chap7 lean

8/12/2019 Chap7 Lean

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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.



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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



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Lean Layout with Group TechnologyFinal

Assembly


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


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

chap7 lean

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