PDHonline Course M347 (5 PDH)Geometric Dimensioning & Tolerancing(GD&T) and Design For Six Sigma (DFSS)2012Instructor: Robert P. Jackson, PEPDH Online | PDH Center5272 Meadow Estates DriveFairfax, VA 22030-6658Phone & Fax: 703-988-0088www.PDHonline.orgwww.PDHcenter.comAn Approved Continuing Education Providerwww.PDHcenter.comPDHCourseM247www.PDHonline.orgRobertP.JacksonPage2of39TABLEOFCONTENTSPARTIINTRODUCTION 5DESIGNFORSIXSIGMA(DFSS) 5DFSSTOOLS 7IDENTIFY0RDEFINE 8IMPORTANCEOFSIXSIGMAGOALS 9MEASUREANDANALZSE 11DESIGN 12APPLICATIONSOFTWARE 12DESIGNTOOPTIMIZE 13VALIDATE 14PARTIIGEOMETRICDIMENSIONINGANDTOLERANCING(GD&T) 14GD&TSTANDARDS 15BENEFITS 16RULES 17SYMBOLS 18MODIFYINGTOLERANCESSYMBOLS 19GD&TEXAMPLES 19FEATURECONTROLFRAME 23READINGBASICSYMBOLS 25PARTIIIDFSS&GD&T 28TOLERANCEALLOCATION 28STATISTICALALLOCATION 30EXAMPLES 32www.PDHcenter.comPDHCourseM247www.PDHonline.orgRobertP.JacksonPage3of39LISTOFFIGURESFigure1 FocusforSixSigma(DFSS) 7Figure2 ReliabilityGoalSetting 9Figure3 ProcessCapabilityBetween3Sigmaand6Sigma 10Figure4 DFSSProcess 14Figure5 ToleranceClasses 19Figure6 SplineAssembly 20Figure7 HandleUsingGD&T 20Figure8 LinearDimensioning 21Figure9 Collar(GD&T) 22Figure10 CollarinEnglishOnly 23Figure11 FeatureControlFrame 23Figure12 Flatness,Runout,Perpendicularity 26Figure13 MMC,LMC 26Figure14 BasicDimension 27Figure15 StepsforEvaluatingGapAllocation 31Figure16 GELowerDrawer 32Figure17 LoopDiagram 33Figure18 MotorAssembly 36Figure19 RefrigeratorDoorTrim 36Figure20 RefrigeratorDoorTrimEnlargement 37 LISTOFTABLESTable1 DifferencesBetweenSixSigmaandDFSS 6Table2 SixSigmavsDPMO&RTY 7Table3 DFSSTools 8Table4 GD&TCharacteristics 24Table5 ModifyingToleranceSymbols 25Table6 StandardDeviationvsProcess 29Table7 StandardDeviationvsProcess 29www.PDHcenter.comPDHCourseM247www.PDHonline.orgRobertP.JacksonPage4of39Table8 ToleranceAllocationSpreadsheet 30Table9 DimensionsandMeanValues 32CONCLUSIONS: 38REFERENCES: 39www.PDHcenter.comPDHCourseM247www.PDHonline.orgRobertP.JacksonPage5of39GeometricDimensioning&Tolerancing(GD&T)andDesignForSixSigma(DFSS)RobertP.Jackson,P.E.INTRODUCTION:Thiscourseisbasicallyintendedtoaddresstwodistinct,butrelated,areasofengineeringdesign:1.)DESIGNFORSIXSIGMA(DFSS)and2.)GEOMETRICDIMENSIONINGANDTOLERANCING(GD&T).Bothconceptshavebeenviableapproachestodesignanddetailingforsomeyearsandbothareextremelyvaluableandusefultoolsforthepracticingengineer.DFSSisastatisticalmethodofdesignthatcanserveasapredictivetooltogreatlyimprovequalitycontrol,ifusedproperlyandconsistently.GD&Tisawellacceptedmethodologyofdetailingthecharacteristics,dimensionsandtolerancesofacomponentorassemblyofcomponents.TheGD&TmethodologyisprescribedbyASME/ANSIStandardsY14.5M1994andY14.52009.ThiscourseusesthetenantsofDFSSANDGD&Ttofullydefineamechanicalcomponent,orassemblyofcomponents,sothatnomorethan3.4defectsperonemillionpartswillresultwheninuse.DFSSandGD&Tareusuallytaughtasseparatesubjectsbutcertainlycomplementeachotherasfarasdesigntools.Itismuchmoredifficulttoachievesixsigma(6)resultswithoutusingtheGD&Tapproach.ByusingstandardlineardimensioninginsteadofGD&T,hugeerrorscanbemadethatleaveroomfordoubtwhendesigningtoolsanddiesforfabrication.ThiswillbecomeapparentasweaddressGD&T.Forthisreason,Iamstructuringthecoursetoinclude,andintegrate,bothmethodologies.IwouldliketostatethatthetreatmentofDFSSandGD&Twillbesomewhatgeneralandnotindepthasfarasmathematicalmodeling,whichsometimesaccompaniescoursesofthisnature.ThereareexcellenttextsavailableonbothsubjectsbutnonethatIhavefoundintegratingbothdisciplines.Thecombinationofthesetwoisdefinitelyalogicalpresentationforbluecollar,goaloriented,workingengineersandengineeringmanagers.Thecourseisdividedintofourdistinctdivisions;i.e.1.)DFSSSurvey,2.)GD&TSurvey,3.)ProblemsolvingthatshowshowDFSSandGD&TinteractandcomplimenteachotherAND4.)TeachableQUIZ.PleasenotethatIhavechosentoconstructtheQuizattheendofthecoursetobealearningexperience.SeveralofthequestionshavedescriptiveinformationimportanttounderstandingthebasictenantsofSixSigmaandGD&T.Thisdescriptiveinformationmaynotbeinthebodyofthetextitself.Ihopetoachieveaninterestthatwillprovideimpetusforengineersandengineeringmanagerstoadoptbothdisciplinesfortheircompanies.IwouldalsostatethatbyusingDFSS,GD&TANDthetenantsofReliabilityEngineeringandReliabilityTesting,aproductcanbedesignedandmanufacturedtosatisfythemostcriticalenduser,foreitherconsumerorcommercialproducts.PARTIDESIGNFORSIXSIGMA(DFSS):DFSSistheapplicationofSixSigmaprinciplestothedesignofcomponents,subassemblies,completedproductsandtheirmanufacturingandsupportprocesses.SixSigma,bydefinition,focusesontheproductionphaseofaproduct.DFSSfocusesontheresearch,designanddevelopmentphaseofaprojectandistrulyadesigntoolthatcanandshouldbeusedbythedesignengineertomeetconsumerexpectationsanddemands.ThegoalofDFSSistoimplementtheSixSigmamethodologiesasearlyintheproductorservicelifecycleaspossible,therebyguaranteeingthemaximumreturnoninvestment(ROI).Themethodsusedtoinsurerigorinbothprocessesaresomewhatdifferent.SixSigmausestheDMAICapproach(Define,Measure,Analyze,Improve,Control).DFSSusesDMADV(Define,Measure,Analyze,DesignandVerify).PleasenotethatDFSSstrivestomeetthesamegoalsasSixSigma,thatbeingnomorethan3.4defectspermillion.Inthisrespect,theendresultsarethesame.Thetablebelowwillgiveaverybriefdescriptionofthedifferencesbetweenthetwotechnologies.www.PDHcenter.comPDHCourseM247www.PDHonline.orgRobertP.JacksonPage6of39DIFFERENCESBETWEENSIXSIGMAANDDFSS