4 Lean Operation and Jit

7/14/2019 4 Lean Operation and Jit

1/35

Nigel Slack, Stuart Chambers & Robert Johnston, 2004 Operations Management, 4E: Chapter 15

15.1

Lean Operations

&Just-In-Time


2/35


15.2

Chapter Coverage What are lean operations and JIT?

Differences between traditional approach and

JIT Disadvantage of JIT

Lean philosophy of operations

JIT techniques

JIT planning and control


3/35


15.3

Lean operations:

Is the philosophy of moving towards zero waste inorder to develop an operation that is:

1) faster,

2) more dependable,

3) produces higher quality products and service, and

4) operates at low cost.

Founded on doing the simple things well, on graduallydoing them better and reducing waste every step of the

way.


4/35


15.4

Just In Time, JIT:

1) JIT is an approach of producing goods and services

exactly when they are needed.

2) Minimum inventory if not zero

3) Customers wait

4) Encourages efficiency

5) Quality not sacrificed


5/35


15.5 JIT definitions:(textbook definitions)

JIT aims to m eet demand instant ly, wi th p erfect qual i ty and no w aste

more fully:

imp roved overal l prod uct iv i ty and eliminat ion of waste

cos t-ef fect ive prod uct ion and del ivery of on ly the necessaryquant i ty

of parts at the r ightqual i ty, at the righ tt imeandplace, wh i le usin g a

min imum amoun t of faci l i t ies, equipment , mater ials and human

resources

JIT is dependent on the balance between the suppliers flexibility and

the users flexibility

i t is accomp l ished thro ugh the appl icat ion of elements wh ich requi re

total employee involvement and team -wo rk

a key philosophy of JIT is simplification


6/35


15.6

Traditional approach vs. JITTraditional approach JIT

1) Buffer inventory between each

stage act as insulation and gives

some degree of independence

from upstream stages.

2) More buffer better insulation.

3) Stage A experience breakdown,

Stage B can continue producing

for some time.

4) Stage C can continue for longer

time.

5) Problems in Stage A is not spread

throughout.

1) Parts are produced as they are

orderedno buffer inventory.

2) Stage A experience breakdown,

immediately all stages will have

to stop.

3) Problems in Stage A is apparent

to all and becomes everybody's

responsibility.

4) Improves the chances of problem

being solved.

Cont

Differences between traditional approach and JIT


7/35


15.7

Traditional approach vs. JIT

Cont

Traditional approach JIT

6) Problems are confined within

the stage and go unnoticed for a

period of time.

7) Seek efficiency by protectingeach part of the operation from

disruption.

5) Seek efficiency through

exposure of system problems,

making problems more evident

and change the motivationalstructure of the whole system

towards solving the problem.


8/35


15.8

Traditional approach:

buffer

inventorystage Cstage A stage B

buffer

inventory


9/35


15.9

JIT approach:

stage A

orders

deliveries

stage B stage C

orders

deliveries


10/35


15.10

Disadvantage of JIT:

The main sacrifice of JIT is low capital utilization(see Fig 15.10).

Why is capital utilization in JIT systems low?

i. Produce only when needed.

ii. Any stoppage will affect the rest of the systemcausing complete stoppage.

JIT argument - No point producing output just forits own sake, it is counter productive because extrainventory hides problems and hindersimprovement.


11/35


15.11

TRADITIONAL APPROACH

JIT APPROACH

Disadvantage of JIT:

Low capacity

utilization

focus on high

capacity utilization

more stoppages

because of

problems

high inventory means

less chance of problems

being exposed and

solvedextra production

goes into inventory

because of continuing

stoppages at stages

more production

at each stage

focus on producing

only when needed

fewer stoppages

low inventory so

problems are

exposed and solved

no surplus

production goes

into inventory

lower capacity

utilization, but


12/35


15.12

The problem with inventory

Reduce the level of

invento ry (water) to

reveal the operationsprob lems

WIP

Defectivematerials

ReworkScrapDowntime

productivity

problems

WIP

Defective

materials

ReworkScrap

Downtime

productivity

problems


13/35


15.13

Lean philosophy of operations:1. Eliminate waste

2. The involvement of everyone

3. Continuous improvement


14/35


15.14

Eliminate Waste:

Waste can be defined as an activity which does not addvalue.

Identifying waste is the first step towards elimination.

The seven types of waste are:

1. Over production

2. Waiting time

3. Transport

4. Process

5. Inventory

6. Motion

7. Defective goods


15/35


15.15

1. Over productionproducing more than is

immediately needed by the next process in theoperationgreatest source of waste.

2. Waiting timesMachine and labour waiting timeare considered waste and they are measure in terms

of machine efficiency and labour efficiency.

3. TransportMoving materials around the plant andtogether with the double and triple handling ofWIP, does not add value. Layout changes which

bring processes closer together, improvement intransport methods and workplace organization canreduce waste.


16/35


15.16

4. Processthe process itself can be a source of

waste. For example, some operations may only

exist because of poor component design.

5. Inventoryall inventory should be a target for

elimination. However, it is only by tackling thecauses of inventory that it can be reduced.

6. Motionan operator may look busy but sometimes

no value is being added by the work.

Simplification of work is a rich source of reductionin the waste of motion.


17/35


15.17

7. Defective goodsquality waste is often very

significant in operation, even if actual measure of

quality are limited. Total cost of quality are much

greater than what meets the eye.


18/35


15.18

The involvement of everyone:

Lean approach to people management is calledrespect-for-humans system.

It encourages:

Team based problem solving

Job enrichmentless monotonous, more responsibility,rewarding

Job rotationchange department, stage, function, cell

Multi-tasking

Its intention: High degree of personal responsibility leads to ownership

of job


19/35


15.19

Continuous improvement: Lean objectives are expressed in ideals such as

to eliminate waste completely Can never be fully achieved

Require continuous improvement to move closer.


