JIT and Lean Operations
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Transcript of JIT and Lean Operations
McGraw-Hill/Irwin Copyright © 2007 by The McGraw-Hill Companies, Inc. All rights reserved.
1515
JIT andLean Operations
15-2
Learning ObjectivesLearning 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 ProductionJIT/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 JITGoal 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 Summary JIT Goals and Building BlocksBlocksFigure 15.1
Product Design
ProcessDesign
PersonnelElements
Manufactur-ing Planning
Eliminate disruptions
Make the system flexible Eliminate waste
Abalancedrapid flow
UltimateGoal
SupportingGoals
BuildingBlocks
15-6
Supporting GoalsSupporting Goals
Eliminate disruptions
Make system flexible
Eliminate waste, especially excess inventory
15-7
Sources of WasteSources of Waste
Overproduction
Waiting time
Unnecessary transportation
Processing waste
Inefficient work methods
Product defects
15-8
Kaizen PhilosophyKaizen 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 (cont’d)Kaizen Philosophy (cont’d)
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
15-10
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 JITBig vs. Little JIT
15-11
JIT Building BlocksJIT Building Blocks
Product design
Process design
Personnel/organizationalelements
Manufacturing planning and control
15-12
Product DesignProduct Design
Standard parts
Modular design
Highly capable production systems
Concurrentengineering
15-13
Process DesignProcess 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 SizesBenefits 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 ExchangeSingle-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 FlexibilityProduction Flexibility
Reduce downtime by reducing changeover time
Use preventive maintenance to reduce breakdowns
Cross-train workers to help clear bottlenecks
15-17
Production Flexibility (cont’d)Production Flexibility (cont’d)
Use many small units of capacity Use off-line buffers Reserve capacity for important customers
15-18
Quality ImprovementQuality Improvement
Autonomation
Automatic detection of defects during production
Jidoka
Japanese term for autonomation
15-19
Production FlexibilityProduction 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 Personnel/Organizational ElementsElements
Workers as assets
Cross-trained workers
Continuous improvement
Cost accounting
Leadership/project management
15-21
Manufacturing Planning and Manufacturing Planning and ControlControl
Level loading
Pull systems
Visual systems
Close vendor relationships
Reduced transaction processing
Preventive maintenance
15-22
Pull/Push SystemsPull/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 Kanban Production Control SystemSystem
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 FormulaKanban 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
15-25
Limited Work in ProcessLimited 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 NetworkTraditional Supplier Network
BuyerBuyer
SupplierSupplierSupplierSupplier SupplierSupplier SupplierSupplier
SupplierSupplier
SupplierSupplierSupplierSupplier
Figure 15.4a
15-27
Tiered Supplier NetworkTiered Supplier NetworkFigure 15.4b
SupplierSupplier
SupplierSupplier
SupplierSupplier
SupplierSupplierSupplierSupplier SupplierSupplier
BuyerBuyer
SupplierSupplierFirst Tier SupplierFirst Tier Supplier
Second Tier SupplierSecond Tier Supplier
Third Tier SupplierThird Tier Supplier
15-28
Preventive Maintenance andPreventive Maintenance andHousekeepingHousekeeping
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.
15-29
Housekeeping Five S’sHousekeeping Five S’s
1. Sort
2. Straighten
3. Sweep
4. Standardize
5. Self-discipline
15-30
Comparison of JIT and Comparison of JIT and TraditionalTraditional
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 SystemTransitioning 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 ConversionObstacles to Conversion
Management may not be committed
Workers/management may not be cooperative
Difficult to change company culture
Suppliers may resist Why?
15-33
Suppliers May Resist JITSuppliers 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
15-34
JIT in ServicesJIT 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 IIJIT II
15-36
Benefits of JIT SystemsBenefits of JIT Systems
Reduced inventory levels
High quality
Flexibility
Reduced lead times
Increased productivity
15-37
Benefits of JIT Systems (cont’d)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
15-38
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 JITElements of JITTable 15.4
15-39
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)Elements of JIT (cont’d)Table 15.4