财务管理与财务分析运营管理课件5.ppt

CachonChapter5Batchingandotherflowinterruptionssetuptimesandtheeconomicorderquantitymethod Example batchsize Ittakesoneminutetoproduceonesteersupportunit ofwhichthereisoneperproduct Ittakes60minutestochangeoverthemillingmachinesfromproducingsteersupportstoproducingribs setuptime Ittakes0 5minutetoproduceonerib sincetherearetworibsinaproduct thistranslatestooneminute unitFinally ittakesanother60minutestochangeoverthemillingmachinesbacktoproducingsteersupports Oneproducthastwokindofcomponents onesteersupportunit tworibs Onemachineisusedtoproducebothcomponents Batchof12 Batchof60 Batchof120 Batchof300 Time minutes 60 120 180 240 300 Set upfromRibstoSteersupport Set upfromsteersupporttoribs Produceribs 1boxcorrespondsto24units 12scooters Producesteersupports 1boxcorrespondsto12units 12scooters Productioncycle Productioncycle THEIMPACTOFSET UPSONCAPACITY Calculatecapacity CachonChapter5 page200 Table5 1 BATCHFLOWOPERATIONSCARRYALOTOFINVENTORY Example Movietheatervs aroomfullofDVDplayers Steersupport Rib CAPACITY FLOWTIMEFORABATCHPROCESS Considerthefollowingbatchflowprocessconsistingofthreeprocessstepsperformedbythreemachines Workisprocessedinbatchesateachstep Beforeabatchisprocessedatstep1 themachinehastobesetup Duringaset up themachineisunabletoprocessanyproduct a Assumethatthebatchsizeis50parts Whatisthecapacityoftheprocess CAPACITY FLOWTIMEFORABATCHPROCESS Cont d Step2takesthelongesttimetofinish soitdeterminesthecapacityoftheprocess 60 100 0 6batch hourforabatchof50parts thatis 30parts hour Forabatchsizeof10parts whichstepisthebottleneckfortheprocess Step1takesthelongesttimetofinish sostep1isthebottleneckoftheprocess Itdeterminethecapacityoftheprocess 60 30 2batch hrforabatchof10parts thatis 20parts hour Usingthecurrentproductionbatchsizeof50parts howlongwouldittaketoproduce20partsstartingwithanemptysystem Assumethattheunitsinthebatchhavetostaytogether nosmallertransferbatchesallowed whentransferredtostep2andtostep3 Aunitcanleavethesystemthemomentitiscompletedatstep3 Iftheunitsinthebatchhavetostaytogether by a ittakes70 100 1 5x20 200minutesfor20partstoleavethesystemUsingthecurrentproductionbatchsizeof50parts howlongwouldittaketoproduce20partsstartingwithanemptysystem Assumethattheunitsinthebatchdonothavetostaytogether specifically thatunitsaretransferredtothenextstepthemomenttheyarecompletedatanystep CAPACITY FLOWTIMEFORABATCHPROCESS Cont d Iftheunitsinthebatchdonothavetostaytogether startingwithanemptysystem ittakesthefirstunit 20 1 2 1 5 24 5minutestoleavethesystem Ittakes2moreminutestoproducethesecondunits becauseyoucanscheduletasksonnon bottleneckstepsparallel Asyoucanseeinthefollowinggraph italwaystakes2minutesmoretoproduceonemoreunitafterthefirstunit Therefore ittakesaltogether24 5 2x19 62 5minutesproduce20units CAPACITY FLOWTIMEFORABATCHPROCESS Cont d PROCESSANALYSISWITHBATCHING Capacitycalculationchanges Note Capacityincreaseswithbatchsize Notefurther andsodoesinventory andthusflowtime Seechapter5 ECONOMIESOFSCALEANDOPTIMALBATCH LOT SIZEDECISION 4 PurposesofInventory 1 Tomaintainindependenceofoperations2 Tomeetvariationinproductdemand3 Toallowflexibilityinproductionscheduling4 Toprovideasafeguardforvariationinrawmaterialdeliverytime5 Totakeadvantageofeconomicpurchase ordersize TRADE OFFS YoucannotsellfromanemptycartOURLINEOFCREDIT BUDGET WILLSUPPORTONLYSOMUCH 1ININVENTORYCOSTSABOUT 25 YEAROUT OF STOCKS LOSTSALES LOSTCUSTOMERSIT SIMPOSSIBLETOFORECASTPERFECTLY ThreeQuestionsofinventorySystem Whattoorder Howmanytoorder Whentoorder Timingisacriticalissue InventoryCosts Holding orcarrying costsSetup orproductionchange costsOrderingcostsShortagecosts EOQ ASIMPLEMODEL BookStoreMugSalesDemandisconstant at20unitsaweekFixedordercostof 12 noleadtimeHoldingcostof25 ofinventoryvalueannuallyMugscost 1 00 sellfor 5 00QuestionHowmany whentoorder EOQ CALCULATINGTOTALCOST PurchaseCostConstantHoldingCost Avg Inven HoldingCostOrdering SetupCost NumberofOrders OrderCostGoal FindtheOrderQuantitythatMinimizesTheseCosts EOQ TOTALCOST OrderQuantity 0 0 1000 1500 500 140 120 100 80 60 40 20 160 TotalCost HoldingCost OrderCost Cost EOQ OPTIMALORDERQUANTITY OptimalQuantity Soforourproblem theoptimalquantityis316 2 Demand SetupCost holdingcost 1 VerifythebasicassumptionsoftheEOQmodel replenishmentoccursinstantaneously demandisconstant andnotstochastic thereisafixedset upcostKindependentoftheorderquantity 2 Collectinformationon set up cost K onlyincludeout of pocketcost notopportunitycost flowrate R holdingcost h notnecessarilytheyearlyholdingcost needstohavethesame timeunitastheflowrate 3 Foragivenorderquantity Q compute Inventorycosts unit Set upcosts perunitoftime 4 Theeconomicorderquantityminimizesthesumoftheinventoryandtheset up costsandis Q Theresultingcostsare C Q HOWTOFINDTHEEOQ FlowRateR EconomicOrder QuantityQ Perunitordering andinventory costC Q R Orderingand inventorycostsasa percentageoftotal procurementcosts 200 4284 0 14 14 1 400 6058 0 10 10 4 600 7420 0 08 8 7 800 8568 0 07 7 6 1000 9579 0 06 6 8 SCALEECONOMIESOFTHEEOQ KEYPOINTSFROMBATCHING Indecidingtheoptimallotsizethetradeoffisbetweensetup order costandholdingcost Ifdemandincreasesbyafactorof4 itisoptimaltoincreasebatchsizebyafactorof2andproduce order twiceasoften Cycleinventory indaysofdemand shoulddecreaseasdemandincreases Iflotsizeistobereduced onehastoreducefixedordercost Toreducelotsizebyafactorof2 ordercosthastobereducedbyafactorof4 KEYTAKEAWAYS OPER