15
JIT and
Lean Operations
McGraw-Hill/Irwin
Copyright © 2007 by The McGraw-Hill Companies, Inc. All rights reserved.
Learning Objectives
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Explain what is meant by the term lean operations
system.
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.
15-2
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”
15-3
Goal of JIT
The ultimate goal of JIT is a balanced
system.
Achieves a smooth, rapid flow of
materials through the system
15-4
Summary JIT Goals and Building
Blocks
Figure 15.1
Ultimate
A
Goal balanced
rapid flow
Supporting
Goals
Eliminate disruptions
Make the system flexible
Product
Design
Process
Design
Eliminate waste
Personnel
Elements
Manufacturing Planning
Building
Blocks
15-5
Supporting Goals
 Eliminate disruptions
 Make system flexible
 Eliminate waste, especially excess
inventory
15-6
Sources of Waste
 Overproduction
 Waiting time
 Unnecessary transportation
 Processing waste
 Inefficient work methods
 Product defects
15-7
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
15-8
Kaizen Philosophy (cont’d)
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Supported by a visual system
Focuses attention where value is created
Process orienteted
Stresses main effort of improvement should
come from new thinking and work style
 The essence of organizational learning is to
learn while doing
15-9
Big vs. Little JIT
 Big JIT – broad focus
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Vendor relations
Human relations
Technology management
Materials and inventory management
 Little JIT – narrow focus
 Scheduling materials
 Scheduling services of production
15-10
JIT Building Blocks
 Product design
 Process design
 Personnel/organizational
elements
 Manufacturing
planning and control
15-11
Product Design
 Standard parts
 Modular design
 Highly capable production
systems
 Concurrent
engineering
15-12
Process Design
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Small lot sizes
Setup time reduction
Manufacturing cells
Limited work in process
Quality improvement
Production flexibility
Balanced system
Little inventory storage
15-13
Benefits of Small Lot Sizes
Reduces inventory
Less rework
Less storage space
Problems are more apparent
Increases product flexibility
Easier to balance operations
15-14
Single-Minute Exchange
 Single-minute exchange of die (SMED): A
system for reducing changeover time
 Categorize changeover activities
 Internal – activities that can only be done while
machine is stopped
 External – activities that do not require stopping
the machine
15-15
Production Flexibility
 Reduce downtime by reducing
changeover time
 Use preventive maintenance to
reduce breakdowns
 Cross-train workers to help clear
bottlenecks
15-16
Production Flexibility (cont’d)
 Use many small units of capacity
 Use off-line buffers
 Reserve capacity for important customers
15-17
Quality Improvement
 Autonomation
 Automatic detection of defects during
production
 Jidoka
 Japanese term for autonomation
15-18
Production Flexibility
 Balance system: Distributing the workload
evenly 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
15-19
Personnel/Organizational
Elements
 Workers as assets
 Cross-trained
workers
 Continuous
improvement
 Cost accounting
 Leadership/project
management
15-20
Manufacturing Planning and
Control
 Level loading
 Pull systems
 Visual systems
 Close vendor
relationships
 Reduced transaction
processing
 Preventive maintenance
15-21
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
15-22
Kanban 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.
15-23
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
15-24
Limited Work in Process
 Benefits
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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
15-25
Traditional Supplier Network
Figure 15.4a
Buyer
Supplier
Supplier
Supplier
Supplier
Supplier
Supplier
Supplier
15-26
Tiered Supplier Network
Figure 15.4b
Buyer
First Tier Supplier
Second Tier Supplier
Third Tier Supplier
Supplier
Supplier
Supplier
Supplier
Supplier
Supplier
Supplier
15-27
Preventive Maintenance and
Housekeeping
 Preventative maintenance: Maintaining
equipment 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.
15-28
Housekeeping Five S’s
1.
2.
3.
4.
5.
Sort
Straighten
Sweep
Standardize
Self-discipline
15-29
Table 15.3
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
15-30
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
15-31
Obstacles to Conversion
 Management may not be committed
 Workers/management may not be
cooperative
 Difficult to change company culture
 Suppliers may
resist
 Why?
15-32
Suppliers May Resist JIT
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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
15-33
JIT in Services
The 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.
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Eliminate disruptions
Make system flexible
Reduce setup and lead times
Eliminate waste
Minimize WIP
Simplify the process
15-34
JIT II
 JIT II: a supplier representative works
right in the company’s plant, making
sure there is an appropriate supply on
hand.
15-35
Benefits of JIT Systems
 Reduced inventory levels
 High quality
 Flexibility
 Reduced lead times
 Increased productivity
15-36
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
15-37
Elements of JIT
Table 15.4
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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
15-38
Elements of JIT (cont’d)
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
15-39