jit and lean 14

7/30/2019 JIT and Lean 14

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Chapter 14

Just-In-TimeSystems


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JIT/Lean Production

Just-in-time: Repetitive production system inwhich processing and movement of materials and

goods occur just as they are needed, usually in small

batches

JIT is characteristic of lean production

systems

JIT operates with very little fat


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JIT Goals

Eliminate disruptions

Make system flexible by reduce setup

and lead times

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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Big JITbroad focusVendor relations

Human relations

Technology management

Materials and inventory management

Little JITnarrow focus

Scheduling materials

Scheduling services of production

Big vs. Little JIT


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JIT Building Blocks

Product design Process design

Personnel/organizational

elements Manufacturing

planning and control


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Product Design

Standard parts

Modular design

Highly capable production systems


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Process Design

Small lot sizes

Setup time reduction

Manufacturing cells

Limited work in process

Quality improvement

Production flexibility 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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Production Flexibility

Reduce downtime by reducingchangeover time

Use preventive maintenance to reduce

breakdowns Cross-train workers to help clear

bottlenecks

Reserve capacity for importantcustomers


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Personnel/Organizational Elements

Workers as assets Cross-trained workers

Continuous

improvement

Cost accounting

Leadership/projectmanagement


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Manufacturing Planning and Control

Level loading

Pull systems

Visual systems

Close vendor relationships

Reduced transaction processing

Preventive maintenance


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Pull/Push Systems

Pull system: System for moving work wherea workstation pulls output from the

preceding station as needed. (e.g. Kanban)

Push system: System for moving work whereoutput is pushed to the next station as it is

completed


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Kanban Production Control System

Kanban: Card or other device that communicatesdemand for work or materials from the precedingstation

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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Traditional Supplier Network

Buyer

SupplierSupplier Supplier Suppiler

Supplier

Supplier

Supplier

Figure 16-3a


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Tiered Supplier Network

Figure 16-3b

Supplier

Supplier

Supplier

SupplierSupplier Supplier

Buyer

SupplierFirst Tier Supplier

Second Tier Supplier

Third Tier Supplier


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Summary JIT Goals and Building Blocks

Figure 16-4

ProductDesign

ProcessDesign

PersonnelElements

Manufactur-ing Planning

Eliminate disruptionsMake the system flexible

Reduce setupand lead times

Eliminate wasteMinimize inventories

Abalancedrapid flow

UltimateGoal

SupportingGoals

BuildingBlocks


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Converting 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

Suppliers may

resist


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JIT in Service

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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New challengesMeeting manufacturing requirements

Changing from traditional thinking and

practicesfrequent on-time delivery of small

quantities

Long term relationships with suppliers as

partners

JIT Purchasing


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JIT II: the practice of allowing vendors tomanage some aspects of buying their

products or services for the buyer

JIT II

B


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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 (contd)

Increased equipment utilization Reduced scrap and rework

Reduced space requirements

Pressure for good vendor relationships

Reduced need for indirect labor


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Waste from overproduction

Waste of waiting time

Transportation waste

Inventory waste

Processing waste

Waste of motion

Waste from product defects

Sources of Waste

Table 16-5

E JIT


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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

Table 16-5

Elements of JIT

El f JIT ( d)


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Poka-yokefail safe tools and methods

Preventative maintenance

Good houskeeping

Set-up time reduction

Cross-trained employees

A pull system

Elements of JIT (contd)

Table 16-5

K


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Kanban(the visual system)

What is Kanban? C

XDTN

1

N= Total number of containers

D = Planned usage rate of using WC T= Average wait time + production time

X= Efficiency number (by policy)

C= Capacity per container

2728.1

25

2.112.300

N


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Number of containers N

Planned usage rate WC D 300

Cycle time T 0.12efficicnet factor X 0.2

Parts per container C 15

DT(1+X)

C

43.2

15

= 3

N =

=

= 2.88

jit and lean 14

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