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Load-orientedmanufacturingcontroljust-in-timeproductionforjobshopsProductionPlanning&Control1994Vol.5.WolfgangBechteHannoverconsultantfirm1998/08/18공장자동화실험실송태영IntroductionAtechniqueforjobshopssupportingtheJITconcept-Usingload-orientedorderrelease,entry(Bechte,Kettner1980)-ManufacturingcontrolsystemisdesignedbyKrautzig.-Implementedinmanyfactories(Wiendahl,Bechte1987~1991)Basicprinciples&techniqueforLoad-orientedmanufacturingcontrolDetailedcomputationalprocedurerefertomoretheoreticalpublicationwrittenbyWiendahl(1993),Bechte(1988)content1.Objectivesofload-orientedmanufacturingcontrol2.Structureofload-orientedmanufacturingcontrol3.Basicconceptinload-orientedmanufacturingcontrol4.Overviewofaload-orientedmanufacturingcontrolsystem5.Exampleofthecontrolsystem1.Objectivesofload-orientedmanufacturingcontrolReducinglead-timeandWIP.Keepingactuallead-timeonstablelowestpossiblelevel.-PermanentlyIn/Output,inventoryandaverageleadtimeofW/CaremonitoredandcomparedwiththeirplannedvaluesindynamicwayAtthesametimedetermineBottlenecks,short&mid-termcapacityplanningFurnishingrealisticdue-dateschedulingandcapacityplanning2.Structureofload-orientedmanufacturingcontrolFlowofordersforonesinglemachineIllustratingevents,ahierarchicalcontrollerlevels,sectionsFigure1.FunnelmodelofjobshopMulti-levelclosed-loopcontrolsystemHighercontrollerleveldependsontheperformanceofthelowerone.CompanyDISPOSITIONJobShopMachineSalesDueDateLeadtimeUtilizationMfg.AssemblyReceivingShippingSupplierCustomerDisturbancesProdScheduleLongTermCapacitiesOrderEntryMidtermCapacitiesOrderreleaseShorttermCapacitiesOperationSequencesCapacitiesLoadingFigure2.Multilevelclosed-loopcontrolsystem.3.Basicconceptinload-orientedmanufacturingcontrol3.1BasicrelationshipataWorkcenterFoursimplerulesforregulatingInput,Output,InventoryandLeadtime1)constantinventory-keepIn/Outputthesameonaavg.2)changinginventory-changeinput3)Averageleadtime-adjustIn/Outratio4)Individualleadtimetobeeven-applyFIFOrulewhiledispatchingAvg.leadtime=Avg.Inv.Avg.OutputQueuingordersAvg.OutputAvg.InputAvg.InventoryInputInitialInventoryAvg.LeadtimeAvg.InventoryOutputcurveInputcurveOutputFinalInventoryControlPeriodLoad[Hours]Time[days]CompletedOrdersArrivingOrdersFigure3.BasicrelationshipandthroughputdiagramBasicrelationshipatworkcentertoplantheInput,Output,InventoryandLeadtimeloadlimit=Plannedoutput*(Plannedleadtime+Planningperiod)Planningperiod3.Basicconceptinload-orientedmanufacturingcontrol3.2PrincipleofLoadlimitingandLoadconversionAddingLoadRemainingLoadLoadlimitPlannedInputActualInventoryPlannedleadtimeCaseAcaseBTodayPlanningPeriodPlannedInv.(Buffer)Plannedoutput(capacity)Figure4.Loadlimiting.IncasethatexceedingloadshappensLoadlimitingrejectorpreferordersorvariesRequiredcapacity=presentload*planningperiodplannedleadtime+planningperiodRejectedLoadAllowedloadLoadlimitExceedingloadPresentLoadPlannedleadtimeRequiredBufferRequiredcapacityFigure5.Short-termcapacityplanningusingtheloadlimitRequiredInputCurveRequiredoutputcurve.OrderreleaseshouldconsidertheworkcenterloadsandcapacitiesFourtypeofloadsIncaseofB,Dastatisticalestimationisneeded;Loadconversionfactordepreciationfactor=plannedoutput/Loadlimit=planningperiodplannedleadtime+planningperiodLimitingandbalanceworkinprocessbyorderrelease.PlannedInv.(I)(D)LoadlimitPlannedleadtimeTodayPlannedInv.(Buffer)Plannedoutput(capacity)(D)PlannedRelease(I)IdealReleasedCurveFullloadConvertedLoadFigure6.DerivationofconversionusingtheloadlimitAconsideringtheavailablecapacitiesofashort-termplanningperiods(1~2Week)PlannedorderswerescheduledbackwardSelectsperiodicallythoseoftheplannedordersStep1.EstablishurgentordersStep2.ReleasewotrkableordersTimelimit3.Basicconceptinload-orientedmanufacturingcontrol3.3Techniqueofload-orientedorderrelease.IfcapacitiesisneededLoad-orientedreleaserequireappreciatedecisioncbaacabbacPlanningperiodTimelimittodayTime[Days]DueOverdueFutureNon-UrgentOrder4312WorkableWorkableUnworkableOmissibleABCWorkcentersLoad[Hours]LoadlimitReleasedLoadRemainingLoadFigure7.StepsofLoad-orientedorderrelease3.Basicconceptinload-orientedmanufacturingcontrol3.4Techniqueofload-orientedorderentryTheideasofLoad-orientedorderentryistoavoidoverloadedweeksChecksthescheduledoperationdatesagainstavailablecapacitiesforamidtermplanninghorizon(ex12weeks)Realisticduedatesareofferedandtheexpectedbottlenecksareindicated.InitiationcapacitychangesinadvanceifpossibleOverloadweeksFreedate..CumulativeLoadCumulativeCapacityBacklogOverloadWeeksUnderloadweeksPlanninghorizonTodayTime[week]FreeDateOverloadPortion83%TotalLoad100%Load[hour]Figure8.Cumulativeloadandcapacityofaworkcenter..CisacriticalworkcenterABCDEABCDEOverloadWeeksTodayTime[week]WorkcenterABCDEFreeDateOrderLeadTimeOperationLeadTimeRealisticReleaseDateRealisticDeliveryDatePlanningHorizonFigure9.Establishingarealisticdeliverydateofanorder4.Overviewofaload-orientedmanufacturingcontrolsystem1.Routingdata2.Orderdata3.Itemdata4.Shopcalendar5.Capacitydata6.Transactiondata7.Controldata:detailedtablesforw/candfreedefinablegroup..ShopCalendarCa