SIXSIGMA DFSSDMAIC:Define,Measure,Analyze,Improve,Control DMADV:Define,Measure,Analyze,Design,Validate DMADOV:Define,Measure,Analyze,Design, OptimizeandValidateLooksatexistingprocessesandfixesproblems. Focusesontheupfrontdesignoftheproductand processes.MoreReactive Moreproactive.Dollarbenefitsobtainedfrom6canbequantifiedquickly. Benefitsaremoredifficulttoquantifyandtendto bemorelongterm.Itcantakesixtotwelvemonths afterlaunchofthenewproductbeforeyouwill obtainproperaccountingontheimpact.Productperformanceaccomplishedbybuildandtest. Productperformancemodeledandsimulated.PerformanceandproducibilityproblemsfixedafterDesignedforrobustperformanceandproducibility.Productinuse.Qualitytested Qualitydesignedintotheproduct. Table1:DifferencesBetween6&DFSSWithDFSSyouaredesigningqualityintothecomponentorproductfromtheverystartandhopefullyeliminatingwastebyminimizingmanufacturingvariationbeforeithappens.Thisapproachallowsforcorrectingproblemsupfrontandcansignificantlyreducethecostsofredesignandtesting.Itisalsoagreatwaytomeetcustomerdemandsbyestablishingmeasurablegoals.DFSSattemptstopredicthowthedesignsunderconsiderationwillbehaveandhowtocorrectformanufacturingvariationpriortothefirstproductionrun.AgraphicalrepresentationofthedifferencebetweenDFSSandSixSigmamaybeseenasfollows,relativetoproductcosts.www.PDHcenter.comPDHCourseM247www.PDHonline.orgRobertP.JacksonPage7of39 Figure1FocusforDFSSvsSixSigma[3]Again,youcanseethatwewanttoimplementDFSSattheresearch,designanddevelopmentstagesandearlyenoughintheprojectsothatwemayintroducethecomponentorsubassemblywithminimalmanufacturingvariation.Thisisthepointwherecostsareattheirlowestandchangesaredoableinconsiderablylesstimeandwithconsiderablylessexpenditureofcapitalorhumanresources.DFSSTOOLS:InlookingatthetoolsusedwithDFSS,thefollowing,Table3,representstheentireprocess,brokendownbymajoractionitems.PleasekeepinmindthatwepickandchoosethebestapproachtoIdentify,Design,OptimizeandValidate.Allstepsalongthewaymaynotbeneededandwouldrepresentconsiderableduplicationofeffort.WEWISHTOPRODUCEAMAUNFACTUREDPRODUCTTHATWILLEXHIBITNOMORETHAN3.4DEFECTSPERMILLIONOPPORTUNITIESANDWITHTHEMAXIMUMROLLEDTHORUGHPUTYIELD.Thetablebelowwilldemonstrateourobjectives.CAPABILITY DEFECTSPERMILLIONOPPORTUNITIES ROLLEDTHROUGHPUTYEILD2 308,537 69.1%3 66,807 93.3%4 6,210 99.4%5 233 99.97%6 3.4 99.99966% TABLE2SIXSIGMAVSDPMOANDRTYwww.PDHcenter.comPDHCourseM247www.PDHonline.orgRobertP.JacksonPage8of39TABLE3DFSSTOOLS[3]LetusquicklylookateachactionitemanddefinetheactivityrequiredbeforeadvancingontothenextphaseoftheDFSSprocess.IDENTIFYORDEFINE:Themostcriticalpartoftheprocessistheveryfirstphase,IDENTIFY.Thisisthestepthatbasicallyasksthecustomer,whatdoyouwantthenthatanswer,usuallygiveningeneralities,isquantifiedintoengineeringspecifications.Iwantitthisbig,thiscolor,thisweight,thesefeatures,etcbecomesanengineeringspecificationANDengineeringdrawingthatcanbeinterpretedbyamodelshop,atoolanddiemakerandqualitycontrolinspectors.TheprocessfordoingjustthisiscalledQualityFunctionalDeploymentorQFD.QFDisaprocessthatdetailsandranksthemostdesirablefeaturesdeemedimportantbytheconsumers.Welldefinedandunambiguousrequirementsareabsolutelynecessaryandwilllessentheprobabilityoffalsestartsanddetoursinthedevelopmentprocess.Wewishtominimizetheinconsistenciesbetweenarticulationoffunctionalrequirementsandthedefinitionofsystemrequirementsandparametertargetvalues.Amatrixoffeaturesisdevelopedandratedfordesirabilitysoengineeringcantranslatethosefeaturesintohardspecifications.Thefollowingsketchwillindicateonepossibleapproachfordoingjustthat.www.PDHcenter.comPDHCourseM247www.PDHonline.orgRobertP.JacksonPage9of39Figure2ReliabilityGoalSetting[20]Thisinitialphase;i.e.QFD,allowsforproductionoftheDesignGuidancemodelandultimatelyletsuskickthetiresoftheveryfirstprototype.Wegobacktomarketing,showthemthedrawingsand/orprototypefortheirapproval.Revisionsaremadebasedupontheirdesiresandneeds.Wemaywishtoreconvenethefocusgroupofpotentialuserstogettheirimpressionsandverifythattheirneedsanddemandswillbeultimatelymetbypartsfromthefirstproductionrun.Nextintheprocessis1.)DesignConfirmation,2.)PrePilot,3.)Pilotandfinally,4.)Thefirstproductionofthecomponentorassembly.TheIdentifyphaseisalsowheretheprojectteamisselectedandchargedwiththeresponsibilityforengineeringthecomponent.Ateamleaderischosenaswellasalloftheteammembers,fromCAD,modelshop,evaluationtesting,reliabilitytesting,etc.Itisrecommendedthatrepresentativesfromqualityandmanufacturingbeincludedsothatallcriticalfunctionscanhaveavoiceinthedesignofwhatwillbecomethefinalproduct.Iftheproductissimilartoanexistingdesign,benchmarkingwillbecomenecessarytoevaluatecurrentfieldfailurerates,manufacturingdifficulties,issueswithtooling,problemswithpackagingandshippingsothatthesemistakeswillnotoccurinthenewproduct.Benchmarkingcanidentifypartsthatdonotsurvivestatedreliabilitygoals.ThisisaverycriticalpartofIDENTIFY.OneexcellenttoolforthisexerciseisFAILUREMODEEFFECTANALYSISorFMEA.FMEAisatechniquethatallowsforcatalogingofeachpossiblefailuremodeofacomponentoranassemblyduringnormaluse.Ihighlightthewordnormalhere.TheIDENTIFYphaseselectstheinitialCRITICALTOQUALITYCHARACTERISTICS(CTQs)ofthecomponentsorassemblies.TheseCTQsdefinethemostcriticaldimensions,featuresandspecificationsofpartsANDspecifiesthatthoseitemsMUSTbecheckedonfirstpiecesamplespriortoanypilotorproductionrun.Generally,asamplesizeofthirtypartsorassembliesisrequiredtogatherenoughCTQstatisticallysignificantdata.TheCTQsareperiodicallycheckedafterproductionisinitiatedtomakesurethereisnodepreciationofthemanufacturingprocesses.AuditsaredefinitelyrecommendedtoinsurestrictcompliancewithqualitystandardsfortheseCTQs.IMPORTANCEOFSIXSIGMA:BeforeweleaveIDENTIFY,IwouldliketorestatetheimportanceofmeetingSixSigmagoals.Rightnow,mostmanufacturingcompaniesareproducingtoathreeSigmastandard.ThreeSigmaproducesa93.32%longtermyield.Reachingthesegoalsgivesusthefollowingmeaningof3Sigmagood.20,000lostarticlesofmailperhour.Unsafedrinkingwaterforapproximatelyfifteenminutesperday.5,000incorrectsurgicaloperationsperweek.Twoshortorlonglandingsatmostmajorairportseachday.200,000wrongdrugprescriptionseachyear.Noelectricityforalmostsevenhourseachmonth.www.PDHcenter.comPDHCourseM247www.PDHonline.orgRobertP.JacksonPage10of39Evenifwelookattheprofileofa4companywefindthefollowingcharacteristics1.)Profitableandgrowingbutwithadecreasingmarketshare.2.)Marketpricesdecliningforcertainproductsorproductlines. 3.)Competitorsincreasing4.)HasqualityassuranceprogrambutdeficiencieskeepslippingthroughtheQ.C.process.5.)Spending1025%ofsalesdollarsonrepairingorreworkingproductbeforeitships.(Thisiscrucialandafactthatwillsurfaceduringbenchmarking.)6.)Unawarethatbestinclasscompanieshavesimilarprocessesthataregreaterthan110timesmoredefectfree.7.)Believesthatazerodefectsgoalisneitherrealisticnorachievable.8.)Has10timesthenumberofsuppliersrequiredtorunthebusiness.(Alsocritical.Tocarryasuppliercancostupwardsto$10Kjusttomaintainthedatabase.)9.)510%ofthefirmscustomersaredissatisfiedwithproduct,salesorserviceandwillnotrecommendthatotherspurchaseproductsorservices.Thepossiblereasonforthiscanbeseeninthebellshapedcurvebelow.Lookatthegraphic.ThiswilldemonstratethesavingsingoingfromthreeSigmatosixSigma.FIGURE3PROCESSCAPABILITYBETWEEN3AND6Ifwecanimproveourprocesscapability,wecaneliminatethewastethatoccursbelowthelowerspecificationlimit(LSL)andabovethehigherspecificationlimit(HSL).BothlimitsaredeterminedbythecustomerintheIDENTIFY(DEFINE)phaseofourDMAICprocess.PleasenoticethatthelowerbellshapedcurverepresentsasixsigmaCENTEREDprocessthatyieldsadefectratebelow4partspermillion(PPM).Thisisdefinitelywherewewishtobe.Criticaltotheeffortisthemannerinwhichthecomponentsareultimatelydefinedanddetailed.ThisiswhereapplicationofGD&Tcomesin.Itiscriticalthatcomponentsbedefinedcompletelysotherearenoquestionsastoform,fitandfunction.Ournextsectionwilladdresshowthisisaccomplishedandthosemethodsusedtobringaboutacompletedefinitionofthecomponentorproduct.www.PDHcenter.comPDHCourseM247www.PDHonline.orgRobertP.JacksonPage11of39MEASUREANDANALYZE:AsapartofIdentify,itisalwaysaverygoodpracticetobenchmarkexistingproductsiftheyaresimilartotheproductyouaremodifyingand/orlaunching.Benchmarkingisgenerallydefinedasfollows:Benchmarkingistheprocessofcontinuallysearchingforthebestmethods,practices,andprocessesandeitheradoptingoradaptingtheirgoodfeaturesandimplementingthemtobecomethebestofthebest.[20]Iwouldaddtothisdefinitiontheneedtobenchmarktheproposedproductdesignforcomponentsandsubassemblies.Thisprovidesacomparisonoftheproposeddesignwithexistingcompetitivedesignsandcanhighlightareasofneededimprovement.Thisprocessinvolvesthecustomerandobtainingreliableinformationonproductfieldfailures.Understandingfieldfailuresandtheircauseiscriticalimprovingtheproductperformance.ThefollowingareasarecriticaltotheDFSSbenchmarkingprocess:CompetitiveBenchmarking.(Comparisonsbetweencompetitionsproductsandyourproduct.)ProductDesignBenchmarking(Determiningthesigmavalueofexistingandsimilarproductsnowbeingproducedbyyourcompany.)ProcessBenchmarking(Determiningthesigmaoftheproductionprocesses.)BestPracticesBenchmarking.(Aretherebettermethodstofabricateandassembleyourproducts?)Customerscanbeagreataidinthebenchmarkingprocessandgiveusinformationthatotherwisemightbeverydifficulttoobtain;i.e.fieldfailurerates.Thisapproachallowsforthefollowing:1.)Tofindinformationthatwould,mostlikely,notsurfaceduringatypicalsalescall.2.)Toencouragethecustomertothinkoutoftheboxandfocusonspecificbehaviorsandproductdesignsthatwouldmaketheproductbestinclass.3.)Toprovidedatatoengineeringthatwillpromoteneededchangesinproducts.Customershaveavestedinterestinprovidingtheiraccountswiththebestandlongestlastingproducts.Theygenerallyknowtheircompetition.4.)Tofindoutcustomerconcerns,otherthanprice.5.)Todemonstratelongtermcommitmenttocontinuousproductimprovement.6.)Toencouragecustomerstoprovidedatatosubstantiatetheirperceptions.7.)Tobuildaccountcredibilitybycommittingtoactionswhichaddressproductdesigncomplaints.8.)Toaddressissueswithproductperformanceandgainknowledgeoffieldperformance.9.)Toproactivelydefinecustomerexpectationsbyallowingthemtodefinebestinclassproducts.DESIGN:Thedesignprocesstodayisaccomplished,generally,byusingcomputeraideddesign(CAD)andcomputermodelingandsimulationtechniques.Computershavereplacedthedraftingtableandmanualmethodsforcreatingadrawinganddesigningapart.Definitelyprogress!Withthisbeingthecase,therearemanyexcellentsoftwarepackagesthatprovidesimulationformechanicalmotion,finiteelementanalysis,impactsimulation,fluiddynamics,heattransferandotherdisciplines.TherearestatisticalpackageswhichcangreatlysimplifytheapplicationofSixSigmaandDFSSmethodologies.Softwaresuchasthesecangreatlyaidengineeringeffortstowww.PDHcenter.comPDHCourseM247www.PDHonline.orgRobertP.JacksonPage12of39reachoptimumdesignsquicklyandaccuratelywithoutextendedbuild,test,fix,build,test,fixetc.Manyirritationscanbeomittedsavingmuchtimeandmoneyyetprovidingdesignswhichmeetcustomerexpectationsandmanufacturingcapabilities.IdefinitelyrecommendengineeringdepartmentsadoptCAD,CAMandsimulationsoftwarepackagestospeedtheprocessfromboardtoassemblyline.Iwouldliketolistseveralexcellentexamplesofwhatpackagesareavailabletoaccomplishdesigncompletionandproducethespeedneededtoremaincompetitiveintodaysengineering/manufacturingenvironment.Pleasekeepinmindthattheserepresentafractionofwhatisavailableandnewproductsareintroducedataveryrapidpace.APPLICATIONSOFTWARE:CAD: