庫存決策培訓(xùn)教材

庫存決策CR(2004)PrenticeHall,Inc.Chapter9每一個管理上的失誤最后都會變成庫存?！癊verymanagementmistakeendsupininventory.”MichaelC.BergeracFormerChiefExecutiveRevlon,Inc.1第一頁，共一百三十三頁。產(chǎn)品計劃三角形ProductinthePlanningTriangleCR(2004)PrenticeHall,Inc.PLANNINGORGANIZINGCONTROLLINGTransportStrategy?Transportfundamentals?TransportdecisionsCustomerservicegoals?Theproduct?Logisticsservice?Oc.&info.sys.InventoryStrategy?Forecasting?Inventorydecisions?Purchasingandsupplyschedulingdecisions?Storagefundamentals?StoragedecisionsLocationStrategy?Locationdecisions?Thenetworkplanningprocess計劃組織控制TransportStrategy?Transportfundamentals?TransportdecisionsCustomerservicegoals?Theproduct?Logisticsservice?Oc.&info.sys.InventoryStrategy?Forecasting?Inventorydecisions?Purchasingandsupplyschedulingdecisions?Storagefundamentals?StoragedecisionsLocationStrategy?Locationdecisions?Thenetworkplanningprocess庫存戰(zhàn)略預(yù)測客戶服務(wù)目標(biāo)采購和供應(yīng)時間決策存儲基礎(chǔ)知識存儲決策產(chǎn)品物流服務(wù)訂單管理和信息系統(tǒng)庫存決策運輸戰(zhàn)略運輸基礎(chǔ)知識運輸決策選址戰(zhàn)略選址決策網(wǎng)絡(luò)規(guī)劃流程2第二頁，共一百三十三頁。InventoryDecisionsinStrategyCR(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?Thenetworkplanningprocess3第三頁，共一百三十三頁。CR(2004)PrenticeHall,Inc.什么是庫存WhatareInventories?庫存就是在企業(yè)生產(chǎn)和物流渠道中各點堆積的原材料、供給品、零部件、半成品和成品。4第四頁，共一百三十三頁。CR(2004)PrenticeHall,Inc.WhereareInventories?MaterialsourcesInboundtransportationProductionOutboundtransportationFinishedgoodswarehousingCustomersInventorylocationsFinishedgoodsShippingInventoriesin-processReceivingProductionmaterials9-4原料來源生產(chǎn)內(nèi)向運輸外向運輸成品儲存客戶原材料半成品成品庫存選址5第五頁，共一百三十三頁。CR(2004)PrenticeHall,Inc.9.1對庫存的評述9.1.1庫存原因ReasonsforInventories1.改善客戶服務(wù)2.降低成本首先，保有庫存可以使生產(chǎn)的批量更大、批次更少，運作水平更高，因而產(chǎn)生經(jīng)濟效益其次，保有庫存有助于實現(xiàn)采購和運輸中的成本節(jié)約第三，先期購買可以在當(dāng)前交易的低價位購買額外數(shù)量的產(chǎn)品。第四，抵銷生產(chǎn)和運輸過程中的不確定性第五，應(yīng)付突發(fā)事件。6第六頁，共一百三十三頁。CR(2004)PrenticeHall,Inc.9.1對庫存的評述9.1.1庫存原因ReasonsforInventoriesImprovecustomerserviceProvidesimmediacyinproductavailabilityEncourageproduction,purchase,andtransportation economiesAllowsforlongproductionrunsTakesadvantageofprice-quantitydiscountsAllowsfortransporteconomiesfromlargershipmentsizesActasahedgeagainstpricechangesAllowspurchasingtotakeplaceundermostfavorableprice termsProtectagainstuncertaintiesindemandandleadtimesProvidesameasureofsafetytokeepoperations runningwhendemandlevelsandleadtimescannotbeknown forsureActasahedgeagainstcontingenciesBuffersagainstsucheventsasstrikes,fires,and disruptionsinsupply7第七頁，共一百三十三頁。CR(2004)PrenticeHall,Inc.9.1.2反對保有庫存的原因ReasonsAgainstInventories第一，庫存被認(rèn)為是一種浪費第二，庫存可能掩蓋質(zhì)量問題第三，保有庫存鼓勵人們以獨立的觀點來看待物流渠道整體的管理問題8第八頁，共一百三十三頁。CR(2004)PrenticeHall,Inc.9.1.2反對保有庫存的原因ReasonsAgainstInventoriesTheyconsumecapitalresourcesthatmightbeputto betteruseelsewhereinthefirmTheytoooftenmaskqualityproblemsthatwouldmore immediatelybesolvedwithouttheirpresenceTheydivertmanagement’sattentionawayfromcareful planningandcontrolofthesupplyanddistribution channelsbypromotinganinsularattitudeabout channelmanagement9第九頁，共一百三十三頁。流通渠道Pipeline（Inventoriesintransit）投機SpeculativeGoodspurchasedinanticipationofpriceincreases定期性或周期性特征Regular/Cyclical/SeasonalInventoriesheldtomeetnormaloperatingneeds安全SafetyExtrastocksheldinanticipationofdemandand leadtimeuncertainties倉耗Obsolete/DeadStockInventoriesthatareoflittleornovalueduetobeing outofdate,spoiled,damaged,etc.9.2庫存類型TypesofInventories10第十頁，共一百三十三頁。持久性需求PerpetualdemandContinueswellintotheforeseeablefuture季節(jié)性需求SeasonaldemandVarieswithregularpeaksandvalleysthroughout theyear尖峰需求LumpydemandHighlyvariable規(guī)律性需求RegulardemandNothighlyvariable(3<Mean)終端需求TerminatingdemandDemandgoesto0inforeseeablefuture派生需求DeriveddemandDemandisdeterminedfromthedemandofanother itemofwhichitisapart9.3庫存管理類型的分類9.3.1需求特點NatureofDemandAccuratelyforecastingdemandissinglythemostimportantfactoringoodinventorymanagement11第十一頁，共一百三十三頁。CR(2004)PrenticeHall,Inc.拉動式庫存管理法Pull基于每個倉庫的特定需求以一定的訂貨批量補足庫存每一個存儲點獨立Eachstockinglocationisconsideredindependent最大化控制庫存Maximizeslocalcontrolofinventories推動式庫存管理法Push根據(jù)總需求分配產(chǎn)品到庫存點鼓勵規(guī)模生產(chǎn)準(zhǔn)時生產(chǎn)制Just-in-time同步庫存流量以滿足需求Attemptstosynchronizestockflowssoastojust

