15
JIT and Lean Operations
McGraw-Hill/Irwin
Copyright © 2007 by The McGraw-Hill Companies, Inc. All rights reserved.
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. 15-2
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 ing Goals Eliminate disruptions Make the system flexible
Product Design
Process Design
Eliminate waste
Personnel Elements
Manufacturing Planning
Building Blocks
15-5
ing 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)
ed 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
15-9
Big vs. Little JIT Big JIT – broad focus
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
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 ing
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
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 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
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.
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
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
Poka-yoke – fail safe tools and methods Preventative maintenance Good housekeeping Set-up time reduction
Cross-trained employees
A pull system
15-39
Video: Made for you
15-40
Video: New system
15-41
Video: McDonald’s Process
15-42
Video: Layout Gortrac
15-43