MOTIONCONTROL:MiltibodyKineticsandDynamicsAutoDesk ProE ADAMSSmartDraw DADSSolidWorks AutoDesk,IncTurboCad SimMechanicsTFlexPLMIMPLICITFINITEELEMENTANALYSISLinearandNonlinearMSC.Nastran,MSC.Marc ADINA ABAQUS:StandardandExplicitANYSS ProMECHANICAEXPLICITFINITEELEMENTANALYSIS:ImpactSimulation LSDYNA PAM=CRASH,PAMSTAMPNENSTRAN AUTODESKRADIOSSGENERALCOMPUTATIONALFLUIDDYNAMICSSTARCD PowerFLOW FLUENT,FIDAPCFX4,CFX5PREPROCESSING:FEAandComputationalFluidDynamicsMeshGenerationICEMCFD ANSA FEMB GridPro Gridgen TrueGrid MSCPartran IdeasAltairHyperMeshPOSTPROCESSING:FEAandComputationalFluidDynamicsResultsVisualizationAltairHyperMesh ICEMCFDVisual3.2.0(PVS) FIELDVIEWIdeas EnSight FEMBMSC.Patranwww.PDHcenter.comPDHCourseM247www.PDHonline.orgRobertP.JacksonPage13of39STATISTICALPACKAGES:MINITAB JMP8 BMDP SPLUSXGOBI SAS SPSS MATLABXLISPSTAT ExplorN MANET MassiveDatasetsHEATTRANSFERPACKAGES:BuildingPhysics SAS ThermalDesktopRadCAD ESARAD ESTRANTherearemanysmallerorganizationswhichdonothavetheresourcestopurchase,trainemployeesandusetheabovesoftware.Thatshouldnotbeagreatimpediment.Engineeringcontractservicescanandwillworktoprovidetheneededsimulationsandanalysis.ApplicationofDFSSworksregardlessastowhoisperformingtheprocess.Engineeringdepartmentsareafteranswersandapplicationofthesemethodscanstillsavedaysandweeksoftimewhentimeiscritical.Iwouldaddtothemixtheneedtoperformnecessaryreliabilitytestingtoensurethecomponentorfinishedproductcanmeetyourexpectationsforlongevityinthefieldunderallconditionsofuse.Youwillsaveyourcompanymuchgriefifyoudesignforanacceptableproductlifeandinfrequentdowntimeorprematurereplacement.DESIGNTOOPTIMIZE:OptimizationofadesignoccursasaresultofreliabilitytestingANDfieldtestingpriortothefirstproductionrun.ICANNOTOVEREMPHESIZETHENEEDFORRELIABILITYTESTINGSOTHATAPPROXIMATIONOFDESIGNLIFEMAYBESEEN.Thisistheprocessinwhichweakcomponentsandassembliesareidentified,redesignedandretestedsothatallqualityandreliabilitygoalsaremet.Thistestingwillensuremaximumcustomersatisfactionandminimizefieldfailures.Itwillalsoidentifythosecomponentswhichmustbeexaminedonaregularbasisinordertoprovideforpreventativemaintenanceand/orreplacementofcriticalcomponentparts.Whenperformingthesetests,itisadvisabletouseastatisticalsoftwarepackagetofacilitatethetimeconsuminganalysisthat,bynecessity,mustaccompanyastudyofthisnature.IhaveusedMINITABandExcelforthispurposealthoughImuchpreferMINITABduetotheavailabilityofANOVA,ttail,DOEandmanyotheranalysistools.Also,MINITABallowsyoutoperformandexaminehistograms,boxplots,dotplots,stemandleafplots,scatterplots,timeseriesplotsandallowsyoutoconsidercontinuousANDdescretedata.AnothergreatfeatureofMINITABisregressionanalysis.RegressionanalysisprovidestheformulationoftransferequationswhichcanshowcauseeffectrelationshipsresultingfromDOE(designofexperiments)testing.Also,regressionanalysiscanbeusedtodescribethemathematicalrelationshipsbetweentheresponsevariable(Y)andthevitalXs.PLEASENOTE:TheXsmustbecontinuousdataandnotdiscretedata.ThefollowingchartwillshowthebasicprocessinvolvedwiththeestablishmentofreliabilitygoalsrelativetotheDMADVorDMADOVprocess.Theprocessinthischartequatestothefollowingmajorcharacteristics:GoalSetting=IdentifyMeasure=DevelopSystemModel(Benchmark) Design=DesignReliabilityImprovementTesting=Optimize Design=RedesignWhereNeededValidate=ProductionTestingwww.PDHcenter.comPDHCourseM247www.PDHonline.orgRobertP.JacksonPage14of39 Figure4DFSSPROCESS[PDHonlineG238]VALIDATE:Thevalidationphaseoftheprocessbeginsafterthepilotrun.Pleasenotethat,inmostcompanies,thepilotrunisconsideredtoprovidesaleablegoods.Thisisthephasewhereallofthedesignhasbeenaccomplished,alloftheapprovalsgranted;i.e.UL,CSA,etcandtoolingisinplace.Thevalidationtestingoccursatthispointandcontinuesthroughoutthelifeoftheproduct.AtGeneralElectric,wewouldbringproductsproducedonourassemblylinesinonepermonthforalaboratoryaudit.Duringthefirstproductionrun,wewouldplaceaminimumofthirty(30)productsintoourreliabilitylabforlifecycletesting.TheywouldbetestedtofailuretomakesurethattheMeanTimeToFailure(MTTF)andtheMeanTimeBetweenFailure(MTBF)exceededreliabilitypredictionsANDmetourSixSigmagoalsof3.4PPM.Ofcourse,whentheproductwasretiredandnolongermanufactured,thetestingstopped.PLEASENOTE:ITISIMPORTANTTORETAINTESTDATA,ESPECIALLYTHEAUDITDATA,FORTHELIFEOFTHEPRODUCT.PARTII