庫(kù)存決策第九章產(chǎn)品計(jì)劃三角形ProductinthePlanningTriangleCR(2004)PrenticeHall,Inc.PLANNINGORGANIZINGCONTROLLINGTransportStrategy?Transportfundamentals?TransportdecisionsCustomerservicegoals?Theproduct?Logisticsservice?Ord.proc.&info.sys.InventoryStrategy?Forecasting?Inventorydecisions?Purchasingandsupplyschedulingdecisions?Storagefundamentals?StoragedecisionsLocationStrategy?Locationdecisions?Thenetworkplanningprocess組織控制TransportStrategy?Transportfundamentals?TransportdecisionsCustomerservicegoals?Theproduct?Logisticsservice?Ord.proc.&info.sys.InventoryStrategy?Forecasting?Inventorydecisions?Purchasingandsupplyschedulingdecisions?Storagefundamentals?StoragedecisionsLocationStrategy?Locationdecisions?Thenetworkplanningprocess庫(kù)存戰(zhàn)略預(yù)測(cè)客戶服務(wù)目標(biāo)采購(gòu)和供應(yīng)時(shí)間決策存儲(chǔ)基礎(chǔ)知識(shí)存儲(chǔ)決策產(chǎn)品物流服務(wù)訂單管理和信息系統(tǒng)庫(kù)存決策運(yùn)輸戰(zhàn)略運(yùn)輸基礎(chǔ)知識(shí)運(yùn)輸決策選址戰(zhàn)略選址決策網(wǎng)絡(luò)規(guī)劃流程2InventoryDecisionsinStrategyCR(2004)PrenticeHall,Inc.PLANNINGORGANIZINGCONTROLLINGTransportStrategy?Transportfundamentals?TransportdecisionsCustomerservicegoals?Theproduct?Logisticsservice?Ord.proc.&info.sys.InventoryStrategy?Forecasting?Inventorydecisions?Purchasingandsupplyschedulingdecisions?Storagefundamentals?StoragedecisionsLocationStrategy?Locationdecisions?ThenetworkplanningprocessPLANNINGORGANIZINGCONTROLLINGTransportStrategy?Transportfundamentals?TransportdecisionsCustomerservicegoals?Theproduct?Logisticsservice?Ord.proc.&info.sys.InventoryStrategy?Forecasting?Inventorydecisions?Purchasingandsupplyschedulingdecisions?Storagefundamentals?StoragedecisionsLocationStrategy?Locationdecisions?Thenetworkplanningprocess3CR(2004)PrenticeHall,Inc.什么是庫(kù)存WhatareInventories?庫(kù)存就是在企業(yè)生產(chǎn)和物流渠道中各點(diǎn)堆積的原材料、供給品、零部件、半成品和成品。4CR(2004)PrenticeHall,Inc.WhereareInventories?MaterialsourcesInboundtransportationProductionOutboundtransportationFinishedgoodswarehousingCustomersInventorylocationsFinishedgoodsShippingInventoriesin-processReceivingProductionmaterials9-4原料來(lái)源生產(chǎn)內(nèi)向運(yùn)輸外向運(yùn)輸成品儲(chǔ)存客戶原材料半成品成品庫(kù)存選址5CR(2004)PrenticeHall,Inc.9.1對(duì)庫(kù)存的評(píng)述9.1.1庫(kù)存原因ReasonsforInventories1.改善客戶服務(wù)2.降低成本首先，保有庫(kù)存可以使生產(chǎn)的批量更大、批次更少，運(yùn)作水平更高，因而產(chǎn)生經(jīng)濟(jì)效益其次，保有庫(kù)存有助于實(shí)現(xiàn)采購(gòu)和運(yùn)輸中的成本節(jié)約第三，先期購(gòu)買(mǎi)可以在當(dāng)前交易的低價(jià)位購(gòu)買(mǎi)額外數(shù)量的產(chǎn)品。第四，抵銷(xiāo)生產(chǎn)和運(yùn)輸過(guò)程中的不確定性第五，應(yīng)付突發(fā)事件。6CR(2004)PrenticeHall,Inc.9.1對(duì)庫(kù)存的評(píng)述9.1.1庫(kù)存原因ReasonsforInventoriesImprovecustomerserviceProvidesimmediacyinproductavailabilityEncourageproduction,purchase,andtransportation economiesAllowsforlongproductionrunsTakesadvantageofprice-quantitydiscountsAllowsfortransporteconomiesfromlargershipmentsizesActasahedgeagainstpricechangesAllowspurchasingtotakeplaceundermostfavorableprice termsProtectagainstuncertaintiesindemandandleadtimesProvidesameasureofsafetytokeepoperations runningwhendemandlevelsandleadtimescannotbeknown forsureActasahedgeagainstcontingenciesBuffersagainstsucheventsasstrikes,fires,and disruptionsinsupply7CR(2004)PrenticeHall,Inc.9.1.2反對(duì)保有庫(kù)存的原因ReasonsAgainstInventories第一，庫(kù)存被認(rèn)為是一種浪費(fèi)第二，庫(kù)存可能掩蓋質(zhì)量問(wèn)題第三，保有庫(kù)存鼓勵(lì)人們以獨(dú)立的觀點(diǎn)來(lái)看待物流渠道整體的管理問(wèn)題8CR(2004)PrenticeHall,Inc.9.1.2反對(duì)保有庫(kù)存的原因ReasonsAgainstInventoriesTheyconsumecapitalresourcesthatmightbeputto betteruseelsewhereinthefirmTheytoooftenmaskqualityproblemsthatwouldmore immediatelybesolvedwithouttheirpresenceTheydivertmanagement’sattentionawayfromcareful planningandcontrolofthesupplyanddistribution channelsbypromotinganinsularattitudeabout channelmanagement9流通渠道Pipeline（Inventoriesintransit）投機(jī)SpeculativeGoodspurchasedinanticipationofpriceincreases定期性或周期性特征Regular/Cyclical/SeasonalInventoriesheldtomeetnormaloperatingneeds安全SafetyExtrastocksheldinanticipationofdemandand leadtimeuncertainties倉(cāng)耗Obsolete/DeadStockInventoriesthatareoflittleornovalueduetobeing outofdate,spoiled,damaged,etc.9.2庫(kù)存類(lèi)型TypesofInventories10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(kù)存管理類(lèi)型的分類(lèi)9.3.1需求特點(diǎn)NatureofDemandAccuratelyforecastingdemandissinglythemostimportantfactoringoodinventorymanagement11CR(2004)PrenticeHall,Inc.拉動(dòng)式庫(kù)存管理法Pull基于每個(gè)倉(cāng)庫(kù)的特定需求以一定的訂貨批量補(bǔ)足庫(kù)存每一個(gè)存儲(chǔ)點(diǎn)獨(dú)立Eachstockinglocationisconsideredindependent最大化控制庫(kù)存Maximizeslocalcontrolofinventories推動(dòng)式庫(kù)存管理法Push根據(jù)總需求分配產(chǎn)品到庫(kù)存點(diǎn)鼓勵(lì)規(guī)模生產(chǎn)準(zhǔn)時(shí)生產(chǎn)制Just-in-time同步庫(kù)存流量以滿足需求Attemptstosynchronizestockflowssoastojust

