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2212-82712013TheAuthors.
PublishedbyElsevierB.
V.
Selectionandpeer-reviewunderresponsibilityofProfessorPedroFilipedoCarmoCunhadoi:10.
1016/j.
procir.
2013.
06.
041ProcediaCIRP7(2013)610–615FortySixthCIRPConferenceonManufacturingSystems2013BeyondLeanandSixSigma;Cross-CollaborativeImprovementofTolerancesandProcessVariations-ACaseStudyLarsKrogstiea,c,KristianMartinsena,baGjvikUniversityCollege,Teknologivn22,2815Gjvik,NorwaybSINTEFRaufossManufacturingAS,Po.
Box163,2831Raufoss,NorwaycNTNU,NorwegianUniversityofScienceandTechnology,7491Trondheim,NorwayCorrespondingauthor.
Tel.
:+47-6113-5100;fax:+47-6113-5170.
E-mailaddress:Lars.
Krogstie@hig.
noAbstractGoodtolerance-andvariationmanagementisessentialtoachievehighvalueaddingproductswithcost-effectiveprocesses.
ThelinkbetweenToleranceEngineeringandpopularmanufacturingimprovementphilosophiessuchasLeanandSixSigmais,however,notalwaysthatclear.
ThepossibilitiesandlimitationsofthesetwoapproachesonToleranceEngineeringarediscussedinthispaper.
Thecasedescribescross-collaborativeimprovementworkwithinindustryontoleranceandvariationmanagementwhichexistingdrawingsandtolerancespecificationsforthemanufacturingofproductswithalonglifetime.
AlthoughbothLeanandSix-Sigmahavebeenimportantfortheimprovementworkinthecasecompanyforseveralyears,thereisstillagaptobefilledontoleranceandvariationmanagement.
Thenoveltyofthispaperisfoundinthelinkbetweenanindustrialcaseonimprovementsandanacademicmodel(CLTE)forcross-collaborativeengineeringonvariationandtolerances.
2013TheAuthors.
PublishedbyElsevierB.
V.
Selectionand/orpeer-reviewunderresponsibilityofProfessorPedroFilipedoCarmoCunhaKeywords:Tolerances;Variation;Lean;SixSigma;CLTE;Collaboration;1.
IntroductionThemanagementofproductspecifications,processvariationsandqualityinspectionsiscentraltoanymanufacturingcompany,andtolerancesrepresentthemainwaytospecifylimitstogeometryandotherparameters.
Optimaltolerancesareimportantforproductfunction,correctfitinassemblyprocesses,selectionofprocesssteps,inspectionstrategyandmanufacturingmethods,andthusbridgeseveralstepsintheproductlifecycle.
Lackofcoherencebetweentheproductdesign,manufacturingandtheinspectioncanleadtoqualityproblems.
ThetolerancestandardssuchasGeometricalDimensioningandTolerancing(GD&T)[1]canbeseenthelimitsofspecificationsrelatedtogeometricalparameters.
Zhang[2]states:funct.
.
Creveling[3]tolerancesarecriticaltothesuccessfulmanufactureandperformanceoftheproduct.
Optimisationsoftwarehasgiventhedesignernewtoolsforoptimisingtolerances.
Thelinktomanufacturingandinspectionis,howeverstillcrucialtoachievecost-efficientmanufacturingwithgoodquality.
CurrentqualityandefficiencyparadigmssuchasTQM,LeanandSixSigma[4]dotosomeextentaddressvariationsmanagementinmanufacturingandqualityinspection.
Thereis,however,stillalackofagoodconnectionbetweentolerancesynthesisinthedesignphase,manufacturingprocesscapabilitiesandvariationsaswellasqualityinspection.
Thecaseinthispapershowshowcollaborationfocusedontolerance-andvariation-topicsenabledtobridgethegapbetweenproductdevelopment,manufacturing&inspection;anapproachsimilartoClosedLoopToleranceEngineering[5].
2.
TheoreticalBackgroundInspiteofthecentralroletolerancesplayinmanufacturing,theyseemnottohaveaprominentplaceAvailableonlineatwww.
sciencedirect.
com2013TheAuthors.
PublishedbyElsevierB.
V.
Selectionandpeer-reviewunderresponsibilityofProfessorPedroFilipedoCarmoCunhaOpenaccessunderCCBY-NC-NDlicense.
OpenaccessunderCCBY-NC-NDlicense.
611LarsKrogstieandKristianMartinsen/ProcediaCIRP7(2013)610–615inengineeringandacademicliterature.
LiteraturesuchasDay[6]andthestandardssuchasASMEY14.
5M[7]coverstheessentialsofGD&Tbutfocusingontheirpurposeastolerancingnormsmainlyintheproductdesignphase.
