面向负荷的生产控制与JIT

1、Load-oriented manufacturing control just-in-time production for job shopsProduction Planning & Control1994 Vol.5. Wolfgang BechteHannover consultant firm1998/08/18 IntroductionA technique for job shops supporting the JIT concept - Using load-oriented order release, entry (Bechte, Kettner 1980)- Manu

2、facturing control system is designed by Krautzig.- Implemented in many factories (Wiendahl, Bechte 19871991)Basic principles & technique for Load-oriented manufacturing control Detailed computational procedure refer to more theoretical publication written by Wiendahl(1993), Bechte(1988)content1. Obj

3、ectives of load-oriented manufacturing control2.Structure of load-oriented manufacturing control3. Basic concept in load-oriented manufacturing control4.Overview of a load-oriented manufacturing control system5.Example of the control system1. Objectives of load-oriented manufacturing controlReducing

4、 lead-time and WIP .Keeping actual lead-time on stable lowest possible level. - Permanently In/Out put, inventory and average lead time of W/C are monitored and compared with their planned values in dynamic wayAt the same time determine Bottlenecks, short & mid-term capacity planningFurnishing reali

5、stic due-date scheduling and capacity planning2. Structure of load-oriented manufacturing controlFlow of orders for one single machineIllustrating events, a hierarchical controller levels, sectionsFigure 1.Funnel model of job shopMulti-level closed-loop control systemHigher controller level depends

6、on theperformance of the lower one.CompanyDISPOSITIONJob ShopMachineSalesDue DateLead timeUtilizationMfg.AssemblyReceivingShippingSupplierCustomerDisturbancesProd ScheduleLong Term CapacitiesOrder EntryMid termCapacitiesOrder releaseShort termCapacitiesOperation SequencesCapacities LoadingFigure2. M

7、ultilevel closed-loop control system.3. Basic concept in load-oriented manufacturing control3.1 Basic relationship at a Work centerFour simple rules for regulating Input, Output, Inventory and Lead time1) constant inventory - keep In/Output the same on a avg.2) changing inventory - change input3) Av

8、erage lead time - adjust In/Out ratio4) Individual lead time to be even - apply FIFO rule while dispatchingAvg.lead time = Avg. Inv. Avg. OutputQueuing ordersAvg. OutputAvg. InputAvg. InventoryInputInitialInventoryAvg. Lead timeAvg.InventoryOutput curveInput curveOutputFinal InventoryControl PeriodL

9、oadHoursTimedaysCompleted OrdersArriving OrdersFigure 3. Basic relationship and throughput diagramBasic relationship at work center to plan the Input, Output, Inventory and Lead timeload limit = Planned output* (Planned lead time + Planning period) Planning period3. Basic concept in load-oriented ma

10、nufacturing control3.2 Principle of Load limiting and Load conversionAdding LoadRemainingLoadLoadlimitPlannedInputActualInventoryPlannedlead timeCase Acase BTodayPlanning PeriodPlanned Inv.(Buffer)Plannedoutput(capacity)Figure4. Load limiting.In case that exceeding loads happensLoad limiting reject

11、or prefer orders or variesRequired capacity = present load * planning periodplanned lead time + planning periodRejectedLoadAllowedloadLoadlimitExceeding loadPresent LoadPlannedlead timeRequiredBufferRequiredcapacityFigure5. Short-term capacity planning using the load limitRequired Input CurveRequire

12、doutput curve.Order release should consider the work center loads and capacitiesFour type of loads In case of B,D a statistical estimation is needed ; Load conversion factordepreciation factor =planned output / Load limit =planning periodplanned lead time + planning periodLimiting and balance work i

13、n process by order release.Planned Inv. (I)(D)LoadlimitPlannedlead timeTodayPlanned Inv.(Buffer)Plannedoutput(capacity)(D)Planned Release(I)Ideal Released CurveFull loadConverted LoadFigure6. Derivation of conversion using the load limitA considering the available capacities of a short-term planning

14、 periods(12Week)Planned orders were scheduled backwardSelects periodically those of the planned ordersStep1. Establish urgent ordersStep2. Release wotrkable ordersTime limit3. Basic concept in load-oriented manufacturing control3.3 Technique of load-oriented order release.If capacities is needed Loa

15、d-oriented release require appreciate decisioncbaacabbacPlanning periodTime limittodayTimeDaysDueOver dueFutureNon-UrgentOrder 4312WorkableWorkableUnworkableOmissibleABCWork centersLoadHoursLoad limitReleasedLoadRemainingLoadFigure 7. Steps of Load-oriented order release3. Basic concept in load-orie

16、nted manufacturing control3.4 Technique of load-oriented order entryThe ideas of Load-oriented order entry is to avoid overloaded weeksChecks the scheduled operation dates against available capacities for a midterm planning horizon (ex 12 weeks)Realistic due dates are offered and the expected bottle

17、necks are indicated. Initiation capacity changes in advance if possibleOverload weeks Free date.Cumulative LoadCumulative CapacityBacklogOverload WeeksUnderloadweeksPlanning horizonTodayTime weekFree DateOverloadPortion83%TotalLoad100%LoadhourFigure 8. Cumulative load and capacity of a work center.C

18、 is a critical work centerABCDEABCDEOverload WeeksTodayTime weekWorkcenterABCDEFree DateOrder Lead TimeOperation Lead TimeRealistic Release DateRealistic Delivery DatePlanning HorizonFigure 9. Establishing a realistic delivery date of an order4.Overview of a load-oriented manufacturing control syste

19、m1. Routing data2. Order data3. Item data4. Shop calendar5. Capacity data6. Transaction data7. Control data: detailed tables for w/c and free definable group.ShopCalendarCapacityDataPlanningDataTransactionDataItemDataOrderDataRouteingDataPROGRAMTransactionDataPROGRAMControlDataPROGRAMShopCalendarPro

20、gramGraphsReportsPROGRAMOperationSequencingPROGRAMOrderReleasePROGRAMOrderEntryDIALOGCapacitiesDIALOGOperationCompleteDIALOGOrderReleaseDIALOGOrderEntryCapacitiesEntriesCapacitiesReleaseCapacitiesSequencesGraphsReportsControlDataCONTROL SYSTEM(PC)BASIC SYSTEM(HOST)PLANNING SYSTEM(PC)Figure 10. Load-

21、oriented manufacturing control system showing the data flow5.Example of the control system1. The method of basic throughput diagrams is extended(Figure 1 with diagrams)2. Operation Throughput Element3. Planned and actual average lead time are computed for each inventory as well as average due-date d

22、ev. For release,input, output and deliveryEntryReleaseInputOutputDeliveryDispositionIndirectDirectDownstreamUpstreamOpenCycleTotal lead timeWait after operationTransportWait before operationSetupRunInteroperation timeProcess timeDirect Load time.4. Pump-building factory characteristics products 9000 pumps Manufactured parts 26000 different itemsManpower(Job shop) 180 persons Work centers 130