JIT-Lean Production.ppt
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Transcript of JIT-Lean Production.ppt
1
Just-in-Time/Lean Production
A repetitive production system
in which the processing and movement of materials and goods occur
just as they are needed!
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Pre-JIT: Traditional Mass Production
Big lot sizesLots of inventory”PUSH” material to nextstage
Lowerper unit
cost
Big purchase shipments
Big “pushes” of finished goodsto warehouses or customers
???
3
Post-JIT: “Lean Production”
Tighter coordination along the supply chainGoods are pulled along
— only make and ship what is neededSmaller lotsFaster setupsLess inventory, storage space”PULL” material to next stage
Minimalor no
inventoryholding
cost
Smaller shipments
Goods are pulled out ofplant by customer demand
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JIT Goals(throughout the supply chain)
• Eliminate disruptions
• Make the system flexible
• Reduce setup times and lead times
• Minimize inventory
• Eliminate waste
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WasteDefinition:
Waste is ‘anything other than the minimum amount of equipment, materials, parts, space, and worker’s time, which are absolutely essential to add value to the product.’
— Shoichiro Toyoda President, Toyota
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Forms of Waste:
• Overproduction
• Waiting time
• Transportation
• Processing
• Inventory
• Motion
• Product Defects
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Inventory as a Waste
• Requires more storage space
• Requires tracking and counting
• Increases movement activity
• Hides yield, scrap, and rework problems
• Increases risk of loss from theft, damage, obsolescence
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Building Blocks of JIT
• Product designStandard partsModular designQuality
• Process design• Personnel and organizational elements• Manufacturing planning and control
MPC
Staff ORG
Process Design
Product Design
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Process Design
• “Focused Factories”
• Group Technology
• Simplified layouts with little storage space
• Jidoka and Poka-Yoke
• Minimum setups
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Personnel and Organizational Elements
• Workers as assets
• Cross-trained workers
• Greater responsibility at lower levels
• Leaders as facilitators, not order givers
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Top Management
Long-term planningProduct line decisions
Expansion issues
Middle management
Planning, purchasinghiring, and capital decisions
Monitor costs
Supervisors
Control activities in specific areasMonitor quality, delivery, etc.
Direct Labor
Perform predetermined tasks
Technical Staff
Work methods, QCProcess improvements,
MIS
Planning Info
Control Info
Detailed Methods,Schedules
Classic Organizational View
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JIT Organization View
Top Management
Long-term planningProduct line decisions
Expansion issues
Middle management
Planning, less purchasinghiring, and capital decisions
Monitor costs and assist labor
Direct Labor (self-supervising)
Task performance and schedule attainmentControl specific areas of activity
Monitor quality, delivery, etc.Participate in hiring and continuous
improvement
Technical Staff
Training and TechnicalSupport
Planning Info
Control Info
Te
chn
ica
l Id
eas
13
Planning and Control Systems
• “Small” JIT
• Stable and level schedules
– Mixed Model Scheduling
• “Push” versus “Pull”
– Kanban Systems
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Kanban
Uses simple visual signals to control production
• Examples:
empty slot in hamburger chute
empty space on floor
kanban card
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Kanban Example
Workcenter B uses parts produced by Workcenter A
How can we control the flow of materials so that B alwayshas parts and A doesn’t overproduce?
Workcenter A Workcenter B
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When a container is opened by Workcenter B, its kanban card is removed and sent back to Workcenter A.This is a signal to Workcenter A to produce another box of parts.
Kanban card: Signal to produceWorkcenter A Workcenter B
Kanban Card
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Empty Box: Signal to pull
Empty box sent back. Signal to pull another full box intoWorkcenter B.Question: How many kanban cards here? Why?
Workcenter A Workcenter B
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How Many Kanbans?
y = number of kanban cardsD = demand per unit of timeT = lead timeC = container capacityX = fudge factor
Cx)DT(1
y
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Example
• Hourly demand = 300 units• Lead time = 3 hours• Each container holds 300 units• Assuming no variation in lead-time or
demand (x = 0):
y = (300 3) / 300 = 3 kanban cards
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Extending the pull system
B
A
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Note:
• For a kanban system to work, we NEED CONSISTENT demand across the work centers
• How do we ensure this?
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Mixed Model Sequencing
Largest integer that divides evenly into daily requirement is 10:
A: 40 / 10 = 4B: 40 / 10 = 4C: 10 / 10 = 1
Mixed model sequence: A-B-A-B-A-B-A-B-C
Product Monthly Demand
Daily Requirement
A 800 40
B 800 40
C 200 10
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Implementing JIT
EliminateSurprises
IncreaseFlexibility
Simplify
Drive OutWaste
What about automation?
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Putting the Squeeze on Resources
Squeeze!
– Simplify– Eliminate Uncertainty– Increase Flexibility
NO
PAIN? YES