jit & lean 1

7/28/2019 JIT & Lean 1

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McGraw-Hill/Irwin Copyright © 2007 by The McGraw-Hill Companies, Inc. All rights reserved.

15

JIT and

Lean Operations

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Learning Objectives

Explain what is meant by the term lean operationssystem.

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 areneeded,

JIT lean production

JIT pull (demand) system

JIT operates with very little “fat”

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Goal of JIT

The ultimate goal of JIT is a balancedsystem.

Achieves a smooth, rapid flow of materials through the system

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Summary JIT Goals and Building

Blocks Figure 15.1

Product

Design

Process

Design

Personnel

Elements

Manufactur-

ing Planning

Eliminate disruptions

Make the system flexible Eliminate waste

A

balanced

rapid flow

Ultimate

Goal

Supporting

Goals

BuildingBlocks

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Supporting Goals

Eliminate disruptions

Make system flexible

Eliminate waste, especially excessinventory

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Sources of Waste

Overproduction

Waiting time

Unnecessary transportation Processing waste

Inefficient work methods

Product defects

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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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Kaizen Philosophy (cont’d)

Supported by a visual system Focuses attention where value is created

Process oriented

Stresses main effort of improvement shouldcome from new thinking and work style

The essence of organizational learning is to

learn while doing

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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

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JIT Building Blocks

Product design

Process design

Personnel/organizationalelements

Manufacturingplanning and control

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Product Design

Standard parts

Modular design

Highly capable productionsystems

Concurrent

engineering

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Process Design

Small lot sizes

Setup time reduction

Manufacturing cells Limited work in process

Quality improvement

Production flexibility Balanced system

Little inventory storage

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Benefits of Small Lot Sizes

Reduces inventory

Less storage space

Less rework

Problems are more apparent

Increases product flexibility

Easier to balance operations

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Single-Minute Exchange

Single-minute exchange of die (SMED): Asystem for reducing changeover time

Categorize changeover activities

Internal – activities that can only be done whilemachine is stopped

External – activities that do not require stopping

the machine

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Production Flexibility

Reduce downtime by reducing

changeover time

Use preventive maintenance to

reduce breakdowns

Cross-train workers to help clear

bottlenecks

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Production Flexibility (cont’d)

Use many small units of capacity Use off-line buffers

Reserve capacity for important customers

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Quality Improvement

Autonomation Automatic detection of defects during

production

Jidoka

Japanese term for autonomation

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Production Flexibility

Balance system: Distributing the workloadevenly 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

P l/O i ti l

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Personnel/Organizational

Elements

Workers as assets

Cross-trained

workers

Continuous

improvement

Cost accounting

Leadership/project

management

Man fact ring Planning and

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Manufacturing Planning and

Control

Level loading

Pull systems

Visual systems Close vendor

relationships

Reduced transactionprocessing

Preventive maintenance

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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

K b P d ti C t l

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Kanban Production Control

System

Kanban: Card or other device thatcommunicates 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 comesfrom a downstream process.

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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 partsX = Policy variable set by management

- possible inefficiency in the system

C = Capacity of a standard container

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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

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Traditional Supplier Network

Buyer

Supplier Supplier Supplier Supplier

Supplier

Supplier

Supplier

Figure 15.4a

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Tiered Supplier Network Figure 15.4b

Supplier

Supplier

Supplier

Supplier Supplier Supplier

Buyer

Supplier First Tier Supplier

Second Tier Supplier

Third Tier Supplier

Preventive Maintenance and

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Preventive Maintenance and

Housekeeping

Preventative maintenance: Maintainingequipment 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. Sort2. Straighten

3. Sweep

4. Standardize

5. Self-discipline

Comparison of JIT and

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Comparison of JIT and

Traditional

Factor Traditional JIT

Inventory Much to offset forecast

errors, late deliveries

Minimal necessary to operate

DeliveriesFew, large Many, small

Lot sizes Large Small

Setup; runs Few, long runs Many, short runs

Vendors Long-term relationshipsare unusual

Partners

Workers Necessary to do the work Assets

Table 15.3

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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 becooperative

Difficult to change company culture

Suppliers may

resist Why?

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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

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JIT in Services

The basic goal of the demand flowtechnology in the service organization is toprovide 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: a supplier representative worksright in the company’s plant, making

sure there is an appropriate supply on

hand.

JIT II

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Benefits of JIT Systems

Reduced inventory levels

High quality

Flexibility

Reduced lead times

Increased productivity

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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

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Smooth flow of work (the ultimate goal) Elimination of waste

Continuous improvement

Eliminating anything that does not addvalue

Simple systems that are easy tomanage

Use of product layouts to minimizemoving materials and parts

Quality at the source

Elements of JIT 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

Elements of JIT (cont’d) Table 15.4

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Video: Made for you

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’

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Video: McDonald’s Process

Vid L G

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Video: Layout Gortrac

jit & lean 1

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