JITDemand-PullLogic(英文版)

1、JITISQA 459 Mellie Pullman1Just-In-Time (JIT)Just-In-Time (JIT)DefinedDefined JIT can be defined as an integrated set of activities designed to achieve high-volume production using minimal inventories (raw materials, work in process, and finished goods). JIT also involves the elimination of waste in

2、 production effort. JIT also involves the timing of production resources (e.g., parts arrive at the next workstation “just in time”). 2The Japanese Approach to The Japanese Approach to ProductivityProductivity Elimination of waste Efforts concentrated on shop floor Respect for people Quality improve

3、ment focus3Waste in OperationsWaste in Operations(1) Waste from overproduction(2) Waste of waiting time(3) Transportation waste(4) Inventory waste(5) Processing waste(6) Waste of motion(7) Waste from product defects 4JIT Demand-Pull LogicJIT Demand-Pull LogicCustomersSubSubFabFabFabFabVendorVendorVe

4、ndorVendorFinal Assembly5Minimizing Waste: Minimizing Waste: Focused Factory NetworksFocused Factory NetworksFinal AssemblyCoordinationSystem Integration6Traditional ConveyanceABCACBSporadic and Infrequent Deliveries from Individual Suppliers7Mixed-Load DeliveryABCABCRegular and Frequent Deliveries

5、from Many Suppliers8Minimizing Waste: Minimizing Waste: Group Technology Group Technology Using Departmental Specialization for plant layout can cause a lot of unnecessary material movement. SawSawLathePressPressGrinderLatheLatheSawPressHeat TreatGrinder9Minimizing Waste: Minimizing Waste: Group Tec

6、hnology Group Technology Revising by using Group Technology Cells can reduce movement and improve product flow. PressLatheGrinderGrinderA2BSawHeat TreatLatheSawLathePressLathe110Minimizing Waste: Minimizing Waste: Uniform Plant LoadingUniform Plant LoadingNot uniformJan. UnitsFeb. UnitsMar. UnitsTot

7、al1,2003,5004,3009,000UniformJan. UnitsFeb. UnitsMar. UnitsTotal3,0003,0003,0009,000Suppose we operate a production plant that produces a single product. The schedule of production for this product could be accomplished using either of the two plant loading schedules below. How does the uniform load

8、ing help save labor costs? or 11Mixed Batch Example Company produces three products with a mixed model assembly line. Operates 16 hours per day for 250 days/yr. Determine the mixed model MPS for a daily batch. Determine minimum batch MPS and the mix schedule for a day.ProductsForecasts (year)120,000

9、210,00035,00012Calculations #1#2#3Year Forecast 20000100005000Daily Batchdivide by 250804020Hourly Batchdivide by 1652.51.25Minimum Batch MPS 421For every unit of #3 (minimum batch), we need twice as many #2 and 4 timesAs many #1 so for minimum batch:Produce during each day produce #1,1,1,1,2,2,3 -

10、repeated 20 times13Mixed Batch Example Company produces four products with a mixed model assembly line. Operates 8hours per day for 250 days/yr. Determine the mixed model MPS for a daily and hourly batch . Determine mix schedule for a day.ProductsForecasts (year)I500II1500III4500IV600014Minimizing W

11、aste: Just-In-Time Minimizing Waste: Just-In-Time ProductionProduction Management philosophy “Pull” system though the plantWHAT IT IS Employee participation Industrial engineering/basics Continuing improvement Total quality control Small lot sizesWHAT IT REQUIRES Attacks waste Exposes problems and b

12、ottlenecks Achieves streamlined productionWHAT IT DOES Stable environmentWHAT IT ASSUMES15Minimizing Waste: Inventory Minimizing Waste: Inventory Hides ProblemsHides ProblemsWork inprocess queues(banks)ChangeordersEngineering designredundanciesVendordelinquenciesScrapDesignbacklogsMachine downtimeDe

13、cisionbacklogsInspectionbacklogsPaperworkbacklogExample: By identifying defective items from a vendor early in the production process the downstream work is saved.Example: By identifying defective work by employees upstream, the downstream work is saved.16Minimizing Waste: Minimizing Waste: Kanban P

14、roduction Control Kanban Production Control SystemsSystemsStorage Part AStorage Part AMachine CenterAssembly LineMaterial FlowCard (signal) FlowWithdrawal kanbanProduction kanban17Determining the Number of Determining the Number of Kanbans NeededKanbans Needed Setting up a kanban system requires det

15、ermining the number of kanbans (or containers) needed. Each container represents the minimum production lot size. An accurate estimate of the lead time required to produce a container is key to determining how many kanbans are required.18The Number of Kanban Card The Number of Kanban Card SetsSetsCS

16、dLk)(1container theof SizestockSafety timelead during demand Expectedk = Number of kanban card sets (a set is a card)d = Average number of units demanded over some time periodL = lead time to replenish an order (same units of time as demand)S = Safety stock expressed as a percentage of demand during

17、 lead timeC = Container size 19Example of Kanban Card Example of Kanban Card Determination: Problem DataDetermination: Problem Data A switch assembly is assembled in batches of 4 units from an “upstream” assembly area and delivered in a special container to a “downstream” control-panel assembly oper

18、ation. The control-panel assembly area requires 5 switch assemblies per hour. The switch assembly area can produce a container of switch assemblies in 2 hours. Safety stock has been set at 10% of needed inventory.20Example of Kanban Card Example of Kanban Card Determination: CalculationsDeterminatio

19、n: Calculations3or ,75. 245(2)(1.1)(1container theof SizestockSafety timelead during demand ExpectedCSdLkAlways round up!21JIT Requirements: Design JIT Requirements: Design Flow ProcessFlow Process Link operations Balance workstation capacities Re-layout for flow Emphasize preventive maintenance Red

20、uce lot sizes Reduce setup/changeover time 22JIT Requirements: Improve JIT Requirements: Improve Product DesignProduct Design Standard product configuration Standardize and reduce number of parts Process design with product design Quality expectations 23Respect for PeopleRespect for People Level pay

21、rolls Cooperative employee unions Subcontractor networks Inverted pyramid management style Small group involvement activities 24JIT Requirements: Total Quality JIT Requirements: Total Quality ControlControl Worker responsibility Measure SQC Enforce compliance Fail-safe (Poke-yoke) methods Automatic inspection 25POKE-YOKEs address MistakesDamaged partsMissing partsReversed partsWrong partsWrong size or shapeWrong chemical propertiesWrong physical propertiesWrong item shippedWrong labelWrong packageDamaged finished productOmitting a partOmitting a processPerforming a process incorre