库存决策培训教材

库存决策CR(2004)PrenticeHall,Inc.Chapter9每一个管理上的失误最后都会变成库存。“Everymanagementmistakeendsupininventory.”MichaelC.BergeracFormerChiefExecutiveRevlon,Inc.1产品计划三角形ProductinthePlanningTriangleCR(2004)PrenticeHall,Inc.PLANNINGORGANIZINGCONTROLLINGTransportStrategy•Transportfundamentals•TransportdecisionsCustomerservicegoals•Theproduct•Logisticsservice•Oc.&info.sys.InventoryStrategy•Forecasting•Inventorydecisions•Purchasingandsupplyschedulingdecisions•Storagefundamentals•StoragedecisionsLocationStrategy•Locationdecisions•Thenetworkplanningprocess计划组织控制TransportStrategy•Transportfundamentals•TransportdecisionsCustomerservicegoals•Theproduct•Logisticsservice•Oc.&info.sys.InventoryStrategy•Forecasting•Inventorydecisions•Purchasingandsupplyschedulingdecisions•Storagefundamentals•StoragedecisionsLocationStrategy•Locationdecisions•Thenetworkplanningprocess库存战略预测客户服务目标采购和供应时间决策存储基础知识存储决策产品物流服务订单管理和信息系统库存决策运输战略运输基础知识运输决策选址战略选址决策网络规划流程2InventoryDecisionsinStrategyCR(2004)PrenticeHall,Inc.PLANNINGORGANIZINGCONTROLLINGTransportStrategy•Transportfundamentals•TransportdecisionsCustomerservicegoals•Theproduct•Logisticsservice•Oc.&info.sys.InventoryStrategy•Forecasting•Inventorydecisions•Purchasingandsupplyschedulingdecisions•Storagefundamentals•StoragedecisionsLocationStrategy•Locationdecisions•ThenetworkplanningprocessPLANNINGORGANIZINGCONTROLLINGTransportStrategy•Transportfundamentals•TransportdecisionsCustomerservicegoals•Theproduct•Logisticsservice•Oc.&info.sys.InventoryStrategy•Forecasting•Inventorydecisions•Purchasingandsupplyschedulingdecisions•Storagefundamentals•StoragedecisionsLocationStrategy•Locationdecisions•Thenetworkplanningprocess3CR(2004)PrenticeHall,Inc.什么是库存WhatareInventories?库存就是在企业生产和物流渠道中各点堆积的原材料、供给品、零部件、半成品和成品。4CR(2004)PrenticeHall,Inc.WhereareInventories?MaterialsourcesInboundtransportationProductionOutboundtransportationFinishedgoodswarehousingCustomersInventorylocationsFinishedgoodsShippingInventoriesin-processReceivingProductionmaterials9-4原料来源生产内向运输外向运输成品储存客户原材料半成品成品库存选址5CR(2004)PrenticeHall,Inc.9.1对库存的评述9.1.1库存原因ReasonsforInventories1.改善客户服务2.降低成本首先，保有库存可以使生产的批量更大、批次更少，运作水平更高，因而产生经济效益其次，保有库存有助于实现采购和运输中的成本节约第三，先期购买可以在当前交易的低价位购买额外数量的产品。第四，抵销生产和运输过程中的不确定性第五，应付突发事件。6CR(2004)PrenticeHall,Inc.9.1对库存的评述9.1.1库存原因ReasonsforInventoriesImprovecustomerserviceProvidesimmediacyinproductavailabilityEncourageproduction,purchase,andtransportation economiesAllowsforlongproductionrunsTakesadvantageofprice-quantitydiscountsAllowsfortransporteconomiesfromlargershipmentsizesActasahedgeagainstpricechangesAllowspurchasingtotakeplaceundermostfavorableprice termsProtectagainstuncertaintiesindemandandleadtimesProvidesameasureofsafetytokeepoperations