JIT_系统介绍英文版

Just-In-TimeSystems(LeanProduction),OriginsofJITandLeanProduction,PioneeredbyToyotaAdoptedbyotherJapanesemanufacturersDiscoveredmuchlaterbyWesternmanufacturersKnownbymanynames:ToyotaProductionSystemJustInTimeLeanproductionFlowproduction,LeanProductionBenefits,Doublelabourproductivity90%reductioninthroughputtimes90%reductionininventoryImprovedqualityReducedtimetomarket,HowLongdoesitTake?,WomackandJonesdocumentmanycaseswheremajorimprovementsareachievedinamatterofdays,HowMuchdoesitCost?,ThecostisusuallyverylowInmanycases,companiesreplaceexpensiveequipmentwithmuchsimplerandcheaperequipmentLeanproductiondoesnotemphasizetechnologyorautomation,HewlettPackardsCupertinoCaliforniaplant,1982(beforeJIT),1986(afterJIT),15days,11.3hours,$670,000,$20,000,200,2,TheLeanTransformationatLantech,From:WomackandJones,LeanThinking,p.121,RelativePerformanceinAutoIndustry,1993-94,fromWomackandJones,LeanThinking,RelativePerformanceinAutoIndustry,1993-94,fromWomackandJones,LeanThinking,PorschesLeanTransition,Source:WomackandJones,LeanThinking,PorschesLeanTransition,Source:WomackandJones,LeanThinking,WhatisJIT/LeanProduction?,Producingonlywhatisneeded,whenitisneededAphilosophyAnintegratedmanagementsystemJITsmandate:Eliminateallwaste,ExamplesofWaste,WatchingamachinerunWaitingforpartsCountingpartsProducingpartsthatarentneededMovingpartsoverlongdistancesStoringinventoryLookingfortoolsorpartsMachinebreakdownReworkandscrapProductsthatdontmeettheneedsofcustomers,LeanPrinciples,SpecifyvaluedefinedbythecustomerIdentifyvaluestreameliminateallactivitiesthatdontaddvalueFlowproductsshouldflowalongvaluestream,LeanPrinciples,Pullletthecustomerpullproductstheywant,ratherthanpushingproductstheymaynotwantPerfectionstriveforperfectionthroughcontinuousimprovement,TargetsforEliminatingWaste,ZerodefectsZerosetuptimeZeroinventoriesZeroparthandlingZerobreakdownsZeroleadtimeLotsizeofoneMatchproductstocustomerneeds,ZeroDefects,ThetraditionalassumptionisthatacertainlevelofdefectsisunavoidableTraditionalmanufacturingmeasuresdefectratesandcomparesthemtoacceptablequalitylevelsacceptancesamplingaverageoutgoingqualityJITstrivestoeliminateonceandforallthecausesofdefects,ZeroInventories,Intraditionalmanufacturing,inventoriesareseenasassetsInventoriesprovideasafetybuffer,andresultfrommaximizingmachineutilizationJITviewsinventoryaswasteInventoryisevidenceofpoordesign,poorcoordination,andpooroperationofamanufacturingsystem,InventoryHidesProblems,PoorQuality,UnreliableSupplier,MachineBreakdown,InefficientLayout,BadDesign,LengthySetups,LowerLevelsOfInventoryToExposeProblems,PoorQuality,UnreliableSupplier,MachineBreakdown,InefficientLayout,BadDesign,LengthySetups,ZeroSetupTime,TraditionalthinkingconsidersthesetuptimetobegivenandirreducibleTraditionalEconomicOrderQuantityandEconomicProductionLotformulasfindatradeoffbetweensetupcostandinventorycostJITthinkingrecognizestheimportanceofreducingthesetuptimeIfthesetuptimeiszero,theoptimallotsizeisone,ZeroLeadTime,ShortsetupsandsmalllotsleadnaturallytoshortleadtimesTheplanninghorizoncanbecloser,andtheforecastsmoreaccurateThesystemcanchangequicklyinresponsetochangingdemandTheflexibilityisthusimproved,ZeroPartsHandling,JITconsidersallparthandlingtobeawaste,sinceitdoesnotaddvalueParthandlingincludescomponentfeedingcomponenthandlingpartsinspectionshippingandtransportation,ZeroPartsHandling,UnnecessaryhandlingcanbeeliminatedbycarefuldesignoftheproductandtheprocessdesignforassemblydesignformanufacturabilitycellularmanufacturingJITdeliveriestopoint-of-use,ZeroBreakdowns,MaintainequipmentintopconditionImplementTotalProductiveMaintenanceDontwaitforproblemstooccurTheoldsaying“Ifitaintbroke,dontfixit”iswrong!,ZeroLeadtimes,LotSizeofOne,Ifsetuptimesarezero,lotsizeofoneisfeasibleLotsizeofoneallowscontinuousflowinsteadofbatch-and-queueWIPandleadtimeswillbeslashedasaresult,MatchingProductDesigntoMarketDemand,ConcurrentengineeringreducesthedesigncycleGreaterproductvarietyisachievedthroughmodulardesignReducednumberofpartsandcomponentsisachievedthroughgooddesign,andthroughstandardizationandreuseofcommonitems.,MassCustomization,ProvideeverycustomerwithanindividualizedproductMaketoorder(customerpull)Maximizevalue,KeystoMassCustomization,Definevalue(QFD)DesignmodularproductarchitecturesStandardizecomponents,minimizeunnecessaryvarietyConfigureindividualproductsfromstandardmodules,BasicElementsofJIT,1.Flexibleresources2.Cellularlayouts3.Pullproductionsystem4.Kanbanproductioncontrol5.Small-lotproduction6.Quicksetups7.Uniform(mixedmodel)production8.Qualityatthesource9.Totalproductivemaintenance10.Suppliernetworks,FlexibleResources,Flexiblelabourmultifunction,adaptableoperatorsthenumberofoperatorscanbechangedtochangecapacityFlexibleequipmentavarietyofproductsareproducedonthesameequipmentthisrequiresmultifunctionalmachinesAchievablewithbasictechnology!,ProductFamilies,GroupTechnology(GT)iscommonlyusedtoidentifyproductfamiliesbasedonsimilaritiesindesignorprocessingGThelpsreduceunnecessaryduplicationinproductdesignGTidentifiesproductfamilieswithsimilarprocessingrequirementsThesefamiliescanbemanufacturedinwell-definedmanufacturingcells,CellularManufacturing,GroupdissimilarmachinesinmanufacturingcelltoproducefamilyofpartsWorkflowsinonedirectionthroughcellOneworkertendsseveralmachinesCycletimeadjustedbychangingnumberofworkers,ManufacturingCellWithWorkerRoutes,Enter,Worker1,Worker2,Worker3,Exit,Key:,ProductrouteWorkerroute,Machines,FlowBasedProduction,CellularmanufacturingachievesthebenefitsofflowbasedmanufacturingThissimplifiesmaterialflowcomparedtoatraditionalprocesslayoutOwnershipandresponsibilityforaproductrestswiththeoperatorsofthecell,TheTraditionalPushSystem,Intraditionalmanufacturing,anitemisreleasedforproductionataspecifiedtime,withanassociatedduedateTheitemmovesthroughasequenceofoperations,TheTraditionalPushSystem,Whenoneoperationisfinished,theitemis“pushed”tothenextoperationFinally,theproductispushedtoinventory,tomeetforecastdemandThisisclassicalpush-typeproduction,asincorporatedintheMRPapproach,ThePullSystem,ThepullsystemfocusesontheoutputofthesystemratherthantheinputFinishedproductsare“pulled”fromthefinaloperationinresponsetofirmcustomerorders,ThePullSystem,Thisleadstoachainreaction,witheachstationpullingmaterialfromitsprecedingstationJITusesthe“Kanban”systemtocontroltheflowofmaterialwithverylittlework-in-processinventory,TheKanbanSystem,TheKanbansystemusessimplecardstostrictlycontrolproductionThebasicideaisthatnostationispermittedtoproducemorethanisimmediatelyrequiredbythesucceedingstationThissimpleideapreventsthebuildupofinventoryNocomputerisrequired!,KanbanProductionControlSystem,KanbancardindicatesstandardquantityofproductionDerivedfromtwo-bininventorysystemKanbanmaintainsdisciplineofpullproductionProductionkanbanauthorizesproductionWithdrawalkanbanauthorizesmovementofgoods,ASampleKanban,MachiningM-2,AssemblyA-4,Partno.:7412Description:Sliprings,From:,To:,Boxcapacity25BoxTypeAIssueNo.3/5,TheOriginOfKanban,Q=orderquantityR=reorderpoint=demandduringleadtime,Bin1,Bin2,Q-R,ReorderCard,Kanban,a.Two-bininventorysystemb.KanbanInventorySystem,DualKanbans,P,W,Containerwithwithdrawalkanban,Containerwithproductionkanban,XXX,X,X,Flowofwork,Flowofkanban,KanbanSquares,X,X,X,X,Flowofwork,Flowofinformation,TypesOfKanbans,KanbanSquaremarkedareadesignedtoholditemsSignalKanbantriangularkanbanusedtosignalproductionatthepreviousworkstationMaterialKanbanusedtoordermaterialinadvanceofaprocessSupplierKanbansrotatebetweenthefactoryandsuppliers,DeterminingNumberOfKanbans,whereN=numberofkanbansorcontainersd=averagedemandoversometimeperiodL=leadtimetoproducepartsS=safetystockC=containersize,KanbanCalculationExample,Problemstatement:d=150bottlesperhourL=30minutes=0.5hoursdL=(150)(0.5)=75S=10%dL=10%x75=7.5C=25bottlesSolution:Roundupto4(allowsomeslack)ordownto3(forceimprovement),Small-LotProduction,ThepullsystemreducesinventorybyminimizingthenumberofkanbansThisresultsinfrequentmaterialmovementorproduction,insmalllotsSmall-lotproductionhasmanyadvantages,Small-LotProduction,ReducesinventoryRequireslessspace&capitalinvestmentMovesprocessesclosertogetherMakesqualityproblemseasiertodetectMakesprocessesmoredependentoneachother,SetupTimeReduction,Smalllotsrequireshortsetups!SetuptimescanbereducedfromhourstominutesShingodevelopedSingleMinuteExchangeofDies(SMED)systemdiechangeunder10minutes,SMEDPrinciples,1.Separateinternalsetupfromexternalsetup2.Convertinternalsetuptoexternalsetup3.Streamlineallaspectsofsetup4.Performsetupactivitiesinparalleloreliminatethementirely,SetupReductionTechniques,PresetdesiredsettingsUsequickfastenersUselocatorpinsPreventmisalignmentsEliminatetoolsMakemovementseasier,MixedModelProduction,JITpermitsthemanufactureorassemblyofarangeofproductssimultaneously,usingthesameproductionequipmentThisisknownasmixedmodelproductionTheresultisrepetitiveflowproductionversustraditionalbatchproductionMixedmodelproductionrequiressmallbatchesandshortsetups,Exampleofmixedmodelscheduling,TraditionalBatchSchedule,JITSchedule,JITProductionSchedule,Mixedmodelproductionofsixdifferentproductsrepeatsona48minutecycle.,AdvantagesofLevelScheduling,BatchproductionbecomesrepetitiveLowinventoriesFlexibleandresponsiveSimpletocontrol-computersarenotneeded!,QualityAtTheSource,JidokaisauthoritytostopproductionlineAndonlightssignalqualityproblemsUndercapacityschedulingallowsforplanning,problemsolving&maintenanceVisualcontrolmakesproblemsvisiblePoka-yokepreventsdefects,VisualControl,Libraryshelf,Workstation,Visualkanbans,Toolboard,Machinecontrols,Better,Good,Best,30-50,Howto,sensor,Kaizen,ContinuousimprovementRequirestotalemploymentinvolvementEssenceofJITiswillingnessofworkerstospotqualityproblemshaltproductionwhennecessarygenerateideasforimprovementanalyzeproblemsperformdifferentfunctions,TotalProductiveMaintenance(TPM),BreakdownmaintenancerepairstomakefailedmachineoperationalPreventivemaintenancesystemofperiodicinspection&maintenancetokeepmachinesoperatingTPMcombinespreventivemaintenance&totalqualityconcepts,TPMRequiresManagementTo,DesignproductsthatcanbeeasilyproducedonexistingmachinesDesignmachinesforeasieroperations,changeover,maintenanceTrain&retrainworkerstooperatemachinesPurchasemachinesthatmaximizeproductivepotent