View
526
Download
11
Category
Preview:
Citation preview
Nathan & Nathan Consultants Pvt. Ltd. NNCPL/PPT/005 1.
DESIGN FMEADESIGN FMEA
to the
Training Seminar on
FAILURE MODE & EFFECT ANALYSISFAILURE MODE & EFFECT ANALYSIS
DFMEADFMEA
Nathan & Nathan Consultants Pvt. Ltd. NNCPL/PPT/005 2.
DESIGN FMEADESIGN FMEAF
ME
A
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.
Nathan & Nathan Consultants Pvt. Ltd. NNCPL/PPT/005 3.
DESIGN FMEADESIGN 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
FM
EA
Nathan & Nathan Consultants Pvt. Ltd. NNCPL/PPT/005 4.
DESIGN FMEADESIGN FMEAF
ME
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
Nathan & Nathan Consultants Pvt. Ltd. NNCPL/PPT/005 5.
DESIGN FMEADESIGN FMEAF
ME
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
Nathan & Nathan Consultants Pvt. Ltd. NNCPL/PPT/005 6.
DESIGN FMEADESIGN FMEAF
ME
A QS-9000 requirements
FMEA shall consider special characteristics Aiming defect prevention rather than defect detection Use FMEA manual & CFT approach
Potential – Design FMEA
Potential Means ‘Anticipated’
It is an analytical technique to assure that potential failure
mode and their associated causes have been considered and
addressed.
Nathan & Nathan Consultants Pvt. Ltd. NNCPL/PPT/005 7.
DESIGN FMEADESIGN FMEADesign FMEA supports the Design process in reducing the risk of failures by :
Aiding in the objective evaluation of design requirements and design
alternatives Aiding in the initial design for manufacturing and assembly requirements Increasing the probability that potential failure modes and their effects on
system and vehicle operation have been considered in the design/
development process. Providing additional information to aid in the planning of thorough and
efficient design test and development programs Developing a list of potential failure modes ranked according to their effect
on the "customer", thus establishing a priority system for design
improvements and development testing Providing format for recommending and tracking risk reducing actions. Providing future reference to aid in analysing field concerns, evaluating
design changes and developing advanced designs.
FM
EA
Nathan & Nathan Consultants Pvt. Ltd. NNCPL/PPT/005 8.
DESIGN FMEADESIGN FMEAF
ME
A B
LO
CK
DIA
GR
AM
DESIGN FMEA - BLOCK DIAGRAMHelps to analyze the inter-relationship between various parts/subsystems within each subsystem/ system.
Example :
2
3
4 1 4
5 5
SWITCHON/OFF
C
HOUSINGA
BATTERIESB
BULBASSEMBLY
D
PLATEE+
SPRINGF
COMPONENTS
A. HOUSINGB. BATTERIES (2 D CELL)C. ON/OFF SWITCHD. BULB ASSEMBLYE. PLATEF. SPRING
ASSEMBLY METHOD
1. SKIP FIT2. RIVETS3. THREAD4. SNAP FITCOMPRESSIVE FIT
Nathan & Nathan Consultants Pvt. Ltd. NNCPL/PPT/005 9.
DESIGN FMEADESIGN FMEAIT
EM
FU
NC
T. W
OR
K S
HE
ET FOR ITEM FUNCTION WORK SHEET
CLICK HERE
FOR FMEA FORMAT
CLICK HERE
Nathan & Nathan Consultants Pvt. Ltd. NNCPL/PPT/005 10.
DESIGN FMEADESIGN FMEAIT
EM
, FU
NC
TIO
NS
& F
IAL
UR
E
System Level Sub system level Component level
Bicycle
DESIGN OBJECTIVE
1 Minimum 3000 hr. of riding withoutneed for maintenance & 10,000 hr.of riding for design life2 Accommodates mate auditscomfortably to the 99.5 th percentile3 etc.
