justintime供应链管理理念整理.docx
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justintime供应链管理理念整理.docx
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justintime供应链管理理念整理
SupplyChainManagement:
JustInTime
Introduction
Intherealmofsupplychainmanagement,“Justintime”referstoaninventorystrategythatitusedtoimproveabusiness’sreturnoninvestmentthroughareductionofinprocessinventoryandallrelatedcosts.Justintimeisdrivenbyaseriesofsignals,referredtoasKanban,whichtellproductionprocesseswhenitisnecessarytomakethenextpart.Kanbancanbevisualsignals,butaregenerally“tickets.”Whenimplementedinacorrectfashion,“Justintime”canhelpaproducerimproveinsuchareasasquality,efficiency,aswellasthereturnoninvestment.
Whenstockdropstoacertainlevel,newstockshavetobeordered.Thishelpsmaintainspaceinthewarehouseandkeepscostsdowntoareasonableamount.Onedrawbackof“Justintime”howeveristhatthere-orderlevelisdeterminedbythepreviousdemand.Ifthedemandrisesabovethatamount,theninventorywillbedepletedalotfasterthanusualandmightcausecustomerserviceproblems.Inordertomaintainaninetyfivepercentservicerate,thecompanyshouldalwayscarrytwostandarddeviationsofsafetystock.AroundtheKanban,shiftsindemandshouldbeforecastuntiltrendsareestablishedtoresetthecorrectKanbanlevel.SomefeelthatrecyclingKanbanataquickerpacecanhelpthesystemflexbyuptothirtypercent.Recently,producershavestartedtoutingathirteenweekaverageasabetterpredictorthanpreviousforecastswouldprovide.
Anothertermemployedin“Justintime”isKaizen.Itmeansliterallythecontinuousimprovementoftheprocess.
HistoryofJustinTime
TheFordMotorCompanyfirstemployed“Justintime”.Itdescribesthe“docktofactoryfloor”concept,inwhichincomingmaterialswerenotevenkeptinstorage,butwentdirectlyintoproduction.Ofcourse,thisconceptrelieduponausefulfreightmanagementsystem;theoneemployedisdescribedinFord’sTodayandTomorrowoftheyear1926.Later,thistechniquewastakenupbyJapan’sToyotaMotorCorporationinitsToyotaProductionSystem.
BusinessesinJapanarenotabletoaffordlargewarehousespaces.Priortothe1950s,thiswasamajordisadvantagebecauseitforcedtheproductionlotsizetobebelowthatoftheeconomiclotsize.Thus,apoorreturncouldbeexpectedonafactoryinvestment.
TaiichiOhnowasToyota’smainengineerinthe1950s.Afterexaminingseveralaccountingassumptions,Ohnocametotherealizationthatanothermethodwouldbepossible.
Itwouldbepossibleforthefactorytoimplement“Justintime.”Thiswouldrequirethefactorytoincreaseintheirflexibility,whilesimultaneouslyreducingtheiroverheadcostsrelatedtoretooling.Effectively,thiswouldalsoreducetheeconomiclotsize,whichwouldbemadetofitthecurrentwarehousespace.“Justintime”thusemergedasoneofthemainpillarsofToyota’sProductionSystem.
Overthenextfewyears,Toyotare-designedcarmodelstoaidsuchproductionprocessesasweldingandpaintspraying.Toyotawasoneofthefirstautomobilemanufacturerstouserobotstoperformsuchtasks.Someofthechangeswereratherminor;oneofthemwastosimplystandardizeholesizesthatwereusedtohangpartsonhooks.Fastenernumbersandtypeswerereducedsoastostandardizetheassemblytoolsandprocess.Therewereeveninstanceswhenidenticalsubassemblieswereemployed.
ItwasthendeterminedbyleadingengineersatToyotathatwhatneededtobemendedintheretoolingprocesswastheamountoftimethatwasrequiredtochangethestampingdiesthatbodypartsused.Usingcrowbarsandwrenches,thesepartshadtobeadjustedbyhand.SometimesitwouldtakeaperiodofseveraldaystoinstalllargediesetsandadjustittofitToyota’shighqualitystandards.Sincetheyhadtobeinstalledoneatatimebyseveralexperts,sometimesthiswouldtakeuptoseveralweeksalltold.
Toremedythissituation,ToyotadecidedtoimplementastrategyinventedbyShigeoShingocalledSingleMinuteExchangeofDie,orSMED.Usingthisstrategywithsimplefixtures,measurementscouldbesubstitutedforadjustments.Itwouldthentakediechangesonlyafewhours,ratherthanseveraldays.Thisalsoreducedtheskilllevelthatwasrequired,asthestampings’qualitywasthencontrolledbyawrittenformula.Theremainingtimewasthentypicallyutilizedtosearchforhandtoolsandmovedies.Diechangetimeswerereducedtoaboutfortysecondsthankstotheuseoftoolracksaswellasmajorproceduralalterations.Thesedays,diesarechangedthroughthefactoryinarippleprocessasthenewproductbeginstoflow.
OnceSingleMinuteExchangeofDiewasimplementedinToyotafactories,economiclotsizesfelltoaslittleasasinglecar.Aslittleasonepartcouldbestoredineachassemblystation,thankstothefactthattheprocesswascarriedoverintopartsstorage.Wheneverapartwasgone,asignal(Kanban)wasemittedforareplacementpart.