meetdemandasitoccurs最小化庫存Minimizestheneedforinventory9.3.2管理思想InventoryManagementPhilosophies12第十二頁，共一百三十三頁。CR(2004)PrenticeHall,Inc.拉動式庫存管理法PullDrawsinventoryintothestockinglocationEachstockinglocationisconsideredindependentMaximizeslocalcontrolofinventories推動式庫存管理法PushAllocatesproductiontostockinglocationsbasedon overalldemandEncourageseconomiesofscaleinproduction準(zhǔn)時生產(chǎn)制Just-in-timeAttemptstosynchronizestockflowssoastojust meetdemandasitoccursMinimizestheneedforinventory9.3.2管理思想InventoryManagementPhilosophies13第十三頁，共一百三十三頁。CR(2004)PrenticeHall,Inc.供給驅(qū)動Supply-Driven供應(yīng)量和時間未知Supplyquantitiesandtimingareunknown所有的供應(yīng)必須接受和處理Allsupplymustbeacceptedandprocessed通過需求控制庫存Inventoriesarecontrolledthroughdemand聯(lián)合控制AggregateControl項目分類項目組根據(jù)基于80-20法則確定的銷售水平為3個或以上的產(chǎn)品組合允許不同的庫存策略9.3.2管理思想InventoryManagementPhilosophies14第十四頁，共一百三十三頁。PlantWarehouse#1Warehouse#2Warehouse#3A1A2A3A=AllocationquantitytoeachwarehouseQ=Requestedreplenishmentquantity

byeachwarehouseQ1Q2Q3DemandforecastDemandforecastDemandforecastPULL-ReplenishinventorywithordersizesbasedonspecificneedsofeachwarehousePUSH

