Life-cycleorienteddevelopmentofmachinetoolsB.Denkena1,A.Harms1,J.Jacobsen1,H.-C.Mhring1,D.Lange2,H.Noske31UniversityofHannover,InstituteforProductionEngineeringandMachineTools,Germany2ArtisGmbH,Germany3IngenieurbroDr.Noske,GermanyAbstractFortheinvestmentdecisionfornewproductionequipmentitbecomesmoreandmorecommontoguaranteethetotalamountoflife-cycle-costs(LCC).IntheresearchprojectLoeWe,fundedbytheGermanFederalMinistryofEducationandResearch(BMBF),methodsaredevelopedtominimizelifecyclecostsinthedevelopment,operationandrecyclingphase.ExemplarilythedevelopmentofaninnovativeverticalturningmachinedemonstratesvariousstrategiestominimizeLCC.Exchangeabletechnologymodulesextendtheeconomiclifeandmonitoringofselectedmachinecomponentshelptoavoidunplannedservicestandstill.ALCCnavigatoroptimizesthebalanceofpurchasingandconsequentialcosts.KeywordsLifeCycle,Machine,Monitoring1INTRODUCTIONIntheautomotiveindustryageneraltendencytowardsalifecyclecostcalculationisobvious.Machinetoolmanufacturersareobligedtoforeseeandguaranteetheconsequentialcostsoftheirproductforapreviouslydefinedlifetime.Ifmoreserviceandmaintenanceisrequiredthanforecasted,theprofitofthemachinetoolproviderisreduced.Machineswithlessdowntimeandlongerserviceintervalsbecomemoreprofitable.Thereforeahighermachinetoolqualityandalongerandpredictablecomponentlifetimebecomemoreimportant.Consequently,automotiveindustryinvestorsdonottendtopreferthemachinetoolwiththelowestinvestmentcostsanymore.Themodifiedcalculationbasehasseveralconsequencesregardingthemachinetooldesign.Higherqualitycomponentscanbeapplied.Hydraulicsupply,normallyrequiredtodrivetheclampingsystemofthemainspindle,causeshighmaintenancecosts.Anapproachtoavoidthesecostsforanewmachinetoolseriesdevelopedwithintheresearchproject“LoeWe”,whichisanacronymforlife-cycleorientedmachinetool,istoabandonallhydrauliccomponents.Monitoringmechanicalpartsasforexampleballscrews,allowstoreplacethecomponentswhenitisnecessaryandnotatthecalculatedlifetime.Thisalsoenlargesserviceintervals.AnLCCnavigatorisbeingdevelopedwithintheproject.Thissoftwaretoolhelpstooptimizethechoiceofcomponentswithrespecttolowlife-cycle-costsinthedesignstage.Italsocanbeusedinthedevelopmentofmachinetoolcomponentslikeclampingdevices.Asitofferstheopportunitytoclearlyidentifythemaincostfactors(includinglife-cycle-costs),itcanbederivedwhichcomponentsareworthtobemonitoredovertheirlife-cycle.2CUSTOMERVS.MANUFACTURERDEMANDSEndusersofmachinetoolshavetoreactflexibleonchangingmarketdemandstoproducehigh-qualityproductsatagrowingvarietybutshrinkinglotsizes.Todaysmachinetoolsandproductionsystemshavealifetimeof10to15years.Theproductseriesthatarebeingmanufacturedontheseworkshopfacilitieshaveasignificantlowerlifetimeingeneral.Itmighthappenthatnewproductgenerationsthathavetobemanufacturedontheoldworkshopfacilitiesoverstraintheprocessfacilitiesoftheoldmachinetools.Toovercometheselimitations,companieswanttoinvestintoflexibleandreconfigurablemachinetoolsthatofferabroadvarietyofmachiningoperationsatminimumset-uptime.Theoperationofsuchmultifunctionalandflexiblemachinetoolsmightbeinefficientforfinancialaccountingpurposes,asmanysmallandmediummachinetooloperatingcompaniescannotpredicttheirfuturemanufacturingprocessesclearly.Thereforetheydonotknowiftheywouldeverneedoverqualifiedmachinetoolsfromtheiractualpointofview.Inconsequencetheaimoftheinvestmentplanningshouldbetoevaluatethemachinetoolstobeboughtregardingtheircapabilityandtheircost-effectiveness.Nexttothepureinvestmentcostsofaproductionfacility,moreandmorecompaniesalsoconsiderthetotallifecyclecostsastherecanbesignificantdifferencesregardingi.e.investmentcosts,maintenancecosts,energycostsandproductivity.Thisleadstodifferencesinthecostsperpieceofthemachinetoolstobecompared.Themachinetoolmanufacturerswanttoproducemachinesatlowmanufacturingcostswhilebeingabletoofferahighdiversityofmachinetooltypes.Furthermoretheywanttobemoreefficientindesignandproductionandwanttoreduceservicecostsandworkwithinthewarrantyperiod(figure1).Customerdemandslozenge4Productivity,quality,flexibilitylozenge4Processorientatedmachinetoolslozenge4Highavailabilityandreliabilitylozenge4Exploitationofthemachinesfullcapacitylozenge4CosttransparencyatpurchaseanduseCustomerorientationSalesconversationService/maintenanceM/42622eIFWMachinetoolmanufacturerdemandslozenge4Lowmanufacturingcostsatmax.diversitylozenge4Valueanalysisandcompliancewithcostslozenge4Moreefficiencyindesignandproductionlozenge4Reductionofservicecostsandworklozenge4TransparencyofcostsatdevelopmentFigure1:Customerdemandsvs.manufacturerdemands693Asmoreandmorecompaniestendtobuymachinesonlywithguaranteedlife-cycle-costs,themachinetoolmanufacturershavetoundertakethetaskofcreatingappropriateoffers.Acommondifficultywithlife-cycle-costsoftechnicalequipmentistotransformtechnicalfeaturesandconditionsintoeconomicvalues.2.1ResultsofacustomersurveyInordertoevaluatetheneedsofmachinetoolusers,acustomersurveyamongseveralmachinetooluserswithdifferentcompanysizesandbrancheshasbeenaccomplished.Thenumberofmachinetoolsformetalcuttinginusevariedfrom5to1500.Twoimportantresultsfromthesurveyconcerningtheinvestmentdecisionandtheproductivityarepresentedhere.Forallcustomers,technologyandqualityhavethehighestpriorityforaninvestmentdecision.Ofminorimportancearelife-cycle-costsandinvestmentcosts.Thesurveyrevealedthatonlysomeofthebiggercompaniestendtodecideontheirinvestmentsaccordingtoguaranteedlife-cycle-costs.Asanexample,thedeveloperoftheTCOstandard(TotalCostofOwnership),Daimler-Chrysler,onlybuysmachinetoolsandproductionlinesaccordingtoaTCOcontractwherethetotallife-cycle-costsareassuredbycontractfor10years1.Othercompanieswillfollowinthefuture.Regardingtheproductivity,theavailabilityandprocesssafetyofmachinetoolsareofhighestimportanceforthemachinetoolusers.Speedandaccelerationareofminorimportance(figure2).Ha/42623eIFWunimportantratherunimportantminorimportantimportantveryimportantInvestmentdecisionProductivitySurveyfrom20040%10%20%30%40%50%60%70%80%90%100%ConditionsLife-cycle-costsTechnologyServiceQualitySpeedAccelerationAvailabilityProcesssafetySet-uptimeFigure2:Resultsofacustomersurvey2.2Costtransparencywithlifecyclenavigator“Design-to-Cost”istheheadlineoverthemostdevelopmentsofmachinetoolstoday.Theresultofsuchadevelopmentprocessisapurchasepriceoptimisedmachinetool.ButisthisresulttheoptimumconcerningtheLife-Cycle-Costsofthemachinetoolandthereforethemoneybagofthecustomer?IfanyLCC-calculationsofmachinetoolsaredonetodaytheyarerealisedafterthedevelopmentprocessofthemachine.HowwillthedesignofamachinetoolbemodifiedifaminimumoftheLife-Cycle-Costsisthebenchmarkofthedesign?TargetoftheLoeWeresearchprojectwherealsocomponentsupplierslikeBergSpanntechnikGmbH,FranzKesslerGmbH,A.Mannesmann,ArtisGmbHandSiemensareinvolved,isthedevelopmentofaLCC-optimisedmachinetool.ThismainideaguidesthewholedevelopmentprocessofthemachinetoolsincethefirstreflectionoftheLoeWemachine.ItwasacceptedthatthepurchasecostsoftheLoeWemachineexceededthepurchasecostsofacomparableconventionalmachinetoolifonlytheLoeWemachinewillshowarigorousbetterLCC-schedulecomparedtotheconventionalmachinetool(figure3).Inthisresearchproject,anexistingsoftwaretool,theCostNavigatorwhicheffectsgoodresultsincommonDesign-to-Costprojectsofmachinetoolsandothercapitalequipments2,isenhancedtotheLCCNavigator.Dr.NosketLife-cycle-costs0Aftersalescosts-Tools-Service-Maintenance-Energyetc.10yearscommonmachinetoolLoeWe-machinetoolInvestmentcosts5yearsLife-cycle-costsFigure3:CostscheduleofLoeWe-machinetoolvs.conventionalmachinetoolUsingtheLCCNavigatortheLife-Cycle-Costsofthemachinetool,includingmanufacturingandaftersalecosts,willbeextrapolatedduringthewholedevelopmentprocess.EachdecisionconcerningtheapplicationorthedesignofacomponentwillbemadeconsideringthecalculatedvaluesoftheLCCNavigatoralreadyintheearliestdesignphase.TheapplicationoftheLCCNavigatorwillbeexemplarilydemonstratedatthedesignoftheworkpiececlampingdeviceoftheLoeWeturninglathe.Dr.Noske26,1%26,4%47,5%33,4%11,4%0,0%10,0%20,0%30,0%40,0%50,0%60,0%70,0%80,0%90,0%100,0%conventionalclampingdeviceLoeWeclampingdevicemaintenancecostswithin10yearsotheraftersalescostswithin10yearsinvestmentcostsFigure4:LCCextrapolationoftheworkpiececlampingsystemofLoeWe-machinetoolvs.conventionalmachine694PROCEEDINGSOFLCE2006Normallyahydraulicclampingdeviceisusedfortheworkpiececlampingfunctioninaturninglathe.ConsideringtheclampingfunctionfromthepointofviewofLCC,acompletenewsolutionfortheclampingoftheworkpiecehasbeenrealizedwithintheLoeWeproject.Themaincostcomponentsofahydraulicclampingdevicewithin10yearsaremaintenancecostsespeciallyforthehydraulicsupplyunit(figure4).Thismaintenancecostsriseevenabovethepurchasecostsofthewholeclampingdeviceduring10yearsofoperation.ThenewelectricalclampingdeviceoftheLoeWeturninglatheisfreeofmaintenanceandgeneratesthereforenomaintenancecostsduringitslifetime.RegardingonlythepurchasecoststheconventionalclampingdevicehasanadvantagecomparedtotheLoeWedevicebecauseoflowerpurchasecosts.ThebenefitforthecustomerbecomesapparentonlyaftertheextrapolationoftheentireLCC.OthercomponentsoftheLoeWemachinetoolareLCCoptimizede.g.theballscrews,thelinearbearingunitsandcomponentsofthecontrolunitbasedonLCCNavigatorcalculations.ItcanbesummarisedthatanLCC-optimizedmachinetooldesign(Design-to-LCC)createsasignificantlydifferentmachinecomparedtoadesignundertheaspectsofonlypurchasingcosts.3MODULARMACHINETOOLTheinvolvedmachinetoolmanufacturerGildemeisterfocusesonamodularconceptforthemachinetoolseriesthatallowstheusageofasmanystandardpartsaspossible.Themachinetoolserieswillbeavailableinseveralstagesofextension(i.e.thenumberofmainspindles,theirmaximumtorquesandrotationalspeeds,differentturretsandtoolingsystems),whereasthemachinebasisremainsthesameforalltypes.Amodeloftheverticallathewiththeintegratedfeaturesforreducingthelife-cycle-costsispresentedinfigure5.Eventhoughthemachinetoolprototypeisdevelopedinamodulardesign,itisdifficulttoensureawidelyreconfigurablemachinetool.Ithastobedistinguishedbetweenareconfigurationtobeperformedbythemachinetoolmanufacturerandareconfigurationthatcanberealizedbythemachinetooloperator.MainspindlewithintegratedB-axisBallscrewwithwearmonitoringElectricclampingdeviceMachine/processmonitoringInterchangeabletechnologymodulesRFIDtechnologyforquick-setupLCCNavigatorHa/42627eIFWX-AxisY-AxisZ-AxisZ-AxisZ-AxisFigure5:Modelofthelife-cycleorientedmachinetool3.1ReconfigurationbymachinetoolmanufacturerTheverticallathewillbeavailableinseveralstagesofextension.ThebasicversionisequippedwithastandardspindlewithoutB-axis.ToreconfigurethismachinetooltoonewithB-axis,extensivechangeswouldbenecessary,thatcanberatherpracticableonlyforthemachinetoolmanufacturer.Thusthecross-slideforthex-andz-axiswouldhavetobechanged.Thiswouldalsoimplyachangeoftheinnerenclosureofthemachinetool.Componentsthatremainthesameforallthemachinetypesarethemachinebed,thebedsaucer,theouterenclosure,theelectricalcontrolunitbox,thecoolingunitandtheoperatorpanel.3.2ReconfigurationbymachinetooloperatorTheLoeWemachinetoolincorporatesaplatformthatallowsthemachinetoolusertousespecializedtechnologymodulesinthemachine(figure5).Thisplatformincorporatesastandardizeddockingsystemthatallowsthereferencedpositioningandclampingofthesemodulesinsidethemachinetool.Bythistheoperatorcanusehismachinetooleasilyformanufacturingprocessesthatwouldnothavebeenpossiblewithinthestandardmachinetoolconfiguration.Theutilizationofaplatformtobeequippedwithpalletsystemsinsidetheworkspaceofthemachinetoolallowstheuseofagreatvarietyofadditionalmanufacturingprocessesthatcanbeeasilyinstalledbytheoperator.Thiscanbei.e.largediameterdrilling,grindingetc.Palletbasedtechnologymodules,likeforexamplegrindingspindles,havetobeequippedwithasupplyofenergyandcompressedairaswellaswithanappropriateelectricalconnectionformonitoringsensorsignals.Asolutionfortheintegrationoftheseconnectionsintothemechanicalinterfaceiscurrentlyinvestigated.4COMBININGINFORMATIONANDCOMPONENTRelevantcomponentsoftheLoeWemachinetoolprototypewillbeequippedwithdatastoragedevicesthatallowthestorageofspecificcomponentdataforidentificationpurposeslikemanufacturer,type,serialnumberaswellaslife-cyclerelatedmaintenanceinformation.Fourselectedcomponentsliketheballscrewdrive,theelectricclampingdevice,thetechnologymodulesandthemainspindleareequippedwithRFIDbasedtransponderchips.TheelectricclampingsystemisequippedwithaRFID-chipthatstoresallrelevantinformationforanautomatedconfigurationofthemachinetoolcontrol.FurthermoretheintegratedRFID-chipwillbeusedtostorelife-cyclerelateddata.Thisallowstoidentifythecomponentanditsactualstateevenifitisdetachedfromthemachinetool.Toreadthetransponderchip,anantennahastobeplacedclosetotheRFID-chipasdataandenergyaretransmittedviaaradiofrequencyfield.Dependingontherequireddatarate,differentsystemsoperatingatvarioustransmissionfrequenciesandrangescanbeused.Inordertoassureanacceptabletransmissionrangethatcanbeupto7mmforaRFID-chipwith2kBmemorycapacity,itneedstobeinsulatedfromthemetalsurfacegrounditismountedon.Machinetoolcomponentsthatwillbeoftenexchangedasforexampleapalettebasedclampingsystemareequippedwithahard-wiredantennaintegratedintothestationarypartandanRFID-chipintegratedintotheexchangeablepart.OtherRFID-chipequippedmachinetoolcomponentslikeaballscrewdrivethathavetobeinstalledonlyonceortwiceduringthemachinetoollife-cyclewillbeidentifiedwithahandheldantennaconnectedtothemachinetoolcontrolforinstallationandmaintenancepurposes(figure6).13thCIRPINTERNATIONALCONFERENCEONLIFECYCLEENGINEERING695MachinetoolcontrolwithcentraldatastorageRFID-basedcomponentmemoryDemountedcomponentwithRFID-chipS.VogelerITAFigure6:Combininginformationandcomponent5COMPONENTMONITORING5.1EstimationofremaininglifetimeofballscrewsOftenthemachinetoolutilizationtimeexceedstheballscrewlifetime.Whenthereisnoextraordinaryincidence,theyareexchangedafteracertaincumulatedtraversepathregardlessoftheirwearstate.Thisisthestateofthearttominimizetheriskofunplannedfailure.Whenaballscrewfailsduetoitswear,theaxisbecomeslessprecise；inparticular,theclearancebecomesmuchhigher.Thereforeitisnotpossibletochoosehardlong-termstablecontrolparameter.Dirtorchipsontheballscrewcanleadtoabreakdownoranenlargedwearoftheballsortheballtrackbeforereachingthenominallifetime.Thisalsodemandsanunplannedexchangeduetotheexceedingofworkpiecetolerances.Especiallyinautomaticlineoperations,adowntimeofseveralhoursorevendayscausessubstantiallosses.Thereforeareliablemonitoringstrategyofballscrewsisimportanttoavoidtheseadditionalcostsforthemachinetooluser.Aweardetectionandpredictionoftheremaininglifetimeallowstoplantheexchangeoftheballscrewinadvancetoavoidunplanneddowntime.Lossofpre-loadAutomaticwearmeasurementsshouldbedoneatthemostloadedlocationofthespindle.Becausesomespaceisrequiredforthemeasurementtraversepath,thetestcannotbeexecutedatthemarginsofthespindle.Experiencesfromballscrewmanufacturersshowthatwearofballscrewtrailsalsoreproduceswearontheballs.Therefore,analternativewearmeasurementatanotherpositionofthemachinetoolaxisrepresentsthemeanwearofthescrew.Inthefollowing,twopossiblemethodsofwearmeasurementarepresented.Botharebasedonpre-loadlossdetection,duetoareducedballdiameterbypittingeffects.TheybaseoninvestigationsofhorizontallyarrangedballscrewswithinaprojectfundedbyDFG(GermanResearchFoundation)3.Anaimofthein