GEOMETRICDIMENSIONINGANDTOLERANCING(GD&T):GeometricDimensioning&Tolerancing(GD&T)isasetofguidelinesspecificallyfordimensioninganddetailingsoacomponentcanbecorrectlyinterpreted.TheGD&Tontheprintprovidestheguidelinesportrayedbythatdrawingfordimensionalinspection.Itisauniversallanguageusedbydesignengineeringtofaithfullycaptureandtransmitthedesignersintentthroughallactivitiesintheproductcycle.Ithasfoundthegreatestapplicationinmassproduction,whereinterchangeabilityofblindlyselectedpartsisessential.Justintimemanufacturingincreasesthedemandforpartsthatabsolutelymustfitatassembly.Acompanyismuchlesslikelytohavesparepartswaitinginthewarehouse;therefore,PARTSSIMPLYMUSTFITTOGETHERATASSEMBLY.Thereisnootherwaytoensurethattheallowablevariationofpartgeometryisadequatelydefined.Dimensionalvariationswhichoccurineachcomponentpartofanassemblyaccumulatestatisticallyandpropagatekinematically,causingtheoverallassemblydimensionstovaryaccordingtothenumberofcontributingsourcesofvariation.Theresultantcriticalclearancesandfits,whichaffectperformance,arethussubjecttovariationduetotolerancestackupofcomponentpartvariations.Therearethreemajorsourcesofvariationinassembliesasfollows:1.Dimensional(lengthsandangles)2.Geometricfeatures(ANSIY14.5)3.Kinematic(smallinternaladjustments)Weareprimarilyinterestedinitemnumber2;i.e.geometricfeatures,andwillconcentrateonthisissueforPartIIofthiscourse.www.PDHcenter.comPDHCourseM247www.PDHonline.orgRobertP.JacksonPage15of39Understandingthecauseandeffectofdimensionalandgeometricvariationsisamajorconcerninthedesignandmanufactureofmechanicalproducts.Designersareessentiallyconcernedwiththefollowinggeometricdimensionsandtolerances:1.Functionalityand/ortheabilitytobeassembled2.ToleranceAnalysis:consequencesofaproposedGD&Tscheme(Pleasenotethatthemethodofmanufacturingthepartplaysasignificantroleintheresultingtolerancesforeachcomponent.Thisisdiscussedlaterinthecourse.)3.ToleranceAllocation:determininghowtodistributetheallowablevariationonthedimensionofinterestamongalloftheindependentcontributors.STANDARDS:GD&ThasbeenadoptedbytheInternationalStandardsOrganization(ISO)andtheAmericanNationalStandardsInstitute(ANSI)[6].Itincludesallofthesymbols,definitions,mathematicalformulas,andapplicationrulesnecessarytoembodyaviableengineeringlanguagesothatpeopleeverywherecanread,write,understandandapplythemethodology.ThestandardmostcommonlyusedintheUnitesStatestodescribeGD&TisASMEY14.5M2009althoughthefollowingstandardsareinplayonaninternationalbasis.GD&TstandardsGD&Tstandardsfortechnicaldrawings(2D)ASMEY14.5M1994DimensioningandTolerancingASMEY14.5.1M1994MathematicalDefinitionofDimensioningandTolerancingPrinciplesISO2861:1988ISOsystemoflimitsandfitsPart1:Basesoftolerances,deviationsandfitsISO2862:1988ISOsystemoflimitsandfitsPart2:TablesofstandardtolerancegradesandlimitdeviationsforholesandshaftsISO1101:2005GeometricalProductSpecifications(GPS)GeometricaltolerancingTolerancingofform,orientation,locationandrunoutISO5458:1998GeometricProductSpecifications(GPS)GeometricaltolerancingPositionaltolerancingISO5459:1981TechnicaldrawingsGeometricaltolerancingDatumsanddatumsystemsforgeometricaltolerancesGD&TstandardsforCADsystems(3D)ASMEY14.412003DigitalProductDefinitionDataPracticesISO16792:2006TechnicalproductdocumentationDigitalproductdefinitiondatapractices(Note:ISO16792:2006wasderivedfromASMEY14.412003bypermissionofASME.)GD&TstandardsfordataexchangeandintegrationISO10303IndustrialautomationsystemsandintegrationProductdatarepresentationandexchangewww.PDHcenter.comPDHCourseM247www.PDHonline.orgRobertP.JacksonPage16of39oISO1030347:1997Integratedgenericresource:ShapevariationtolerancesoISO/TS103031130:2006Applicationmodule:DerivedshapeelementoISO/TS103031050:2006Applicationmodule:DimensiontoleranceoISO/TS103031051:2006Applicationmodule:GeometrictoleranceoISO/TS103031052:2005Applicationmodule:DefaulttoleranceoISO/TS103031666:2006Applicationmodule:ExtendedgeometrictoleranceoISO10303203:2007/8Applicationprotocol:Configurationcontrolled3DdesignofmechanicalpartsandassembliesoISO10303210:2001Applicationprotocol:Electronicassembly,interconnection,andpackagingdesignoISO10303214:2003Applicationprotocol:CoredataforautomotivemechanicaldesignprocessesoISO10303224:2006Applicationprotocol:MechanicalproductdefinitionforprocessplanningusingmachiningfeaturesoISO10303238:2007Applicationprotocol:Applicationinterpretedmodelforcomputerizednumericalcontrollers(STEPNC)BENEFITS:Ifproperlyused,GD&Thasthefollowingsignificantbenefits:Clearlydefinestheintentofthepartandprovidesdescriptivegeometry,dimensions,orthographicprojectionsandtolerancing.Itisaprecisecommunicationtool.OptimallyusesthepartsavailabletoleranceandallowsfortheuseofDFSSmethodologyIncreasesthecorrelationbetweencustomerandsupplierProvidesthebasistocorrectlydeterminewhetherafabricatedpartisacceptableornotbyprovidingthebasisforproduceability.Theuseofmaterialconditionmodifiersallowsbonustoleranceswhichleadtogreateaseinassembly.ExplicitlycontrolsALLaspectsofpartgeometry,particularlytheshape.GD&Tisimportantforcalculatingtoleranceanalysisaccurately.Manycompaniesstilluselineardimensioningtodetailtheircomponentpartsandassemblies.AnexampleoflineardimensioningisshownbyFigure8.Thiscanbefullyacceptablebutthereareconsequencestothisprocess.Theseareasfollows:ThepartsfailinspectionbutarestillfunctionalThepartspassinspectionbutdonotworkordonotworkasintendedLackofcorrelationbetweencustomer/supplierwithdifficultyindeterminingwhythereareissuesInabilitytomakepass/failanalysisduringinspectionThebasicideabehindGD&Tistodeterminethedatumfeaturesofthepartorassemblyofparts.This,ofcourse,involvesphysicalpositionsandrelationships.Thedatumsareselectedastheoriginsfordimensioningandtheapplicationoftolerancesortolerancezones.YouMUSTselectfunctionaldatums.Afunctionaldatumissimplyonethatusestheproductfeatureswhichphysicallylocatethepartrelativetothefinalproduct.Usinganyotherdatumsystem;i.e.centerlines,willaddvariationinthefinaltolerancestackup.