Presentation on theme: "Just-In-Time Philosophy"— Presentation transcript:
1 Just-In-Time Philosophy The philosophy of JIT can be traced back to Henry Ford, but formalized JIT originated in Japan as the Toyota Production System. W. Edwards Deming’s lesson of variability reduction was a huge influence.JIT is a long-term approach to process improvement. It uses timeliness as a lever to lower costs, improve quality and improve responsiveness. However, JIT requires enormous commitment. It took Toyota more than 25 years to get right!The focus of JIT is to improve the system of production by eliminating all forms of WASTE.
2 Just-in-TimeDownstream processes take parts from upstream as they need.Get what you wantwhen you want itin the quantity you want.
3 4. Just In Time-- What is It? Just-in-Time: produce the right parts, at the right time, in the right quantityRequires repetitive, not big volumeBatch size of oneShort transit times, keep 0.1 days of supply
4 Characteristics of Just-in-Time Pull method of materials flowConsistently high qualitySmall lot sizesUniform workstation loadsStandardized components and work methodsClose supplier tiesFlexible workforceLine flowsAutomated productionPreventive maintenanceThis slide builds the key characteristics of JIT as described in the text.
5 Push versus PullPush system: material is pushed into downstream workstations regardless of whether resources are availablePull system: material is pulled to a workstation just as it is needed
6 From a a « push » to a « pull » System Work is pushed to the next station as it is completedSUPLIERCUSTOMER
7 From a a « push » to a « pull » System A workstation pulls output as neededSUPLIERCUSTOMER
8 JIT Demand-Pull Logic Vendor Fab Sub Customers Here the customer starts the process, pulling an inventory item from Final Assembly…JIT Demand-Pull LogicCustomersSubFabVendorFinalAssemblyThen sub-assembly work is pulled forward by that demand…The process continues throughout the entire production process and supply chain4
9 Pull Versus Push Systems A pull system uses signals to request production and delivery from upstream stationsUpstream stations only produce when signaledSystem is used within the immediate production process and with suppliers
10 Pull Versus Push Systems By pulling material in small lots, inventory cushions are removed, exposing problems and emphasizing continual improvementManufacturing cycle time is reducedPush systems dump orders on the downstream stations regardless of the need
11 Waste in Operations Waste from overproduction Waste of waiting time Transportation wasteInventory wasteProcessing wasteWaste of motionWaste from product defectsUnderutilization of people6
12 Streamlined Production Flow with JITTraditional FlowCustomersSuppliersProduction Process (stream of water)Inventory (stagnant ponds)Material (water in stream)
15 Lowering Inventory Reduces Waste Reducing WIP makesproblem very visibleSTOP
16 Lowering Inventory Reduces Waste Reduce WIP again to findnew problems
17 Reduce Variability Inventory level Process downtime Scrap Setup time Late deliveriesQuality problems
18 Reduce Variability Inventory level Process downtime Scrap Setup time Quality problemsLate deliveries
19 Causes of VariabilityEmployees, machines, and suppliers produce units that do not conform to standards, are late, or are not the proper quantityEngineering drawings or specifications are inaccurateProduction personnel try to produce before drawings or specifications are completeCustomer demands are unknown
20 Variability Reduction JIT systems require managers to reduce variability caused by both internal and external factorsVariability is any deviation from the optimum processInventory hides variabilityLess variability results in less waste
21 Performance and WIP Level Less WIP means products go through system fasterreducing the WIP makes you more sensitive to problems, helps you find problems fasterStream and Rocks analogy:Inventory (WIP) is like water in a streamIt hides the rocksRocks force you to keep a lot of water (WIP) in the stream
22 Reduce Lot Sizes Q1 When average order size = 200 200 –100 –InventoryTimeQ1 When average order size = 200average inventory is 100Q2 When average order size = 100average inventory is 50
23 Reducing Lot Sizes Increases the Number of Lots Customer orders 10Lot size = 5Lot 1Lot 2Lot size = 2Lot 1Lot 2Lot 3Lot 4Lot 5
24 Reduce Lot SizesIdeal situation is to have lot sizes of one pulled from one process to the nextOften not feasibleCan use EOQ analysis to calculate desired setup timeTwo key changesImprove material handlingReduce setup time
25 Reduce Setup Times Initial Setup Time 90 min —60 min —45 min —25 min —15 min —13 min ——Step 1Separate setup into preparation and actual setup, doing as much as possible while the machine/process is operating(save 30 minutes)Step 2Move material closer and improve material handling (save 20 minutes)Step 3Standardize and improve tooling (save 15 minutes)Use one-touch system to eliminate adjustments (save 10 minutes)Step 4Step 5Training operators and standardizing work procedures (save 2 minutes)Repeat cycle until subminute setup is achieved
26 Kanban Japanese for ‘signboard’ Method for implementing JIT In order to produce, you need both material to work on, and an available kanban.Each work station has a fixed # kanbans.