-Allocatesupplytoeachwarehousebasedontheforecastforeachwarehouse拉動式或推動式庫存管理思想Pullvs.PushInventoryPhilosophiesCR(2004)PrenticeHall,Inc.9-11推動式——基于每個倉庫的預(yù)測將供給分配給各個倉庫拉動式——基于每個倉庫的特定需求以一定訂貨批量補足庫存A—將產(chǎn)品分配到各個倉庫Q—每個倉庫需要的補貨量15第十五頁，共一百三十三頁。9.3.3產(chǎn)品匯總程度多數(shù)庫存管理是針對每一種產(chǎn)品的庫存進(jìn)行控制?！韵露戏硪环N方法是管理一類產(chǎn)品而不是管理單獨一種產(chǎn)品——自上而下法16第十六頁，共一百三十三頁。9.3.4多層級庫存供應(yīng)鏈管理鼓勵管理者將供應(yīng)渠道中更多的部分包括到計劃過程中來，供應(yīng)渠道中多個層級的庫存也成為核心問題。17第十七頁，共一百三十三頁。9.3.5虛擬庫存虛擬庫存即將自己將來所可能需要而又沒有的東西的所有相關(guān)信息建立檔案，包括品名規(guī)格價格數(shù)量等，在需要時能使用上。18第十八頁，共一百三十三頁。9.4庫存目標(biāo)InventoryManagementObjectivesGoodinventorymanagementisacarefulbalancingactbetweenstockavailabilityandthecostofholdinginventory.CustomerService,

i.e.,StockAvailabilityInventoryHoldingcostsServiceobjectivesSettingstockinglevelssothatthereisonlya specifiedprobabilityofrunningoutofstockCostobjectivesBalancingconflictingcoststofindthemost economicalreplenishmentquantitiesandtimingCR(2004)PrenticeHall,Inc.19第十九頁，共一百三十三頁。9.4.1產(chǎn)品的現(xiàn)貨供應(yīng)比率服務(wù)水平=1-每年產(chǎn)品缺貨件數(shù)的期望值/年需求總量20第二十頁，共一百三十三頁。CR(2004)PrenticeHall,Inc.采購成本Procurementcosts準(zhǔn)備訂單的成本Costofpreparingtheorder訂單傳輸成本Costofordertransmission產(chǎn)品安裝成本Costofproductionsetupifappropriate接受地物料搬運或加工成本Costofmaterialshandlingorprocessingatthe receivingdock商品價格Priceofthegoods9.4.2庫存管理相關(guān)成本CostsRelevanttoInventoryManagement21第二十一頁，共一百三十三頁。CR(2004)PrenticeHall,Inc.RelevantCosts(Cont’d)采購成本ProcurementcostsCostofpreparingtheorderCostofordertransmissionCostofproductionsetupifappropriateCostofmaterialshandlingorprocessingatthe receivingdockPriceofthegoods22第二十二頁，共一百三十三頁。CR(2004)PrenticeHall,Inc.庫存持有成本Carryingcosts空間成本。庫存成本隨時間推移Costforholdingtheinventoryovertime資金成本。庫存服務(wù)成本庫存風(fēng)險成本23第二十三頁，共一百三十三頁。CR(2004)PrenticeHall,Inc.9.4.2庫存管理相關(guān)成本CostsRelevanttoInventoryManagement庫存持有成本CarryingcostsCostforholdingtheinventoryovertimeTheprimarycostisthecostofmoneytiedupin inventory,butalsoincludesobsolescence（報廢）, insurance,personalpropertytaxes,andstorage costsTypically,costsrangefromthecostofshortterm capitaltoabout40%/year.Theaverageisabout 25%/yearoftheitemvalueininventory.24第二十四頁，共一百三十三頁。CR(2004)PrenticeHall,Inc.RelevantCosts(Cont’d)缺貨成本Out-of-stockcosts銷售損失成本Lostsalescost利潤損失Profitimmediatelyforegone商譽損失Futureprofitsforegonethroughlossofgoodwill缺貨成本Backordercost額外訂單處理費用Costsofextraorderhandling額外的運輸和處理費用Additionaltransportationandhandlingcosts可能的安裝費用Possiblyadditionalsetupcosts25第二十五頁，共一百三十三頁。Inventory’sConflictingCostPatternsCost補給量Replenishmentquantity缺貨成本Stockoutcost采購成本Procurementcost庫存持有成本Carryingcost總成本Totalcost最低訂貨成本MinimumcostreorderquantityCR(2004)PrenticeHall,Inc.9-1626第二十六頁，共一百三十三頁。術(shù)語匯編GlossaryofTermssold