[18].Successfulapplicationofwww.PDHcenter.comPDHCourseM247www.PDHonline.orgRobertP.JacksonPage17of39GD&Tinvolvesconcurrentdesignandengineeringteamsconsistingofrepresentativesfromresponsiblefunctions;i.e.engineering,qualitycontrol,reliabilitytesting,purchasing,etc.arechosenforthisprocess.RULES:Thefollowingrulesdetailthefundamentalsinaveryconciseandreadablemethod.Theserulesaretakenfromreference[1].Alldimensionsmusthaveatolerance.Everyfeatureoneverymanufacturedpartissubjecttovariation;therefore,thelimitsofallowablevariationmustbespecified.Plusandminustolerancesmaybeapplieddirectlytodimensionsorappliedfromageneraltoleranceblockorgeneralnote.Forbasicdimensions,geometrictolerancesareindirectlyappliedinarelatedFeatureControlFrame.Theonlyexceptionsarefordimensionsmarkedasminimum,maximum,stockorreference.Dimensioningandtolerancingshallcompletelydefinethenominalgeometryandallowablevariation.Measurementandscalingofthedrawingisnotallowedexceptincertaincases.Engineeringdrawingsdefinetherequirementsoffinished(complete)parts.Everydimensionandtolerancerequiredtodefinethefinishedpartshallbeshownonthedrawing.Ifadditionaldimensionswouldbehelpful,butarenotrequired,theymaybemarkedasreference.Dimensionsshouldbeappliedtofeaturesandarrangedinsuchawayastorepresentthefunctionofthefeatures.Descriptionsofmanufacturingmethodsshouldbeavoided.Thegeometryshouldbedescribedwithoutexplicitlydefiningthemethodofmanufacture.Ifcertainsizesarerequiredduringmanufacturingbutarenotrequiredinthefinalgeometry(duetoshrinkageorothercauses)theyshouldbemarkedasnonmandatory.Alldimensioningandtolerancingshouldbearrangedformaximumreadabilityandshouldbeappliedtovisiblelinesintrueprofiles.Whengeometryisnormallycontrolledbygagesizesorbycode(e.g.stockmaterials),thedimension(s)shallbeincludedwiththegageorcodenumberinparenthesesfollowingorbelowthedimension.Anglesof90areassumedwhenlines(includingcenterlines)areshownatrightangles,butnoangulardimensionisexplicitlyshown.(Thisalsoappliestootherorthogonalanglesof0,180,270,etc.)Alldimensionsandtolerancesarevalidat20Cunlessotherwisestatedonthedrawing.Unlessexplicitlystated,alldimensionsandtolerancesarevalidwhentheitemisinafreestate.Dimensionsandtolerancesapplytothefulllength,width,anddepthofafeature.Dimensionsandtolerancesonlyapplyatthelevelofthedrawingwheretheyarespecified.Itisnotmandatorythattheyapplyatotherdrawinglevels,unlessthespecificationsarerepeatedonthehigherleveldrawing(s).SYMBOLS:ItisimportanttonotethatASMEY14.5givesthefollowingdescriptiveinformationrelativetothegeometryusedtodefinethepart.Wewilldiscussexamplesofhowthesegeometrictermsandsymbolsareusedtodescribeform,fitandfunction. SYMBOLDESCRIPTION GEOMETRYDEFINED Angularity Orientation Concentricity Location Cylindricity Formwww.PDHcenter.comPDHCourseM247www.PDHonline.orgRobertP.JacksonPage18of39 Flatness Form Parallelism Orientation Perpendicularity Orientation Position Location Profile Profile ProfileofaLine Profile Circularity Form Runout Runout Straightness Form Symmetry Location TotalRunout RunoutIfweuseagraphicmethodtodisplaytheorganizationofthegeometriccharacteristics,itwouldlooksomethinglikethefollowing: Figure5ToleranceClasses[26]MODEFYINGTOLERANCESYMBOLS:AnintegralpartoftheFeatureControlFrameisthemodifyingtolerancesymbols.ThesearedefinedbyY14.5andrepresentedlateroninthecourse.Thelistingforthesemodifiersisasfollows: FreeStatewww.PDHcenter.comPDHCourseM247www.PDHonline.orgRobertP.JacksonPage19of39 LeastMaterialCondition(LMC) MaximumMaterialCondition(MMC) ProjectedToleranceZone RegardlessofFeatureSize TangentPlane UnilateralDG&TEXAMPLES:LetustakeaquicklookatthetypeofdimensioningusedfordrawingsthatadoptGD&Tmethodology.ThethreedimensionalmodelsANDthedrawingshowthebasicsofthepartsandtheapplicationofGD&T.ThedimensionsareinMM.Forthepartgiveninfigure6,pleasenotethatthedatumAisspecifiedasthecircumference,ortheoutersurface,ofthepart.Theeighteenserrationsorsplineshavearunouttoleranceof0.02MMsrelativetodatumA.Asyoucanseefromthesolidmodel,therunoutiscriticalbecausethereisamatingparttothetotalassembly.Theouterdiameteris60MMwithatoleranceof0.01MM.Theinternaldiameteris45MMwithatoleranceof0.01MM.Theinternaldiameter,attheserrations,is40MMwithatoleranceof0.020MM.Figure6SplineAssemblyThedrawingbelowwillshowahandledimensionedusingGD&T.ThedatumsurfaceshavebeenselectedasA,BandC.Thebasicdimensionsareincludedinrectangularblocks.Figures6and7areverybasicbuttheydorepresentexamplesofappliedDG&T.www.PDHcenter.comPDHCourseM247www.PDHonline.orgRobertP.JacksonPage20of39 Figure7HandleUsingGD&TThepartshownbelowisanactualpartIhavebeenaskedtofabricate.Itisanexampleoflineardimensioning.MyclientisaFortune500companyyetdoesnotuseGD&TasprotocolduringtheCADprocess.Idontwanttobeoverlycritical,butthereareseveralglaringomissionsrelativetothisdrawingandthenotesforthedrawing.Thereisnospecificationforflatness.(Iknowhowthepartisusedanditmusthaveaflatnessofatleast0.060inchesrelativetotopandbottomparallelsurfaces.)Thereisnospecificationfortheperpendicularityofsides.(ItcouldbeaparallelogramoratrapezoidandstillcomplywiththedrawingBUT,itwouldnotfittheconvectionfanplatformitisdesignedtomatewith!)Thereisnospecificationfortheparallelismofsides.Theydoneedtobeparallelandwithinaspecifictolerancezone.Thematerialspecificationisveryincomplete.ThereneedstobeanASMEorASMspecificationforclarity.Thenoteparttobeinspectedtosheetmetaltolerancesisreallybogus.Thedrawingshouldincludetherequiredtoleranceforeachdimension.Note4callsforsymmetryaboutthecenterlines.Acenterlineisverydifficulttomeasureanddoesnotrepresentasuitabledatum,especiallysincethereisnocallforparallelismorperpendicularity.AdatumisaphysicalentityacenterlineisNOT.