TheISO/TC213committee[8],[9]worksonjointGD&Tprinciplesfordesign,manufacturingandmetrologicalprinciples.
Thehumanaspectinthetolerancemanagementprocessis,however,notaddressed.
AlackofawarenessoftolerancinginengineeringeducationisaddressedbyauthorssuchasWatts[10]enremovedfromthecurriculumatuniversitiesandhasbeenreplacedbyotherproductdevelopmentcourses.
Zhangetal.
[11]addressthistosomeextent,describingGD&Ttobe.
Wattsaddresseswhathecallstheasheclaimstoseethatofthelackofcinmechanicalengineeringdesigncourses.
ParameterDesignactivitiesafterthe1950,suchastheTaguchiMethod[12],takeaDesignofExperiments(DoE)approachtoproductandprocessdesign,andNair[13]organizesthediscussionbetweenengineeringandstatistical-basedapproachesatanearlystage.
AnaccessibleentrypointtotoleranceengineeringcanbefoundinaliteraturereviewsuchasthatbyHong[14].
Horvàth[15]justifiesthelatesttrendtowardshumanaspectsinengineeringdesignasseeninbooksbyLindemann[16],Badke-Schaub[17]orFrankenberger[18].
ProductdesignliteraturesuchasCross[19],Ulrich&Eppinger[20],Ehrlenspiel[21]andPahl&Beitz[22]areallexampleswhereGD&Tunfortunatelyisgivenlittlefocus.
CrevelingaddressescollaborationontolerancesdirectlyinhisbookonToleranceDesign[3].
3.
TolerancinginLeanandSixSigmaLeanisaphilosophythatpromotescontinuousimprovementswithitsrootsintheJapaneseautomotiveindustry[23].
Six-SigmaisanotherstrategyforproblemsolvingandengineeringimprovementswithitsrootsintheAmericanelectronicsindustry.
Bothinitiativeshavebeenpowerfulmovementsforimprovedproductquality,optimisedmaterialflow,reducedwasteandnumbersofdefectswithinmanufacturingandserviceworldwide.
Thezerodefectsphilosophyintheseapproachesimpliesaneedforunderstandingandreductionofvariationinmanufacturing.
Tolerancemanagementis,however,onlyindirectlyaddressed.
Deming[24]focusesdirectlyondoesnotaddresstolerancesassuch.
EventhoughLeanandSixSigmainitiativeshavefurtherbeenmovedtowardsproductdevelopmentthroughinitiativessuchasLeanProductDevelopment(LPD)andthelooselydefinedDesignforSixSigma(DfSS)[25],thefocusonTolerancingisstilllacking.
Anillustrativecomparisonbetweentheprinciples,practicesandtoolsofLPDandDFSSisprovidedbyFouquetet.
al.
[26].
Hasenkamp[27]arguesthattheimportantdriverforimplementingarobustdesignistheawarenessofvariation.
Wewillarguethatawarenessoftolerancesandtheirlinktomanufacturingvariationholdssimilarimportance.
4.
ClosedLoopToleranceEngineering.
ThemodelofClosedLoopToleranceEngineering(CLTE)ispresented[5]asacontributiontoclosingthegapbetweenproductdesign,manufacturing,inspectionandproductperformance.
TheCLTEmodel(seeFig1)containsfouractivities;(i)definingfunctionalrequirements,(ii)definingtolerances,(iii)consideringproductioncapabilitiesand,(iv)confirmingfunctionalperformance.
CLTEactivitiesareorganisedintotwodimensions;(a)Thenormativedimensionwhichincludestheactivities(i)&(ii),and(b)theempiricaldimension,whichincludestheactivities(iii)&(iv).
Abridgeisneededtoconnecttheproductdevelopmentparticipants(howthingsshouldbe)andthemanufacturingparticipants(howthingsreallyare)withregardtotheirworkontolerances.
Eachactivitystandsinarelationtoafollowingorprecedingactivity.
CLTEcontainsaltogether6pairsclosedloopsofrelations.
Eachrelationhassomekeyelementswhichrepresenttypicalexamplesofthecontext-dependentcontentineachrelation.
Anexplanationoftheparticipants,practices,information,knowledgeandtoolsforthiscontextislistedin[5].
Fig.
1:Fouractivitiesandthe6pairsofclosedlooprelationsinCLTECLTEincludesseveralparticipantsasitcanbeconsideredasanintegratedengineeringworkmode.
Theneedforcooperationacrossfunctionalborderswithinproductdevelopmentisdescribedamongothersby[28]and[21].
InatypicalCLTEcontext,participantswillbe;designers,projectleaders,qualityassurance(QA)engineers(incl.
meteorology),manufacturingoperators,testengineers,processengineers,foremenetc.
TheCLTEtoolsandpracticessupporttheparticipantsin