1、Just-In-Time Systems(Lean Production)Origins of JIT and Lean ProductionlPioneered by Toyota lAdopted by other Japanese manufacturerslDiscovered much later by Western manufacturerslKnown by many names:Toyota Production System Just In Time Lean production Flow productionLean Production BenefitslDouble
2、 labour productivityl90%reduction in throughput timesl90%reduction in inventorylImproved qualitylReduced time to marketHow Long does it Take?lWomack and Jones document many cases where major improvements are achieved in a matter of daysHow Much does it Cost?lThe cost is usually very lowlIn many case
3、s,companies replace expensive equipment with much simpler and cheaper equipmentlLean production does not emphasize technology or automationHewlett Packards Cupertino California plant1982(before JIT)1986(after JIT)15 days11.3 hours$670,000$20,000lead timework in processno.of back orders2002The Lean T
4、ransformation at LantechBatch andQueue/1991Flow/1995Product Development Time3-4 years1 yearEmployee hours per machine16080Manufacturing space per machine100 sq.ft.55 sq.ft.Delivered defects per machine80.8Dollar value of inventory(with doubledsales)$2.6 million$1.9 millionThroughput time16 weeks14 h
5、ours 5daysDelivery lead time4 20 weeks1-4 weeksFrom:Womack and Jones,Lean Thinking,p.121Relative Performance in Auto IndustryToyota Japan(average)USA(average)Europe(average)ProductivityAssembly1st-tier suppliers100100838565715462Quality(delivered defects)Assembly(per 100 cars)1st-tier suppliers(PPM)
6、2nd-tier suppliers(PPM)3054005519390061263610061137347231993-94,from Womack and Jones,Lean ThinkingRelative Performance in Auto IndustryToyota Japan(average)USA(average)Europe(average)Deliveries(percent late)1st-tier suppliers2nd-tier suppliers0.040.50.22.60.613.41.95.4Stocks(1st-tier suppliers)Hour
7、sStock turns(per year)Na248378113569138451993-94,from Womack and Jones,Lean ThinkingPorsches Lean Transition1991 1993 1995 1997TimeConcept to launchWelding to finished car7 years6 weeks-5 days3 years3 daysInventoriesDays on hand17.04.24.23.2EffortHours to assemble120957645Source:Womack and Jones,Lea
8、n ThinkingPorsches Lean Transition1991 1993 1995 1997ErrorsSupplied parts(PPM)Finished cars(index)10,0001004,000601,0004510025Sales3,1021,9132,607-ProfitsHours to assemble+17-239+2-Source:Womack and Jones,Lean ThinkingWhat is JIT/Lean Production?lProducing only what is needed,when it is neededlA phi
9、losophy lAn integrated management systemlJITs mandate:Eliminate all wasteExamples of WastelWatching a machine runlWaiting for partslCounting partslProducing parts that arent neededlMoving parts over long distanceslStoring inventorylLooking for tools or partslMachine breakdownlRework and scraplProduc
10、ts that dont meet the needs of customersLean PrincipleslSpecify value defined by the customerlIdentify value stream eliminate all activities that dont add valuelFlow products should flow along value streamLean PrincipleslPull let the customer pull products they want,rather than pushing products they
11、 may not wantlPerfection strive for perfection through continuous improvementTargets for Eliminating WastelZero defectslZero setup timelZero inventorieslZero part handlinglZero breakdownslZero lead timelLot size of onelMatch products to customer needsZero DefectslThe traditional assumption is that a
12、 certain level of defects is unavoidablelTraditional manufacturing measures defect rates and compares them to acceptable quality levels acceptance sampling average outgoing qualitylJIT strives to eliminate once and for all the causes of defectsZero InventorieslIn traditional manufacturing,inventorie
13、s are seen as assetslInventories provide a safety buffer,and result from maximizing machine utilizationlJIT views inventory as wastelInventory is evidence of poor design,poor coordination,and poor operation of a manufacturing systemInventory Hides ProblemsPoor QualityUnreliableSupplierMachineBreakdo
14、wnInefficientLayoutBadDesignLengthySetupsLower Levels Of Inventory To Expose ProblemsPoor QualityUnreliableSupplierMachineBreakdownInefficientLayoutBadDesignLengthySetupsZero Setup TimelTraditional thinking considers the setup time to be given and irreducible Traditional Economic Order Quantity and
15、Economic Production Lot formulas find a tradeoff between setup cost and inventory costlJIT thinking recognizes the importance of reducing the setup time If the setup time is zero,the optimal lot size is oneZero Lead TimelShort setups and small lots lead naturally to short lead timeslThe planning hor
16、izon can be closer,and the forecasts more accuratelThe system can change quickly in response to changing demandlThe flexibility is thus improvedZero Parts HandlinglJIT considers all part handling to be a waste,since it does not add valuelPart handling includes component feeding component handling pa