runningwhendemandlevelsandleadtimescannotbeknown forsureActasahedgeagainstcontingenciesBuffersagainstsucheventsasstrikes,fires,and disruptionsinsupply7CR(2004)PrenticeHall,Inc.9.1.2反对保有库存的原因ReasonsAgainstInventories第一，库存被认为是一种浪费第二，库存可能掩盖质量问题第三，保有库存鼓励人们以独立的观点来看待物流渠道整体的管理问题8CR(2004)PrenticeHall,Inc.9.1.2反对保有库存的原因ReasonsAgainstInventoriesTheyconsumecapitalresourcesthatmightbeputto betteruseelsewhereinthefirmTheytoooftenmaskqualityproblemsthatwouldmore immediatelybesolvedwithouttheirpresenceTheydivertmanagement’sattentionawayfromcareful planningandcontrolofthesupplyanddistribution channelsbypromotinganinsularattitudeabout channelmanagement9流通渠道Pipeline（Inventoriesintransit）投机SpeculativeGoodspurchasedinanticipationofpriceincreases定期性或周期性特征Regular/Cyclical/SeasonalInventoriesheldtomeetnormaloperatingneeds安全SafetyExtrastocksheldinanticipationofdemandand leadtimeuncertainties仓耗Obsolete/DeadStockInventoriesthatareoflittleornovalueduetobeing outofdate,spoiled,damaged,etc.9.2库存类型TypesofInventories10持久久性性需需求求PerpetualdemandContinueswellintotheforeseeablefuture季节节性性需需求求SeasonaldemandVarieswithregularpeaksandvalleysthroughouttheyear尖峰峰需需求求LumpydemandHighlyvariable规律律性性需需求求RegulardemandNothighlyvariable(3<Mean)终端需求TerminatingdemandDemandgoesto0inforeseeablefuture派生需求DeriveddemandDemandisdeterminedfromthedemandofanother itemofwhichitisapart9.3库存管管理类型的分分类9.3.1需需求特点NatureofDemandAccuratelyforecastingdemandissinglythemostimportantfactoringoodinventorymanagement11CR(2004)PrenticeHall,Inc.拉动式库存管管理法Pull基于每个仓库库的特定需求求以一定的订订货批量补足足库存每一个存储点点独立Eachstockinglocationisconsideredindependent最大化控制库库存Maximizeslocalcontrolofinventories推动式库存管管理法Push根据总需求分分配产品到库库存点鼓励规模生产产准时生产制Just-in-time同步库存流量量以满足需求求Attemptstosynchronizestockflowssoastojustmeetdemandasitoccurs最小化库存Minimizestheneedforinventory9.3.2管管理思想InventoryManagementPhilosophies12CR(2004)PrenticeHall,Inc.拉动式库存管管理法PullDrawsinventoryintothestockinglocationEachstockinglocationisconsideredindependentMaximizeslocalcontrolofinventories推动式库存管管理法PushAllocatesproductiontostockinglocationsbasedon overalldemandEncourageseconomiesofscaleinproduction准时生产制Just-in-timeAttemptstosynchronizestockflowssoastojustmeetdemandasitoccursMinimizestheneedforinventory9.3.2管管理思想InventoryManagementPhilosophies13CR(2004)PrenticeHall,Inc.供给驱动Supply-Driven供应量和时间间未知Supplyquantitiesandtimingareunknown所有的供应必必须接受和处处理Allsupplymustbeacceptedandprocessed通过需求控制制库存Inventoriesarecontrolledthroughdemand联合控制AggregateControl项目分类项目组根据基基于80-20法则确定定的销售水平平为3个或以上上的产品组合合允许不同的的库存策略9.3.2管管理思想InventoryManagementPhilosophies14PlantWarehouse#1Warehouse#2Warehouse#3A1A2A3A=AllocationquantitytoeachwarehouseQ=Requestedreplenishmentquantity