(ThisdrivesQCinspectorscrazy!!!!!!)www.PDHcenter.comPDHCourseM247www.PDHonline.orgRobertP.JacksonPage21of39Figure8ExampleofLinearDimensioningWehavealreadylookedattwofairlysimpledrawings,andtheirsolidmodels,butnowletusconsideramuchmorecomplexpartthatisproperlydimensionedusingGD&T.AllofthedimensionsandtolerancesareincludedwithinthefeaturecontrolframesandeverycriticaldimensionhasfeaturecontrolframesWITHtolerancesgiven.Thedatums;i.e.AandB,havebeenselectedsoastoprovideabaselinefromwhichalldetailsaregiven.ThedatumpositionsAREphysicalfeaturesofthepart,notcenterlines.Thefeaturecontrolframescarryinformationondiameter,position,maximummaterialcondition,perpendicularity,profile,parallelismandflatness.Also,eachdimensionisdulynotedwithatolerancecallout.Youmaythinkthisisabusydrawingbutalloftherequireddataisgivenforfabricationandinspection.Thereisnoambiguityasfaraswhatshape,dimensionsandtolerancesarerequired.IcouldsubmitthisdrawingintheUnitedStates,China,NewZealand,Canada,Mexico,etcandacompanyorpersonunderstandingGD&Tcouldmakethepartwithnodifficulties.Asamatteroffact,Iwouldsuspectallpartssubmittedbyindividualsforinspectionfromthesecountrieswouldproduceverysimilarproducts.Thisisexactlywhatwewant.Wewilldiscussthesymbolsandtolerancemodifierslateroninthecourse.www.PDHcenter.comPDHCourseM247www.PDHonline.orgRobertP.JacksonPage22of39 Figure9Collar[2]Idontwanttobelaborthepointbut,whatifwewantedtouseEnglishtodetailthispart?Nodimensions,notolerances,justgoodoldEnglish.Thisisaninterestingexerciseandwilldemonstratethehopelessfeelingyougetwhentryingtoputittowords.GivenbelowinFigure10iswhatwewouldhave.Asyoucansee,weincreasetheambiguityonethousandfoldandmakethedrawingbasicallyunreadable.Notesmighthelpbutthemeaningisreallycloudedwithambiguity.www.PDHcenter.comPDHCourseM247www.PDHonline.orgRobertP.JacksonPage23of39 Figure10CollarinEnglishOnly[2]FEATURECONTROLFRAME:WenowwishtoconsidertheFeatureControlFrameandthelayoutofthatframe.Nexttoselectingthedatumreferences,thefeaturecontrolframeisthemostdescriptivecharacteristicofanyonedrawingusingGD&Tandcarriesthebulkoftheinformationneededfordetailingthepart.Thelayoutisasfollows:Figure11FeatureControlFrame[2]Theplacementofthegeometriccharacteristics,tolerancevalues,modifyingsymbols,datumselectionandmaterialconditionmodifiersisveryspecificandMUSTnotbeappliedinarandomfashion.Wealwaysapplythefeatureslefttorightwithinthefeaturecontrolframeandinthefollowingorder:1.Geometriccharacteristics2.Tolerancemodifyingsymbols3.Tolerancevalue(s)www.PDHcenter.comPDHCourseM247www.PDHonline.orgRobertP.JacksonPage24of394.Primarydatumreference5.Secondarydatumreference6.Tertiarydatumreference7.DatummaterialconditionsThetablebelowwillsummarizetheapplicationoptionsandrulesforeachofthefourteen(14)typesofgeometriccharacteristics.Pleasenotethecharacteristic,symbol,andthetypeoffeaturecontrolledisgiven.Thesecharacteristicsareplacedinthefirstboxofthefeaturecontrolframe.Table4GD&TCharacteristic[2]Inadditiontogeometriccharacteristics,therearemodifyingtolerancesymbolsnecessaryforacompletedescriptionofthepart.Theseareasfollows:www.PDHcenter.comPDHCourseM247www.PDHonline.orgRobertP.JacksonPage25of39 Table5ModifyingToleranceSymbols[2]ThesearequiteimportantandsomewhatselfexplanatorybutIwouldliketoexplainthreethatarefrequentlyconfusedandoneverypertitenanttoDFSSandsixsigma.MaximumMaterialCondition(MMC)Theconditioninwhichafeaturecontainsthemostamountofmaterialeverywherewithinthestatedlimitsofsize.LeastMaterialCondition(LMC)Theconditioninwhichthefeaturecontainstheleastamountofmaterialeverywherewithinthestatedlimitsofsize.StatisticalToleranceThestatisticaltolerancesymboldenotesthatdimensionortolerancewhichwasderivedorestablishedbyusingstatisticalmethodsand/orsixsigmacalculations.Generally,thesetoleranceswereestablishedbymeasuringcomponentsduringthebenchmarkingprocess.WewillbeconsideringthismodifierlaterwhenwemarryDFSSandGD&T.Anotherdeterminationofstatisticaltolerancingisderivedfromprocesscapabilitystudies;i.e.howgoodismyprocessandwhattolerancesresultfrominvestigatingthosetolerancesduringtheprocess.READINGBASICSYMBOLS:Nowanexplanationastohowtoreadthesebasicsymbols.Eachgeometrictoleranceclassisrepresentedbyaregionorzone;theshapeofthezonedependsuponthetolerancetypeandthefeaturebeingtoleranced.Thesizedependsuponthetolerancevalue,materialconditionmodifiersandcertainrules;theposition/orientationofthezonedependsuponthetolerancetypeanddatumsselected.Figure12belowshowsthezonesforperpendicularity,flatnessandrunout.