15 JIT and Lean Operations

Copyright © 2014 by McGraw-Hill Education (Asia). 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.

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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 are needed,  JIT   lean production  JIT  pull (demand) system  JIT operates with very little “fat”

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Toyota Approach



Muda



Kanban



Pull System



Heijunka



Kaizen



Jidoka



Poka-yoke

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Team concept

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Goal of JIT

The ultimate goal of JIT is a balanced system.

Achieves a smooth, rapid flow of materials through the system.

Makes processing time as short as possible by using resources in best possible way.

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Summary JIT Goals and Building Blocks Figure 15.1

Ultimate Goal A balanced rapid flow Supporting Goals Eliminate disruptions Make the system flexible Eliminate waste Product Design Process Design Personnel Elements Building Blocks Manufactur ing Planning 15-6

Supporting Goals

 Eliminate disruptions  Make system flexible  Eliminate waste, especially excess inventory

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Sources of Waste

 Overproduction  Waiting time  Unnecessary transportation  Processing waste  Inefficient work methods  Product defects

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Waste in Operations

16-9 Copyright 2009 John Wiley & Sons,

Waste in Operations (cont.)

16-10 Copyright 2009 John Wiley & Sons,

Waste in Operations (cont.)

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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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Small Lot sizes

Inventory Hides Problems John Wiley &

Small Lot sizes

Less Inventory Exposes Problems John Wiley &

Benefits of Small Lot Sizes

Reduces inventory Less rework Less storage space Problems are more apparent Increases product flexibility Easier to balance operations 15-20

Setup Time Reduction

 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

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Common Techniques for Reducing Setup Time

16-22 Copyright 2009 John Wiley & Sons,

Common Techniques for Reducing Setup Time (cont.)

16-23 Copyright 2009 John Wiley & Sons,

Common Techniques for Reducing Setup Time (cont.)

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Manufacturing Planning and Control  Level loading  Pull systems  Visual systems  Limited work-in-process (WIP)  Close vendor relationships  Reduced transaction processing  Preventive maintenance

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Level Loading

John Wiley &

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

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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

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Sample Kanban

16-34 Copyright 2009 John Wiley & Sons,

Origin of Kanban

a) Two-bin inventory system Bin 1 Bin 2 Reorder card Q - R

R

b) Kanban inventory system Kanban Q = order quantity R = reorder point - demand during lead time

R

16-35 Copyright 2009 John Wiley & Sons,

Kanban Formula

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 to reflect possible inefficiency in the system C = Capacity of a standard container

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Types of Kanban

John Wiley &

Types of Kanban

John Wiley &

Types of Kanban

John Wiley &

Examples of Visual Control

16-40 Copyright 2009 John Wiley & Sons,

Examples of Visual Control (cont.)

16-41 Copyright 2009 John Wiley & Sons,

Examples of Visual Control (cont.)

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Limited Work-in-Process (WIP)

 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 Figure 15.4A

Buyer

Supplier Supplier Supplier Supplier Supplier Supplier Supplier

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Figure 15.4B

Tiered Supplier Network

Buyer

First Tier Supplier Second Tier Supplier Supplier Third Tier Supplier Supplier Supplier Supplier Supplier Supplier Supplier

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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.

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Housekeeping Five S’s

1. Sort 2. Straighten 3. Sweep 4. Standardize 5. Self-discipline

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Benefits of Five S’s

1. Increased productivity 2. Improved employee morale 3. Decreased risk of accidents 4. Improved appearance for visitors

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Comparison of JIT and Traditional Systems Table 15.3

Factor Traditional JIT

Inventory Deliveries Much to offset forecast errors, late deliveries Few, large Lot sizes Large Setup; runs Few, long runs Vendors Workers Minimal necessary to operate Many, small Small Many, short runs Long-term relationships are unusual Partners Necessary to do the work Assets

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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 be cooperative  Difficult to change company culture  Suppliers may resist 

Why?

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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

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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

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JIT II

 JIT II: a supplier representative works right in the company’s plant, making sure there is an appropriate supply on hand.

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Summary of Benefits of JIT

 Reduced inventory levels  High quality  Flexibility  Reduced lead times  Increased productivity

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Summary of Benefits of JIT

 Increased equipment utilization  Reduced scrap and rework  Reduced space requirements  Pressure for good vendor relationships  Reduced need for indirect labor

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