供应链管理(第13讲-1).ppt

CHAPTER8 ManagingUncertaintyinaSupplyChain SafetyInventory LearningObjectives Todeterminethecostsofholdinginventory Toidentifythecostsassociatedwithastockout TounderstandtheEOQconcept Todifferentiatethevariousinventoryflowpatterns Toappreciatethecontemporaryapproachestomanaginginventory OverviewofInventoryManagement Inventoriesarestocksofgoodsandmaterialsthataremaintainedformanypurposes themostbeingtosatisfynormaldemandpatterns Inventorymanagementisakeycomponentofsupply chainmanagement inpartbecauseinventorydecisionareoftenastartpoint ordriver forotherbusinessactivitiessuchaswarehousing transportation andmaterialshandling Differentfunctionalareashavedifferentinventoryobjectives Marketingtendstowanttoensurethatsufficientinventoryisavailableforcustomerdemandinordertoavoidpotentialstockoutsituations higherinventorylevels Financegroupgenerallyseekstominimizethecostsassociatedwithholdinginventory lowerinventorylevels Oneofthemostprominentconcernsaboutinventoryisitscost whichispresentedingreaterdetaillaterinthischapter Finishedgoodsinventoriesaremuchmoreexpensivetoholdthanrawmaterialsorworkinprocess Thefocusoninventorycostshasintensifiedinrecentyearsbecauseofconcernwithinventoryturnover Inventoryturnoveristhenumberoftimesthatinventoryissoldina1 yearperiod Inventoryturnover costofgoodssolddividedbyaverageinventoryatcost costofgoodssold inventoryturnoveraverageinventory 200 000 inventoryissold4timesperyear 50 000Inventoryturnoverfigurescanprovideimportantinsightsaboutanorganization scompetitivenessandefficiency Comparewithcompetitorsorbenchmarkedcompanies Lowinventoryturnover highinventorycarryingcosts little orno stockoutcosts Highinventoryturnover lowinventorycarryingcosts highstockoutcosts It seasytosaythatorganizationsshouldstriveforaproperbalanceofinventory actuallyachievingitcanbequitedifficultbecauseoftrade offsthatareinvolved Managingthetradeoffisimportanttomaintainservicelevels InventoryClassifications It simportanttoknowthekeyclassificationsofinventorybecausetheclassificationinfluencesthewaythatinventoryismanaged Inventoryismostfrequentlyclassifiedas Psychicstock Cycleorbasestock Safetyorbufferstock Pipelineorin transitstock Speculativestock Whileinventorygenerallyexiststoservicedemand insomesituationsinventoryiscarriedtostimulatedemand alsoknownaspsychicstock Retailstoresstockhugeamountsofcertainmerchandise Cycle orbase stockreferstoinventorythatisneededtosatisfynormaldemandduringthecourseofanordercycle Weuseoneeggperdayandwebuyeggsevery12days Safety orbuffer stockreferstoinventorythatisheldinadditiontocyclestocktoguardagainstuncertainindemandand orleadtime makingathree eggomelet buyingeggsevery14days Pipeline orin transit stockisinventorythatisenroutebetweenvariousnodes i e fixedfacilitiessuchasaplant warehouse store inalogisticssystem eggsintransitbetweentheretailstoreandyourkitchen Speculativestockreferstoinventorythatisheldforseveralreasons includingseasonaldemand projectedpriceincreases andpotentialshortagesofproduct SpringFestival tendstocauseanincreaseindemandforeggs Inventory RelatedCosts Inventory relatedcostsaremostfrequentlyclassifiedas Inventorycarrying holding costs Stockoutcosts Inventorycarrying holding costsincluding ObsolescenceInventoryshrinkageStoragecostsandhandlingcostsTaxesInterestchargesOpportunitycost Ingeneral inventorycarryingcostsareexpressedinpercentageterms andthispercentageismultipliedbytheinventory svalue However thecalculationofacarryingcostpercentagecanbequiteunstructured Stockoutcosts Suchcostscanaccrueduringstockouts whencustomersdemanditemsthataren timmediatelyavailable Althoughcalculationofstockcostscanbedifficultandinexact