Failure Modes and Effects Analysis (FMEA) is a systematic, proactive methodology used in Lean Six Sigma to identify and prioritize potential failures in a process, product, or service before they occur. During the Measure Phase, FMEA serves as a critical tool for understanding process risks and gui…Failure Modes and Effects Analysis (FMEA) is a systematic, proactive methodology used in Lean Six Sigma to identify and prioritize potential failures in a process, product, or service before they occur. During the Measure Phase, FMEA serves as a critical tool for understanding process risks and guiding improvement efforts.
The FMEA process involves cross-functional teams examining each step of a process to identify what could go wrong (failure modes), why it might happen (causes), and what the consequences would be (effects). For each potential failure, the team assigns three numerical ratings on a scale typically from 1 to 10:
1. Severity (S): How serious is the impact if the failure occurs?
2. Occurrence (O): How likely is the failure to happen?
3. Detection (D): How easily can the failure be detected before reaching the customer?
These three scores are multiplied together to calculate the Risk Priority Number (RPN): RPN = S × O × D. Higher RPN values indicate greater risk and help teams prioritize which failure modes require attention first.
FMEA provides several benefits during the Measure Phase. It establishes a baseline understanding of process vulnerabilities, identifies critical-to-quality characteristics, and creates documentation that supports data collection planning. The analysis helps teams focus measurement efforts on high-risk areas where failures are most likely or most impactful.
There are two primary types: Design FMEA (DFMEA) focuses on product design weaknesses, while Process FMEA (PFMEA) examines manufacturing or service delivery processes.
After identifying high-priority risks, teams develop action plans to reduce severity, decrease occurrence through preventive measures, or improve detection capabilities. FMEA is considered a living document that should be updated as processes change or new information becomes available, making it valuable throughout the entire DMAIC cycle.
Failure Modes and Effects Analysis (FMEA) - Complete Guide
What is Failure Modes and Effects Analysis (FMEA)?
Failure Modes and Effects Analysis (FMEA) is a systematic, proactive method used to identify potential failures in a process, product, or system before they occur. It evaluates the severity, occurrence probability, and detectability of each potential failure mode to prioritize improvement efforts.
FMEA is a cornerstone tool in the Measure Phase of Six Sigma, helping teams understand where processes are most vulnerable and where resources should be focused.
Why is FMEA Important?
• Prevents problems before they occur - Identifies risks early in the process • Reduces costs - Fixing issues during design is cheaper than after production • Improves customer satisfaction - Leads to more reliable products and services • Prioritizes actions - Helps teams focus on the most critical failure modes • Documents institutional knowledge - Creates a record of potential failures and preventive actions • Supports regulatory compliance - Required in many industries like automotive and healthcare
How FMEA Works - The Process
Step 1: Identify the Process or Product Define the scope of the analysis and break down the process into individual steps or components.
Step 2: Identify Potential Failure Modes For each step, ask: What could go wrong? List all possible ways the process could fail.
Step 3: Determine Effects of Each Failure Describe the consequences if each failure mode occurs. Consider impact on customers, downstream processes, and safety.
Step 4: Assign Severity Rating (S) Rate the seriousness of the effect on a scale of 1-10, where 10 is most severe.
Step 5: Identify Causes of Failure Determine the root cause or mechanism that could lead to each failure mode.
Step 6: Assign Occurrence Rating (O) Rate how likely the cause is to occur on a scale of 1-10, where 10 is most likely.
Step 7: Identify Current Controls List existing controls that either prevent the failure or detect it before reaching the customer.
Step 8: Assign Detection Rating (D) Rate how likely current controls will detect the failure on a scale of 1-10, where 10 means detection is very unlikely.
Step 9: Calculate Risk Priority Number (RPN) RPN = Severity × Occurrence × Detection RPN ranges from 1 to 1,000. Higher numbers indicate higher priority for action.
Step 10: Develop and Implement Actions Create action plans for high-priority items, assign responsibilities, and recalculate RPN after improvements.
Types of FMEA
• Design FMEA (DFMEA) - Focuses on potential failures in product design • Process FMEA (PFMEA) - Focuses on potential failures in manufacturing or business processes • System FMEA - Analyzes failures at the overall system level
Key Terms to Remember
• Failure Mode - The way in which a component, subsystem, or system could potentially fail • Effect - The consequence of the failure mode • Cause - The reason why the failure mode could occur • RPN - Risk Priority Number used to prioritize failures • Current Controls - Existing measures to prevent or detect failures
Exam Tips: Answering Questions on FMEA
1. Memorize the RPN Formula Remember: RPN = S × O × D. Many exam questions will ask you to calculate RPN or identify which component affects it.
2. Understand the Rating Scales All three ratings (Severity, Occurrence, Detection) use a 1-10 scale. Note that for Detection, a higher score means harder to detect, which is counterintuitive for some candidates.
3. Know the Purpose of Each Rating • Severity measures impact • Occurrence measures frequency/probability • Detection measures ability to catch the failure
4. Focus on Prioritization FMEA is primarily about prioritizing which failures to address first. Higher RPN = higher priority.
5. Recognize When FMEA is Applied FMEA is a proactive tool used before failures occur, not as a reactive measure.
6. Distinguish Between DFMEA and PFMEA Design FMEA addresses product design issues; Process FMEA addresses manufacturing or operational process issues.
7. Practice Scenario Questions Be prepared to identify appropriate actions based on which rating is highest. For example, if Severity is high but unchangeable, focus on reducing Occurrence or improving Detection.
8. Remember the Team Approach FMEA is conducted by cross-functional teams, not individuals working alone. This ensures comprehensive identification of failure modes.