[26]www.PDHcenter.comPDHCourseM247www.PDHonline.orgRobertP.JacksonPage26of39 Figure12Flatness,RunoutandPerpendicularity[26]Asyoucansee,thereisaboundary,zoneorregionthatdefinesthegeometriccharacteristic.Lookingatthefeaturecontrolframerelativetoflatness,thereisatoleranceof0.003incheswhichthepartmustconformtorelativetodatumD.This0.003representstwoparallelsurfaces0.003inchesapart.Theflatnessmustliewithinthiszonetobewithinspecifications.ThepartmustalsobeperpendiculartodatumDwithin0.010inches.Runoutisthesame.Therunoutofthepartontherightmustbewithin0.005inchesrelativetodatumsAandB.Thisisazonewithsurfaces0.005inchesapart.Wediscussed,briefly,MMC.Inordertoallowfortradeoffsbetweenfeaturesizeandcertaintypesofgeometrictolerances,suchasposition,thestandardsusematerialmodifiers;i.e.MMC,LMC,etctoindicatewhatthegeometrictoleranceiswhenthesizeisatitslargestorsmallestvalue.Whenthefeaturesizedeviatesfromthatvalue,abonustoleranceisaddedtothegeometrictolerance;i.e.tradingpositionvariationforsizevariation;whenamodifierisappliedtoadatumfeatureofsize,thegeometrictolerancezonesshift,whichisequivalenttoalargerzone.Thisisshownwiththefigurebelow. Figure13MMC,LMC[26]Iwouldliketogobacknowandprovideseveralbulletsforfigure9.ThesefurtherexplaintheuseandmethodologyforGD&T.Alldimensionsareininches.Thelargestinsidediametermeasures7.00incheswithatoleranceof0.02inches.Thepositionofthesurfacerepresentsthemaximummaterialcondition.Thesecondlargestinternaldiameteris5.50incheswithatoleranceof0.020inches.ItrepresentsanMMCconditionandmustbeperpendiculartodatumAwithin0.01inches.www.PDHcenter.comPDHCourseM247www.PDHonline.orgRobertP.JacksonPage27of39ThethicknessofthematerialatDatumAis0.250inches.Theprofileofthesurfaceofthecollarhubmustbe0.020inchesrelativetoDatumAThismeansitmustbeinatolerancezoneof0.020inches.Thediameterofthefive(5)holesonthepartmustbelocatedonaboltcircle(BC)andwithinadiameterof4.50inches.Theymustbe0.515inchesindiameterandwithatoleranceof0.0050inches.TheBCmusthaveatoleranceof0.015inchesrelativetoDatumsAandBwhenthepartisintheMMCBeforeweforget,theapplicationofabasicdimensiontoadrawing,usingGD&T,looksasfollows:Figure14BasicDimensions[1]Pleasenotethattherearenotolerancesappliedtothebasicdimension.TolerancesareusedonlyinFeatureControlFrames.IwouldliketoemphasizethattherearemanysourcesfortrainingandconsultationregardingGD&T.Severalaregivenbelowasfollows:YourlocaltechnicalcommunitycollegeDimensionalManagementSystems,LLCTecEase,Inc.GeometricLearningSystems,Inc.AdvancedDimensionalManagement,LLCInternationalInstituteofGD&TEngineersEdgeJamesD.Meadows&Associates,Inc.TheQCGroupPARTIIIDFSSANDGD&T:InthissectionwewillattempttoshowhowDFSSANDGD&Tareinterrelated.WewillfindthatGD&TisamethodologycriticaltoDFSSifrepeatabilityandpredictiveassemblyaretobeaccomplished.DFSSisinvolvedwithTOLERANCEALLOCATION.Toleranceallocationisamethodwhichwillallocatetolerancestovariouscomponentsandanassemblyofmatingcomponentssoastopredicttheoutcome.Inthisfashion,wecanusethewww.PDHcenter.comPDHCourseM247www.PDHonline.orgRobertP.JacksonPage28of39tenantsofsixsigma;i.e.bellshapedcurve,USLandLSL,toaidourefforts.Westartwithdefinedgoalsfortheassembly,decidehoweachpartistobemanufactured,andallocatewhattolerancesANDstandarddeviationshouldbeappliedtoeachdimensionsothatthepartcanbeeconomicallyproducedandassemblyrequirementsaremet.OnemethodofobtaininginformationrelativetoUSL,LSLandstandarddeviationisStatisticalProcessControl.ManycompanieshaveadoptedSPCintheirfabricationprocessestodetermineCpkforpurposesofcontrollingtheoutcomeofanymanufacturingmethodwiththehopesofreducingoreliminatingunusable(scrap)components.Ifproductiondataisnotavailable,youcanestimaterecommendedtolerancesandstandarddeviationfromexistingdatabasesrelativetoindividualmanufacturingmethods.Usingtheseconcepts,weassigntolerances;i.e.GD&Ttodrawingsknowingthatgoodpracticewillallowustobewithingenerallyaccepteddimensionaldeviations.Thepurposeoftoleranceanalysisistostudytheaccumulationofvariationsonthegeometricattributesofinterest;i.e.dimension,location,orientation,etc.Theneedforthisarisesfromthefactthattheanalyzeddimensionsarenotexplicityspecified.Themostcommoncaseistheanalysisofclearancesinassemblies.Alldimensionsandtolerancesthataffecttheclearancearecontributors.Thistolerancechainiscalledthestackpathandusuallydoesinvolvemultiplecomponentsandpossiblymultipleassemblies.Worstcaseanalysisisdonetodeterminethemaximumorminimumvaluesresultingfromthelimitsspecifiedbythecontributors.Statisticalanalysisisusedtodeterminethefrequencydistributionofthecontributors.Worstcasedesignguarantees100%interchangeabilityofparts.TOLERANCEALLOCATION:Iwouldlikenowtopresentatablethatwillindicatethesecondbasicsteptotoleranceallocationandtoleranceanalysis.ThefirststepisthestructuringofaLOOPdiagramtodefinethelayoutofthecomponentsandtheassemblyofcomponents.Pleasenotethatthistableisjustapartialtableofwhatdataisavailablethroughouttheliterature.Thelistliterallygoesonandon,butthemostimportantpointisthatthedataforstandarddeviationisavailableifyouhavenotdevelopeditthroughStatisticalProcessControl(SPC)relativetoyourindividualprocesses.Thestandarddeviationsgivenbelowareprocessspecificrelativetotheindividualmanufacturingmethod.Thesevaluesrepresentaverygoodstartingpointforthetoleranceanalysisthatistofollow. PROCESS STANDARDDEVIATION PROCESS STANDARDDEVIATION (INCHES) (INCHES) N/CMILLING 0.00026 JBENDMILLING 0.000105N/CSIDEMILLING 0.00069 JBSIDEMILLING 0.000254N/CSIDEMILLING>6IN. 0.00093 JBBOREHOLES16SQIN 0.00009TURNINGID 0.000127 TREYPANID 0.000127TURNINGOD 0.000132 GRINDINGLAP 0.000027GRINDINGSURFACE 0.000029 GRINDINGOD 0.000029 Table6StandardDeviationvsProcesswww.PDHcenter.comPDHCourseM247www.PDHonline.orgRobertP.JacksonPage29of39Again,thetablebelowisapartialtablebutwilldemonstratewhatdataisavailablerelativetothemanufacturingprocess. PROCESS STANDARDDEVIATION PROCESS STANDARDDEVIATION (INCHES) (INCHES) ALUMINUMCASTING(INCHES) STEELCASTING(INCHES) CASTUPTO0.250 0.00083 CASTUPTO0.250 0.00059CASTUPTO0.0500 0.001035 CASTUPTO0.500 0.00106CASTUPTO1.000 0.001597 CASTUPTO1.000 0.001346CASTUPTO2.000 0.002102 CASTUPTO2.000 0.002099CASTUPTO3.000 0.00.2662 CASTUPTO3.250 0.003064CASTUPTO11.00 0.008126 CASTOVER11.00 0.011711CASTFLAT