chapter 15

Slack, Chambers and Johnston, Operations Management 5th Edition © Nigel Slack, Stuart Chambers, and Robert Johnston 2007

Chapter 15

Lean operations and JIT

Source: Tibbet and Britten



Operations strategy

Design Improvement

Planning and control

Operations management


The operation supplies … the delivery of products and services only when needed

The market requires … specified time, quantity and

quality of products and services


‘The key principle of lean operations is relatively

straightforward to understand: it means moving

towards the elimination of all waste in order to

develop an operation that is faster and more

dependable, produces higher quality products

and services and, above all, operates at low cost.’


Synonyms

continuous flow manufacture

high value-added manufacture

stockless production

low-inventory production

fast-throughput manufacturing

lean manufacturing

Toyota production system

short cycle time manufacturingSource: Corbis/Denis Balihouse


Traditional approach

JIT approach

stage A

orders

deliveries

orders

deliveries

JIT material flow

buffer inventory

stage B

buffer inventory

stage C

stage A stage Cstage B


JIT approach

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

Traditional approach

focus on high capacity utilization

more stoppages because of problems

high inventory means less chance of problems being

exposed and solved

extra productiongoes into inventory

because of continuing stoppages at stages

more production at each stage

JIT and capacity utilization


JIT aims to meet demand instantly, with perfect quality and no waste

JIT definitions

More fully:

Improved overall productivity and elimination of waste

Cost-effective production and delivery of only the necessary quantity of parts at the right quality, at the right time and place, while using a minimum amount of facilities, equipment, materials and human resources

JIT is dependent on the balance between the supplier’s flexibility and the user’s flexibility

JIT is accomplished through the application of elements that require total employee involvement and teamwork

A key philosophy of JIT is simplification

Source: Empics


The lean philosophy of operations is the basis for JIT techniques that include JIT methods of planning and control

The lean philosophy of operations

Eliminate waste Involve everyone Continuous improvement

JIT as a set of techniques for managing operations

Basic working practices

Design for manufacture

Operations focus

Small, simple machines

Flow layout

TPM

Set-up reduction

Total people involvement

Visibility

JIT supply

JIT as a method of planning and control

Pull scheduling

‘Kanban’ control

Levelled scheduling

Mixed modelling

Synchronization


The 5 S’s

Sort (Seiri) Eliminate what is not needed and keep what is needed.

Straighten (Seiton) Position things in such a way that they can be easily reached whenever they are needed.

Shine (Seiso) Keep things clean and tidy; no refuse or dirt in the work area.

Standardize (Seiketsu) Maintain cleanliness and order – perpetual neatness.

Sustain (Shitsuke) Develop a commitment and pride in keeping to standards.


‘Value stream’ mapping focuses on value-adding activities. It distinguishes

between value-adding and non-value-adding activities. It is similar to

process mapping but different in four ways:

It uses a broader range of information than most process maps.

It is usually at a higher level (5–10 activities) than most process maps.

It often has a wider scope, frequently spanning the whole supply chain.

It can be used to identify where to focus future improvement activities.

‘Value stream’ mapping


‘Value stream’ map for an industrial air-conditioning installation service

T/T = Task timeTTT = Total throughput timeV-A T = Value-added timeC/T = Cycle time

Survey Order Assemble Frame

Wait in branch

Wait for assembly

Ship to branch and

wait

Wait for installers

Install

T/T = 0.5Avail = 100%C/T = 30

T/T = 0.5Avail = 100%C/T = 10

T/T = 5.0Avail = 100%C/T = 12.5

T/T = 0.75Avail = 100%C/T = 17

T/T = 0.75Avail = 100%C/T = 35

Cash management

Completion confirmation

Operations planning

Job tracking confirmations

Sales office

Forecasts Invoice status

30 mins

58 hrs

30 mins

96 hrs

5 hrs

48 hrs

60 mins48 hrs

60 mins

TTT = 258 hrs

V-A T = 8 hrs


Inventory level

Delivering smaller quantities more often can reduce inventory levels

Inventory level


operation

movement

inspection

storage

Activities:

Waste (muda) Which of these symbols signify non-value- adding activities?

influencing the throughput efficiency

Types of waste:

delay

over-production

waiting time

transport

process

inventory

motion

defective goods


WIPDefective materials

ReworkScrap

Downtime

productivity problems

WIPDefective materials

ReworkScrap

Downtime

productivity problems

Reduce the levelof inventory (water) to reveal the operations’ problems

The problem with inventory


Small machines

The conventional Western approach is to purchase large machines to get ‘economies of scale’.

These often have long, complex set-ups, and make big batches, quickly creating ‘waste’.


JIT small machines approach:

emphasis: flexibilityeconomies of scope

Using several small machines rather than one large one allows simultaneous processing, is more robust

and is more flexible

easy to move (layout)quick set-upflexible scheduling optionscheaper tooling

fewer set-ups neededplanned maintenance easier


continuous improvement insmall steps, to expose wasteand eliminate it

gradual reduction of inventory

identify exposed problems

emphasis:

In JIT systems:

eliminate these problems

repeat the cycle

Visible, enforced improvement

‘Traditional’ production systems often accept waste and use the insurance of all types of inventory


Levelled scheduling equalizes the mix of products made each day

250A

250A

100A

150B

50B

200C

250A

250A

100A

150B

50B

200C

600 A 200 B200 C

600A

200 B200 C

Batch size A = 600, B = 200, C = 200

Scheduling in large batches

Batch size A = 150, B = 50, C = 50

Levelled scheduling

150 A50 B50 C

150A50B50C

150A50B50C

150A50B50C

150A50B50C

150A50B50C

150A50B50C

150A50B50C

150A50B50C

150 A50 B50 C

150 A50 B50 C

150 A50 B50 C

150 A50 B50 C

150 A50 B50 C

150 A50 B50 C

150 A50 B50 C


complex structures

simple structures JIT

MRPJIT and/or

MRP

PERT

simple routings complex routings

JIT, MRP, or both?


Key Terms TestJust-in-time (JIT)A method of planning and control and an operations

philosophy that aims to meet demand instantaneously with perfect quality and no waste.

KaizenJapanese term for continuous improvement.

Set-up reductionThe process of reducing the time taken to change over a

process from one activity to the next; also called single minute exchange of dies (SMED) after its origins in the metal pressing industry.


Key Terms Test

Single minute exchange of dies (SMED)Alternative term for set-up reduction.

AndonA light above a workstation that indicates its state: whether

working, waiting for work, broken down, etc. Andon lights may be used to stop the whole line when one station stops.


Key Terms Test

KanbanJapanese term for card or signal; it is a simple controlling

device that is used to authorize the release of materials in pull control systems such as those used in JIT.

Levelled scheduling (Heijunka)The idea that the mix and volume of activity should even

out over time so as to make output routine and regular, sometimes known by the Japanese term ‘heijunka’.

chapter 15

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