byeachwarehouseQ1Q2Q3DemandforecastDemandforecastDemandforecastPULL-ReplenishinventorywithordersizesbasedonspecificneedsofeachwarehousePUSH

-Allocatesupplytoeachwarehousebasedontheforecastforeachwarehouse拉动式或推动动式库存管理理思想Pullvs.PushInventoryPhilosophiesCR(2004)PrenticeHall,Inc.9-11推动式——基基于每个仓库库的预测将供供给分配给各各个仓库拉动式——基基于每个仓库库的特定需求求以一定订货货批量补足库库存A—将产品分分配到各个仓仓库Q—每个仓库库需要的补货货量159.3.3产产品汇总程度度多数库存管理理是针对每一一种产品的库库存进行控制制。——自下下而上法另一种方法是是管理一类产产品而不是管管理单独一种种产品——自自上而下法169.3.4多多层级库存供应链管理鼓鼓励管理者将将供应渠道中中更多的部分分包括到计划划过程中来，，供应渠道中中多个层级的的库存也成为为核心问题。。179.3.5虚虚拟库存虚拟库存即将将自己将来所所可能需要而而又没有的东东西的所有相相关信息建立立档案，包括括品名规格价价格数量等，，在需要时能能使用上。189.4库存目目标InventoryManagementObjectivesGoodinventorymanagementisacarefulbalancingactbetweenstockavailabilityandthecostofholdinginventory.CustomerService,

i.e.,StockAvailabilityInventoryHoldingcostsServiceobjectivesSettingstockinglevelssothatthereisonlyaspecifiedprobabilityofrunningoutofstockCostobjectivesBalancingconflictingcoststofindthemosteconomicalreplenishmentquantitiesandtimingCR(2004)PrenticeHall,Inc.199.4.1产产品的现货供供应比率服务水平=1-每年产产品缺货件数数的期望值/年需求总总量20CR(2004)PrenticeHall,Inc.采购成本Procurementcosts准备订单的成成本Costofpreparingtheorder订单传输成本本Costofordertransmission产品安装成本本Costofproductionsetupifappropriate接受地物料搬搬运或加工成成本Costofmaterialshandlingorprocessingatthe receivingdock商品价格Priceofthegoods9.4.2库库存管理相关关成本CostsRelevanttoInventoryManagement21CR(2004)PrenticeHall,Inc.RelevantCosts(Cont’’d)采购成本ProcurementcostsCostofpreparingtheorderCostofordertransmissionCostofproductionsetupifappropriateCostofmaterialshandlingorprocessingatthereceivingdockPriceofthegoods22CR(2004)PrenticeHall,Inc.库存持持有成成本Carryingcosts空间成成本。。库存存成本本随时时间推推移Costforholdingtheinventoryovertime资金成成本。。库存服服务成成本库存风风险成成本23CR(2004)PrenticeHall,Inc.9.4.2库存存管理理相关关成本本CostsRelevanttoInventoryManagement库存持持有成成本CarryingcostsCostforholdingtheinventoryovertimeTheprimarycostisthecostofmoneytiedupininventory,butalsoincludesobsolescence（报废废）,insurance,personalpropertytaxes,andstoragecostsTypically,costsrangefromthecostofshorttermcapitaltoabout40%/year.Theaverageisabout25%/yearoftheitemvalueininventory.24CR(2004)PrenticeHall,Inc.RelevantCosts(Cont’d)缺货成成本Out-of-stockcosts销售损损失成成本Lostsalescost利润损损失Profitimmediatelyforegone商誉损损失Futureprofitsforegonethroughlossofgoodwill缺货成成本Backordercost额外订订单处处理费费用Costsofextraorderhandling额外的的运输输和处处理费费用Additionaltransportationandhandlingcosts可能的的安装装费用用Possiblyadditionalsetupcosts25Inventory’sConflictingCostPatternsCost补给量量Replenishmentquantity缺货成成本Stockoutcost采购成成本Procurementcost库存持持有成成本Carryingcost总成本本Totalcost最低订订货成成本MinimumcostreorderquantityCR(2004)PrenticeHall,Inc.9-1626术语汇汇编GlossaryofTermssold

