FMEA Failure Mode And Effect Analysis
FMEA is an analytical technique that combines the technology and experience of people in identifying foreseeable failure modes of a product or process and planning for its elimination.
FMEA is defined as a systematic group of activities intended to recognize and evaluate the potential failure of a product/ process and the effects of that failure, identify actions that could eliminate or reduce the chance of the occurrence of potential failure.
It is a group of activities that involves the following:1. Recognize the potential failure of a product or process.2. Identify actions that eliminate / reduce the potential failure.3. Document the process.FMEA Failure Mode And Effect AnalysisPURPOSE OF FMEA:
Continually measuring the reliability of a machine, product or process.
To detect the potential product - related failure mode.
FMEA evaluation to be conducted immediately following the design phaseContEngineers from - Assembly - Manufacturing - Materials - Quality - Service - Supplier - Customer FMEA TEAM:
Most important characteristics of any product
Reliability may be defined as the probability of the product to perform as expected for a certain period of time, under the given operating conditions , and at a given set of product performance characteristics.
Safety is an important characteristic of reliability
Reliability Requirements
Customer and supplier may have different opinions on Failures and also about reliability
The common agreement on what contributes reliability should be defined in terms of influence on other related systems, the reliability of past similar systems, the complexity of the failure and the relative criticality of failure.ReliabilityBased on the main system such as Part, Assembly, or process under consideration, the following should be computed the reliability of each sub system and the factors involved in the reliability must be found their appropriate relationship should be computed.
This information helps in managing the probability of non conformity, probability being undetected and shipped to the customer.ContMajority of the products follow a similar pattern of failures
Failures are classified into 3 types
Debug high failure at initial stage due to flaws in the designChance failure due to accidents, poor maintenance, or limitations on the design.Wear Out covers failure after the expected performance of the product or process.A successful design should fail only in the last methodFailure RateThe probability of survival are reliability can be represented as
Rt = e t
=e t/
Rt - the reliability or probability of survival - the failure ratet - the time specified for operation without failure - the mean time to failureContFailure rate = 0.002
Find the probability that it will survive or be reliable during the first 100 hours of operation???Eg., ProblemSpecifying Possibilities
FunctionsPossible Failure ModesRoot CausesEffectsDetection/Prevention
Quantifying Risk
Probability of causeSeverity of EffectEffectiveness of control to prevent causeRisk Priority Number
Stages of FMEACorrecting High Risk Causes
Prioritizing WorkDetailing ActionAssigning Action ResponsibilityCheck Points on Completion
Re-evaluation of Risk
Recalculation of Risk Priority NumberContRisk priority Number
RPN = S * O * D
S Severity
O Occurrence
D - Detection
RPN can range from 1 to 1000. 1 being the smallest risk possible.Cont.FMEA Flow ChartAssign a label to each process or system componentList the function of each componentList potential failure modesDescribe effects of the failuresDetermine failure severityDetermine probability of failure
Determine detection rate of failureAssign RPNTake action to reduce the highest riskSystem focuses on global system functions
Design focuses on components & subsystems
Process focuses on manufacturing and assembly process
Service focuses on service function
Software focuses on software function
Five major types of FMEATwo important types of FMEA are
Design FMEAAids in the design process by identifying the known and foreseeable failure modesRanking the failures based on the impact
Process FMEATo identify potential process failure modesRanking the failures and help establishing priorities
ContAnalytical technique used by FMEA teams to ensure that to the extent possible , potential failure modes and their causes/ mechanisms are considered and addressed before the design is confirmed.
