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Actions and Mitigation

Learn how to define and track corrective actions to reduce FMEA risk.

Overview​

After identifying high-RPN failure modes, the next step is defining and implementing corrective actions to reduce risk.

Mitigation Strategies​

1. Reduce Severity​

Goal: Redesign to eliminate or reduce the effect

Approaches:

  • Eliminate failure mode entirely (best option)
  • Add redundancy (backup systems)
  • Add safety features (airbags, shutoffs)
  • Isolate failure (prevent propagation)

Example:

  • Original: Battery fire (S=10)
  • Mitigation: Add thermal fuse that cuts power → S=6 (no fire, just shutdown)
Hardest to Reduce

Severity is inherent to the design and hardest to change. Often requires significant redesign.

2. Reduce Occurrence​

Goal: Prevent the cause from happening

Approaches:

  • Improve design robustness
  • Tighten tolerances
  • Use better materials
  • Add preventive controls
  • Design for manufacturing

Example:

  • Original: Weld defect (O=5)
  • Mitigation: Automated welding with real-time monitoring → O=2
Easiest to Reduce

Occurrence is often the easiest to address through design improvements or better controls.

3. Reduce Detection​

Goal: Catch failures before customer receives product

Approaches:

  • Add automated inspection
  • Improve test coverage
  • Error-proofing (poka-yoke)
  • 100% inspection vs sampling
  • Earlier testing in process

Example:

  • Original: Visual spot check (D=8)
  • Mitigation: Automated 100% inspection with reject mechanism → D=2

Defining Actions​

Action Description​

Be specific about what will be done:

✅ Good Actions:

  • "Redesign bracket with 2X safety factor (FEA analysis)"
  • "Add redundant temperature sensor (Part #TS-123) with automatic shutoff"
  • "Implement 100% automated ultrasonic weld inspection"

❌ Poor Actions:

  • "Improve design" (too vague)
  • "Better testing" (not specific)
  • "Review process" (no concrete action)

Assign Responsibility​

Clear ownership:

  • Name specific person or role
  • Include contact information
  • Ensure they have authority/resources

Examples:

  • "John Doe, Design Engineer (john@company.com)"
  • "Manufacturing Team Lead"
  • "Quality Assurance Department"

Target Date​

Realistic deadlines:

  • Based on action complexity
  • Consider resource availability
  • Critical items (RPN > 200) should be fast-tracked

Guidelines:

  • Critical (RPN > 200): 30-60 days
  • High (RPN 100-200): 60-90 days
  • Medium (RPN 50-100): 90-180 days

Action Taken​

Document what was actually done:

  • Design changes with revision numbers
  • New part numbers
  • Procedure updates
  • Test results

Example: "Added redundant temperature sensor (Part #TS-123-R2) and implemented automatic charging cutoff at 45°C. Updated design spec to Rev C. Verified through 500 charge/discharge cycles."

Tracking Actions​

Status​

Track progress:

  • Open: Not started
  • In Progress: Work underway
  • Closed: Complete and verified

Verification​

Confirm effectiveness:

  • Test new design
  • Validate new ratings
  • Monitor field data
  • Close the loop

Re-Rating After Mitigation​

After implementing actions, re-rate S, O, D:

Example: Battery Overheat​

Before Mitigation:

  • S=10, O=4, D=6
  • RPN=240 (CRITICAL)

Action: Add temperature sensor with auto-shutoff

After Mitigation:

  • S=9 (still serious, but less likely to cause fire)
  • O=2 (much rarer with new control)
  • D=3 (sensor provides detection)
  • RPN=54 (MEDIUM - acceptable)

Best Practices​

Prioritization​

Focus efforts on:

  1. RPN > 200 (critical - immediate action)
  2. High severity (S > 8) regardless of RPN
  3. RPN 100-200 (high priority)
  4. High occurrence with moderate severity

Cost-Effective Actions​

Consider:

  • Impact vs. cost
  • Implementation timeline
  • Resource requirements
  • Long-term benefits

Sometimes multiple small improvements are better than one expensive redesign.

Follow-Through​

Essential steps:

  1. Assign clear ownership
  2. Set realistic deadlines
  3. Track progress regularly
  4. Verify effectiveness
  5. Update FMEA
  6. Close the loop

Common Pitfalls​

❌ Avoid:

  • Vague action descriptions
  • No assigned owner
  • Unrealistic deadlines
  • Not verifying effectiveness
  • Closing actions prematurely

✅ Do:

  • Specific, measurable actions
  • Clear ownership
  • Achievable timelines
  • Test and verify
  • Document results

Example Action Plan​

Failure Mode: Fuel Pump Failure​

Initial Assessment:

  • Item: Electric fuel pump
  • Failure Mode: Pump fails to deliver pressure
  • Effect: Engine stalls, safety hazard (S=9)
  • Cause: Bearing wear (O=6)
  • Controls: Pressure test at assembly (D=7)
  • RPN: 378 (CRITICAL)

Action Plan:

  1. Redesign Pump (Reduce Occurrence)

    • Action: Upgrade to ceramic bearing (Part #BR-456)
    • Responsibility: John Smith, Mechanical Engineer
    • Target: 2026-02-15
    • Expected: O=6→2

  2. Add Monitoring (Reduce Detection)

    • Action: Add pressure sensor with dashboard warning
    • Responsibility: Sarah Lee, Electrical Engineer
    • Target: 2026-03-01
    • Expected: D=7→3

After Implementation:

  • S=9 (unchanged - inherent to design)
  • O=2 (improved bearing life)
  • D=3 (pressure monitoring)
  • New RPN: 54 (86% reduction!)
  • Status: Closed
  • Verification: 50,000 mile durability test passed

What's Next?​