Failure Modes Effect Analysis
(FMEA)
1
Objectives
• What is FMEA?
• Why FMEA?
• When FMEA?
• Type of FMEA
• FMEA Terms
• FMEA Tools
• FMEA Procedure
• Severity, Occurrence, Detection and RPN
• FMEA Form
• Summary
• Appendices
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FMEA
Failure mode and Effect analysis is a step by step approach for identifying all possible failure in a design, manufacturing, product or
service and prevent their occurrence.
A team approach is necessary.
Team should be led by the Process Owner who is the responsible manufacturing engineer or technical person, or other similar
individual familiar with FMEA.
The following should be considered for team members:
– Engineering – Quality
– Manufacturing – Marketing
– Maintenance – Suppliers
– Purchasing
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FMEA
Why:
• Methodology that facilitates process improvement.
• Identifies and eliminates concerns early in the development of a process or design.
• Improve internal and external customer satisfaction.
• Focuses on prevention.
• FMEA may be a customer requirement.
• Reduce costs, Field failure and Scrap.
• Prioritizes risk.
A structured approach to:
• Identifying the ways in which a product or process can fail.
• Estimating risk associated with specific causes.
• Prioritizing the actions that should be taken to reduce risk.
• Evaluating design validation plan or current control plan.
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FMEA
When:
• When new systems, products, and processes are being designed.
• When existing designs or processes are being changed.
• When carry-over designs are used in new applications.
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Type of FMEA
Design:
• Analyzes product design before release to production,
focuses on failure mode associated with the product functions.
Process:
• Used to analyze manufacturing and assembly processes,
focuses on failure mode associated with the process functions.
System:
• Analyzes system and subsystem in early concept and design stages,
focuses on failure mode of function and interfaces.
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FMEA Terms
Failure:
• The loss of a function under stated condition.
Failure Mode:
• The way in which the component, subassembly, product, input, or process could fail to perform its intended function.
• If it is not detected and either corrected or removed, it may cause a negative “Effect” to occur.
• Things that could go wrong is failure mode.
Effect:
• Studying the consequences of failure mode to determine their severity.
• The adverse impact on customer requirements.
• A product or process that does not perform satisfactorily to design.
Cause:
• Whatever causes the Failure Mode to occur.
• How a specific part of the process (operation or component) can cause a Failure Mode.
• A worn spindle (cause) may cause a dimension to be out of tolerance (mode) which may cause the part to not fit (effect).
Current Controls:
• Systematized methods/devices in place to prevent or detect failure Modes or Causes (before causing effects).
• Prevention-based controls may include mistake proofing, automated controls, setup verifications, preventive maintenance,
and control charts.
• Detection-based controls may include audits, checklists, inspection, laboratory testing, and control charts.
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FMEA Terms
Function:
Describe the function in terms that can be measured.
Noun-Verb-Measurable format.
Function should be quantify in “How much (acceptance criteria)” and “When (under what condition)”
Example:
• Screw driver - Transmit Torque (when-30 N force , How much-60 N-m).
• Door handle – Transmit Force (when-applied in y direction up to 10mm, how much-30 N force).
• Steering – Road feel/Grip (when-100 km/h, how much-zero play).
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Example:
Cause Mode (Defect) Effect
Drill not properly Hole not drilled sharpened Part will not assemble straight
Part not clamped Hole not drilled square in fixture Part will not assemble straight
Drill not properly sharpened Hole not drilled Part will not assemble to proper
diameter
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FMEA Tools
Boundary Diagram:
• Boundary diagram indicates the flow of information,
energy, force, fluid etc.
• Objective of Boundary diagram is to understand
the deliverables (Input/Output) and process
(Function) from the block.
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FMEA Tools
Interface Matrix:
• Illustrates the relationships between the subsystems,
assemblies and components with in the object
as well as the interface with the neighboring systems
and environments.
• Interface matrix documents the details as type of Interface,
importance of interface and potential effect of interface.
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FMEA Tools
P-Diagram:
• P-Diagram help to understand the inputs and outputs for the design as well as those controlled and uncontrolled factors
which can impact the performance of design.
• Once inputs and outputs are identified, error state, noise factors, control factors are then established.
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FMEA Tools
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FMEA Procedure
• For each process input (start with high value inputs), determine the ways in which the input can go wrong (failure mode).
• For each failure mode, determine effects (Select a severity level for each effect).
• Identify potential causes of each failure mode (Select an occurrence level for each cause).
• List current controls for each cause (Select a detection level for each cause).
• Calculate the Risk Priority Number (RPN).
• Develop recommended actions to reduce RPN and take actions to reduce RPN.
(Give priority to high RPNs)
(MUST look at severities rated a 10)
• Assign the predicted severity, occurrence, and detection levels and compare RPNs.
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FMEA Procedure
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Severity, Occurrence, Detection and RPN
Severity
• An assessment of how serious the failure effect (due to the failure mode) is to the customer requirements.
• 1 = Not Severe, 10 = Very Severe
Occurrence
• Frequency with which a given cause occurs and creates failure modes (obtain from past data if possible).
• 1 = Not Likely, 10 = Very Likely
Detection
• The ability of the current control scheme to detect (then prevent) a given cause (may be difficult to estimate early in process
operations).