POTENTIAL FAILURE MODE :1 Difficult to steer2 difficult to pedal
FUNCTION1 provide reliable transportation
POTENTIAL FAILURE MODE ( S )
1 Chain break frequency2 Tires require frequency
FUNCTIONS :
Frame
FUNCTION1 provide stable attachment for seatsupport
POTENTIAL FAILURE MODE ( S )
1 Structural failure of seat support2 Excessive defection of seat support
FUNCTIONS :
Provide pleasing appearance
POTENTIAL FAILURE MODE ( S )
1 Finish deteriorates2 Paint chips
Handle bar Assembly
Front wheel Assembly
Rear wheel Assembly
Sprocket Assembly
Upper frame
FUNCTION1 provide structural support
POTENTIAL FAILURE MODE ( S )
1 Structural failure2 Excessive defection
FUNCTIONS :
Provide dimensional control for correctfinishing frame geometry
POTENTIAL FAILURE MODE ( S )
1 Length of frame mounting points toolong
2 Length of frame mounting points are tooshort
Lower front Tube
Lower Rear Tube
Sprocket Tube
FOR DESIGN FMEA CHECKLIST
CLICK HERE
Nathan & Nathan Consultants Pvt. Ltd. NNCPL/PPT/005 11.
DESIGN FMEADESIGN FMEAE
XP
LA
NA
TIO
NS Item
FunctionPotent
ialFailur
eMode
PotentialEffect(s)of Failure
Specify the descriptionand Function of the item
ExampleItem function Occupant protection from
weather, noise and sideimpact
Support anchorage fordoor hardware
Nathan & Nathan Consultants Pvt. Ltd. NNCPL/PPT/005 12.
DESIGN FMEADESIGN FMEAE
XP
LA
NA
TIO
NS Potential Failure Mode Potential
Effect(s) ofFailure
Sev
Review of the past things-gone-wrong, concerns reports, andgroup brainstorming is required.
List the failure modes those arepossible to occur against therequirements specified in theprevious column.
Apart from Engg. specification ,what would a customer considerobjectionable
ExampleCracked, Deformed, Loosened,Oxidised, Leaking
Nathan & Nathan Consultants Pvt. Ltd. NNCPL/PPT/005 13.
DESIGN FMEADESIGN FMEAE
XP
LA
NA
TIO
NS Potential Effect(s) of Failure Sev
Class
List the effects of failure mode on thefunction, as perceived by thecustomer.
Describe the effects using theterminology specified in Severityrating table
For each failure mode, more than oneeffect can be listed
Example- Noise- Erratic Operation- Poor Appearance- Unstable- Intermittent Operation- Rough- Inoperative
Nathan & Nathan Consultants Pvt. Ltd. NNCPL/PPT/005 14.
DESIGN FMEADESIGN FMEAE
XP
LA
NA
TIO
NS
SeverityClass
PotentialCause(s) /
Mechanism (s)of Failure
Assess the seriousness ofthe effect in a 1-10 scale
This rating applies toEFFECT only (i.e. previouscolumn)
Safety related effectsshould be rated in Nos.9 or10
FOR SEVIORITY RANKING
CLICK HERE
Nathan & Nathan Consultants Pvt. Ltd. NNCPL/PPT/005 15.
DESIGN FMEADESIGN FMEAE
XP
LA
NA
TIO
NS
Classification
PotentialCause(s) /
Mechanism(s) of Failure
Occur
Classify special productcharacteristics (e.g. critical,key, major)
Nathan & Nathan Consultants Pvt. Ltd. NNCPL/PPT/005 16.
DESIGN FMEADESIGN FMEA
Potential Cause(s) /Mechanism (s) of Failure
Occur
CurrentProcessControl
sPreventi
on
CurrentProces
sControl
sDetecti
on
Indication of Designweakness, the consequenceof which is the failure mode.