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n)('nsLTSLTCzxsrzMAXTROPQPEspksCISdDLT'zd=====================27第二十七頁，共一百三十三頁。9.5推動式庫存管理1.通過預(yù)測或其他手段確定從現(xiàn)在到下一次生產(chǎn)或采購期間的需求量2.找出每個存儲點現(xiàn)有的庫存量3.設(shè)定每個存儲點庫存的現(xiàn)貨供應(yīng)水平4.計算總需求5.計算凈需求6.在平均需求速率的基礎(chǔ)上，將超過總凈需求的部分分配到各存儲點7.在凈需求加上分配的超量部分得到需分配到每個存儲點的貨物總量28第二十八頁，共一百三十三頁。9.6基本的拉動式庫存管理（1）需求是一次性的、高季度性的或持續(xù)性的情況（2）訂貨程序在某一庫存水平上啟動或由庫存盤點程序啟動（3）需求和補貨提前期存在不同程度不確定性的情況29第二十九頁，共一百三十三頁。CR(2004)PrenticeHall,Inc.9.6.1一次性訂貨量SingleOrderPurchasingMakeaone-timepurchaseofanitem.Howmuchtoorder?Procedure:

平衡利潤增加額與損失增加額利潤=單位價格-單位成本損失=單位成本-單位殘值如果考慮一定量產(chǎn)品被售出的概率CPn，預(yù)期收益和預(yù)期損失在以下點得到平衡CPnx損失=(1-CPn)x利潤or

CPn=利潤/(利潤+損失)CPn代表至多售出n個單位產(chǎn)品的累積概率Dailystockingofnewspapersinvendingmachinesisagoodexample9-1830第三十頁，共一百三十三頁。CR(2004)PrenticeHall,Inc.9.6.1一次性訂貨量SingleOrderPurchasingMakeaone-timepurchaseofanitem.Howmuchtoorder?Procedure:Balanceincrementalprofitagainstincrementalloss.Profit=PriceperunitCostperunitLoss=CostperunitSalvagevalueperunitIfCPnisprobabilityofnunitsbeingsold,thenCPnxLoss=(1CPn)xProfitor

CPn=Profit/(Profit+Loss)Now,increaseorderquantityuntilCPnjustmatchescumulativeprobabilityofsellingadditionalunits.Dailystockingofnewspapersinvendingmachinesisagoodexample9-1831第三十一頁，共一百三十三頁。CR(2004)PrenticeHall,Inc.SingleOrderPurchasing(Cont’d)ExampleAclothingitemispurchasedforaseasonalsale.Itcosts$35,butithasasalepriceof$50.Aftertheseasonisover,itismarkeddownby50%toclearthemerchandise.Theestimatedquantitiestobesoldare:Numberofitems,nProbabilityofsellingexactlynitemsCumulativeprobability100.150.15150.200.35200.300.65250.200.85300.100.95350.05

1.001.009-1932第三十二頁，共一百三十三頁。CR(2004)PrenticeHall,Inc.9.6.1一次性訂貨量SingleOrderPurchasing(Cont’d)SolutionProfit=$50-35=$15Loss=$35-(0.5)(50)=$10CPn=15/(15+10)=0.60CPnisbetween15and20items,roundupandorder20items.33第三十三頁，共一百三十三頁。9.6.2重復(fù)訂貨量1.即刻補貨TC—每年總的相關(guān)成本（美元）Q—補充存貨的訂單批量（件）D—對庫存產(chǎn)品的年需求量（件）S—采購成本（美元/訂單）C—庫存產(chǎn)品的價值（美元/件）I—庫存持有成本占產(chǎn)品價值的比例（%/年）Developasimplecontrolsystembyfindingthereplenishmentquantity(Q)andthereorderpoint(ROP).Therelevanttotalcostis:總成本=采購成本和庫存成本注:需求和提前期確定—周期性的庫存管理9-2134第三十四頁，共一百三十三頁。9.6.2重復(fù)訂貨量1.即刻補貨TC—每年總的相關(guān)成本（美元）Q—補充存貨的訂單批量（件）D—對庫存產(chǎn)品的年需求量（件）S—采購成本（美元/訂單）C—庫存產(chǎn)品的價值（美元/件）I—庫存持有成本占產(chǎn)品價值的比例（%/年）Developasimplecontrolsystembyfindingthereplenishmentquantity(Q)andthereorderpoint(ROP).Therelevanttotalcostis:總成本=采購成本和庫存成本Note:Nouncertaintyindemandorleadtime—manageregular(cycle)stockonly9-2135第三十五頁，共一百三十三頁。CR(2004)PrenticeHall,Inc.0TimeLeadtimeLeadtimeOrderPlacedOrderPlacedOrderReceivedOrderReceivedInventoryLevelReorderpoint,RQReorderPointMethodUnderCertaintyforaSingleItemQuantityon-handpluson-order9-2236第三十六頁，共一百三十三頁。9.6.2重復(fù)訂貨量Given:

d=50units/week

I=10%/year

S=$10/order

C=$5/unit

LT=3weeksNote:Nouncertaintyindemandorleadtime—manageregular(cycle)stockonly9-212.有提前期的補貨37第三十七頁，共一百三十三頁。CR(2004)PrenticeHall,Inc.Usingdifferentialcalculus,theoptimalvalueforQwillbe:Thereorderpointis:

ROP=d(LT)=3(50)=150unitsFamousEOQformulaRule

Whentheinventoryleveldropsto150units(ROP)thenreorder322units(Q*).9-2338第三十八頁，共一百三十三頁。3.對不準(zhǔn)確數(shù)據(jù)的敏感性盡管我們不一定總能知道需求和成本的確切水平，經(jīng)濟訂貨批量的計算對估計錯誤的數(shù)據(jù)并不敏感。39第三十九頁，共一百三十三頁。4.非即刻補貨EOQ模型中有一個基本假設(shè)，即任何訂貨批量都可以及時補進(jìn)。在有些制造和再供應(yīng)環(huán)節(jié)中，生產(chǎn)要持續(xù)一定時間，并且可能和需求同步進(jìn)行。p是生產(chǎn)速率，d是需求速率40第四十頁，共一百三十三頁。CR(2004)PrenticeHall,Inc.9.7高級拉動式庫存管理9.7.1需求不確定下的再訂貨點模型1.計算Q*和ROPGoodmethodforproducts:OfhighvalueThatarepurchasedfromonevendororplantHavingfeweconomiesofscaleinproduction,purchasing,ortransportation9-24FindQ*andROP41第四十一頁，共一百三十三頁。CR(2004)PrenticeHall,Inc.9.7高級拉動式庫存管理9.7.1需求不確定下的再訂貨點模型Given:

d=50units/weekC=$5/unit

sd=10units/weekLT=3weeks

I=10%/yearP=99%duringleadtime

S=$10/orderFindQ*andROPFromtheEOQformulaGoodmethodforproducts:OfhighvalueThatarepurchasedfromonevendororplantHavingfeweconomiesofscaleinproduction,purchasing,ortransportation9-2442第四十二頁，共一百三十三頁。CR(2004)PrenticeHall,Inc.ReorderPointControlforaSingleItemROPQuantityonhand0QQReceiveorderPlaceorderStockoutLTTimeLTDDLTP9-2543第四十三頁，共一百三十三頁。CR(2004)PrenticeHall,Inc.ROPQ0InventorylevelLTLTTimeSafetystockReorderPointControlforaSingleItemActualonhandQuantityonhand+onorderbackordersQuantityforcontrol9-2644第四十四頁，共一百三十三頁。Weeklydemandisnormallydistributedwithameanofd=100andastandarddeviationofsd=10Leadtimeis3weeksReorderPointControl(Cont’d)Findingthereorderpointrequiresanunderstandingofthedemand-during-lead-timedistributionsd=10d

=100sd=10d

=100sd=10d

=100++=Week3Week2Week1zPDDLTX=300ROPS’=17.39-2745第四十五頁，共一百三十三頁。CR(2004)PrenticeHall,Inc.ReorderPointControl(Cont’d)where2.33isthenormaldeviateataprobabilityof0.01takenfromanormaldistributiontable.46第四十六頁，共一百三十三頁。2.平均庫存成本平均庫存=經(jīng)常性庫存+安全庫存A/L=Q/2+z(s'd)在前例中，平均庫存=322/2+2.33*17.32=201(個）47第四十七頁，共一百三十三頁。ReorderPointControl(Cont’d)3.總相關(guān)成本TotalrelevantcostThetotalrelevantcostequationisnowextendedtoincludethecostsofsafetystockaswellasout-of-stock.Theout-of-stockcost(k)is$2/unit.Thepricetermisdropped.Hence,whereE(z)=0.0034fromaunitnormallosstableatazvalueof2.339-2948第四十八頁，共一百三十三頁。4.服務(wù)水平服務(wù)水平=1-每年產(chǎn)品缺貨件數(shù)的期望值/年需求總量49第四十九頁，共一百三十三頁。CR(2004)PrenticeHall,Inc.9.7.2缺貨成本已知情況下的再訂貨成本W(wǎng)ithknownstockoutcostsk如果缺貨成本已知，就沒必要規(guī)定客戶服務(wù)水平了，可以將服務(wù)和成本的最佳平衡點計算出來?？捎梅磸?fù)迭代的方法1