17、rts inspection shipping and transportationZero Parts HandlinglUnnecessary handling can be eliminated by careful design of the product and the process design for assembly design for manufacturability cellular manufacturing JIT deliveries to point-of-useZero BreakdownslMaintain equipment in top condit
18、ionlImplement Total Productive MaintenancelDont wait for problems to occurlThe old saying“If it aint broke,dont fix it”is wrong!Zero Leadtimes,Lot Size of OnelIf setup times are zero,lot size of one is feasiblelLot size of one allows continuous flow instead of batch-and-queuelWIP and lead times will
19、 be slashed as a resultMatching Product Design to Market DemandlConcurrent engineering reduces the design cyclelGreater product variety is achieved through modular designlReduced number of parts and components is achieved through good design,and through standardization and reuse of common items.Mass
20、 CustomizationlProvide every customer with an individualized productlMake to order(customer pull)lMaximize valueKeys to Mass CustomizationlDefine value(QFD)lDesign modular product architectureslStandardize components,minimize unnecessary varietylConfigure individual products from standard modulesBas
21、ic Elements of JIT1.Flexible resources2.Cellular layouts3.Pull production system4.Kanban production control5.Small-lot production6.Quick setups7.Uniform(mixed model)production8.Quality at the source9.Total productive maintenance10.Supplier networksFlexible ResourceslFlexible labour multifunction,ada
22、ptable operators the number of operators can be changed to change capacitylFlexible equipment a variety of products are produced on the same equipment this requires multifunctional machineslAchievable with basic technology!Product FamilieslGroup Technology(GT)is commonly used to identify product fam
23、ilies based on similarities in design or processinglGT helps reduce unnecessary duplication in product designlGT identifies product families with similar processing requirementslThese families can be manufactured in well-defined manufacturing cellsCellular ManufacturinglGroup dissimilar machines in
24、manufacturing cell to produce family of partslWork flows in one direction through celllOne worker tends several machineslCycle time adjusted by changing number of workersManufacturing Cell With Worker RoutesEnterWorker 1Worker 2Worker 3ExitKey:Product routeWorker routeMachinesFlow Based ProductionlC
25、ellular manufacturing achieves the benefits of flow based manufacturing lThis simplifies material flow compared to a traditional process layoutlOwnership and responsibility for a product rests with the operators of the cellThe Traditional Push SystemlIn traditional manufacturing,an item is released
26、for production at a specified time,with an associated due datelThe item moves through a sequence of operationsThe Traditional Push SystemlWhen one operation is finished,the item is“pushed”to the next operationlFinally,the product is pushed to inventory,to meet forecast demandlThis is classical push-
27、type production,as incorporated in the MRP approachThe Pull SystemlThe pull system focuses on the output of the system rather than the inputlFinished products are“pulled”from the final operation in response to firm customer ordersThe Pull SystemlThis leads to a chain reaction,with each station pulli
28、ng material from its preceding stationlJIT uses the“Kanban”system to control the flow of material with very little work-in-process inventoryThe Kanban SystemlThe Kanban system uses simple cards to strictly control productionlThe basic idea is that no station is permitted to produce more than is imme
29、diately required by the succeeding stationlThis simple idea prevents the buildup of inventorylNo computer is required!Kanban Production Control SystemlKanban card indicates standard quantity of productionlDerived from two-bin inventory systemlKanban maintains discipline of pull productionlProduction
30、 kanban authorizes productionlWithdrawal kanban authorizes movement of goodsA Sample KanbanMachiningM-2AssemblyA-4Part no.:7412Description:Slip ringsFrom:To:Box capacity 25Box Type AIssue No.3/5The Origin Of KanbanQ=order quantityR=reorder point =demand during lead timeBin 1Bin 2Q-RRReorder CardKanb
31、ana.Two-bin inventory systemb.Kanban Inventory SystemDual KanbansPWContainer with withdrawal kanbanContainer with production kanbanPWPXXXXXFlow of workFlow of kanbanKanban SquaresXXXXXXFlow of workFlow of informationTypes Of KanbanslKanban Square marked area designed to hold itemslSignal Kanban tria
32、ngular kanban used to signal production at the previous workstationlMaterial Kanban used to order material in advance of a processlSupplier Kanbans rotate between the factory and suppliersDetermining Number Of KanbanswhereN=number of kanbans or containersd=average demand over some time periodL=lead