27 Kanban Worker 2 finishes a part, outbound moves over Flow of work23Worker 2 finishes a part, outbound moves over2 has a blue tag avaliable, so 2 gets another part to work on:2 takes off 1’s green tag giving it back to 1, andputs on her blue tag and moves it into position.
28 Kanban When 3 finishes a part, Finished parts move over one spot Flow of work23When 3 finishes a part,Finished parts move over one spotHe has to have a red tag available to put on,He gets a part from 2’s outbound pile,And gives the blue back to 2
29 Kanban When 3 finishes a part, Flow of work23When 3 finishes a part,Finished parts move over one spotHe has to have a red tag available to put on,He gets a part from 2’s outbound pile,And gives the blue back to 23’s production will be taken by 4, offstage right.Tag goes back into 3’s bin
30 Kanban Red finishes his part next. 23Red finishes his part next.But 4 hasn’t freed up any of the red kanbans, so there is nothing for 3 to work on now.3 could maintain his machine, or see if 4 needs help23
31 The Number of Cards or Containers Need to know the lead time needed to produce a container of partsNeed to know the amount of safety stock neededNumber of kanbans =Demand during Safety lead time + stockSize of container
32 Number of Kanbans Example Daily demand = 500 cakesProduction lead time = 2 days(wait time +material handling time +processing time)Safety stock = 1/2 dayContainer size = 250 cakesDemand during lead time = 2 days x 500 cakes = 1,000Number of kanbans = = 51,250
33 Example dL (1+S) 5(2)(1.1) = = = 2.75 or 3 C 4 A switch is assembled in batches of 4 units at an “upstream” work area.delivered in a bin to a “downstream” control-panel assembly area that requires 5 switch assemblies/hour.The switch assembly area can produce a bin of switch assemblies in 2 hours.Safety stock = 10% of needed inventory.ksize of containerExpected demand during lead time + safety stock=dL (1+S)5(2)(1.1)===2.75 or 3C418
34 Scheduling Small Lots A B C A C B Time JIT Level Material-Use Approach Large-Lot ApproachTime
35 Minimizing Waste: Uniform Plant Loading Suppose 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.Not uniform Jan. Units Feb. Units Mar. Units Total1,200 3,500 4,300 9,000orUniform Jan. Units Feb. Units Mar. Units Total3,000 3,000 3,000 9,000How does the uniform loading help save labor costs?12
36 Mixed Batch ExampleCompany 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)120,000210,00035,000
37 Calculations #1 #2 #3 Year Forecast 20000 10000 5000 Daily Batch #1#2#3Year Forecast20000100005000Daily Batchdivide by 250804020Hourly Batchdivide by 1652.51.25Minimum Batch MPS421For 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 - repeated 20 times
38 Characteristics of JIT Partnershps Few, nearby suppliersSupplier just like in-house upstream processLong-term contract agreementsSteady supply rateFrequent deliveries in small lotsBuyer helps suppliers meet qualitySuppliers use process control chartsBuyer schedules inbound freight
39 Cellular Layout Promote flow with little WIP Facilitate workers staffing multiple machinesU-shaped cellsMaximum visibilityMinimum walkingFlexible in number of workersFacilitates monitoring of work entering and leaving cellWorkers can conveniently cooperate to smooth flow and address problemsInbound StockOutbound Stock
40 Assignment of individual products to product families Group TechnologyAn engineering and manufacturing philosophy that identifies physical similarities of parts and establishes their effective production.Assignment of individual products to product families
41 Cellular Manufacturing Assignment of product families to manufacturing cells
42 Group Technology (Part 1) Note how the flow lines are going back and forthUsing Departmental Specialization for plant layout can cause a lot of unnecessary material movementSawSawSawGrinderGrinderHeat TreatLatheLatheLathePressPressPress8
43 Group Technology (Part 2) Revising by using Group Technology Cells can reduce movement and improve product flowGrinder12LathePressSawLatheHeat TreatGrinderABLathePressSawLathe9
44 Group Technology (con’d) A set of machines dedicated to processing one or more familyArrange machines in a narrow UWorkers rotate among several machines
45 Group Technology (con’d) AdvantagesReduce cycle timeMove timeQueue timeSet up timeAdjust the output rate by increasing or decreasing the number of workers in a cellFacilitate job trainingPromote job satisfaction
46 Typical Benefits of JIT Cost savings: inventory reductions, reduced scrap, fewer defects, fewer changes due to both customers and engineering, less space, decreased labor hours, less rework.Revenue increases: better service and quality to the customer.Investment savings: less space, reduced inventory, increased the volume of work produced in the same facility.Workforce improvements: more satisfied, better trained employees.Uncovering problems: greater visibility to problems that JIT allows, if management is willing to capitalize on the opportunity to fix these problems.