Fmea Process
Transcript of Fmea Process
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PROCESS FMEAPROCESS FMEA
FAILURE MODE & EFFECT ANALYSISFAILURE MODE & EFFECT ANALYSIS
PFMEAPFMEA
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OriginUS-Space program and defence safety system in 1960’s
Common Definitions Function :
Function of the item being analysed to meet the Design intent. Includes information regarding the environment in which this system operates.
Failure Mode:
A ‘Failure Mode’ is the manner in which a component, assembly or system could potentially fail to meet the design intent. Typical failure mode may includes, not limited to :
Yield; Fatigue; Material Instability; creep; wear; corrosion;
Cracked Deformed; Leaking.
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PROCESS FMEAPROCESS FMEAWhat is FMEA?
FMEA is a systemised group of activities to:
1. recognise and evaluate the potential failure of a product /
process and its effects
2. identify actions which could eliminate or reduce the chance
of potential failure occurring
3. document the process
Why FMEA ?
1. For a company policy where continuous improvement is
emphasized for its product, process
2. FMEA is a living document
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A Who should do FMEA?
1. Cross Functional Team Effort – with a leader
2. Team of knowledgeable individuals Ex. Expertise in Design,
Mfg., Assly., Quality., etc.
3. Team should include representatives of sub-contractors and/or
customers
When FMEA should be done ?
1. Essence is timeliness
2. Pro-Active rather than reactive
3. Before process failure mode occurs
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A Advantages of FMEA
1. Avoids late change crisis
2. Reduces or eliminates chance of
implementing corrective change
3. excellent technique for preventive action
4. interactive process which is never ending
Types of FMEA
1. System FMEA – Power transmission system
2. Design FMEA – Axle shaft
3. Process FMEA – Heat treatment
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A QS-9000 requirements
FMEA shall consider special characteristics Aiming defect prevention rather than defect detection Use FMEA manual & CFT approach
Potential – Process FMEA
Potential Means ‘Anticipated’
It is an analytical technique to assure that potential failure
mode and their associated causes have been considered and
addressed.
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FOR FMEA FORMAT
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Function/ RequirementsPotential Failure
Mode
PotentialEffect(s) of
Failure
Specify the description andFunction of the process
List out Outputs of the Process
ExampleProcess function / description- Manual application of wax
inside door- Machining of outer diameter
Requirements- To cover inner door at minimum
thickness to retard corrosion- Outer diameter, run-out, free
from tool mark
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Potential Failure Mode PotentialEffect(s) of
Failure
Sev
Two Assumptions are1. Consider all inputs are acceptable2. Consider the Design is acceptable List the failure modes those are
possible to occur against therequirements specified in theprevious column.
Apart from Engg. Specification, whatwould a customer considerobjectionable
CUSTOMER is- Next opn.- Subsequent Opn.- End user
ExampleBent, Diameter oversize, Diameterundersize, Cracked, Deformed, OpenCircuited, BurredOD not clear – Is it a failure mode inmachining of casting / forging?
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Potential Effect(s) of Failure Sev Class List the effects of failure in
- Next operation- Subsequent operations- Customer- End user/ Environment
Describe the effects using theterminology specified in Severity ratingtable
For each failure mode, more than oneeffect can be listed
Example- Cannot locate- Cannot face- Does not fit- Does not match- Scrap, re-work- Vehicle / item inoperable- Loss of primary function- Customer dissatisfaction
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FOR SEVIORITY RANKING
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Severity ClassPotential Cause(s)/ Mechanism (s) of
Failure
Assess the seriousness of the effect ina 1-10 scale
This rating applies to EFFECT only(i.e. previous column)
Consider the Design FMEA Consult subsequent Mfg./ Assembly
plant Safety related effects should be rated
in Nos.9 or 10 While giving ranking consider only the
required criteria (i.e. next opn. /vehicle)
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Classification
PotentialCause(s) /
Mechanism(s) of Failure
Occur
Classify special productcharacteristics (e.g. critical,key, major)
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Potential Cause(s) / Mechanism (s) of FailureOccur
CurrentProcessControl
prevention
CurrentProcessControl
detection
List the first level potential causes such as- man- machine- tool- process parameter- fixture etc.
List the root causes under the first level causesusing WHY? WHY? analysis
Describe the causes in such a way that can beeliminated or controlled
Don’t use ambiguous statements such as- operator mal-functioning- fixture problem etc.
Use the cause and effect diagram, if required consider input materials in last iteration of cause
analysis
Contd.….