meetdemandasitoccurs最小化庫(kù)存Minimizestheneedforinventory9.3.2管理思想InventoryManagementPhilosophies12CR(2004)PrenticeHall,Inc.拉動(dòng)式庫(kù)存管理法PullDrawsinventoryintothestockinglocationEachstockinglocationisconsideredindependentMaximizeslocalcontrolofinventories推動(dòng)式庫(kù)存管理法PushAllocatesproductiontostockinglocationsbasedon overalldemandEncourageseconomiesofscaleinproduction準(zhǔn)時(shí)生產(chǎn)制Just-in-timeAttemptstosynchronizestockflowssoastojust meetdemandasitoccursMinimizestheneedforinventory9.3.2管理思想InventoryManagementPhilosophies13CR(2004)PrenticeHall,Inc.供給驅(qū)動(dòng)Supply-Driven供應(yīng)量和時(shí)間未知Supplyquantitiesandtimingareunknown所有的供應(yīng)必須接受和處理Allsupplymustbeacceptedandprocessed通過(guò)需求控制庫(kù)存Inventoriesarecontrolledthroughdemand聯(lián)合控制AggregateControl項(xiàng)目分類(lèi)項(xiàng)目組根據(jù)基于80-20法則確定的銷(xiāo)售水平為3個(gè)或以上的產(chǎn)品組合允許不同的庫(kù)存策略9.3.2管理思想InventoryManagementPhilosophies14PlantWarehouse#1Warehouse#2Warehouse#3A1A2A3A=AllocationquantitytoeachwarehouseQ=Requestedreplenishmentquantity