利用基本EOQ公式得出訂貨量的近似值SolveinitiallyforQ2

通過下式計算提前期內(nèi)現(xiàn)貨供應(yīng)的概率UsingQ,find如果缺貨允許Ifbackorderingisallowedor如果銷售出現(xiàn)損失Ifsalesarelost50第五十頁，共一百三十三頁。CR(2004)PrenticeHall,Inc.ReorderPointControl(Cont’d)3

計算Q的修正值UsingP,findrevisedQ4

重復(fù)2,3步直到P和Q不再變化Repeatsteps2and3untilnofurtherchange5

計算ROP和其他所需的統(tǒng)計值ComputeROPandotherstatistics51第五十一頁，共一百三十三頁。CR(2004)PrenticeHall,Inc.ReorderPointControl(Cont’d)ExampleGiven:每月需求預(yù)測,d 11,107units

預(yù)測標(biāo)準(zhǔn)差,sd 3,099units

補貨提前期,LT 1.5months

產(chǎn)品價值,C $0.11/unit

處理訂單的成本,S $10/order

庫存持有成本,I 20%/year缺貨成本,k$0.01/unitBackorderingisallowed允許缺貨FindoptimalQandP52第五十二頁，共一百三十三頁。CR(2004)PrenticeHall,Inc.ReorderPointControl(Cont’d)ExampleGiven:Monthlydemandforecast,d 11,107units

Std.errorofforecast.,sd 3,099units

Replenishmentlead-time,LT 1.5months

Itemvalue,C $0.11/unit

Costforprocessing

vendororder,S $10/order

Carryingcost,I 20%/yearStockoutcost,k$0.01/unitBackorderingisallowedFindoptimalQandP53第五十三頁，共一百三十三頁。CR(2004)PrenticeHall,Inc.ReorderPointControl(Cont’d)SolutionEstimateQEstimatePReviseQFindAppA,z@0.82=0.92andfrom

AppB,E(0.92)=0.0968Forthesedata,s'd

waspreviouslycalculatedas3,795units54第五十四頁，共一百三十三頁。CR(2004)PrenticeHall,Inc.ReorderPointControl(Cont’d)RevisePNow,z@0.79=0.81andE(0.81)=0.118155第五十五頁，共一百三十三頁。CR(2004)PrenticeHall,Inc.ReorderPointControl(Cont’d)ReviseQContinuetoreviseQandPuntilnofurtherchangeoccurs.P=78%andQ=13,395units.Note

Althoughthein-stockprobabilityduringtheleadtimeis78%,theactualservicelevelisSL=96%56第五十六頁，共一百三十三頁。9.7.3需求和提前期不確定條件下的再訂貨點法ReorderpointcontrolwithdemandandleadtimeuncertaintiesCaution:Canresultinveryhighsafetystocklevelswhenlead-timevariabilityishigh9-37在需求和提前期不確定的情況下找到正態(tài)分布的標(biāo)準(zhǔn)差s'd。這可以通過將需求波動和提前期波動累加獲得。由此s'd得到修正公式sLT是提前期的標(biāo)準(zhǔn)差57第五十七頁，共一百三十三頁。CR(2004)PrenticeHall,Inc.SupplyChainExample(Cont’d)DistributorOutboundtransportInboundtransportPoolpointSupplierXspp==1012,.Xsii==4102,.Xsoo==20252,.ProcessingtimeTransporttimeTransporttime供應(yīng)商內(nèi)向運輸集散地加工時間供應(yīng)商58第五十八頁，共一百三十三頁。CR(2004)PrenticeHall,Inc.PullMethods(Cont’d)SupplychainexampleSupposethatinventoryistobemaintainedonadistributor’sshelfforanitemwhosedemandisforecastedtobed=100unitsperdayandsd=10unitsperday.Areorderpointisthemethodofinventorycontrol.Thesupplychannelisshowninthediagram.Determinetheaverageinventorytobeheldatthedistributorwherewehave:

I=10%/yearC=$5/unit

S=$10/orderP=0.99duringleadtime59第五十九頁，共一百三十三頁。CR(2004)PrenticeHall,Inc.SupplyChainExample(Cont’d)SolutionThereorderpointinventorytheoryapplies.However,determiningthestatisticsofthedemand-during-lead-timedistributionrequirestakingthelead-timefortheentirechannelintoaccount.Recall,60第六十頁，共一百三十三頁。CR(2004)PrenticeHall,Inc.SupplyChainExample(Cont’d)AverageleadtimeNowand61第六十一頁，共一百三十三頁。CR(2004)PrenticeHall,Inc.9.7.4需求不確定條件下的定期盤點模型Periodicreviewcontrolwithdemanduncertainty

按預(yù)先確定的周期（T)核查某種產(chǎn)品的庫存。盤點后的訂貨量就是最大值（M)與盤點時所持有的庫存量之差。因此可以通過設(shè)定T*和M*控制庫存。Given:

d=50units/weekC=$5/unit

sd=10units/weekLT=3weeks

I=10%/yearP=0.99

S=$10/orderk=$2/unitGoodmethodforproducts:OflowvalueThatarepurchasedfromthesamevendorHavingeconomiesofscaleinproduction,purchasing,andtransportation9-3862第六十二頁，共一百三十三頁。9-39Q1StocklevelreviewedTTLTLTOrderreceivedQ2Mq0QuantityonhandTime

M=maximumlevel最高庫存M-q=replenishmentquantity補貨量

LT=leadtime提前期T=reviewinterval盤點周期q=quantityonhand持有庫存量Qi=orderquantity訂購量~單一產(chǎn)品定期盤點PeriodicControlforaSingleItem盤點時庫存63第六十三頁，共一百三十三頁。CR(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)64第六十四頁，共一百三十三頁。CR(2004)PrenticeHall,Inc.PeriodicReview(Cont’d)PDD(T*+LT)X=d(T*+LT)MAXs′Z(s′)65第六十五頁，共一百三十三頁。PeriodicReview(Cont’d)whereFindMAX

MAX=d(T*+LT)+z(s’)=50(6.4+3)+2.33(30.66)=470+71.44=541unitsRuleReviewtheinventoryevery6.4weeksandplaceanorderforthedifferencebetweentheMAXlevelof541unitsandthequantityonhand+quantityonorder–backorders.CR(2004)PrenticeHall,Inc.9-4266第六十六頁，共一百三十三頁。CR(2004)PrenticeHall,Inc.PeriodicReview(Cont’d)總相關(guān)成本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

與再訂貨的點的方法比（$182），定期盤點因為安全程度更高，所以成本相對較高（$198）67第六十七頁，共一百三十三頁。PullMethods(Cont’d)9-4468第六十八頁，共一百三十三頁。PullMethods(Cont’d)聯(lián)合訂貨聯(lián)合訂貨的庫存管理包括確定聯(lián)合訂貨的所有產(chǎn)品的共同盤點時間，然后根據(jù)其成本和服務(wù)水平求出每種產(chǎn)品的最高庫存水平。whereO=commonprocurementcost,$/order訂購采購的聯(lián)合成本下標(biāo)i代表某種特定產(chǎn)品Note:

Q*=T*xdCR(2004)PrenticeHall,Inc.9-4969第六十九頁，共一百三十三頁。每種產(chǎn)品的最高庫存水平總相關(guān)成本=訂購成本+經(jīng)營性庫存持有成本+安全庫存持有成本+缺貨成本70第七十頁，共一百三十三頁。CR(2004)PrenticeHall,Inc.JointOrderingExample