Describe the causes in sucha way that can be eliminatedor controlled
Typical cause include : Incorrect material
specified Inadequate Design life
assumption Over-stressing Insufficient Lubrication
Capability
Typical Failure causes mayinclude, but not limited to
1 Incorrect materialspecification
2 Inadequate design lifeassumption.
3 Over stressing4 Insufficient lubrication
capability5 Inadequate / improper
Maintenance instruction6 Incorrect algorithm7 Improper software
specification / surfacefinish specification / travelspecification
8 Excessive heat9 Improper tolerance
specified
EX
PL
AN
AT
ION
S
Nathan & Nathan Consultants Pvt. Ltd. NNCPL/PPT/005 17.
DESIGN FMEADESIGN FMEA
Occurrence
CurrentProcessControlspreventi
on
CurrentProces
sControl
sDetecti
on Estimate the probability of
occurrence on a 1-10 scale Rate against each causes Use past data as a basis
(rejection %) for ranking Document the basis of
occurrence ranking For a new design, if there is no
previous experience, use teamjudgement
Don’t consider failure-detectingmeasures while giving ranking(Prototype testing, etc.)
EX
PL
AN
AT
ION
S
FOR OCCURANCE RANKING
CLICK HERE
Nathan & Nathan Consultants Pvt. Ltd. NNCPL/PPT/005 18.
DESIGN FMEADESIGN FMEAEstimate the likelihood of occurrence of potential failure cause /mechanism on 1 to 10 scale. In determining this estimate,questions such as following should be considered.
1 What is the service history / field experience with similarcomponents , sub system , or systems ?
2 Is component a carryover or similar to previous levelcomponent , subsystem or systems ?
3 How significant are changes from previous level component,subsystem or systems ?
4 Is component is radically different from previous levelcomponent, subsystem or systems?
5 Is component is completely new ?6 Has the component application changed ?7 What are the environmental changes?8 Has an engineering analysis been used to estimate the
expected the comparable occurrence rate for the application ?9 Have preventive Controls been put in place ?
EX
PL
AN
AT
ION
S
Nathan & Nathan Consultants Pvt. Ltd. NNCPL/PPT/005 19.
DESIGN FMEADESIGN FMEAE
XP
LA
NA
TIO
NS
Current Design ControlsPrevention
Current Design ControlsDetection
Detect
RPN
Type of ControlsLevel Type
PreventionPrevention of Cause ( Design Features/Design Changes)
Detection
Detection of Cause and Lead to Correctiveaction(Simulation, Model testing)Detection of Defects(Design Verification &Validation)
List the existing controls, which can detect the causes or failuremode
If one column form is used then, the following prefixes should beused P – before each prevention control D – before each Detection control
Nathan & Nathan Consultants Pvt. Ltd. NNCPL/PPT/005 20.
DESIGN FMEADESIGN FMEADetection RPN
Recommended Action
Assess the probability ofcontrols listed in the previouscolumn, which will detect thecause or failure mode
While giving ranking, assumethe failure is occurred
Don’t assume ranking is lowbecause the occurrence is low
One detection ranking can beassigned to multiple controls
FOR DETECTION RANKING
CLICK HERE
EX
PL
AN
AT
ION
S
Nathan & Nathan Consultants Pvt. Ltd. NNCPL/PPT/005 21.
DESIGN FMEADESIGN FMEAE
XP
LA
NA
TIO
NS
RPNRecommended Action
Responsibility & TargetCompletion
Date
Risk Priority Numberis the multiplication ofseverity x occurrencex detection.
While calculatingRPN, consider onlyhighest severity ratingof each failure mode
Nathan & Nathan Consultants Pvt. Ltd. NNCPL/PPT/005 22.
DESIGN FMEADESIGN FMEAE
XP
LA
NA
TIO
NS Recommended Action
Responsibility& Target
Completion DateAction Results
Policy for RPN to take action- define a target RPN and anything above that
can be considered for action. For Ex. It can be50.
