Download - JIT Lean Production
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Just-in-Time/Lean Production
A repetitive production systemin 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 sizes
Lots of inventory
PUSH material to next
stage
Lower
per unitcost
Big purchase shipments
Big pushes of finished goods
to warehouses or customers
???
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Post-JIT: Lean Production
Tighter coordination along the supply chain
Goods are pulled along
only make and ship what is needed
Smaller lots
Faster setups
Less inventory, storage space
PULL material to next stage
Minimal
or no
inventory
holding
cost
Smaller shipments
Goods are pulled out of
plant 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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Waste
Definition:
Wasteis anything other than the minimum
amount of equipment, materials, parts,
space, and workers 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 design
Standard parts
Modular design
Quality
Process design
Personnel and organizational elements
Manufacturing planning and control
MPC
Staff ORG
Process Design
Product Design
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Top Management
Long-term planningProduct line decisions
Expansion issues
Middle management
Planning, purchasinghiring, and capital decisions
Moni tor costs
Supervisors
Control activities in specific areasMonitor qual i ty, del ivery, 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 decisionsMoni tor cos ts and assis t 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
TechnicalIdeas
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Planning and Control Systems
Small JIT
Stable and level schedules
Mixed Model Scheduling
Push versus Pull
Kanban Systems
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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 always
has parts and A doesnt 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 produce
Workcenter A Workcenter B
Kanban Card
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Empty Box: Signal to pull
Empty box sent back. Signal to pull another full box into
Workcenter B.
Question: How many kanban cards here? Why?
Workcenter A Workcenter B
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How Many Kanbans?
y = number of kanban cards
D = demand per unit of time
T = lead timeC = container capacity
X = fudge factor
C
x)DT(1y
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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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Note:
For a kanban system to work, we NEED
CONSISTENTdemand 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 = 4
B: 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
Eliminate
Surprises
Increase
FlexibilitySimplify
Drive Out
Waste
What about
automation?
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Putting the Squeeze on Resources
Squeeze!
Simplify
Eliminate Uncertainty
Increase Flexibility
NO
PAIN? YES