byeachwarehouseQ1Q2Q3DemandforecastDemandforecastDemandforecastPULL-ReplenishinventorywithordersizesbasedonspecificneedsofeachwarehousePUSH-Allocatesupplytoeachwarehousebasedontheforecastforeachwarehouse拉動(dòng)式或推動(dòng)式庫(kù)存管理思想Pullvs.PushInventoryPhilosophiesCR(2004)PrenticeHall,Inc.9-11推動(dòng)式——基于每個(gè)倉(cāng)庫(kù)的預(yù)測(cè)將供給分配給各個(gè)倉(cāng)庫(kù)拉動(dòng)式——基于每個(gè)倉(cāng)庫(kù)的特定需求以一定訂貨批量補(bǔ)足庫(kù)存A—將產(chǎn)品分配到各個(gè)倉(cāng)庫(kù)Q—每個(gè)倉(cāng)庫(kù)需要的補(bǔ)貨量159.3.3產(chǎn)品匯總程度多數(shù)庫(kù)存管理是針對(duì)每一種產(chǎn)品的庫(kù)存進(jìn)行控制。——自下而上法另一種方法是管理一類(lèi)產(chǎn)品而不是管理單獨(dú)一種產(chǎn)品——自上而下法169.3.4多層級(jí)庫(kù)存供應(yīng)鏈管理鼓勵(lì)管理者將供應(yīng)渠道中更多的部分包括到計(jì)劃過(guò)程中來(lái)，供應(yīng)渠道中多個(gè)層級(jí)的庫(kù)存也成為核心問(wèn)題。179.3.5虛擬庫(kù)存虛擬庫(kù)存即將自己將來(lái)所可能需要而又沒(méi)有的東西的所有相關(guān)信息建立檔案，包括品名規(guī)格價(jià)格數(shù)量等，在需要時(shí)能使用上。189.4庫(kù)存目標(biāo)InventoryManagementObjectivesGoodinventorymanagementisacarefulbalancingactbetweenstockavailabilityandthecostofholdinginventory.CustomerService,

i.e.,StockAvailabilityInventoryHoldingcostsServiceobjectivesSettingstockinglevelssothatthereisonlya specifiedprobabilityofrunningoutofstockCostobjectivesBalancingconflictingcoststofindthemost economicalreplenishmentquantitiesandtimingCR(2004)PrenticeHall,Inc.199.4.1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20CR(2004)PrenticeHall,Inc.采購(gòu)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(yùn)或加工成本Costofmaterialshandlingorprocessingatthe receivingdock商品價(jià)格Priceofthegoods9.4.2庫(kù)存管理相關(guān)成本CostsRelevanttoInventoryManagement21CR(2004)PrenticeHall,Inc.RelevantCosts(Cont’d)采購(gòu)成本ProcurementcostsCostofpreparingtheorderCostofordertransmissionCostofproductionsetupifappropriateCostofmaterialshandlingorprocessingatthe receivingdockPriceofthegoods22CR(2004)PrenticeHall,Inc.庫(kù)存持有成本Carryingcosts空間成本。庫(kù)存成本隨時(shí)間推移Costforholdingtheinventoryovertime資金成本。庫(kù)存服務(wù)成本庫(kù)存風(fēng)險(xiǎn)成本23CR(2004)PrenticeHall,Inc.9.4.2庫(kù)存管理相關(guān)成本CostsRelevanttoInventoryManagement庫(kù)存持有成本CarryingcostsCostforholdingtheinventoryovertimeTheprimarycostisthecostofmoneytiedupin inventory,butalsoincludesobsolescence（報(bào)廢）, insurance,personalpropertytaxes,andstorage costsTypically,costsrangefromthecostofshortterm capitaltoabout40%/year.Theaverageisabout 25%/yearoftheitemvalueininventory.24CR(2004)PrenticeHall,Inc.RelevantCosts(Cont’d)缺貨成本Out-of-stockcosts銷(xiāo)售損失成本Lostsalescost利潤(rùn)損失Profitimmediatelyforegone商譽(yù)損失Futureprofitsforegonethroughlossofgoodwill缺貨成本Backordercost額外訂單處理費(fèi)用Costsofextraorderhandling額外的運(yùn)輸和處理費(fèi)用Additionaltransportationandhandlingcosts可能的安裝費(fèi)用Possiblyadditionalsetupcosts25Inventory’sConflictingCostPatternsCost補(bǔ)給量Replenishmentquantity缺貨成本Stockoutcost采購(gòu)成本Procurementcost庫(kù)存持有成本Carryingcost總成本Totalcost最低訂貨成本MinimumcostreorderquantityCR(2004)PrenticeHall,Inc.9-1626術(shù)語(yǔ)匯編GlossaryofTermssold