33、time to produce partsS=safety stockC=container sizeNo.of kanbans=mand during lead time+safety stockcontainer sizeaverage deNdLSCKanban Calculation ExampleProblem statement:d=150 bottles per hourL=30 minutes=0.5 hoursdL=(150)(0.5)=75S=10%dL=10%x 75=7.5C=25 bottlesSolution:Round up to 4(allow some sla
34、ck)or down to 3(force improvement)NdLSCx(.).150 0 57 525757 5253.3 kanbans or containersSmall-Lot ProductionlThe pull system reduces inventory by minimizing the number of kanbanslThis results in frequent material movement or production,in small lotslSmall-lot production has many advantagesSmall-Lot
35、ProductionlReduces inventorylRequires less space&capital investmentlMoves processes closer togetherlMakes quality problems easier to detectlMakes processes more dependent on each otherSetup Time ReductionlSmall lots require short setups!lSetup times can be reduced from hours to minuteslShingo develo
36、ped Single Minute Exchange of Dies(SMED)system die change under 10 minutesSMED Principles1.Separate internal setup from external setup2.Convert internal setup to external setup3.Streamline all aspects of setup4.Perform setup activities in parallel or eliminate them entirelySetup Reduction Techniques
37、lPreset desired settingslUse quick fastenerslUse locator pinslPrevent misalignmentslEliminate toolslMake movements easierMixed Model ProductionlJIT permits the manufacture or assembly of a range of products simultaneously,using the same production equipmentlThis is known as mixed model productionlTh
38、e result is repetitive flow production versus traditional batch productionlMixed model production requires small batches and short setupsExample of mixed model schedulingProductMonthly demandDaily average outputA120060B40020C160080D40020E60030F60030Totals4800240Traditional Batch ScheduleProductWeek
39、1Week 2Week 3Week 4A1200B400C800800D400E600F600Total1200120012001200JIT ScheduleProductWeek 1Week 2Week 3Week 4A300300300300B100100100100C400400400400D100100100100E150150150150F150150150150Total1200120012001200JIT Production ScheduleProductNumber per lotA6B2C8D2E3F324 every 48 minutesMixed model pro
40、duction of six different products repeatson a 48 minute cycle.Advantages of Level SchedulinglBatch production becomes repetitivelLow inventorieslFlexible and responsivelSimple to control-computers are not needed!Quality At The SourcelJidoka is authority to stop production linelAndon lights signal qu
41、ality problemslUndercapacity scheduling allows for planning,problem solving&maintenancelVisual control makes problems visiblelPoka-yoke prevents defectsVisual ControlLibrary shelfWork stationVisual kanbansTool boardMachine controlsBetterGoodBest30-50HowtosensorKaizenlContinuous improvementlRequires
42、total employment involvementlEssence of JIT is willingness of workers to spot quality problems halt production when necessary generate ideas for improvement analyze problems perform different functionsTotal Productive Maintenance(TPM)lBreakdown maintenance repairs to make failed machine operationall
43、Preventive maintenance system of periodic inspection&maintenance to keep machines operatinglTPM combines preventive maintenance&total quality conceptsTPM Requires Management TolDesign products that can be easily produced on existing machineslDesign machines for easier operations,changeover,maintenan
44、celTrain&retrain workers to operate machineslPurchase machines that maximize productive potentiallDesign preventive maintenance plan spanning life of machineThe Relationship with Suppliers lTraditional relationship with suppliers is adversarial Relationships are short term,based solely on cost Large
45、 number of suppliers are played against one anotherThe Relationship with SupplierslJIT views the supplier relationship as critical Fewer suppliers The relationships are long-term,based on cooperation Suppliers must strive to continuously improvelTo achieve frequent deliveries of small lots,just in t
46、ime,suppliers must adopt JIT methods as wellTrends In Supplier Policies1.Locate near to the customer2.Use small,side loaded trucks and ship mixed loads3.Consider establishing small warehouses near to the customer or consolidating warehouses with other suppliers4.Use standardized containers and make
47、deliveries according to a precise delivery schedule5.Become a certified supplier and accept payment at regular intervals rather than upon deliveryBenefits Of JIT 1.Reduced inventory 2.Improved quality 3.Lower costs 4.Reduced space requirements 5.Shorter lead time 6.Increased productivity7.Greater flexibility8.Better relations with suppliers9.Simplified scheduling and control activities10.Increased capacity11.Better use of human resources12.More product variety