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n)('nsLTSLTCzxsrzMAXTROPQPEspksCISdDLT'zd=====================279.5推动动式库库存管管理1.通通过预预测或或其他他手段段确定定从现现在到到下一一次生生产或或采购购期间间的需需求量量2.找找出每每个存存储点点现有有的库库存量量3.设设定每每个存存储点点库存存的现现货供供应水水平4.计计算总总需求求5.计计算净净需求求6.在在平均均需求求速率率的基基础上上，将将超过过总净净需求求的部部分分分配到到各存存储点点7.在在净需需求加加上分分配的的超量量部分分得到到需分分配到到每个个存储储点的的货物物总量量289.6基本本的拉拉动式式库存存管理理（1））需求求是一一次性性的、、高季季度性性的或或持续续性的的情况况（2））订货货程序序在某某一库库存水水平上上启动动或由由库存存盘点点程序序启动动（3））需求求和补补货提提前期期存在在不同同程度度不确确定性性的情情况29CR(2004)PrenticeHall,Inc.9.6.1一次次性订订货量量SingleOrderPurchasingMakeaone-timepurchaseofanitem.Howmuchtoorder?Procedure:平衡衡利利润润增增加加额额与与损损失失增增加加额额利润润=单位位价价格格-单单位位成成本本损失失=单位位成成本本-单单位位残残值值如果果考考虑虑一一定定量量产产品品被被售售出出的的概概率率CPn，预预期期收收益益和和预预期期损损失失在在以以下下点点得得到到平平衡衡CPnx损失失=(1-CPn)x利润润orCPn=利润润/(利润润+损失失)CPn代代表表至至多多售售出出n个个单单位位产产品品的的累累积积概概率率Dailystockingofnewspapersinvendingmachinesisagoodexample9-1830CR(2004)PrenticeHall,Inc.9.6.1一一次次性性订订货货量量SingleOrderPurchasingMakeaone-timepurchaseofanitem.Howmuchtoorder?Procedure:Balanceincrementalprofitagainstincrementalloss.Profit=PriceperunitCostperunitLoss=CostperunitSalvagevalueperunitIfCPnisprobabilityofnunitsbeingsold,thenCPnxLoss=(1CPn)xProfitorCPn=Profit/(Profit+Loss)Now,increaseorderquantityuntilCPnjustmatchescumulativeprobabilityofsellingadditionalunits.Dailystockingofnewspapersinvendingmachinesisagoodexample9-1831CR(2004)PrenticeHall,Inc.SingleOrderPurchasing(Cont’’d)ExampleAclothingitemispurchasedforaseasonalsale.Itcosts$35,butithasasalepriceof$50.Aftertheseasonisover,itismarkeddownby50%toclearthemerchandise.Theestimatedquantitiestobesoldare:Numberofitems,nProbabilityofsellingexactlynitemsCumulativeprobability100.150.15150.200.35200.300.65250.200.85300.100.95350.051.001.009-1932CR(2004)PrenticeHall,Inc.9.6.1一次次性订货货量SingleOrderPurchasing(Cont’d)SolutionProfit=$50-35=$15Loss=$35-(0.5)(50)=$10CPn=15/(15+10)=0.60CPnisbetween15and20items,roundupandorder20items.339.6.2重复复订货量量1.即刻刻补货TC—每每年总的的相关成成本（美美元）Q—补充充存货的的订单批批量（件件）D—对库库存产品品的年需需求量（（件）S—采购购成本（（美元/订单））C—库存存产品的的价值（（美元/件）I—库存存持有成成本占产产品价值值的比例例（%/年）Developasimplecontrolsystembyfindingthereplenishmentquantity(Q)andthereorderpoint(ROP).Therelevanttotalcostis:总成本=采购购成本和库存存成本注:需求和提前期期确定—周期性的库存存管理9-21349.6.2重重复订货量1.即刻补货货TC—每年总总的相关成本本（美元）Q—补充存货货的订单批量量（件）D—对库存产产品的年需求求量（件）S—采购成本本（美元/订订单）C—库存产品品的价值（美美元/件）I—库存持有有成本占产品品价值的比例例（%/年））Developasimplecontrolsystembyfindingthereplenishmentquantity(Q)andthereorderpoint(ROP).Therelevanttotalcostis:总成本=采购购成本和库存存成本Note:Nouncertaintyindemandorleadtime—manageregular(cycle)stockonly9-2135CR(2004)PrenticeHall,Inc.0TimeLeadtimeLeadtimeOrderPlacedOrderPlacedOrderReceivedOrderReceivedInventoryLevelReorderpoint,RQReorderPointMethodUnderCertaintyforaSingleItemQuantityon-handpluson-order9-22369.6.2重重复订货量Given:d=50units/weekI=10%/yearS=$10/orderC=$5/unitLT=3weeksNote:Nouncertaintyindemandorleadtime—manageregular(cycle)stockonly9-212.有提前期期的补货37CR(2004)PrenticeHall,Inc.Usingdifferentialcalculus,theoptimalvalueforQwillbe:Thereorderpointis:ROP=d(LT)=3(50)=150unitsFamousEOQformulaRuleWhentheinventoryleveldropsto150units(ROP)thenreorder322units(Q*).9-23383.对不准确确数据的敏感感性尽管我们不一一定总能知道道需求和成本本的确切水平平，经济订货货批量的计算算对估计错误误的数据并不不敏感。394.非即刻补补货EOQ模型中中有一个基本本假设，即任任何订货批量量都可以及时时补进。在有有些制造和再再供应环节中中，生产要持持续一定时间间，并且可能能和需求同步步进行。p是生产速率率，d是需求求速率40CR(2004)PrenticeHall,Inc.9.7高级拉拉动式库存管管理9.7.1需需求不确定下下的再订货点点模型1.计算Q*和ROPGoodmethodforproducts:OfhighvalueThatarepurchasedfromonevendororplantHavingfeweconomiesofscaleinproduction,purchasing,ortransportation9-24FindQ*andROP41CR(2004)PrenticeHall,Inc.9.7高级拉拉动式库存管管理9.7.1需需求不确定下下的再订货点点模型Given:d=50units/weekC=$5/unitsd=10units/weekLT=3weeksI=10%/yearP=99%duringleadtimeS=$10/orderFindQ*andROPFromtheEOQformulaGoodmethodforproducts:OfhighvalueThatarepurchasedfromonevendororplantHavingfeweconomiesofscaleinproduction,purchasing,ortransportation9-2442CR(2004)PrenticeHall,Inc.ReorderPointControlforaSingleItemROPQuantityonhand0QQReceiveorderPlaceorderStockoutLTTimeLTDDLTP9-2543CR(2004)PrenticeHall,Inc.ROPQ0InventorylevelLTLTTimeSafetystockReorderPointControlforaSingleItemActualonhandQuantityonhand+onorderbackordersQuantityforcontrol9-2644Weeklydemandisnormallydistributedwithameanofd=100andastandarddeviationofsd=10Leadtimeis3weeksReorderPointControl(Cont’’d)Findingthereorderpointrequiresanunderstandingofthedemand-during-lead-timedistributionsd=10d=100sd=10d=100sd=10d=100++=Week3Week2Week1zPDDLTX=300ROPS’=17.39-2745CR(2004)PrenticeHall,Inc.ReorderPointControl(Cont’d)where2.33isthenormaldeviateataprobabilityof0.01takenfromanormaldistributiontable.462.平均库库存成本平均库存=经常性库库存+安全全库存A/L=Q/2+z(s'd)在前例中，，平均库存=322/2+2.33*17.32=201(个）47ReorderPointControl(Cont’d)3.总相关关成本TotalrelevantcostThetotalrelevantcostequationisnowextendedtoincludethecostsofsafetystockaswellasout-of-stock.Theout-of-stockcost(k)is$2/unit.Thepricetermisdropped.Hence,whereE(z)=0.0034fromaunitnormallosstableatazvalueof2.339-29484.服务水水平服务水平=1-每年年产品缺货货件数的期期望值/年年需求总量量49CR(2004)PrenticeHall,Inc.9.7.2缺货成本本已知情况况下的再订订货成本Withknownstockoutcostsk如果缺货成成本已知，，就没必要要规定客户户服务水平平了，可以以将服务和和成本的最最佳平衡点点计算出来来。可用反反复迭代的的方法1利用基本EOQ公式式得出订货货量的近似似值SolveinitiallyforQ2通过下式计计算提前期期内现货供供应的概率率UsingQ,find如果缺货允允许Ifbackorderingisallowedor如果销售出出现损失Ifsalesarelost50CR(2004)PrenticeHall,Inc.ReorderPointControl(Cont’d)3计算Q的修修正值UsingP,findrevisedQ4重复2,3步直到P和Q不再再变化Repeatsteps2and3untilnofurtherchange5计算ROP和其他所所需的统计计值ComputeROPandotherstatistics51CR(2004)PrenticeHall,Inc.ReorderPointControl(Cont’d)ExampleGiven:每月需求预预测,d11,107units预测标准差差,sd3,099units补货提前期期,LT1.5months产品价值,C$0.11/unit处理订单的的成本,S$10/order库存持有成成本,I20%/year缺货成本,k$0.01/unitBackorderingisallowed允许缺货FindoptimalQandP52CR(2004)PrenticeHall,Inc.ReorderPointControl(Cont’d)ExampleGiven:Monthlydemandforecast,d11,107unitsStd.errorofforecast.,sd3,099unitsReplenishmentlead-time,LT1.5months

