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McGraw-Hill/Irwin Copyright © 2007 by The McGraw-Hill Companies, Inc. All rights reserved.
15
JIT and
Lean Operations
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Learning Objectives
Explain what is meant by the term lean operationssystem.
List each of the goals of JIT and explain its
importance.
List and briefly describe the building blocks of JIT.
List the benefits of the JIT system.
Outline the considerations important in converting
a traditional mode of operations to a JIT system.
List some of the obstacles that might be
encountered when converting to a JIT system.
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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 areneeded,
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 balancedsystem.
Achieves a smooth, rapid flow of materials through the system
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Summary JIT Goals and Building
Blocks Figure 15.1
Product
Design
Process
Design
Personnel
Elements
Manufactur-
ing Planning
Eliminate disruptions
Make the system flexible Eliminate waste
A
balanced
rapid flow
Ultimate
Goal
Supporting
Goals
BuildingBlocks
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Supporting Goals
Eliminate disruptions
Make system flexible
Eliminate waste, especially excessinventory
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Sources of Waste
Overproduction
Waiting time
Unnecessary transportation Processing waste
Inefficient work methods
Product defects
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Kaizen Philosophy
Waste is the enemy Improvement should be done gradually and
continuously
Everyone should be involved Built on a cheap strategy
Can be applied anywhere
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Kaizen Philosophy (cont’d)
Supported by a visual system Focuses attention where value is created
Process oriented
Stresses main effort of improvement shouldcome from new thinking and work style
The essence of organizational learning is to
learn while doing
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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/organizationalelements
Manufacturingplanning and control
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Product Design
Standard parts
Modular design
Highly capable productionsystems
Concurrent
engineering
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Process Design
Small lot sizes
Setup time reduction
Manufacturing cells Limited work in process
Quality improvement
Production flexibility Balanced system
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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Single-Minute Exchange
Single-minute exchange of die (SMED): Asystem for reducing changeover time
Categorize changeover activities
Internal – activities that can only be done whilemachine is stopped
External – activities that do not require stopping
the machine
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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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Production Flexibility
Balance system: Distributing the workloadevenly among work stations
Work assigned to each work station must be
less than or equal to the cycle time Cycle time is set equal to the takt time
Takt time is the cycle time needed to match
customer demand for final product
P l/O i ti l
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Personnel/Organizational
Elements
Workers as assets
Cross-trained
workers
Continuous
improvement
Cost accounting
Leadership/project
management
Man fact ring Planning and
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Manufacturing Planning and
Control
Level loading
Pull systems
Visual systems Close vendor
relationships
Reduced transactionprocessing
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
K b P d ti C t l
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Kanban Production Control
System
Kanban: Card or other device thatcommunicates 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 comesfrom 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 partsX = Policy variable set by management
- possible inefficiency in the system
C = Capacity of a standard container
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Limited Work in Process
Benefits Lower carrying costs
Increased flexibility
Aids scheduling Saves cost of rework and scrap
Two general approaches
Kanban – focuses on individual work stations Constant work in process (CONWIP) – focuses
on the system as a whole
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Traditional Supplier Network
Buyer
Supplier Supplier Supplier Supplier
Supplier
Supplier
Supplier
Figure 15.4a
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Tiered Supplier Network Figure 15.4b
Supplier
Supplier
Supplier
Supplier Supplier Supplier
Buyer
Supplier First Tier Supplier
Second Tier Supplier
Third Tier Supplier
Preventive Maintenance and
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Preventive Maintenance and
Housekeeping
Preventative maintenance: Maintainingequipment in good condition and replacing
parts that have a tendency to fail before they
actually fail. Housekeeping : Maintaining a workplace that
is clean and free of unnecessary materials.
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Housekeeping Five S’s
1. Sort2. Straighten
3. Sweep
4. Standardize
5. Self-discipline
Comparison of JIT and
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Comparison of JIT and
Traditional
Factor Traditional JIT
Inventory Much to offset forecast
errors, late deliveries
Minimal necessary to operate
DeliveriesFew, large Many, small
Lot sizes Large Small
Setup; runs Few, long runs Many, short runs
Vendors Long-term relationshipsare unusual
Partners
Workers Necessary to do the work Assets
Table 15.3
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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 becooperative
Difficult to change company culture
Suppliers may
resist Why?
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Suppliers May Resist JIT
Unwilling to commit resources Uneasy about long-term commitments
Frequent, small deliveries may be difficult
Burden of quality control shifts to supplier
Frequent engineering changes may cause
JIT changes
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JIT in Services
The basic goal of the demand flowtechnology in the service organization is toprovide 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 worksright 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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Benefits 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 addvalue
Simple systems that are easy tomanage
Use of product layouts to minimizemoving materials and parts
Quality at the source
Elements of JIT Table 15.4
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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 15.4
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Video: Made for you
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’
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Video: McDonald’s Process
Vid L G
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Video: Layout Gortrac