Failure Mode and Effects Analysis (FMEA) - Complete Guide for Six Sigma Black Belt

Failure Mode and Effects Analysis (FMEA)

Why FMEA is Important

FMEA is a critical tool in the Analyze phase of Six Sigma because it helps organizations:

• Identify potential failures before they occur in production or affect customers
• Prevent problems rather than react to them after they happen
• Reduce risk by prioritizing which failures pose the greatest threat
• Improve quality and customer satisfaction by eliminating defects early
• Save costs by addressing issues before they become expensive problems
• Meet compliance requirements in regulated industries like automotive and aerospace

What is FMEA?

FMEA stands for Failure Mode and Effects Analysis. It is a systematic, proactive methodology used to identify all possible ways a product, process, or service could fail and assess the impact of those failures. FMEA helps teams understand:

• Failure modes: The ways something can go wrong
• Effects: What happens when the failure occurs
• Causes: Why the failure might happen
• Controls: Current preventive or detective measures in place

There are several types of FMEA:

• Design FMEA (DFMEA): Analyzes potential failures in product design
• Process FMEA (PFMEA): Analyzes potential failures in manufacturing or service processes
• System FMEA: Analyzes failures at the system level involving multiple components

How FMEA Works

FMEA follows a structured approach with these key steps:

Step 1: Define the Scope

Clearly define what product, process, or service will be analyzed. Establish boundaries and determine the level of detail needed.

Step 2: Assemble a Cross-Functional Team

Bring together people from different departments (engineering, manufacturing, quality, customer service) who have expertise and knowledge about the process or product.

Step 3: Identify Failure Modes

Brainstorm all possible ways the process or product could fail. Think about what could go wrong at each step. Document every potential failure mode, even those that seem unlikely.

Step 4: Determine Effects

For each failure mode, describe what would happen if it occurred. Consider impacts on:

• Customer satisfaction
• Product or service quality
• Safety
• Regulatory compliance
• Costs

Step 5: Assess Severity

Rate the severity of each effect on a scale of 1-10:

• 10: Dangerous without warning; safety hazard
• 9: Very high severity; customer very dissatisfied
• 8: High severity; major impact on customer
• 7: Moderate to high severity
• 6: Moderate severity
• 5: Low to moderate severity
• 4: Low severity
• 3: Minor severity
• 2: Very minor severity
• 1: No effect

Step 6: Identify Causes

Determine the root causes that could lead to each failure mode. Use cause-and-effect diagrams or 5-Why analysis to dig deeper.

Step 7: Assess Occurrence

Rate the likelihood that each cause will occur on a scale of 1-10:

• 10: Very high probability of occurrence
• 9: Very frequent occurrence
• 8: Frequent occurrence
• 7: Moderate occurrence
• 6: Moderate occurrence
• 5: Occasional occurrence
• 4: Low occurrence
• 3: Very low occurrence
• 2: Extremely low occurrence
• 1: No known occurrence

Step 8: Identify Current Controls

Document existing preventive controls (actions to prevent the failure) and detective controls (actions to detect the failure if it occurs).

Step 9: Assess Detection

Rate the ability of current controls to detect the failure mode before it reaches the customer on a scale of 1-10:

• 10: Unlikely to detect; no detection method
• 9: Very remote chance of detection
• 8: Remote chance of detection
• 7: Low chance of detection
• 6: Moderate chance of detection
• 5: Moderate to high chance of detection
• 4: Good chance of detection
• 3: Very good chance of detection
• 2: Nearly certain to detect
• 1: Certain to detect

Step 10: Calculate Risk Priority Number (RPN)

RPN = Severity × Occurrence × Detection

The RPN ranges from 1 to 1,000 and prioritizes which failure modes need the most attention. Higher RPN values indicate higher risk and require immediate action.

Step 11: Prioritize and Take Action

Focus on failure modes with the highest RPN values. Identify actions to:

• Reduce severity (design changes)
• Reduce occurrence (process improvements)
• Improve detection (better controls)

Step 12: Implement and Verify

Execute recommended actions, monitor effectiveness, and recalculate RPN after improvements are made.

FMEA Documentation

FMEA results are typically documented in a table format with these columns:

• Process/Component Step
• Potential Failure Mode
• Potential Effect(s)
• Severity
• Potential Cause(s)
• Occurrence
• Current Controls (Preventive)
• Current Controls (Detective)
• Detection
• RPN
• Recommended Actions
• Responsibility
• Target Completion Date
• Action Taken
• New Severity/Occurrence/Detection
• New RPN

Key Considerations in FMEA

• Team expertise: The quality of FMEA depends on team knowledge and participation
• Brainstorming: Encourage creative thinking to identify non-obvious failures
• Honesty: Be realistic about ratings; don't minimize severity or occurrence to appear better
• Continuous improvement: FMEA is not a one-time activity; update it when processes change
• Focus areas: Prioritize based on RPN, but also consider strategic importance and customer impact

Exam Tips: Answering Questions on Failure Mode and Effects Analysis (FMEA)

Tip 1: Understand the RPN Formula

Know this cold: RPN = Severity × Occurrence × Detection. Exam questions often test your ability to calculate RPN and interpret what it means. Practice calculating RPN with different values and understand that higher RPN indicates higher risk requiring immediate attention.