• 1 = Easy to Detect, 10 = Not easy to Detect
RPN
• RPN is the product of the severity, occurrence, and detection scores.
Severity X Occurrence X Detection = RPN
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FMEA Form
Identify failure modes and Identify causes of the Prioritize Determine and assess
their effects failure modes actions
and controls
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FMEA Form
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Summary
An FMEA:
• Identifies the ways in which a product or process can fail.
• Estimates the risk associated with specific causes.
• Prioritizes the actions that should be taken to reduce risk.
FMEA is a team tool
There are two different types of FMEAs:
• Design
• Process
• System
Inputs to the FMEA include several other Process tools such as C&E Matrix and Process Map.
Inputs Outputs
C&E Matrix
List of actions
Process Map
to prevent causes
Process History
FMEA or detect failure modes
Procedures
History of
Knowledge
actions taken
Experience
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Appendices
Effect Criteria: Severity of Effect on Product (Customer Effect) Rank
Potential failure mode affects safe use of product and / or noncompliance with government regulation. Failure will
10
occur WITHOUT warning.
Failure to Meet Safety and/or Regulatory
Requirements
Potential failure mode affects safe use of product and / or involves noncompliance with government regulation.
9
Failure will occur WITH warning.
Loss of primary function (product inoperable, does not affect safe operation of product). 8
Loss or Degradation of Primary Function
Degradation of primary function (product operable, but at reduced level of performance.) 7
Loss of secondary function. Product / item usable but comfort / convenience functions are inoperable. 6
Moderate
Degradation of secondary function. Product / item usable but comfort / convenience functions at a reduced level of
5
performance.
Appearance or Audible Noise, product operable, item does not conform and noticed by most customers (> 75%). 4
Low Appearance or Audible Noise, product operable, item does not conform and noticed by many customers (50%). 3
Appearance or Audible Noise, product operable, item does not conform and noticed by discriminating customers (<
2
25%).
None No effect. 1
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Appendices
Likelihood of Criteria: Occurrence of Cause Probable failure Rate
Rank
Failure (Design life/reliability of item/vehicle) (Incidents per item)
> 100 per thousand
Very High New Technology/new design with no history 10
> 1 in 10
50 per thousand
Fail is inevitable with new design, new application, or change in duty cycle/operating conditions 9
1 in 20
20 per thousand
High Failure is likely with new design, new application, or change in duty cycle/ operating conditions. 8
1 in 50
10 per thousand
Failure is uncertain with new design, new application, or change in duty cycle/ operating conditions. 7
1 in 100
2 per thousand
Frequent failures associated with similar designs or in design simulation and testing. 6
1 in 500
0.5 per thousand
Moderate Occasional failures associated with similar designs or in design simulation and testing. 5
1 in 2000
0.1 per thousand
Isolated failures associated with similar designs or in design simulation and testing. 4
1 in 10,000
0.01 per thousand
Only isolated failures associated with almost identical design or in design simulation and testing. 3
1 in 100,000
Low
< 0.001 per thousand
No observed failures associated with almost identical design or in design simulation and testing. 2
1 in 1,000,000
Failure is eliminated through preventive
Very Low Failure is eliminated through preventive control. 1
control.
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Appendices
Likelihood of
Opportunity for Detection Criteria: Likelihood of Detection by Design Control Rank
Detection
No detection opportunity No current design control; Cannot detect or is not analyzed. 10 Almost Impossible
Design analysis/detection controls have a weak detection capability; Virtual Analysis (e.g., CAE, Very
Not likely to detect at any stage 9
FEA, etc.) is not correlated to expected actual operating conditions Remote
Product verification/validation after design freeze and prior to launch with pass/fail testing
(subsystem or system testing with acceptance criteria such as ride and handling, shipping 8 Remote
evaluation, etc.).
Product verification/validation after design freeze and prior to launch with test to failure testing
Post Design Freeze and prior to launch (subsystem or system testing with acceptance criteria such as ride and handling, shipping 7 Very Low
evaluation, etc.).
Product verification/validation after design freeze and prior to launch with degradation testing
(subsystem or system testing with acceptance criteria such as ride and handling, shipping 6 Low
evaluation, etc.).
Product validation (reliability testing, development or validation tests) prior to design freeze 5 Moderate
using pass/fail testing (e.g., acceptance criteria for performance, function checks, etc.).
Prior to Design Freeze Product validation (reliability testing, development or validation tests) prior to design freeze 4 Moderately High
using test to failure testing (e.g., acceptance criteria for performance, function checks, etc.).
Product validation (reliability testing, development or validation tests) prior to design freeze 3 High
using degradation testing (e.g., acceptance criteria for performance, function checks, etc.).
Design analysis/detection controls have a strong detection capability. Virtual analysis (e.g., CAE, 2 Very High
Virtual Analysis - Correlated FEA, etc.) is highly correlated with actual or expected operating conditions prior to design freeze.
Failure cause or failure mode can not occur because it is fully prevented through design solution 1 Almost Certain
Detection not applicable; Failure Prevention (e.g., proven design standard, best practice or common material, etc.).
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