SupplyChainManagement:
JITPhilosophy
Itshouldbekeptinmindthat“justintime”isnotasimplestepbystepmethod,butanentirephilosophythatmustbeobservedinordertoavoidthedownfalls.Theideascomprising“justintime”philosophycomefrommanydifferentfields,suchasindustrialengineering,behavioralscience,statistics,andproductionmanagement.Whenitcomestohowinventoryistreatedaccordingtothe“justintime”scheme,onemustlearnhowinventoryistobeviewed,thewayitexpressescertainpracticeswithinthecompany’smanagement,aswellasthephilosophy’smainprinciples.
Asopposedtothetraditionalviewofinventory,“justintime”viewsinventoryasbeingwasteful,inthatitincurscosts,ratherthanaddingvaluetoacompany.Thisdoesnotmeanthatinventoryshouldberemovedaltogetherattheexpenseofmanufacturing.Rather,itexpoundstheideathatacompanycouldsavecostsbyeliminatinginventorythatdoesnotcompensateforissuesrelatedtomanufacturing.Also,processesmustbeconstantlyupgradedsothattheneedforinventoryisreduced.
Whatismore,anytimethatinventoryispermittedtoaccumulate,adownwardspiralbeginswhereinanyandallinventoryisadmitted.Asaresult,themanagementofacompanymightwishtoaccumulateinventorytomaskanyproblemswithintheproductionprocess,ratherthandealingwiththeproblemdirectly.Suchproblemsmightincludemachineryrelateddifficulties,alackofflexibilityamongemployees,backupproblemsatworkstations,orinadequatecapacity.
Withinthe“justintime”system,managersadoptthepolicythatitisbesttohavetherightmaterialsattherightmomentintherightplaceandintherightamount.
ImplementationofJustinTime
WhilesomeofthefirstresultsatToyotawerelessthanideal,thecompanynonethelessfounditselfmakingalotmoremoney,asinventorywasbuiltoutandthensold.Thus,uppermanagementbecameincrediblyenthusiasticabout“justintime”rightoffthebat.Anotherpositiveeffectof“justintime”wasthefactthatthefactory’sresponsetimefelltojustoneday.Customersatisfactionthusresulted,ascarscouldthenbeprovidedwithinacoupledaysoftheminimumeconomicshippingdelay.Carscouldalsobebuilttoorderallofasudden,whichmeanteliminatingtheriskthattheymightnotgetsold.Thiseliminatedalotoftheriskinvolved,asToyota’sreturnonequitywasimprovedgreatly.
Everypartinthefactoryhadtoperfectlyfit,becausetherewasnolongeranychoiceaboutwhichparttouse.Asaresult,therewasaqualityassurancecrisis,aswellasamajorimprovementinthequalityofproducts.Toyotaeventuallydecidedtoredesigneverysinglepartoftheircarsinordertogetrideoftolerances.Atthesametime,theyimplementedstatisticalcontrols.Suppliersofpartshadtobetestedandtrainedtoassuredeliveryaswellasquality.Inmanycases,multiplesupplierswereeliminatedaltogether.
Wheneveraproblemoccurredontheproductionline,itwouldhavetobestoppedoratleastsloweddownsignificantly.Iftherewasnoinventory,thatmeanttoalinecouldnotoperatefrominprocessinventoryuntiltheproblemwasfixed.AlotofpeopleworkingatToyotaduringthistimethoughtthatthatwouldbetheendof“justintime.”Thefirstweekthattheprocesswasimplemented,linestopsoccurrednearlyeveryhour.Butbythetimethefirstmonthcametoanend,linestopsonlyoccurredacoupletimesaday.Attheendofsixmonths’time,therewassolittleeconomiceffectresultingfromlinestopsthatToyotaallowedanyworkeronthelinetopullastoptoinspecttheproductforqualityimprovements.Evenwiththisinstalled,therewereonlyafewlinestopsperweek.
Ads
Thus,Toyota’sfactorybecametheenvyofeveryoneintheworldofmanufacturing.Sincethen,tonsoffactoriesaroundtheworldhaveadoptedthe“justintime”process.
“Justintime”asaphilosophyhasbeenusedwidelyoneverylevelofthesupplychain–notjustintheautomobileindustry,either.Intherealmofcommerce,implementinga“justintime”strategyresultedintheeliminationofwarehousespacesthatpreviouslylinkedthefactorytoaretailer.
“Justintime”allowsforsuppliestocirculatearoundtheclock.Thiskeepstheworkersworking,whilethemanagementcanfocustheirenergiesonturnoveraswellasmeetingdeadlines.Thecompanythusworkshardertomeetgoalsandattainbenefits,whichcancomeintheformofwageincreasesorpromotion.
JustInTimeManagementPhilosophy&Practice
DifficultiesandIssuesofJustInTimetobeawareofbeforeintroducingitinyourcompanyasamanagingphilosophyandtechniqueforimprovingefficiency
ByDr.MichaelMKisembo
Introduction
JustinTime(JIT)isaJapangrownmanagementphilosophy,whichh
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- justintime 供应 管理 理念 整理