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n)('nsLTSLTCzxsrzMAXTROPQPEspksCISdDLT'zd=====================279.5推動(dòng)式庫(kù)存管理1.通過(guò)預(yù)測(cè)或其他手段確定從現(xiàn)在到下一次生產(chǎn)或采購(gòu)期間的需求量2.找出每個(gè)存儲(chǔ)點(diǎn)現(xiàn)有的庫(kù)存量3.設(shè)定每個(gè)存儲(chǔ)點(diǎn)庫(kù)存的現(xiàn)貨供應(yīng)水平4.計(jì)算總需求5.計(jì)算凈需求6.在平均需求速率的基礎(chǔ)上，將超過(guò)總凈需求的部分分配到各存儲(chǔ)點(diǎn)7.在凈需求加上分配的超量部分得到需分配到每個(gè)存儲(chǔ)點(diǎn)的貨物總量289.6基本的拉動(dòng)式庫(kù)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(kù)存水平上啟動(dòng)或由庫(kù)存盤(pán)點(diǎn)程序啟動(dòng)（3）需求和補(bǔ)貨提前期存在不同程度不確定性的情況29CR(2004)PrenticeHall,Inc.9.6.1一次性訂貨量SingleOrderPurchasingMakeaone-timepurchaseofanitem.Howmuchtoorder?Procedure:

平衡利潤(rùn)增加額與損失增加額利潤(rùn)=單位價(jià)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(diǎn)得到平衡CPnx損失=(1-CPn)x利潤(rùn)or

CPn=利潤(rùn)/(利潤(rùn)+損失)CPn代表至多售出n個(gè)單位產(chǎn)品的累積概率Dailystockingofnewspapersinvendingmachinesisagoodexle9-1830CR(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.Dailystockingofnewspapersinvendingmachinesisagoodexle9-1831CR(2004)PrenticeHall,Inc.SingleOrderPurchasing(Cont’d)ExleAclothingitemispurchasedforaseasonalsale.Itcosts$35,butithasasalepriceof$50.Aftertheseasonisover,itismarkeddownby50%toclearthemerchandise.Theestimatedquantitiestobesoldare:Numberofitems,nProbabilityofsellingexactlynitemsCumulativeprobability100.150.15150.200.35200.300.65250.200.85300.100.95350.05

1.001.009-1932CR(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.339.6.2重復(fù)訂貨量1.即刻補(bǔ)貨TC—每年總的相關(guān)成本（美元）Q—補(bǔ)充存貨的訂單批量（件）D—對(duì)庫(kù)存產(chǎn)品的年需求量（件）S—采購(gòu)成本（美元/訂單）C—庫(kù)存產(chǎn)品的價(jià)值（美元/件）I—庫(kù)存持有成本占產(chǎn)品價(jià)值的比例（%/年）Developasimplecontrolsystembyfindingthereplenishmentquantity(Q)andthereorderpoint(ROP).Therelevanttotalcostis:總成本=采購(gòu)成本和庫(kù)存成本注:需求和提前期確定—周期性的庫(kù)存管理9-21349.6.2重復(fù)訂貨量1.即刻補(bǔ)貨TC—每年總的相關(guān)成本（美元）Q—補(bǔ)充存貨的訂單批量（件）D—對(duì)庫(kù)存產(chǎn)品的年需求量（件）S—采購(gòu)成本（美元/訂單）C—庫(kù)存產(chǎn)品的價(jià)值（美元/件）I—庫(kù)存持有成本占產(chǎn)品價(jià)值的比例（%/年）Developasimplecontrolsystembyfindingthereplenishmentquantity(Q)andthereorderpoint(ROP).Therelevanttotalcostis:總成本=采購(gòu)成本和庫(kù)存成本Note:Nouncertaintyindemandorleadtime—manageregular(cycle)stockonly9-2135CR(2004)PrenticeHall,Inc.0TimeLeadtimeLeadtimeOrderPlacedOrderPlacedOrderReceivedOrderReceivedInventoryLevelReorderpoint,RQReorderPointMethodUnderCertaintyforaSingleItemQuantityon-handpluson-order9-22369.6.2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(bǔ)貨37CR(2004)PrenticeHall,Inc.Usingdifferentialcalculus,theoptimalvalueforQwillbe:Thereorderpointis:

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

Whentheinventoryleveldropsto150units(ROP)thenreorder322units(Q*).9-23383.對(duì)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(jì)訂貨批量的計(jì)算對(duì)估計(jì)錯(cuò)誤的數(shù)據(jù)并不敏感。394.非即刻補(bǔ)貨EOQ模型中有一個(gè)基本假設(shè)，即任何訂貨批量都可以及時(shí)補(bǔ)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(shí)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40CR(2004)PrenticeHall,Inc.9.7高級(jí)拉動(dòng)式庫(kù)存管理9.7.1需求不確定下的再訂貨點(diǎn)模型1.計(jì)算Q*和ROPGoodmethodforproducts:OfhighvalueThatarepurchasedfromonevendororplantHavingfeweconomiesofscaleinproduction,purchasing,ortransportation9-24FindQ*andROP41CR(2004)PrenticeHall,Inc.9.7高級(jí)拉動(dòng)式庫(kù)存管理9.7.1需求不確定下的再訂貨點(diǎn)模型Given:

d=50units/weekC=$5/unit

sd=10units/weekLT=3weeks

I=10%/yearP=99%duringleadtime

S=$10/orderFindQ*andROPFromtheEOQformulaGoodmethodforproducts:OfhighvalueThatarepurchasedfromonevendororplantHavingfeweconomiesofscaleinproduction,purchasing,ortransportation9-2442CR(2004)PrenticeHall,Inc.ReorderPointControlforaSingleItemROPQuantityonhand0QQReceiveorderPlaceorderStockoutLTTimeLTDDLTP9-2543CR(2004)PrenticeHall,Inc.ROPQ0InventorylevelLTLTTimeSafetystockReorderPointControlforaSingleItemActualonhandQuantityonhand+onorder

backordersQuantityforcontrol9-2644Weeklydemandisnormallydistributedwithameanofd=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.平均庫(kù)存成本平均庫(kù)存=經(jīng)常性庫(kù)存+安全庫(kù)存A/L=Q/2+z(s'd)在前例中，平均庫(kù)存=322/2+2.33*17.32=201(個(gè)）47ReorderPointControl(Cont’d)3.總相關(guān)成本TotalrelevantcostThetotalrelevantcostequationisnowextendedtoincludethecostsofsafetystockaswellasout-of-stock.Theout-of-stockcost(k)is$2/unit.Thepricetermisdropped.Hence,whereE(z)=0.0034fromaunitnormallosstableatazvalueof2.339-29484.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49CR(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(méi)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(diǎn)計(jì)算出來(lái)?？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(guò)下式計(jì)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(xiāo)售出現(xiàn)損失Ifsalesarelost50CR(2004)PrenticeHall,Inc.ReorderPointControl(Cont’d)3

計(jì)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(jì)算ROP和其他所需的統(tǒng)計(jì)值ComputeROPandotherstatistics51CR(2004)PrenticeHall,Inc.ReorderPointControl(Cont’d)ExleGiven:每月需求預(yù)測(cè),d 11,107units