A Design FMEA is an analytical technique utilized primarily by a Design FMEA team to ensure potential failure modes and their associated causes are identified, considered and addressed
Design FMEAThe hierarchy of system has to be understood
Cont..Sub system 1SystemSub system 1Sub system 1Sub system 1Subsub system 1Subsub system 1Subsub system 1Subsub system 1Subsub system 2Subsub system 2Subsub system 2Subsub system 2Applied to improving the process in contrast to the design in DFMEA
The process FMEA addresses production operations
Process FMEA results inIdentifies the process functions Identifies potential product and process related failure modesAssess the effects of failureIdentifies the causesIdentifies process variables to establish control to eliminate or reduce failureDevelops a ranked list of failure modes for prioritizing the corrective actionDocuments the RPN
Process FMEADocument and Understand existingProducts and Processes
Review current DOCUMENTATION methods for existing Products and Processes, where applicable Evaluate successes, failures, and relevance of existingDOCUMENTS
Visualize how existingProducts and Processes can be improved (or how these should be changed) utilizing FMEA methods
Consider Benchmarking (understanding best practice in the relevant industry or sector) and obtain information which could be useful for Product and/or Process improvement(s),including DOCUMENTATION Procedures
Understand the causes and magnitude of problems with existing products and/or processes, so effort is focused where it is most required
Implement plant-wide standardized forms and methods to assure consistency for FMEA DOCUMENTATION
Provide training in DOCUMENTATION proceduresDocumentation - Steps
Cont1. Part Name/No.
Enter the name and number of the system, subsystem, or component being analyzed
2. Design Responsibility
Enter the original equipment manufacturer(OEM), department, and group. Also, includethe supplier name if known.
3. Prepared by
Enter the name, telephone number, companyof the individual (engineer) responsible forpreparing the FMEA.
4. Key Date
Enter the initial FMEA due date, whichshould not exceed the scheduled productiondesign release date.
5.FMEA Date (Orig.)(Rev.)
Enter the date the original FMEA wascompiled, and the latest revision date,when applicable.
6. Core Team
List the names of the responsible individualsand departments which have the authority toidentify and/or perform tasks.(It isrecommended that all team members names,departments, telephone numbers, addresses,etc. be included on a distribution list.)
Cont7. FMEA Number
Enter the FMEA document number, which may be used for tracking
8. Item/Number
Enter the name and number of the item beinganalyzed. Use the nomenclature and show thedesign level as indicated on the engineeringdrawing.
Cont9.Potential Failure Mode
Potential Failure Mode is defined as themanner in which a component, subsystem, orsystem could potentially fail to meet the purpose.
10.Potential Effect(s) of FailurePotential Effect(s) of Failure are defined asthe effects of the failure mode on functions,as perceived by the customerCont11. Severity (S)
Severity is an assessment of the seriousnessof the effect of the potential failure mode tothe next component, subsystem, system, orcustomer .
Severity applies to the effect only.Severity should be estimated ona 1 to 10 scale.
12. Classification
This column is intended to be used toclassify any special product characteristics forcomponents, subsystems, or systems thatmay require additional process controls.
Cont13. Potential Cause(s)/Mechanism(s)of Failure
Potential cause of failure is defined as anindication of a design weakness, theconsequence of which is the failure mode. Can be corrected
14.Occurrence (O)
Occurrence is the likelihood that a specificcause/mechanism will occur. The likelihood of occurrence of potential failure cause/mechanism is estimated on a 1 to 10 scale
Cont15.Current Design/ Process Controls
There are three types of controls/features to consider, those that:
(1) prevent the cause/mechanism or failure mode/effect from occurring, or reducetheir rate of occurrence,
(2) detect the cause/mechanism and lead to correctiveactions, and
(3) detect the failure mode.
Cont16. Detection (D)
Detection is an assessment of the ability of thecurrent design/ process controls to detect a potential cause/mechanism or to detect the subsequent failure mode, before the component, subsystem, or system is released for production.
Ranking is on a scale of 1 to 10 dependent on the detection level.
17.Risk Priority Number (RPN):
The Risk Priority Number is the product of theSeverity (S), Occurrence (O), and Detection (D) ranking.
The RPN is a measure of design riskand will compute between 1 and 1,000.
Cont18.Recommended Action(s)
When the failure modes have been rankordered by RPN, corrective action should befirst directed at the highest ranked concernsand critical items.
The intent of any recommended action is to reduce any one or all of the occurrence, severity, and/ordetection rankings.
19.Responsibility and Target Completion Dates
Individuals responsible for the recommended actions and target completion dates should be mentioned for future reference.
Cont20.Actions Taken
After implementing an action, a brief description and its effective date should be mentioned
21.Resulting RPN
After corrective actions, S, O & D is calculated and RPN is re estimated and recorded.Cont