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Potential Cause(s) / Mechanism (s) of FailureOccur
CurrentProcessControl
Prevention
CurrentProcessControl
detectionExampleUnder Man
- Fails to clean- Fails to assemble- Fails to tight- Mis-locate
Under machine- inadequate lubrication- excessive vibration- excessive spindle run-out
Under process- improper time / temperature- inadequate gating / venting
Under design- Symmetric design- Difficult to assemble
Under Raw Material- Mixed material- New source- Alternate material- Excessive hardness
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Occurrence
CurrentProcessControlspreventi
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CurrentProces
sControl
sDetecti
on Estimate the probability of
occurrence on a 1-10 scale Rate against each causes Use past data as a basis
(cpk/rejection %) for ranking Document the basis of
occurrence ranking For a new process, if there is no
previous experience, use teamjudgement
Don’t consider failure-detectingmeasures while giving ranking(100% inspection.)
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PreventionCurrent Process Control
Detection
Detect
RPN
Type of Controls
Level Type ExamplesP-Prevention
Prevention ofcauses
Mistake proofing
D-Detection
Detection of causes& leading tocorrective actionsDetection of defect
SPC, Visualcontrol etc. 100%inspection, patrolinspection
List the existing controls, which can detect the causes or failure mode While listing, specify the frequency of detection measures
Examples- Visual Check, one per shift for film thickness- SPC chart five pieces in an hour- On-line monitoring of crimping force- Auto-control of temperature- 100% on-line inspection- Visual monitoring of Ammeter
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Detection RPNRecommended
Action
Assess the probability of controlslisted in the previous column,which will detect the cause orfailure mode
While giving ranking, assume thefailure is occurred
Don’t assume ranking is lowbecause the occurrence is low
Random controls should notinfluence detection ranking
One detection ranking can beassigned to multiple controls
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RPNRecommended Action
Responsibility & TargetCompletion
Date
Risk Priority Numberis the multiplication ofseverity x occurrencex detection.
While calculatingRPN, consider onlyhighest severity ratingof each failure mode
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Recommended Action
Responsibility& Target
CompletionDate
ActionResults
Policy for RPN to take action- define a target RPN and anything
above that can be considered foraction. For Ex. It can be 50.Considering 95% of the failures areattended
- consider only high priority no. fortake action and review periodically
As a first priority, take action on causesto reduce occurrence ranking
The next priority is to consider actionon controls to reduce detection ranking
severity ranking can be reduced by- elimination of failure mode by
change in processes or design
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Responsibility & TargetCompletion Date
Actions
Taken
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Specify the responsibilityand target completion datefor every actions identified
During APQP, the FMEAcompletion dates should beprior to Production run
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Action Results
Actions TakenSev
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Det RPN
Describe the verification results Where effectiveness measure is
required, specify the target dateaccordingly
After the assessment of theactions taken, re-assess thevalues of severity, occurrence,detection and RPN
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Follow up actions
The Process - responsible engineer is responsible for ensuring that all
actions recommended have been implemented or adequately addressed
. FMEA is a living document and should always reflect the latest design
level as well as the latest relevant actions.
The Process responsible engineer has several means of ensuring that
concerns are identified and that recommended actions are implemented .
they includes but not limited to followings :
1 Ensuring design requirements are achieved
2 Reviewing engineering drawings & specifications
3 Conforming incorporation in assembly / manufacturing
documentation &
4 Reviewing process FMEA & Control plans
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PROCESS FMEA QUALITY OBJECTIVES
1 PROCESS IMPROVEMENTS: The FMEA drives process improvement asprimary objective. With an emphasis on Error / Mistake proofing solutions
2 HIGH RISK FAILURE MODES: The FMEA address all high-risk failuremodes as identified by FMEA team, with executable action plans. All otherfailure modes are considered.
3 CONTROL PLANS: The pre launch and production Control Plan consider thefailure modes from the process FMEA.
4 INTEGRATION: The FMEA is integrated and consistent with process flowdiagram and the process control plan. The process FMEA considers thedesign FMEA, if available as part of its analysis.
5 LESSONS LEARNED: The FMEA considered all major “ lessons learned “ asinput to failure mode identification
6 SPECIAL OR KEY CHARACTERISTICS: the FMEA identifies appropriatekey characteristics candidates as input to the key characteristics selectionprocess , if applicable due to company policy.
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ES 7 TIMING: The FMEA is completed during the “ Window of opportunity “
where it could most efficiently impact the product design of product or
process.
8 TEAM: The right people participate as part of the FMEA team through
out the analysis and are adequately trained in FMEA methods
9 DOCUMENTATION: the FMEA is completely filled out “ by the book ”
including “ action plan ” and new RPN values.
10 TIME USAGE: Time spent by FMEA team as early as possible is an
effective & efficient use of time, with a value –added result. This
assumes recommended actions are identified as required and the
actions are implemented.
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