Inventory Management(仓储管理)

Copyright2006JohnWiley&Sons,Inc.BeniAsllaniUniversityofTennesseeatChattanoogaInventoryManagementOperationsManagement-5thEditionChapter12RobertaRussell&BernardW.Taylor,IIICopyright2006JohnWiley&Sons,Inc.12-2LectureOutlineElementsofInventoryManagementInventoryControlSystemsEconomicOrderQuantityModelsQuantityDiscountsReorderPointOrderQuantityforaPeriodicInventorySystemCopyright2006JohnWiley&Sons,Inc.12-3WhatIsInventory?StockofitemskepttomeetfuturedemandPurposeofinventorymanagementhowmanyunitstoorderwhentoorderCopyright2006JohnWiley&Sons,Inc.12-4TypesofInventoryRawmaterialsPurchasedpartsandsuppliesWork-in-process(partiallycompleted)products(WIP)ItemsbeingtransportedToolsandequipmentCopyright2006JohnWiley&Sons,Inc.12-5InventoryandSupplyChainManagementBullwhipeffectdemandinformationisdistortedasitmovesawayfromtheend-usecustomerhighersafetystockinventoriestoarestoredtocompensateSeasonalorcyclicaldemandInventoryprovidesindependencefromvendorsTakeadvantageofpricediscountsInventoryprovidesindependencebetweenstagesandavoidsworkstop-pagesCopyright2006JohnWiley&Sons,Inc.12-6TwoFormsofDemandDependentDemandforitemsusedtoproducefinalproductsTiresstoredataGoodyearplantareanexampleofadependentdemanditemIndependentDemandforitemsusedbyexternalcustomersCars,appliances,computers,andhousesareexamplesofindependentdemandinventoryCopyright2006JohnWiley&Sons,Inc.12-7InventoryandQualityManagementCustomersusuallyperceivequalityserviceasavailabilityofgoodstheywantwhentheywantthemInventorymustbesufficienttoprovidehigh-qualitycustomerserviceinTQMCopyright2006JohnWiley&Sons,Inc.12-8InventoryCostsCarryingcostcostofholdinganitemininventoryOrderingcostcostofreplenishinginventoryShortagecosttemporaryorpermanentlossofsaleswhendemandcannotbemetCopyright2006JohnWiley&Sons,Inc.12-9InventoryControlSystemsContinuoussystem(fixed-order-quantity)constantamountorderedwheninventorydeclinestopredeterminedlevelPeriodicsystem(fixed-time-period)orderplacedforvariableamountafterfixedpassageoftimeCopyright2006JohnWiley&Sons,Inc.12-10ABCClassificationClassA5–15%ofunits70–80%ofvalueClassB30%ofunits15%ofvalueClassC50–60%ofunits5–10%ofvalueCopyright2006JohnWiley&Sons,Inc.12-11ABCClassification:Example1$6090235040330130480605301006201807101708320509510601020120PARTUNITCOSTANNUALUSAGECopyright2006JohnWiley&Sons,Inc.12-12ABCClassification:Example(cont.)Example10.11$6090235040330130480605301006201807101708320509510601020120PARTUNITCOSTANNUALUSAGETOTAL%OFTOTAL%OFTOTALPARTVALUEVALUEQUANTITY%CUMMULATIVE9$30,60035.96.06.0816,00018.75.011.0214,00016.44.015.015,4006.39.024.044,8005.66.030.033,9004.610.040.063,6004.218.058.053,0003.513.071.0102,4002.812.083.071,7002.017.0100.0$85,400ABC%OFTOTAL%OFTOTALCLASSITEMSVALUEQUANTITYA9,8,271.015.0B1,4,316.525.0C6,5,10,712.560.0Copyright2006JohnWiley&Sons,Inc.12-13EconomicOrderQuantity(EOQ)ModelsEOQoptimalorderquantitythatwillminimizetotalinventorycostsBasicEOQmodelProductionquantitymodelCopyright2006JohnWiley&Sons,Inc.12-14AssumptionsofBasicEOQModelDemandisknownwithcertaintyandisconstantovertimeNoshortagesareallowedLeadtimeforthereceiptofordersisconstantOrderquantityisreceivedallatonceCopyright2006JohnWiley&Sons,Inc.12-15InventoryOrderCycleDemandrateTimeLeadtimeLeadtimeOrderplacedOrderplacedOrderreceiptOrderreceiptInventoryLevelReorderpoint,ROrderquantity,Q0Copyright2006JohnWiley&Sons,Inc.12-16EOQCostModelCo-costofplacingorderD-annualdemandCc-annualper-unitcarryingcostQ-orderquantityAnnualorderingcost=CoDQAnnualcarryingcost=CcQ2Totalcost=+CoDQCcQ2Copyright2006JohnWiley&Sons,Inc.12-17EOQCostModelTC=+CoDQCcQ2=+CoDQ2Cc2TCQ0=+C0DQ2Cc2Qopt=2CoDCcDerivingQoptProvingequalityofcostsatoptimalpoint=CoDQCcQ2Q2=2CoDCcQopt=2CoDCcCopyright2006JohnWiley&Sons,Inc.12-18EOQCostModel(cont.)OrderQuantity,QAnnualcost($)TotalCostCarryingCost=CcQ2Slope=0MinimumtotalcostOptimalorderQoptOrderingCost=CoDQCopyright2006JohnWiley&Sons,Inc.12-19EOQExampleCc=$0.75peryardCo=$150D=10,000yardsQopt=2CoDCcQopt=2(150)(10,000)(0.75)Qopt=2,000yardsTCmin=+CoDQCcQ2TCmin=+(150)(10,000)2,000(0.75)(2,000)2TCmin=$750+$750=$1,500Ordersperyear=D/Qopt=10,000/2,000=5orders/yearOrdercycletime=311days/(D/Qopt)=311/5=62.2storedaysCopyright2006JohnWiley&Sons,Inc.12-20ProductionQuantityModelAninventorysysteminwhichanorderisreceivedgradually,asinventoryissimultaneouslybeingdepletedAKAnon-instantaneousreceiptmodelassumptionthatQisreceivedallatonceisrelaxedp-dailyrateatwhichanorderisreceivedovertime,a.k.a.productionrated-dailyrateatwhichinventoryisdemandedCopyright2006JohnWiley&Sons,Inc.12-21ProductionQuantityModel(cont.)Q(1-d/p)Inventorylevel(1-d/p)Q2Time0OrderreceiptperiodBeginorderreceiptEndorderreceiptMaximuminventorylevelAverageinventorylevelCopyright2006JohnWiley&Sons,Inc.12-22ProductionQuantityModel(cont.)p=productionrated=demandrateMaximuminventorylevel=Q-d=Q1-QpdpAverageinventorylevel=1-Q2dpTC=+1-dpCoDQCcQ2Qopt=2CoDCc1-dpCopyright2006JohnWiley&Sons,Inc.12-23ProductionQuantityModel:ExampleCc=$0.75peryardCo=$150D=10,000