- consider only high priority no. for take actionand review periodically
As a first priority, severity ranking can be reducedby elimination of failure mode by change in design
The next priority is to take action on causes toreduce occurrence ranking
consider action on controls to reduce detectionranking
Action such as , be not limited to following shouldbe considered- Review design Geometry and / or Tolerances- Revised material Specification.- DOE or other problem solving methods- Revised Test plan
Nathan & Nathan Consultants Pvt. Ltd. NNCPL/PPT/005 23.
DESIGN FMEADESIGN FMEAE
XP
LA
NA
TIO
NS
Responsibility & TargetCompletion Date
Actions
Taken
Sev
Occ
Det
RPN
Specify the responsibilityand target completion datefor every actions identified
During APQP, the FMEAcompletion dates should beprior to Design Release
Nathan & Nathan Consultants Pvt. Ltd. NNCPL/PPT/005 24.
DESIGN FMEADESIGN FMEAE
XP
LA
NA
TIO
NS
Action Results
Actions TakenSev
Occ
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
Nathan & Nathan Consultants Pvt. Ltd. NNCPL/PPT/005 25.
DESIGN FMEADESIGN FMEAE
XP
LA
NA
TIO
NS Follow up actions
The design responsible engineer is responsible for ensuring thatall actions recommended have been implemented or adequatelyaddressed .
The design responsible engineer has several means of ensuringthat concerns are identified and that recommended actions areimplemented . they includes but not limited to followings :
1 Ensuring design requirements are achieved2 Reviewing engineering drawings & specifications3 Conforming incorporation in assembly / manufacturing
documentation &Reviewing process FMEA & Control plans
Nathan & Nathan Consultants Pvt. Ltd. NNCPL/PPT/005 26.
DESIGN FMEADESIGN FMEAP
OIN
TS
TO
CO
NS
IDE
R POINTS TO CONSIDER :
Develop the Block diagram before proceeding with Design FMEA
While deciding the effect of the failure modes of the item, consider the nextsub-assembly stage onwards upto the level of end-user
Give the occurrence rating, as far as possible, based on the existing data onsimilar previous items
While listing out the Causes/ mechanism of failure, consider the indication ofDesign weakness, which leads to the failure mode.
While deciding the actions, the priority will be to
Identify design changes leading to reduction in severity Elimination of Design causes of failure leading to reduction in occurrence If any of the above is not possible, introduction of new design controls to
reduce the detection.
Nathan & Nathan Consultants Pvt. Ltd. NNCPL/PPT/005 27.
DESIGN FMEADESIGN FMEAD
FM
EA
QU
AL
ITY
OB
JEC
TIV
ES
DESIGN FMEA QUALITY OBJECTIVES
1 DESIGN IMPROVEMENTS : The FMEA drives design improvement as primaryobjective.
2 HIGH REISK FAILURE MODES : The FMEA address all high risk failure modesas identified by FMEA team , with executable action plans. All other failuremodes are considered .
3 A/D/V/ OR DVP & R PLANS : the analysis / Development / validation ( A/D/V)and / or Design verification plan and report ( DVP & R ) considered the failuremode .
4 INTERFACES : The FMEA scope includes integration and interface failuremodes in both block diagram & analysis
5 LESSONS LEARNED : The FMEA considered all major “ lessons learned “ asinput to failure mode identification
6 SPECIAL OR KEY CHARACTERISTICS : the FMEA identifies appropriate keycharacteristics candidates as input to the key characteristics selection process ,if applicable due to company policy.
Nathan & Nathan Consultants Pvt. Ltd. NNCPL/PPT/005 28.
DESIGN FMEADESIGN FMEAD
FM
EA
QU
AL
ITY
OB
JEC
TIV
ES 7 TIMING : The FMEA is completed during the “ Window of opportunity “
where it could most efficiently impact the product design
8 TEAM : The right people participate as part of the FMEA team throughout 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 aneffective & efficient use of time , with a value –added result . thisassumes recommended actions are identified as required and theactions are implemented .
Nathan & Nathan Consultants Pvt. Ltd. NNCPL/PPT/005 29.
DESIGN FMEADESIGN FMEA
Recommended