Itemvalue,C$0.11/unit

Costforprocessingvendororder,S$10/order

Carryingcost,I20%/yearStockoutcost,k$0.01/unitBackorderingisallowedFindoptimalQandP53CR(2004)PrenticeHall,Inc.ReorderPointControl(Cont’d)SolutionEstimateQEstimatePReviseQFindAppA,z@0.82=0.92andfromAppB,E(0.92)=0.0968Forthesedata,s'dwaspreviouslycalculatedas3,795units54CR(2004)PrenticeHall,Inc.ReorderPointControl(Cont’d)RevisePNow,z@0.79=0.81andE(0.81)=0.118155CR(2004)PrenticeHall,Inc.ReorderPointControl(Cont’d)ReviseQContinuetoreviseQandPuntilnofurtherchangeoccurs.P=78%andQ=13,395units.NoteAlthoughthein-stockprobabilityduringtheleadtimeis78%,theactualservicelevelisSL=96%569.7.3需需求求和和提提前前期期不不确确定定条条件件下下的的再再订订货货点点法法ReorderpointcontrolwithdemandandleadtimeuncertaintiesCaution:Canresultinveryhighsafetystocklevelswhenlead-timevariabilityishigh9-37在需需求求和和提提前前期期不不确确定定的的情情况况下下找找到到正正态态分分布布的的标标准准差差s'd。。这可可以以通通过过将将需需求求波波动动和和提提前前期期波波动动累累加加获获得得。。由由此此s'd得到到修修正正公公式式sLT是提提前前期期的的标标准准差差57CR(2004)PrenticeHall,Inc.SupplyChainExample(Cont’’d)DistributorOutboundtransportInboundtransportPoolpointSupplierXspp==1012,.Xsii==4102,.Xsoo==20252,.ProcessingtimeTransporttimeTransporttime供应商内向运输输集散地加工时间间供应商58CR(2004)PrenticeHall,Inc.PullMethods(Cont’d)SupplychainexampleSupposethatinventoryistobemaintainedonadistributor’sshelfforanitemwhosedemandisforecastedtobed=100unitsperdayandsd=10unitsperday.Areorderpointisthemethodofinventorycontrol.Thesupplychannelisshowninthediagram.Determinetheaverageinventorytobeheldatthedistributorwherewehave:I=10%/yearC=$5/unitS=$10/orderP=0.99duringleadtime59CR(2004)PrenticeHall,Inc.SupplyChainExample(Cont’d)SolutionThereorderpointinventorytheoryapplies.However,determiningthestatisticsofthedemand-during-lead-timedistributionrequirestakingthelead-timefortheentirechannelintoaccount.Recall,60CR(2004)PrenticeHall,Inc.SupplyChainExample(Cont’d)AverageleadtimeNowand61CR(2004)PrenticeHall,Inc.9.7.4需求求不确定定条件下下的定期期盘点模模型Periodicreviewcontrolwithdemanduncertainty按预先确确定的周周期（T)核查查某种产产品的库库存。盘盘点后的的订货量量就是最最大值（（M)与与盘点时时所持有有的库存存量之差差。因此此可以通通过设定定T*和和M*控控制库存存。Given:d=50units/weekC=$5/unitsd=10units/weekLT=3weeksI=10%/yearP=0.99S=$10/orderk=$2/unitGoodmethodforproducts:OflowvalueThatarepurchasedfromthesamevendorHavingeconomiesofscaleinproduction,purchasing,andtransportation9-38629-39Q1StocklevelreviewedTTLTLTOrderreceivedQ2Mq0QuantityonhandTimeM=maximumlevel最高库存存M-q=replenishmentquantity补货量LT=leadtime提前期T=reviewinterval盘点周期期q=quantityonhand持有库存存量Qi=orderquantity订购量~单一产品品定期盘盘点PeriodicControlforaSingleItem盘点时库库存63CR(2004)PrenticeHall,Inc.EstimateQ*fromtheEOQformulaasifunderdemandcertaintyconditions.RecallthatthisisQ*=322units.Now,T*=Q*/d=322/50=6.4weeksConstructthedemand-during-lead-time-plus-order-cycle-timedistribution.TisorderreviewtimePeriodicReview(Cont’d)64CR(2004)PrenticeHall,Inc.PeriodicReview(Cont’d)PDD(T*+LT)X=d(T*+LT)MAXs′Z(s′)65PeriodicReview(Cont’d)whereFindMAXMAX=d(T*+LT)+z(s’)=50(6.4+3)+2.33(30.66)=470+71.44=541unitsRuleReviewtheinventoryevery6.4weeksandplaceanorderforthedifferencebetweentheMAXlevelof541unitsandthequantityonhand+quantityonorder––backorders.CR(2004)PrenticeHall,Inc.9-4266CR(2004)PrenticeHall,Inc.PeriodicReview(Cont’d)总相关成本本Thetotalrelevantcostforthisdesignis:TC=DS/Q+ICQ/2+ICr+ks’(D/Q)E(z)=2600(10)/322+(.10)(5)(322/2)+(.10)(5)(71)+2(30.66)(2600/322)(.0034)=$198Note与再订货的的点的方法法比（$182），，定期盘点点因为安全全程度更高高，所以成成本相对较较高（$198）67PullMethods(Cont’d)9-4468PullMethods(Cont’d)联合订货联合订货的的库存管理理包括确定定联合订货货的所有产产品的共同同盘点时间间，然后根根据其成本本和服务水水平求出每每种产品的的最高库存存水平。whereO=commonprocurementcost,$/order订购采购的的联合成本本下标i代表表某种特定定产品Note:Q*=T*xdCR(2004)PrenticeHall,Inc.9-4969每种产品的的最高库存存水平总相关成本本=订购成成本+经营营性库存持持有成本+安全库存存持有成本本+缺货成成本70CR(2004)PrenticeHall,Inc.JointOrderingExampleItemABAveragedailydemand(d)3075unitsDemandstd.dev.(sd)810unitsAverageleadtime(LT)1414daysAnnualcarryingcost(I)2525%Procurementcost(S)3020$/orderwithcommoncost(O)80$/orderIn-stockprobability(P)8092%Productvalue(C)170200$/unitOut-of-stockcost(k)2545$/unitSellingdaysperyear365365daysGiven71CR(2004)PrenticeHall,Inc.JointOrderingExample(Cont’d)FindcommonreviewtimeFindtargetquantity(MAX)foritemAthenz@80%=0.8472JointOrderingExample(Cont’d)whichhasanaverageinventoryofFindtargetquantity(MAX)foritemBthenforz@90%=1.41whichhasanaverageinventoryofCR(2004)PrenticeHall,Inc.73CR(2004)PrenticeHall,Inc.9.7.5实用拉动动式库存管管理方法PullMethods(Cont’d)1.最低-最高库存存管理法TheMin-Maxvariant当库存水平平达到再订订货点时，，要订购的的货物数量量就是目标标库存量M（最高点点）与所持持库存量q之差。74CR(2004)PrenticeHall,Inc.Min-MaxInventoryControl~Q1Q2Q*ROPqLTLTTimeQuantityonhandMAddincrementROPqtoordersize9-5475CR(2004)PrenticeHall,Inc.PullMethods(Cont’d)TheT,R,MvariantThisisacombinationofthemin-maxandtheperiodicreviewsystems.Thestocklevelsarereviewedperiodically,butcontrolthereleaseofthereplenishmentorderbywhetherthereorderpointisreached.Thismethodisusefulwheredemandislow,suchthatsmallquantitiesmightbereleasedunderaperiodicreviewmethod.76CR(2004)PrenticeHall,Inc.PullMethods(Cont’d)T,R,MvariantLTLTTTTimeRqInventorylevelT=reviewtimeR=reorderpointM–Q=replenishmentquantity补给量Q1Q2InventorynotbelowR,sodon’tplaceanorder9-5677CR(2004)PrenticeHall,Inc.PullMethods(Cont’d)2.按需需存储Stocktodemand(aperiodicreviewmethod)对某种产产品的需需求速率率进行预预测。