搜索
PlaybookTopic25Page1FailureModesandEffectsAnalysis(FMEA)OverviewWhyAFailureModesandEffectsAnalysis(FMEA)isameanstoidentifywaysthataproductorprocesscanfail.Itoffersastrategytoplanforpreventionoffailure.HowAnFMEAwillidentifypotentialfailuremodesandratetheseverityoftheireffect.Itwillofferanobjectiveevaluationoftheoccurrenceofcausesandtheabilitytodetectwhenthosecauseswilloccur.Itwillrankorderthepoten-tialproductandprocessdeficienciesandfocusoneliminatingproductandprocessconcerns.Inshort,itisatoolthathelpspreventproblemsfromoccurring.TherearethreetermsusedinaspecificwayinFMEA.FailureMode:Themannerinwhichapartorprocesscanfailtomeetspecification.Itisusu-allyassociatedwithadefectornon-conformance.Effect:Theimpactonacustomerifafailuremodeisnotpreventedorcorrected.Thecus-tomercanbeanimmediateoneoronedownstream.Cause:Adeficiencythatresultsinafailuremode.Causesaresourcesofvariabilityassoci-atedwithkeyprocessinputvariables.AnFMEAisbestwhenitispreparedbyateam.Theteamshouldbemadeupofpeoplefromallareasimpactedbytheprocess.TheFMEAisusefulinanumberofapplica-tions:indeterminingXs,helpingtodefinepro-cessimprovementsandcontrols,andothers.TYPESofFMEATherearethreetypesofFMEA:•ASystemFMEAisusedtoanalyzesys-temsandsubsystemsinearlyconceptanddesignstages.Itfocusesonpotentialfailuremodesassociatedwiththefunctionsofasystemcausedbydesign.•ADesignFMEAisusedtoanalyzeprod-uctsbeforetheyarereleasedtoproduction.•AProcessFMEAisusedtoanalyzemanu-facturing,assembly,andtransactionalproc-esses.StepsintheFMEAProcessTherearethreestepstotheprocessofcreatinganFMEA:Preparation;FMEAProcess,andImprovement.Preparation1.AnFMEAbeginswithaprocessmap.Identifytheprocessandmapitskeysteps.2.Listthekeyprocessoutputstosatisfycus-tomerrequirements.3.Listthekeyprocessinputsforeachprocessstep.4.Defineamatrixrelatingproductoutputstoprocessvariables.5.Rankinputsaccordingtotheirimportance.Thegoalinyourpreparationistohaveacom-pleteunderstandingoftheprocessyouareanalyzing.Whatareitssteps?Whatareitsin-putsandoutputs?Howdotheyrelate?ThisstepbeginswithaCauseandEffectdia-gram.Listthewaysprocessinputscanvary,andthecauses.Thenidentifyassociatedfailuremodesandeffects.PLAYBOOKPLAYBOOKPLAYBOOKSixSigmaPLAYBOOKTopic25PlaybookTopic25Page2UsinganFMEAspreadsheet,listothercausesandassociatedfailuremodesandeffects.Assignseverity,occurrenceanddetectionrat-ingstoeachcause.Eachratingisanumericalratingfrom1to10,with10beingtheworst.Ratingsservetoquantifytheanalysis.•Severityratings(SEV)tellhowsignificanttheimpactoftheeffectistothecustomer.•Occurrenceratings(OCC)definethelikeli-hoodofthecauseofthefailuremodetooc-cur.•Detectionratings(DET)tellthelikelihoodthatthecurrentsystemwillnotdetectthecauseorfailuremodeshoulditoccur.Thetableonthenextpagegivessomeguide-linesforratings.PlaybookTopic25Page3RATINGDEGREEOFSEVERITYLIKELIHOODOFOCCURRENCEABILITYTODETECT1Customerwillnotnoticethead-verseeffectoritisinsignificantLikelihoodofoccurrenceisremoteSurethatthepotentialfailurewillbefoundorpreventedbeforereachingthenextcustomer2CustomerwillprobablyexperienceslightannoyanceLowfailureratewithsup-portingdocumentationAlmostcertainthatthepotentialfailurewillbefoundorpreventedbeforereachingthenextcustomer3Customerwillexperienceannoy-anceduetotheslightdegradationofperformanceLowfailureratewithoutsupportingdocumentationLowlikelihoodthatthepotentialfailurewillreachthenextcustomerunde-tected4CustomerdissatisfactionduetoreducedperformanceOccasionalfailuresControlsmaydetectorpreventthepotentialfail-urefromreachingthenextcustomer5CustomerismadeuncomfortableortheirproductivityisreducedbythecontinueddegradationoftheeffectRelativelymoderatefailureratewithsupportingdocu-mentationModeratelikelihoodthatthepotentialfailurewillreachthenextcustomer6Warrantyrepairorsignficantmanufacturingorassemblycom-plaintModeratefailureratewith-outsupportingdocumenta-tionControlsareunlikelytodetectorpreventthepo-tentialfailurefromreach-ingthenextcustomer7Highdegreeofcustomerdissatis-faction.Componentfailurewith-outcompletelossoffunction.Pro-ductivityimpactedbyhighscraporreworklevels.Relativelyhighfailureratewithsupportingdocumen-tationPoorlikelihoodthatthepotentialfailurewillbedetectedorpreventedbe-forereachingthenextcustomer8Veryhighdegreeofdissatisfac-tion.Lossoffunctionwithoutanegativeimpactonsafetyorgov-ernmentalregulations.HighfailureratewithoutsupportingdocumentationVerypoorlikelihoodthatthepotentialfailurewillbedetectedorpresentedbeforereachingthenextcustomer9Customerendangered.Adverseeffectonsafesystemperformancewithwarningbeforefailureorviolationofgovernmentalregula-tionsFailureisalmostcertainbasedonwarrantydataorsignificantDVtestingCurrentcontrolsprobablywillnotevendetectthepotentialfailure10Customerendangered.Adverseeffectonsafesystemperformancewithoutwarningbeforefailureorviolationofgovernmentalregula-tionsAssuredoffailurebasedonwarrantydataorsignificantDVtestingAbsolutecertaintythatthecurrentcontrolswillnotdetectthepotentialfailurePlaybookTopic25Page4CalculatetheRiskPriorityNumber(RPN).Thisisacalculationoftherelativeriskofapar-ti