Tip 2: Distinguish Between DFMEA and PFMEA

Questions may ask you to identify when to use Design FMEA versus Process FMEA. Remember:

• DFMEA is used during product design phase
• PFMEA is used during process design or improvement phase

Know which type of FMEA applies in given scenarios.

Tip 3: Recognize the Proper Sequence of FMEA Steps

Exam questions may ask about the correct order of FMEA activities. The typical sequence is:

1. Define scope
2. Assemble team
3. Identify failure modes
4. Determine effects
5. Assess severity
6. Identify causes
7. Assess occurrence
8. Identify current controls
9. Assess detection
10. Calculate RPN
11. Recommend actions

Tip 4: Know the Rating Scales

Understand that Severity, Occurrence, and Detection are typically rated on a 1-10 scale. Be familiar with what represents high risk (10) and low risk (1) for each rating. Remember that Detection is inverse—a high detection rating (10) means low ability to detect.

Tip 5: Understand the Relationship Between Ratings

A failure mode with:

• High Severity, High Occurrence, High Detection Gap = Highest RPN, top priority
• High Severity, Low Occurrence, Good Detection = Moderate RPN
• Low Severity, High Occurrence, Poor Detection = Moderate RPN

Questions may test your understanding of how different rating combinations create different risk profiles.

Tip 6: Know When to Use FMEA

FMEA is most valuable:

• Early in product or process design
• When introducing new products or processes
• When making significant changes to existing processes
• For high-risk processes or safety-critical applications

Exam questions may ask when FMEA is the most appropriate tool to use.

Tip 7: Understand Prevention vs. Detection

Questions often test your understanding that:

• Preventive controls stop the failure from occurring
• Detective controls identify the failure after it occurs but before reaching the customer

Preventive controls are generally more valuable than detective controls because they eliminate the failure entirely.

Tip 8: Recognize Common FMEA Mistakes

Exam questions may present scenarios with FMEA mistakes. Watch for:

• Incomplete failure mode identification
• Inconsistent or unrealistic severity/occurrence/detection ratings
• Poor team composition lacking necessary expertise
• Failure to take action on high RPN items
• Not updating FMEA after changes are made

Tip 9: Practice RPN Interpretation

Be prepared to:

• Calculate RPN from given values
• Identify which failure mode has highest priority (highest RPN)
• Explain why an action reduces RPN (by lowering Severity, Occurrence, or Detection)
• Determine if recommended actions adequately address the risk

Tip 10: Connect FMEA to Other Six Sigma Tools

Understand how FMEA relates to:

• Cause and Effect Diagram (Fishbone): Used to identify causes in FMEA
• 5-Why Analysis: Used for root cause analysis within FMEA
• Control Plans: Developed based on FMEA findings
• Process Maps: Provide the structure for FMEA analysis

Exam questions may require you to show how these tools work together.

Tip 11: Know the Limitations of FMEA

Be aware that:

• FMEA relies on team expertise and brainstorming—failures can be missed
• It cannot identify unknown failure modes
• Rating subjectivity can affect RPN accuracy
• It requires regular updates as processes change

Tip 12: Study Real-World FMEA Examples

For exam preparation, study FMEA examples from:

• Manufacturing processes
• Service industries
• Software development
• Healthcare

Being familiar with different application contexts will help you answer scenario-based questions.

Tip 13: Understand FMEA Metrics and Outcomes

Know what success looks like in FMEA:

• Reduction in high RPN items
• Improved detection and prevention controls
• Fewer escaped defects
• Increased process robustness

Exam questions may ask about measuring FMEA effectiveness.

Tip 14: Review FMEA Forms and Documentation

Be familiar with standard FMEA documentation templates and know what information each column captures. Some questions may present FMEA tables and ask you to interpret or complete them.

Tip 15: Practice with Sample Questions

Sample question types you should prepare for:

• Calculation: Given Severity = 8, Occurrence = 5, Detection = 7, what is the RPN?
• Scenario: Should Design FMEA or Process FMEA be used for [situation]?
• Prioritization: Which failure mode requires immediate attention?
• Application: How would you reduce RPN for a specific failure mode?
• Team composition: Who should be on the FMEA team?
• Sequencing: What is the correct order of FMEA steps?

Summary

To excel on FMEA exam questions:

• Master the RPN formula and be able to calculate and interpret it
• Know the step-by-step FMEA process and recognize the proper sequence
• Understand the 1-10 rating scales for Severity, Occurrence, and Detection
• Distinguish between DFMEA and PFMEA and when to use each
• Recognize preventive versus detective controls and their relative value
• Understand how FMEA connects to other Six Sigma tools and methodologies
• Practice with realistic scenarios and calculation-based questions
• Be prepared for interpretation questions that test conceptual understanding

With thorough understanding of FMEA methodology and regular practice, you will confidently answer all exam questions related to Failure Mode and Effects Analysis.