预预测值乘乘以一个个代表盘盘点周期期、补货货提前期期，以及及包含需需求预测测和提前前期不确确定性的的时间增增量的因因子，就就得到目目标值。。预测时时还要记记录所持持库存量量，而订订购量就就等于目目标值减减去所持持库存量量。按需需存储库库存控制制法实际际上是一一种定期期盘点的的方法。。78CR(2004)PrenticeHall,Inc.PullMethods(Cont’d)3.多产产品、多多地点的的库存管管理Multipleitem,multiple-locationcontrolThetheorythathasbeendiscussedpreviouslyisusefulwhendesigninginventorycontrolsystemsforthepracticalproblemofcontrollingmanyitemsatmanylocations.Considerhowaspecialtychemicalcompanydesignedsuchapracticalsystem.TASO（订单积积累时间间）isthetimetoaccumulateastockorder(truckload)forallitemsinwarehouse.79Q1StockorderTASOTASOLTOrderreceivedLTQ2M0QuantityonhandTime

M=maximumlevelTASO=timetoaccumulatestockorder

Qi=orderquantityLT=leadtimeTASO~~Q3Multiple-Item,Multiple-LocationControlCR(2004)PrenticeHall,Inc.9-6080CustomerServiceLevelForindividualitemsTheservicelevel(stockavailability)actuallyachievedbyinventorycontrolmethodsisnotbestrepresentedbytheprobability(P)ofastockoutduringtheleadtime.Itismoreaccuratetocomputeitasfollows.Usingdatafromthereorderpointunderuncertaintyexample,theservicelevelwouldbe:Note:HigherthanPCR(2004)PrenticeHall,Inc.9-6181CR(2004)PrenticeHall,Inc.CustomerServiceLevel(Cont’d)ThisactuallevelishigherthanP=0.99thatwasusedtosettheinventorylevel.Thereasonisthatthereareperiodsoftimewhenthestocklevelisabovethereorderpointandthereisnoriskofbeingoutofstock.Methodsfordefiningstockavailabilityinclude:ProbabilityoffillingallitemdemandProbabilityoffillinganordercompletelyProbabilityoffillingapercentofallitemdemandWeightedaverageofitemsfilledonanorder(fillrate)82CR(2004)PrenticeHall,Inc.CustomerServiceLevel(Cont’d)FormultipleitemsonthesameorderIfallitemsonanorderhavethesameservicelevel,whatistheprobabilityoffillingtheordercomplete?Theservicelevelformultipleitemsisthecombinationoftheindividualitemservicelevelsasfollows:SL=SL1xSL2xSL3…xSLnSuppose3itemshavethefollowingservicelevels—0.95,0.89,and0.92.Theprobabilityoffillingtheordercompleteis:SL=0.95x0.89x0.92=0.7883PushInventoryControlExampleThreewarehousesareusedtosupply900retaildrugstores.Eachwarehouseservesapproximately300stores.Alargepurchaseofclockradiosismade,whereradiosweretobeapromotionaliteminthenextforecastperiod.Thespecialbuywillresultinmorestockthanneeded,butthecompanyexpectstosellallstockeventually.Warehousesaretohavea92%in-stockprobability.Allofthepurchasedradiosaretobeallocatedtothewarehousesbasedontheanticipateddemandlevelsateachwarehouse.Accountistakenoftheinventoryalreadyonhand.Atotalof5000radiosispurchased.Thenextpurchasewillbemadeinonemonth.Furtherinformationisgivenbelow.CR(2004)PrenticeHall,Inc.9-6484CR(2004)PrenticeHall,Inc.PushInventoryControl(Cont’’d)Ware-houseCurrentstocklevel,unitsForecasteddemand,unitsForecasterror(std.dev.),units14002,30010023501,4005530900204,