預(yù)測(cè)標(biāo)準(zhǔn)差,sd 3,099units

補(bǔ)貨提前期,LT 1.5months

產(chǎn)品價(jià)值,C $0.11/unit

處理訂單的成本,S $10/order

庫(kù)存持有成本,I 20%/year缺貨成本,k$0.01/unitBackorderingisallowed允許缺貨FindoptimalQandP52CR(2004)PrenticeHall,Inc.ReorderPointControl(Cont’d)ExleGiven: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/unitBackorderingisallowedFindoptimalQandP53CR(2004)PrenticeHall,Inc.ReorderPointControl(Cont’d)SolutionEstimateQEstimatePReviseQFindAppA,z@0.82=0.92andfrom

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

waspreviouslycalculatedas3,795units54CR(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需求和提前期不確定條件下的再訂貨點(diǎn)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(guò)將需求波動(dòng)和提前期波動(dòng)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57CR(2004)PrenticeHall,Inc.SupplyChainExle(Cont’d)DistributorOutboundtransportInboundtransportPoolpointSupplierXspp==1012,.Xsii==4102,.Xsoo==20252,.ProcessingtimeTransporttimeTransporttime供應(yīng)商內(nèi)向運(yùn)輸集散地加工時(shí)間供應(yīng)商58CR(2004)PrenticeHall,Inc.PullMethods(Cont’d)SupplychainexleSupposethatinventoryistobemaintainedonadistributor’sshelfforanitemwhosedemandisforecastedtobed=100unitsperdayandsd=10unitsperday.Areorderpointisthemethodofinventorycontrol.Thesupplychannelisshowninthediagram.Determinetheaverageinventorytobeheldatthedistributorwherewehave:

I=10%/yearC=$5/unit

S=$10/orderP=0.99duringleadtime59CR(2004)PrenticeHall,Inc.SupplyChainExle(Cont’d)SolutionThereorderpointinventorytheoryapplies.However,determiningthestatisticsofthedemand-during-lead-timedistributionrequirestakingthelead-timefortheentirechannelintoaccount.Recall,60CR(2004)PrenticeHall,Inc.SupplyChainExle(Cont’d)AverageleadtimeNowand61CR(2004)PrenticeHall,Inc.9.7.4需求不確定條件下的定期盤(pán)點(diǎn)模型Periodicreviewcontrolwithdemanduncertainty

按預(yù)先確定的周期（T)核查某種產(chǎn)品的庫(kù)存。盤(pán)點(diǎn)后的訂貨量就是最大值（M)與盤(pán)點(diǎn)時(shí)所持有的庫(kù)存量之差。因此可以通過(guò)設(shè)定T*和M*控制庫(kù)存。Given:

d=50units/weekC=$5/unit

sd=10units/weekLT=3weeks

I=10%/yearP=0.99

S=$10/orderk=$2/unitGoodmethodforproducts:OflowvalueThatarepurchasedfromthesamevendorHavingeconomiesofscaleinproduction,purchasing,andtransportation9-38629-39Q1StocklevelreviewedTTLTLTOrderreceivedQ2Mq0QuantityonhandTime

M=maximumlevel最高庫(kù)存M-q=replenishmentquantity補(bǔ)貨量

LT=leadtime提前期T=reviewinterval盤(pán)點(diǎn)周期q=quantityonhand持有庫(kù)存量Qi=orderquantity訂購(gòu)量~單一產(chǎn)品定期盤(pán)點(diǎn)PeriodicControlforaSingleItem盤(pán)點(diǎn)時(shí)庫(kù)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)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.9-4266CR(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(diǎn)的方法比（$182），定期盤(pán)點(diǎn)因?yàn)榘踩潭雀?，所以成本相?duì)較高（$198）67PullMethods(Cont’d)9-4468PullMethods(Cont’d)聯(lián)合訂貨聯(lián)合訂貨的庫(kù)存管理包括確定聯(lián)合訂貨的所有產(chǎn)品的共同盤(pán)點(diǎn)時(shí)間，然后根據(jù)其成本和服務(wù)水平求出每種產(chǎn)品的最高庫(kù)存水平。whereO=commonprocurementcost,$/order訂購(gòu)采購(gòu)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每種產(chǎn)品的最高庫(kù)存水平總相關(guān)成本=訂購(gòu)成本+經(jīng)營(yíng)性庫(kù)存持有成本+安全庫(kù)存持有成本+缺貨成本70CR(2004)PrenticeHall,Inc.JointOrderingExle