Item

ABAveragedailydemand(d)30

75unitsDemandstd.dev.(sd)8

10unitsAverageleadtime(LT)14

14daysAnnualcarryingcost(I)25

25%Procurementcost(S)30

20$/orderwithcommoncost(O)80$/orderIn-stockprobability(P)80

92%Productvalue(C)170

200$/unitOut-of-stockcost(k)25

45$/unitSellingdaysperyear365

365daysGiven71第七十一頁，共一百三十三頁。CR(2004)PrenticeHall,Inc.JointOrderingExample(Cont’d)FindcommonreviewtimeFindtargetquantity(MAX)foritemAthenz@80%=0.8472第七十二頁，共一百三十三頁。JointOrderingExample(Cont’d)whichhasanaverageinventoryofFindtargetquantity(MAX)foritemBthenforz@90%=1.41whichhasanaverageinventoryofCR(2004)PrenticeHall,Inc.73第七十三頁，共一百三十三頁。CR(2004)PrenticeHall,Inc.9.7.5實用拉動式庫存管理方法PullMethods(Cont’d)1.最低-最高庫存管理法TheMin-Maxvariant當(dāng)庫存水平達(dá)到再訂貨點時，要訂購的貨物數(shù)量就是目標(biāo)庫存量M（最高點）與所持庫存量q之差。74第七十四頁，共一百三十三頁。CR(2004)PrenticeHall,Inc.Min-MaxInventoryControl~Q1Q2Q*ROPqLTLTTimeQuantityonhandMAddincrementROPqtoordersize9-5475第七十五頁，共一百三十三頁。CR(2004)PrenticeHall,Inc.PullMethods(Cont’d)TheT,R,MvariantThisisacombinationofthemin-maxandtheperiodicreviewsystems.Thestocklevelsarereviewedperiodically,butcontrolthereleaseofthereplenishmentorderbywhetherthereorderpointisreached.Thismethodisusefulwheredemandislow,suchthatsmallquantitiesmightbereleasedunderaperiodicreviewmethod.76第七十六頁，共一百三十三頁。CR(2004)PrenticeHall,Inc.PullMethods(Cont’d)T,R,MvariantLTLTTTTimeRqInventorylevelT=reviewtimeR=reorderpointM–Q=replenishmentquantity補給量Q1Q2InventorynotbelowR,sodon’tplaceanorder9-5677第七十七頁，共一百三十三頁。CR(2004)PrenticeHall,Inc.PullMethods(Cont’d)2.按需存儲Stocktodemand(aperiodicreviewmethod)對某種產(chǎn)品的需求速率進(jìn)行預(yù)測。預(yù)測值乘以一個代表盤點周期、補貨提前期，以及包含需求預(yù)測和提前期不確定性的時間增量的因子，就得到目標(biāo)值。預(yù)測時還要記錄所持庫存量，而訂購量就等于目標(biāo)值減去所持庫存量。按需存儲庫存控制法實際上是一種定期盤點的方法。78第七十八頁，共一百三十三頁。CR(2004)PrenticeHall,Inc.PullMethods(Cont’d)3.多產(chǎn)品、多地點的庫存管理Multipleitem,multiple-locationcontrolThetheorythathasbeendiscussedpreviouslyisusefulwhendesigninginventorycontrolsystemsforthepracticalproblemofcontrollingmanyitemsatmanylocations.Considerhowaspecialtychemicalcompanydesignedsuchapracticalsystem.TASO（訂單積累時間）isthetimetoaccumulateastockorder(truckload)forallitemsinwarehouse.79第七十九頁，共一百三十三頁。Q1StockorderTASOTASOLTOrderreceivedLTQ2M0QuantityonhandTime

M=maximumlevelTASO=timetoaccumulatestockorder

Qi=orderquantityLT=leadtimeTASO~~Q3Multiple-Item,Multiple-LocationControlCR(2004)PrenticeHall,Inc.9-6080第八十頁，共一百三十三頁。CustomerServiceLevelForindividualitemsTheservicelevel(stockavailability)actuallyachievedbyinventorycontrolmethodsisnotbestrepresentedbytheprobability(P)ofastockoutduringtheleadtime.Itismoreaccuratetocomputeitasfollows.Usingdatafromthereorderpointunderuncertaintyexample,theservicelevelwouldbe:Note:HigherthanPCR(2004)PrenticeHall,Inc.9-6181第八十一頁，共一百三十三頁。CR(2004)PrenticeHall,Inc.CustomerServiceLevel(Cont’d)ThisactuallevelishigherthanP=0.99thatwasusedtosettheinventorylevel.Thereasonisthatthereareperiodsoftimewhenthestocklevelisabovethereorderpointandthereisnoriskofbeingoutofstock.Methodsfordefiningstockavailabilityinclude:ProbabilityoffillingallitemdemandProbabilityoffillinganordercompletelyProbabilityoffillingapercentofallitemdemandWeightedaverageofitemsfilledonanorder(fill rate)82第八十二頁，共一百三十三頁。CR(2004)PrenticeHall,Inc.CustomerS