20/35


15.20

JIT techniques:1) Adopt basic working practices:a. Disciplinecomply to work standards that are in place

for the safety of staff and the environment, and for the

quality of the product.b. Flexibilitygive more responsibility to those capable

even if it is beyond hes grade.

c. Equalitydiscard unfair and divisive personnel policies

e.g. uniforms and pay structured. Autonomydelegate decision making responsibilities

to personnel involve in direct activity


21/35


15.21

e. Development of personnelstaff training

f. Quality of working lifee.g. involvement in decision

making, security of employment, enjoyment and

working area facilities

g. Creativitysome enjoy not just doing a job

successfully by improving it for the next time.

h. Total people involvementtake part in selection of new

recruit, spending improvement budget, quality issues,

etc.

Cont


22/35


15.22

2) Design for ease of processing:

Design determines 70%80% of production cost

Design improvement can reduce product cost and makemore efficient production process.

Example: reduce number of components, use better or

cheaper material.3) Emphasize operations focus:

Concept of simplicity, repetition and experience breedcompetence.

Focus processes on manageable sets of products,technologies, volumes and markets

Structure operations objective so that they are consistentand coherent

Cont


23/35


15.23

4) Use small simple machines:

Use several small machines rather than one big one.

Can produce few different components at a given timeinstead of batch by batch production.

More robust, mobile, layout flexibility and reduce

investment risk.5) Layout for smooth flow:

Long process routes provide opportunity for delay,inventory build up, adds no value to the product and

slow down cycle time Workstations are close together, use U shaped line, use

cell layout.

Cont


24/35


15.24

6) Adopt Total Productive Maintenance (TPM):

Unreliable processes create waste, forexample, waiting time, delays in downstreamoperations. In a JIT system:

operators taught

to care forprocesses:

maintenance

personnels

role

changes:

training operators

long-term planned maintenance

condition monitoring

emphasis:operator involvement

care for equipment

ensuring total reliability

operate correctly

detect problems

lubricate, clean, adjust

collect data

Cont


25/35


15.25

8) Reduce set-up times: Set-up time is the time taken to changeover the process

from one activity to the next. During this timeoperation seizes. It is reduced by cutting out:

time taken to search for tools and equipment,

Pre-preparation of tasks which delay changeoverand

Constant practice of set-up routines

9) Ensure visibility: More transparent operation is easier for staff to share in

its management and improvement.

Problems are easily detected and information becomessimple, fast and visual.

10) Adopt JIT through the supply chain: Expand JIT culture to key suppliers

Cont


26/35


15.26

JIT planning and control

JIT planning and control is based on the principle of

a pull system

What are push planning and control & pull

planning and control?


27/35


15.27 Push philosophies of

planning and control

CENTRAL OPS. PLANNING AND CONTROL SYSTEM

Work

centreDEMANDWork

centre

Work

centre

Work

centre

Instruction onwhat to makeand where to

send it

FORECAST

OR

PUSH CONTROL

Signal pushes work through the process

Activities are scheduled by means of a central system and completed inline with central instructions

No consideration for succeeding stages requirements

High inventory


28/35


15.28

PULL CONTROL

Work

centre

Work

centre

Work

centre

Work

centre DEMAND

Request Request Request Request

Delivery Delivery Delivery Delivery

Pull philosophies of planning

and control

Signal pulls work only when required.

Only customer can trigger movementsets the work pace.

Lesser chances of inventory build-up.

JIT favored.


29/35


15.29

Kanban control

It is a system used of JIT planning and control.

Based on the pull planning and control.

Kanban is the Japanese word for card or signal.

Card or signal used by customer stage to instructsupplier stage to send more materials.

Cont


30/35


15.30

Kanban control

Three types of Kanban:

1. The move or conveyor kanban

Signals a previous stage that material can be withdrawn

from inventory.

2. The production kanban

Signals a production process to start producing a part to be

place in inventory.

3. The vendor kanban

Signals an external supplier to send material to a stage.

Cont


31/35


15.31

Kanban control

Receipt of kanban triggers movement, production

or supply of one unit.

Two kanbans two units

Kanban comes in different formempty container,verbal instruction, color tokens, etc

Two kanban procedure:

Single-card system: either move or vendor kanban

Dual-card system: use move and production kanban

Cont


32/35


15.32

m

Empty standard containerFull standard container

Move kanban

Kanban holding box

Flow path for standard containers

Flow path for move kanban

Work centre A

m

Work centre B

m

Stage A Stage B

Output stock Output stock

mmm

mmm


33/35


15.33

Each stage has a work center and an area for

holding inventory.

Loop 1: Stage B requires more parts

withdraw a container from output stock of

stage A empty container is kanban and sentto stage A work center signal for stage A to

start production

Loop 2: Move kanban taken from holding boxto output stock point signal to move a full

container from stage A to stage B.


34/35


15.34

Kanban rules:

Each container must have a kanban card indicatingpart number and description, user and maker location,and quantity.

The parts are always pulled by the user or customer.

No parts are started without a kanban.

All containers contain exactly their number of parts.

No defective parts may be sent to the user orcustomer.

The maker can only produce enough parts to make upwhat has been withdrawn.

The number of kanbans should be reduced.

The time period should be made shorter


35/35

Ni l Sl k St t Ch b & R b t J h t 2004 Operations Management 4E: Chapter 15

15.35

The End

Date post:	28-Oct-2015
Category:	Documents
Upload:	garima-verma
View:	36 times
Download:	1 times

4 Lean Operation and Jit

Documents