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

365daysGiven71CR(2004)PrenticeHall,Inc.JointOrderingExle(Cont’d)FindcommonreviewtimeFindtargetquantity(MAX)foritemAthenz@80%=0.8472JointOrderingExle(Cont’d)whichhasanaverageinventoryofFindtargetquantity(MAX)foritemBthenforz@90%=1.41whichhasanaverageinventoryofCR(2004)PrenticeHall,Inc.73CR(2004)PrenticeHall,Inc.9.7.5實(shí)用拉動(dòng)式庫(kù)存管理方法PullMethods(Cont’d)1.最低-最高庫(kù)存管理法TheMin-Maxvariant當(dāng)庫(kù)存水平達(dá)到再訂貨點(diǎn)時(shí)，要訂購(gòu)的貨物數(shù)量就是目標(biāo)庫(kù)存量M（最高點(diǎn)）與所持庫(kù)存量q之差。74CR(2004)PrenticeHall,Inc.Min-MaxInventoryControl~Q1Q2Q*ROPqLTLTTimeQuantityonhandMAddincrementROP

qtoordersize9-5475CR(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補(bǔ)給量Q1Q2InventorynotbelowR,sodon’tplaceanorder9-5677CR(2004)PrenticeHall,Inc.PullMethods(Cont’d)2.按需存儲(chǔ)Stocktodemand(aperiodicreviewmethod)對(duì)某種產(chǎn)品的需求速率進(jìn)行預(yù)測(cè)。預(yù)測(cè)值乘以一個(gè)代表盤(pán)點(diǎn)周期、補(bǔ)貨提前期，以及包含需求預(yù)測(cè)和提前期不確定性的時(shí)間增量的因子，就得到目標(biāo)值。預(yù)測(cè)時(shí)還要記錄所持庫(kù)存量，而訂購(gòu)量就等于目標(biāo)值減去所持庫(kù)存量。按需存儲(chǔ)庫(kù)存控制法實(shí)際上是一種定期盤(pán)點(diǎn)的方法。78CR(2004)PrenticeHall,Inc.PullMethods(Cont’d)3.多產(chǎn)品、多地點(diǎn)的庫(kù)存管理Multipleitem,multiple-locationcontrolThetheorythathasbeendiscussedpreviouslyisusefulwhendesigninginventorycontrolsystemsforthepracticalproblemofcontrollingmanyitemsatmanylocations.Considerhowaspecialtychemicalcompanydesignedsuchapracticalsystem.TASO（訂單積累時(shí)間）isthetimetoaccumulateastockorder(truckload)forallitemsinwarehouse.79Q1StockorderTASOTASOLTOrderreceivedLTQ2M0QuantityonhandTime

M=maximumlevelTASO=timetoaccumulatestockorder

Qi=orderquantityLT=leadtimeTASO~~Q3Multiple-Item,Multiple-LocationControlCR(2004)PrenticeHall,Inc.9-6080CustomerServiceLevelForindividualitemsTheservicelevel(stockavailability)actuallyachievedbyinventorycontrolmethodsisnotbestrepresentedbytheprobability(P)ofastockoutduringtheleadtime.Itismoreaccuratetocomputeitasfollows.Usingdatafromthereorderpointunderuncertaintyexle,theservicelevelwouldbe:Note:HigherthanPCR(2004)PrenticeHall,Inc.9-6181CR(2004)PrenticeHall,Inc.CustomerServiceLevel(Cont’d)ThisactuallevelishigherthanP=0.99thatwasusedtosettheinventorylevel.Thereasonisthatthereareperiodsoftimewhenthestocklevelisabovethereorderpointandthereisnoriskofbeingoutofstock.Methodsfordefiningstockavailabilityinclude:ProbabilityoffillingallitemdemandProbabilityoffillinganordercompletelyProbabilityoffillingapercentofallitemdemandWeightedaverageofitemsfilledonanorder(fill rate)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=0.7883PushInventoryControlExleThreewarehousesareusedtosupply900retaildrugstores.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.),units14002,30010023501,4005530900204,600Howshouldtheallocationtothewarehousesbemade?85CR(2004)PrenticeHall,Inc.PushInventoryControl(Cont’d)SolutionTotalrequirements=Forecast+z(Forecasterror)wherez@90%