JIT and Lean Operations
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Transcript of JIT and Lean Operations
McGraw-Hill/Irwin Copyright © 2010 by The McGraw-Hill Companies, Inc. All rights reserved.
15
JIT andLean Operations
15-2
Learning Objectives
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.
15-3
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”
15-4
Goal of JIT
The ultimate goal of JIT is a balanced system.
Achieves a smooth, rapid flow of materials through the system.
15-5
Summary JIT Goals and Building BlocksFigure 15.1
Product Design
ProcessDesign
PersonnelElements
Manufactur-ing Planning
Eliminate disruptions
Make the system flexible Eliminate waste
Abalancedrapid flow
UltimateGoal
SupportingGoals
Building Blocks
15-6
Supporting Goals
Eliminate disruptions
Make system flexible
Eliminate waste, especially excess inventory
15-7
Sources of Waste
Overproduction Waiting time Unnecessary transportation Processing waste Inefficient work methods Product defects
15-8
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
15-9
Kaizen Philosophy
Supported by a visual system Focuses attention where value is created Process oriented Stresses main effort of improvement should
come from new thinking and work style The essence of organizational learning is to
learn while doing
15-10
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
15-11
JIT Building Blocks
Product design Process design Personnel/organizational
elements Manufacturing
planning and control
15-12
Product Design
Standard parts
Modular design
Highly capable production systems
Concurrentengineering
15-13
Process Design
Small lot sizes Setup time reduction Manufacturing cells Limited work-in-process Quality improvement Production flexibility Balanced system Little inventory storage
15-14
Benefits of Small Lot Sizes
Reduces inventory
Less storage space
Less rework
Problems are more apparent
Increases product flexibility
Easier to balance operations
15-15
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
15-16
Production Flexibility
Reduce downtime by reducing changeover time
Use preventive maintenance to reduce breakdowns
Cross-train workers to help clear bottlenecks
15-17
Production Flexibility
Use many small units of capacity Use off-line buffers Reserve capacity for important customers
15-18
Quality Improvement
Autonomation Automatic detection of defects during
production
Jidoka Japanese term for autonomation
15-19
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
15-20
Personnel/Organizational Elements
Workers as assets
Cross-trained workers
Continuous improvement
Cost accounting
Leadership/project management
15-21
Manufacturing Planning and Control
Level loading Pull systems Visual systems Close vendor
relationships Reduced transaction
processing Preventive maintenance
15-22
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
15-23
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
15-24
Kanban Formula
N = DT(1+X)C
N = Total number of containersD = Planned usage rate of using work centerT = 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 systemC = Capacity of a standard container
15-25
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
15-26
Traditional Supplier Network
BuyerBuyer
SupplierSupplierSupplierSupplier SupplierSupplier SupplierSupplier
SupplierSupplier
SupplierSupplierSupplierSupplier
Figure 15.4a
15-27
Tiered Supplier NetworkFigure 15.4b
SupplierSupplier
SupplierSupplier
SupplierSupplier
SupplierSupplierSupplierSupplier SupplierSupplier
BuyerBuyer
SupplierSupplierFirst Tier Supplier
Second Tier Supplier
Third Tier Supplier
15-28
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.
15-30
Comparison of JIT and Traditional Systems
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 15.3
15-31
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
15-32
Obstacles to Conversion
Management may not be committed Workers/management may not be
cooperative Difficult to change company culture Suppliers may resist
Why?
15-33
Why Suppliers 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
15-34
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. Eliminate disruptions Make system flexible Reduce setup and lead times Eliminate waste Minimize WIP Simplify the process
15-35
JIT II: a supplier representative works right in the company’s plant, making sure there is an appropriate supply on hand.
JIT II
15-36
Benefits of JIT Systems
Reduced inventory levels
High quality
Flexibility
Reduced lead times
Increased productivity
15-37
Benefits of JIT Systems
Increased equipment utilization
Reduced scrap and rework
Reduced space requirements
Pressure for good vendor relationships
Reduced need for indirect labor
15-38
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 JIT