Lecture05-MRP

Copyright©2012QiChao.Allrightsreserved.MaterialRequirementsPlanning(MRP)祁超Ph.D.AssociateProfessorInstituteofSystemsEngineeringDepartmentofControlScience&EngineeringHuazhongUniversityofScience&[e-mail]:13297973735Copyright©2012QiChao.Allrightsreserved.2ContentsforProductionPlanningandSchedulingAggregateandWorkforcePlanningMRPJITOperationsschedulingProjectschedulingAggregatePlanningProductionPlanningandControlSchedulingReviewonEconomicOrderQuantity(EOQ)ModelCopyright©2012QiChao.Allrightsreserved.3Copyright©2012QiChao.Allrightsreserved.4TheEconomicOrderQuantity(EOQ)ModelAssumptions:1.Productionisinstantaneous.Thereisnocapacityconstraintandtheentirelotisproducedsimultaneously.2.Deliveryisimmediate.Thereisnotimelagbetweenproductionandavailabilitytosatisfydemand.3.Demandisdeterministic.Thereisnouncertaintyaboutthequantityortimingofdemand.4.Demandisconstantovertime.Infact,itcanberepresentedasastraightline,sothatifannualdemandis365unitsthistranslatesintoadailydemandofoneunit.5Aproductionrunincursaconstantsetupcost.Regardlessofthesizeofthelotorthestatusofthefactory,thesetupcostisthesame.6.Productscanbeanalyzedsingly.Copyright©2012QiChao.Allrightsreserved.5NotationD=Demandrate(inunitsperyear).c=Unitproductioncost,notcountingsetuporinventorycosts(indollarsperunit).A=Constantsetup(ordering)costtoproduce(purchase)alot(indollars).h=HoldingcostQ=Lotsize(inunits);thisisthedecisionvariableCopyright©2012QiChao.Allrightsreserved.6ThemodelInventoryversustimeintheEOQmodelCopyright©2012QiChao.Allrightsreserved.7Themodelaverageinventorylevel:Theholdingcostperunit:Thesetupcostperunit:Theproductioncostperunit:2QDhQDhQ22QAcCopyright©2012QiChao.Allrightsreserved.8Economicorderquantitycondition)order(second2)(conditionorderfirst02)()unitpercost(total2)(3222QAdQQYdQADhdQQdYcQADhQQYCopyright©2012QiChao.Allrightsreserved.9Economicorderquantityquantity)order(economic2conditionorderfirst02)(2hADQQADhdQQdYMaterialRequirementsPlanning(MRP)Copyright©2012QiChao.Allrightsreserved.10Copyright©2012QiChao.Allrightsreserved.11TypesofDemandIndependentdemanditemsarethoseitemsthatweselltocustomers.Dependentdemanditemsarethoseitemswhosedemandisdeterminedbyotheritems.Demandforacartranslatesintodemandforfourtires,oneengine,onetransmission,andsoon.Theitemsusedintheproductionofthatcar(theindependentdemanditem)arethedependentdemanditems.Suppliesareitemssuchascopierpaper,cleaningmaterials,andpensthatarenotuseddirectlyintheproductionofindependentdemanditemsCopyright©2012QiChao.Allrightsreserved.12WhyMRP?Dependentdemandisdifferentfromindependentdemand.Productiontomeetdependentdemandshouldbescheduledsoastoexplicitlyrecognizeitslinkagetoproductiontomeetindependentdemand.Statisticalreorderpointsystemsmissthelinkbetweenindependentanddependentdemand.Buyersarenotsynchronizedwithproducers.Copyright©2012QiChao.Allrightsreserved.13WhatisMRP?ComputerizedInventoryControlProductionPlanningSystemManagementInformationSystemManufacturingControlSystemCopyright©2012QiChao.Allrightsreserved.14WhentouseMRPJobShopProductionComplexProductsPushEnvironmentsDiscreteandDependentDemandItemsCopyright©2012QiChao.Allrightsreserved.15WhatcanMRPdo?ReduceInventoryLevelsReduceComponentShortagesImproveShippingPerformanceImproveCustomerServiceImproveProductivitySimplifiedandAccurateSchedulingReducePurchasingCostImproveProductionSchedulesReduceManufacturingCostReduceLeadTimesLessScrapandReworkHigherProductionQualityCopyright©2012QiChao.Allrightsreserved.16WhatcanMRPdo?ImproveCommunicationImprovePlantEfficiencyReduceFreightCostReductioninExcessInventoryReduceOvertimeImproveSupplySchedulesImproveCalculationofMaterialRequirementsImproveCompetitivePositionCopyright©2012QiChao.Allrightsreserved.17Purchaseorders&jobsThebasicfunctionofMRPistoplanmaterialrequirements.MRPisusedtocoordinateordersfromwithintheplantandfromoutsideOutsideordersarecalledpurchaseordersOrdersfromwithinarecalledjobsThemainfocusofMRPisonschedulingjobsandpurchaseorderstosatisfymaterialrequirementsgeneratedbyexternaldemandCopyright©2012QiChao.Allrightsreserved.18Quantities&timingMRPdeterminesappropriateproductionquantitiesofalltypesofitems,fromfinalproductsthataresold,tocomponentsusedtobuildfinalproducts,toinputspurchasesasrawmaterials.Itmustalsodetermineproductiontiming(i.e.,jobstarttime)thatfacilitatesmeetingorderduedates.Copyright©2012QiChao.Allrightsreserved.19TimebucketsInmanyMRPsystems,timeisdividedintobuckets,althoughsomesystemsarecontinuoustime.Abucketisanintervalthatisusedtobreaktimeanddemandintodiscretechunks.Thedemandthataccumulatesoverthetimeintervalisallconsidereddueatthebeginningofthebucket.Today,mostMRPsystemsusedailybuckets,althoughtherearestillmanysystemsusingweeks.Copyright©2012QiChao.Allrightsreserved.20BOMMRPworkswithbothfinishedproducts,orenditems,andtheirconstituentparts,calledlower-levelitems.Therelationshipbetweenenditemsandlower-levelitemsisdescribedbythebillofmaterial(BOM).Demandforenditemsge