrence.
Verification Steps
You should now see:
- ✅ All three rating columns populated (no cells showing “0 - Unanalyzed”)
- ✅ RPN values calculated in the RPN column (or Action Priority in the AP column)
- ✅ High-severity failure modes highlighted (if cell styling rules are configured)
- ✅ Action Priority “H” items flagged for mitigation planning
Next Step: Proceed to Calculate Action Priority to interpret the risk classification and determine which failure modes require corrective action.
See Also
