8.3 Failure mode and effects analysis (FMEA)

Failure Mode and Effects Analysis (FMEA) is a crucial tool for identifying potential issues in prototypes. It helps teams spot and fix problems early, saving time and money while boosting product quality and safety.

FMEA breaks down prototypes into parts, looking at how each might fail. Teams rate the severity, likelihood, and detectability of issues, creating a Risk Priority Number to focus on the biggest risks first.

FMEA for Prototype Evaluation

Purpose and Benefits of FMEA

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• FMEA proactively identifies potential failures in systems, processes, or products before occurrence
• Improves reliability, safety, and quality by addressing potential issues early in development
• Prioritizes failure modes using Risk Priority Number (RPN) calculated from severity, occurrence, and detection ratings
• Reduces development time and costs while enhancing product reliability and safety features
• Increases customer satisfaction through improved product quality
• Promotes cross-functional teamwork and knowledge sharing among team members
• Provides documented evidence of due diligence in risk management for regulatory compliance and legal protection

FMEA Process and Implementation

• Breaks down prototype into components or functions for systematic examination
• Utilizes cross-functional team brainstorming sessions to identify comprehensive list of potential failures
• Incorporates historical data (past failures, customer complaints, warranty claims) for insights
• Employs complementary tools like Fault Tree Analysis (FTA) and fishbone diagrams to visualize causes
• Uses structured FMEA worksheet to organize and document identified failure modes and causes
• Establishes consistent rating scales and criteria for uniform assessment across failure modes
• Bases assessments on objective data (historical records, test results, statistical analyses) when possible
• Requires continuous monitoring and updating as prototype evolves or new information becomes available

Failure Mode Analysis

Identifying Failure Modes

• Failure modes represent ways components, subsystems, or systems fail to meet design intent or performance requirements
• Causes of failure modes stem from specific mechanisms, defects, or errors leading to failure
• Systematic analysis examines each component or function for potential failures
• Historical data provides valuable insights into potential failure modes (customer complaints, warranty claims)
• Brainstorming sessions with cross-functional teams generate comprehensive failure mode lists
• Fault Tree Analysis (FTA) visually represents potential causes of system-level failures
• Fishbone diagrams (Ishikawa diagrams) categorize potential causes of failure modes (materials, methods, machinery)

Analyzing Failure Causes

• Root cause analysis techniques identify underlying reasons for failure modes
• Physical analysis examines material properties, stress concentrations, and wear patterns
• Environmental factors assessment considers temperature, humidity, vibration, and other external influences
• Human factors analysis evaluates potential user errors or misuse scenarios
• Process capability studies determine if manufacturing processes can consistently meet specifications
• Design reviews scrutinize potential weaknesses in product architecture or component interactions
• Simulation and modeling tools predict failure behavior under various conditions (finite element analysis)

Risk Assessment and Prioritization

Severity, Occurrence, and Detection Ratings

• Severity measures seriousness of failure mode effects on system, customer, or end-user (scale 1-10)
• Occurrence represents likelihood or frequency of specific failure cause (scale 1-10)
• Detection assesses ability to identify potential failure mode before reaching customer (scale 1-10)
• Risk Priority Number (RPN) calculated by multiplying severity, occurrence, and detection ratings (RPN = S x O x D)
• Consistent rating scales ensure uniform assessment across different failure modes
• Severity examples: 1 (no effect), 5 (moderate performance degradation), 10 (safety hazard)
• Occurrence examples: 1 (1 in 1,000,000), 5 (1 in 10,000), 10 (1 in 2)
• Detection examples: 1 (certain detection), 5 (moderate chance of detection), 10 (no known detection method)

Risk Prioritization Techniques

• Rank failure modes based on RPN values (higher RPNs indicate higher priority for corrective action)
• Prioritize critical failures with high severity ratings regardless of RPN to ensure safety and reliability
• Use Pareto analysis to identify the vital few failure modes causing the majority of risk
• Employ risk matrices to visually represent severity and occurrence combinations
• Consider qualitative factors alongside quantitative RPN values (regulatory requirements, customer perception)
• Utilize criticality analysis to focus on failure modes with severe consequences and high occurrence
• Implement risk-based decision making to allocate resources effectively for risk mitigation

Action Plans for Failure Mitigation

Developing Mitigation Strategies

• Focus on reducing occurrence of failure modes, increasing detection ability, or reducing severity of effects
• Implement preventive actions to eliminate root causes of failure modes
• Enhance detection actions to improve identification of failures before reaching customers
• Utilize Design of Experiments (DOE) to optimize design parameters and reduce failure likelihood
• Implement redundancy or fail-safe mechanisms for critical systems
• Develop robust design principles to minimize sensitivity to variation (Taguchi methods)
• Establish maintenance and inspection procedures to detect and prevent failures in service

Implementing and Monitoring Action Plans

• Assign responsibilities and deadlines for each corrective action
• Track implementation progress using project management tools (Gantt charts, action item logs)
• Verify effectiveness of implemented actions through testing and data analysis
• Reassess severity, occurrence, and detection ratings after implementing corrective actions
• Calculate new RPN values to evaluate risk reduction achieved
• Update FMEA documentation to reflect changes and improvements
• Establish feedback loops to capture new failure modes or risks identified during implementation
• Conduct periodic reviews to ensure ongoing relevance and effectiveness of FMEA process