Tool 74: Failure Mode Effect Analysis (FMEA)

AKA

N/A

Classification

Changing/Implementing (CI)

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

→	Select and define problem or opportunity
→	Identify and analyze causes or potential change
→	Develop and plan possible solutions or change
	Implement and evaluate solution or change
	Measure and report solution or change results
	Recognize and reward team efforts

Typically used by

	Research/statistics
	Creativity/innovation
1	Engineering
	Project management
2	Manufacturing
	Marketing/sales
4	Administration/documentation
3	Servicing/support
	Customer/quality metrics
	Change management

links to other tools

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

Design/Process: Power Relay Assembly								Date:xx/xx/xx Issue No.1
Component and No: Relay Coil								Team: Power Operators
Department: Manufacturing								Process Owner: J. K. Nelson
Potential mode of failure	Potential cause of failure	Potential effect of failure	Design/process controls	Probability of failure occurance	Degree of failure severity	Probability of failure detection	Risk priority number	Recommended preventive action	Results or comments
Open winding	Boken coil wire	Relay does not operate	Cp, SPC	2	10	1	20	Pretest	Approved
Intermittent shorting	Lack of insulation	Burn out relay	Visual inspection	3	6	4	72	Change insulation	Assigned to J.P.
Note Scales are 1-10 for occurence, severity, and detection ratings. See description of rating scales for additional informtion.