itisimportantfororganizationtodosobecausesuchknowledgecanbebeneficialwhendetermininghowmuchinventorytohold Estimatingthecostsorpenaltyforastockoutinvolvesanunderstandingofcustomerreactiontoacompanybeingoutofstockwhenacustomerwantstobuyanitem Page273 Table9 1 DeterminationoftheAverageCostofaStockout Thesearehypotheticalfiguresforillustration Asageneralrule thehighertheaveragecostofastockout thebetteritisforthecompanytoholdsomeamountofinventory safetystock toprotectagainststockouts Thehighertheprobabilityofadelayedsale thelowertheaveragestockoutcosts andthelowertheinventorythatneedstobeheldbyacompany Trade offsexistbetweencarryingandstockoutcosts Marginalanalysisfocusesonthetrade offbetweencarryingandstockoutcosts allowacompanytodetermineanoptimumlevelofsafetystocks Marginalanalysishelpsdefinethepointatwhichthecostsofholdingadditionalsafetystockareequaltothesavingsinstockoutcostsavioded Table9 2 DeterminationofSafetyStockLevel 9 27 WhentoOrder Fixedorderquantitysystem Fixedorderintervalsystem Page276 Reorderpoint ROP Page276 ROP DDxRCundercertaintyROP DDxRC SSunderuncertaintyWhereDD dailydemandRC lengthofreplenishmentcycleSS safetystock 9 28 HowMuchtoReorder Thetypicalinventoryordersizeproblem referredtoastheeconomicorderquantity EOQ dealswithcalculatingtheproperordersizewithrespecttotwocosts thecostsofcarryingtheinventoryandthecostsoforderingtheinventory EQQdeterminesthepointatwhichthesumofcarryingcostsandorderingcostsisminimized orthepointatwhichcarryingcostequalorderingcost 9 30 Figure9 1 DeterminingEOQbyUseofaGraph Economicorderquantity EOQ indollarsEOQ 2AB C Page278 WhereEOQ themosteconomicordersize indollarsA annualusage indollarsB administrativecostsperorderofplacingtheorderC carryingcostsoftheinventory 9 32 Economicorderquantity EOQ inunitsEOQ 2DB IC Page278 WhereEOQ themosteconomicordersize inunitsA annualdemand inunitsB administrativecostsperorderofplacingtheorderC carryingcostsoftheinventory I dollarvalueoftheinventory perunit 9 33 Table9 3 EOQCostCalculations Thefiguresfromthefixedorderquantity e g EQQ andthesafetystockcalculationscanbeusedtodevelopaninventoryflowdiagram whichgraphicallydepictsthedemandfor andreplenishmentof inventory InventoryFlows 9 35 Figure9 2 InventoryFlowDiagram Safetystockcanpreventagainsttwoproblemareas IncreasedrateofdemandLonger than normalreplenishmentWhenfixedorderquantitysystemlikeEOQisused timebetweenordersmayvary Whenreorderpointisreached fixedorderquantityisordered ContemporaryApproachestoManagingInventory Severalofthemoreprominentapproachesarepresentedinthissection ABCAnalysis Just inTime JIT Approach Vendor ManagedInventory VMI InventoryTracking ABCAnalysisofinventoryrecognizesthatinventoriesarenotofequalvalueandthatallinventoryshouldnotbemanagedinthesameway MeasuresusedtodetermineABCstatusincludesalesvolume thefastest sellingitems itemprofitability oritemimportance Intermsofitemimportance ABCmightbeoperationalizedasfollows A thehighestcriticality B moderatecriticality C lowcriticality Just inTime JIT Approach Fromaninventoryperspective theJITapproachseekstominimizeinventorybyreducingsafetystock aswellasbyhavingtherequiredamountofmaterialsarriveattheproductionlocationattheexacttimethattheyareneeded TheJITapproachhasanumberofimportantimplicationsforsupply chainefficiency Collaborationamongsupply chainparticipantsiskeytosuccessfulJITinitiatives Vendor ManagedInventory VMI UnderVMI thesizeandtimingofreplenishmentordersaretheresponsibilityofthemanufacturer VIM sbenefitsfordistributorsandretailerstendtoinvolveareducednumberofstockoutsandhigherinventoryturns whilemanufacturerbenefitsincludeimproveddemandforecasting OnepotentialdrawbacktoVIMisinadequatedatasharingbetweenthereleva