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Chapter 7, Lean Thinking and Lean Systems
INTRODUCTION
to
Operations Management
5e, Schroeder
Copyri ght 2011 by The McGraw-H il l Companies, Inc. All ri ghts reserved.McGraw-Hill/Irwin
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Chapter OutlineEvolution of Lean
Lean Tenets
The Lean System
Stabilizing the Master Schedule
Controlling Flow with the Kanban System
Reducing Setup Time and Lot Sizes
Changing Layout and Maintaining Equipment
Cross-Training, Rewarding, and Engaging WorkersGuaranteeing Quality
Changing Relationships with Suppliers
Implementation of Lean
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Evolution of Lean
Toyota Production System (TPS)Developed in the 1960s in Japan
Also known as Just-in-Time (JIT) manufacturing
First introduced into U.S.A. in 1981 at Kawasakimotorcycle plant in Lincoln, Nebraska
Lean Production
Term coined in late 1980s
Popularized in 1990s by Womack, Jones & Roos,
The Machine That Changed the World
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Lean Tenets
Specify exactly what creates value
Improve the value stream
Design the flow to avoid wasteProduce only what the customer pulls
Strive for perfection
5 Whys5 S
Poka-yoke (mistake proofing)
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Elements of Lean System
Level master scheduleUse of Kanban system
Small lot sizes (lot size one)
Quick changeover (set-ups)Multifunction workers
Efficient layout (linear flow, low inventories)
Quality and continuous improvement
Close relationships with suppliers
Frequent deliveries from vendors
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The Seven WastesOverproduction: Producing more than the demand for customers resulting in unnecessary
inventory, handling, paperwork, and warehouse space.
Waiting Time: Operators and machines waiting for parts or work to arrive from suppliers
or other operations. Customers waiting in line.
Unnecessary Transportation: Double or triple movement of materials due to poor
layouts, lack of coordination and workplace organization.
Excess Processing: Poor design or inadequate maintenance or processes requiring
additional labor or machine time.
Too much Inventory: Excess inventory due to large lot sizes, obsolete items, poor
forecasts or improper production planning.
Unnecessary Motion: Wasted movements of people or extra walking to get materials.
Defects: Use of materials, labor and capacity for production of defects, sorting our bad
parts or warranty costs with customers.
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Inventory as Waste
If all our suppliers are guessing, you end
up with inventory, which is the physical
embodiment of bad information.
Paul Bell, Dell, Inc. Europe.
Source: Economist, 1 April 2000, p. 57.
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Figure 7.2, Inventory Covers
Problems
Poor
Quality
Unreliable
Supplier
Machine
BreakdownInefficient
Layout
Bad
Design
Lengthy
SetupsWaterLevel
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Water Level Lowered To
Expose Problems
Poor
Quality
Unreliable
Supplier
Machine
BreakdownInefficient
Layout
Bad
Design
Lengthy
Setups
WaterLev
el
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Water Flows Smoothly
(Problems Pulverized)
WaterLev
el
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Affects every aspect of plant operationsLot sizing
Scheduling
Layout
Suppliers
Labor relations
Affects the rest of the firm
EngineeringMarketing
HR
Finance
The Lean System
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Production horizon set according to demand
Production schedule repeated each day
Supply & demand matched through takttime concept (speed of output)
Level production to create uniform load
Strive for production of lot size one
Produce the right quantity each daynomore and no less.
Stabilizing the Master Schedule
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Kanban means marker
A pull production system
A physical (normally visual) control systemNormally composed of cards and containers
(productioncard andwithdrawalcard), but
can be any type of signalNumber of containers:
Kanban System
C
DTn
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The Kanban System
Signals the need for more parts
The Kanban system uses simple cards or signals to
strictly control production
The basic idea is that no station is permitted toproduce more than is immediately required by the
succeeding station
This simple idea prevents the buildup of inventory
Reducing lead time is the key
No computer is required!
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Figure 7.4: Kanban System
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Figure 7.5: Kanban Cards
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Examples of Kanban Signals
Kanban cards
Tags on a board
Golf balls
Lights
Faxes/phone callsYelling
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Reducing Setup Times andLot Sizes
Reducing setup times:increases available capacity
increases flexibility
reduces inventory
Reduce setup times and run times simultaneously
to reduce lot sizes and throughput times
Single-digit setup Times (Shigeo Shingo [d. 1990]or SMED System)
Small lots require short setups!
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Figure 7.7: Initial Layout Before Lean
Stockrooms
Supplier A Supplier B
Final
AssemblyWork Centers
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Lean Layout
FinalAssembly
Supplier A Supplier B
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Lean Layout with Group TechnologyFinal
Assembly
Supplier A Supplier B
Line 1
Line 2
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Engaging Workers
Multifunction workers
Cross-training
New pay system to reflect skills varietyTeamwork
Suggestion systems
Need full worker understanding andcooperation
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Guaranteeing Quality
Quality is essential in a lean system
Defects produce waste
No inventory to cover up mistakesDefects discovered quickly by the next process
System designed to expose errors and get them
correctedMakes continuous improvement possible
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Changing Relationships with
SuppliersSuppliers required to make radical changes
Viewed as the external factory
Co-locationFewer suppliers
Frequent deliveries to production line
No inspectionhigh qualityIntegrated supplier programs
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Features of Integrated Supplier Programs
1. Early supplier selection, preferably in the
design phase
2. Family of part sourcing to allow supplier to
take advantage of Group Technology
3. Long-term relationships with small number of
suppliers
4. Paperwork reduction in receiving and
inspection to reduce costs
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Implementation of Lean Systems
Establish a cross-functional team
Determine what value the customer needs
Construct a value stream map and use it to eliminate
waste
Flow or pull demand from the customer
Implement the changes
Repeat the cycle on another process
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Summary
Evolution of Lean
Lean Tenets
The Lean System
Stabilizing the Master Schedule
Controlling Flow with the Kanban System
Reducing Setup Time and Lot Sizes
Changing Layout and Maintaining Equipment
Cross-Training, Rewarding, and Engaging WorkersGuaranteeing Quality
Changing Relationships with Suppliers
Implementation of Lean
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End of Chapter Seven
Recommended