Six Sigma Tool Navigator: The Master Guide for Teams

Tool description

A failure mode effect analysis (FMEA) is a technique that allows a cross-functional team to identify potential failure modes or causes of failures that may occur as a result of design or process deficiencies. This analysis, furthermore, produces estimates of the effects and level of severity of failures, and it provides recommendations for corrective design or process changes.

Typical application

• To consider potential failure modes, causes, effects, and corrective action to be taken.

• To predict the reliability of complex products and processes.

• To assess the impact of failures on internal and external customers.

• To identify ways for a product or subsystem to fail meeting specifications.

Problem-solving phase

Typically used by

before

• Fault Tree Analysis (FTA)

• Process flowchart

• Process analysis

• Activity analysis

• Variance analysis

after

• Countermeasures matrix

• Defect map

• Dendrogram

• Pareto chart

• Events log

Notes and key points

Failure mode effect analysis (FMEA) applications:

• Design FMEA: Covers all new designs and major design changes to existing products or systems. Considerations: Process capability, assembling space/access for tooling, performance (test) design deviations.

• Process FMEA: Covers all planned manufacturing of assembly processes. Considerations: Manufacturing/fabrication, assembly, receiving/inspection, testing/inspection.

Optional scales for FMEA applications:

• Probability of failure occurrence (1-10): 1 = remote chance of failing, 10 = very high chance of failing.

• Degree of failure severity (1-10): 1 = not noticeable to the customer, 10- critical failure, probable loss of customer.

• Probability of failure detection (1-10): 1 = extremely low chance of escaping defects; 10 = very high chance of escaping defects.

• Risk Assessment: The higher the risk priority number (RPN), the more important is the task to eliminate the cause of failure.

RPN = occurrence rating severity rating detection rating.

Step-by-step procedure

• STEP 1 A cross-functional team determines the potential failure modes of a design or process. See example Power Relay Switch Design and Assembly.

• STEP 2 FMEA forms are distributed to the team's participants and all items on the form are explained and discussed.

• STEP 3 Scales and ratings for failure occurrence, severity, and detection are agreed upon and respective rating values assigned for each failure mode, as shown in the example.

• STEP 4 The FMEA matrix is completed and checked for accuracy. Finally, recommended action items are assigned.

• STEP 5 The finalized FMEA matrix is dated and presented to the process owner.

Example of tool application

Power Relay Switch Design and Assembly