Transcript
S P CHHEDA & CO
14-1 JIT and Lean Operations
William J. Stevenson
Operations Management
8th edition
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JIT/Lean Production
Just-in-time (JIT): A highly coordinated processing system in which goods move through the system, and services are performed, just as they are needed,
JIT lean production
JIT pull (demand) system
JIT operates with very little “fat”
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Goal of JIT
The ultimate goal of JIT is a balanced system.
Achieves a smooth, rapid flow of materials through the system
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14-5 JIT and Lean OperationsSummary JIT Goals and Building BlocksFigure 14.1
Product Design
ProcessDesign
PersonnelElements
Manufactur-ing Planning
Eliminate disruptions
Make the system flexible Eliminate waste
Abalancedrapid flow
UltimateGoal
SupportingGoals
BuildingBlocks
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Supporting Goals
Eliminate disruptions
Make system flexible
Eliminate waste, especially excess inventory
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Sources of Waste
Overproduction Waiting time Unnecessary transportation Processing waste Inefficient work methods Product defects
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Big JIT – broad focus Vendor relations Human relations Technology management Materials and inventory management
Little JIT – narrow focus Scheduling materials Scheduling services of production
Big vs. Little JIT
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JIT Building Blocks
Product design Process design Personnel/organizational
elements Manufacturing
planning and control
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Product Design
Standard parts
Modular design
Highly capable production systems
Concurrentengineering
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Process Design
Small lot sizes Setup time reduction Manufacturing cells Limited work in process Quality improvement Production flexibility Little inventory storage
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Benefits of Small Lot Sizes
Reduces inventory
Less storage space
Less rework
Problems are more apparent
Increases product flexibility
Easier to balance operations
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Production Flexibility
Reduce downtime by reducing changeover time
Use preventive maintenance to reduce breakdowns
Cross-train workers to help clear bottlenecks
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Production Flexibility (cont’d)
Use many small units of capacity Use off-line buffers Reserve capacity for important customers
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Quality Improvement
Autonomation Automatic detection of defects during production
Jidoka Japanese term for autonomation
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14-16 JIT and Lean OperationsPersonnel/Organizational Elements
Workers as assets
Cross-trained workers
Continuous improvement
Cost accounting
Leadership/project management
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14-17 JIT and Lean OperationsManufacturing Planning and Control
Level loading Pull systems Visual systems Close vendor relationships Reduced transaction
processing Preventive maintenance
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Pull/Push Systems
Pull system: System for moving work where a workstation pulls output from the preceding station as needed. (e.g. Kanban)
Push system: System for moving work where output is pushed to the next station as it is completed
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14-19 JIT and Lean OperationsKanban Production Control System
Kanban: Card or other device that communicates demand for work or materials from the preceding station
Kanban is the Japanese word meaning “signal” or “visible record”
Paperless production control system
Authority to pull, or produce comes from a downstream process.
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Kanban Formula
N = DT(1+X)C
N = Total number of containers
D = Planned usage rate of using work center
T = Average waiting time for replenishment of parts plus average production time for a container of parts
X = Policy variable set by management - possible inefficiency in the system
C = Capacity of a standard container
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Traditional Supplier NetworkTraditional Supplier Network
BuyerBuyer
SupplierSupplierSupplierSupplier SupplierSupplier SupplierSupplier
SupplierSupplier
SupplierSupplierSupplierSupplier
Figure 14.4a
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Tiered Supplier NetworkTiered Supplier NetworkFigure 14.4b
SupplierSupplier
SupplierSupplier
SupplierSupplier
SupplierSupplierSupplierSupplier SupplierSupplier
BuyerBuyer
SupplierSupplierFirst Tier SupplierFirst Tier Supplier
Second Tier SupplierSecond Tier Supplier
Third Tier SupplierThird Tier Supplier
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Comparison of JIT and Traditional
Factor Traditional JIT
Inventory Much to offset forecast errors, late deliveries
Minimal necessary to operate
Deliveries Few, large Many, small
Lot sizes Large Small
Setup; runs
Few, long runs Many, short runs
Vendors Long-term relationships are unusual
Partners
Workers Necessary to do the work
Assets
Table 14.3
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Transitioning to a JIT System
Get top management commitment
Decide which parts need most effort
Obtain support of workers
Start by trying to reduce setup times
Gradually convert operations
Convert suppliers to JIT
Prepare for obstacles
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Obstacles to Conversion
Management may not be committed
Workers/management may not be cooperative
Suppliers may resist Why?
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JIT in ServicesThe basic goal of the demand flow technology in the service organization is to provide optimum response to the customer with the highest quality service and lowest possible cost. Eliminate disruptions Make system flexible Reduce setup and lead times Eliminate waste Minimize WIP Simplify the process
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JIT II: a supplier representative works right in the company’s plant, making sure there is an appropriate supply on hand.
JIT II
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Benefits of JIT Systems
Reduced inventory levels
High quality
Flexibility
Reduced lead times
Increased productivity
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14-29 JIT and Lean OperationsBenefits of JIT Systems (cont’d)
Increased equipment utilization
Reduced scrap and rework
Reduced space requirements
Pressure for good vendor relationships
Reduced need for indirect labor
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Smooth flow of work (the ultimate goal) Elimination of waste Continuous improvement Eliminating anything that does not add
value Simple systems that are easy to manage Use of product layouts to minimize
moving materials and parts Quality at the source
Elements of JITTable 14.4
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Poka-yoke – fail safe tools and methods Preventative maintenance Good housekeeping Set-up time reduction
Cross-trained employees
A pull system
Elements of JIT (cont’d)Table 14.4
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