© Nigel Slack, Stuart Chambers & Robert Johnston, 2004 Operations Management, 4E: Chapter 7 7.1 Layout and Flow.

© Nigel Slack, Stuart Chambers & Robert Johnston, 2004 Operations Management, 4E: Chapter 7

7.1

Layout and Flow


7.2

Chapter coverage• Basic layout types• Selecting a layout type• Detailed design of a layout


7.3

Layout:The layout of an operation is concerned with the physical location of its transforming resources, that is deciding where to put the facilities, machines, equipment and staff in the operation.

Layout types:1) Fixed position layout

2) Process layout

3) Cell layout

4) Product layout


7.4

Fixed position layout1) In a fixed position layout, the transformed resource

does not move between its transforming resources.

2) Equipment, machinery, plant and people who do the processing move as necessary because the product or customer is either:

i. Too large

ii. Too delicate or

iii. Objects being moved


7.5

Process layout1) In a process layout, similar processes or processes

with similar needs are located together because:i. It is convenient to group them together or

ii. The utilization of the transforming resource is improved

2) Different products of customer have different requirements therefore they may take different routes within the process.

3) The flow in a process layout can be very complex.


7.6 An example of a process layout in a library showing the path of just one customer

Entrance Exit

On-line and CD-ROM access room

Loan books in subject order

En

qu

irie

s

Store room Counter staff

Copying areaC

om

pa

ny

re

po

rts

To journal sack

Current journals

Reserve collection

Reference section

Study desks


7.7

Cell layout1) In a cell layout, the transformed resources entering

the operation move into a cell in which all the transforming resources it requires in located.

2) After being processed in the cell, the transformed resource may move to a different cell in the operation or it may be a finished product or service.

3) Each cell may be arranged in either a process or product layout.

4) The cell type layout attempts to bring order to the complex flow seen in a process layout.


7.8 The ground floor plan of a department store showing the sports goods shop-within-a-shop

retail ‘cell’

Sports shop Menswear

Women’s clothes

Luggage and gifts

Confectionery, newspaper,

magazines and stationery

Books and

videos Footwear

Perfume& jewellery

Elevators

Entrance

En

tran

ce


7.9

Product layout1) In a product layout, the transformed resource flow

a long a line of processes that has been prearranged.

2) Flow is clear, predictable and easy to control.


7.10 An army induction centre with uses product layout

Lecture theatre

Uniform issuing

area

Uniform store

Waiting area

Waiting area

Doctor

Doctor

Doctor

Doctor

Doctor

Doctor

Bloodtest

Bloodtest

Bloodtest

X-ray

X-ray

X-ray

Record personal history

and medical details


7.11 A restaurant complex with all four basic layout types

Fixed-position layout service restaurant

Cell layout buffet

Line layout cafeteria

Cool room

Freezer Vegetable prep Grill

Preparation

Ov

en

Process layout kitchen

Main course buffet

Sta

rte

r b

uff

et

De

se

rt

bu

ffe

t

Service line


7.12

Fixed-position layout

Product layout

Cell layout

Process layout

VolumeLow High

Var

iety

Low

High

Flow is intermittent

Regular flow more important

Flow becomes

continuous

Reg

ula

r fl

ow

mo

re f

eas

ible

Volume-variety relationship


7.13

Project process

Jobbing process

Batch process

Mass process

Continuous process

Professional services

Service shops

Mass services

Fixed position layout

Process layout

Cell layout

Product layout

The physical position of all transforming resources

The flow of the operation’s

transformed resources

Process type

Basic layout type

Detailed design of layout

Volume and variety

Strategic performance

objectives

Decision 1

Decision 2

Decision 3

Layout selection steps


7.14

Selecting a layout type


7.151) The nature of the basic layout types

Basic layout types

Manufacturing process types

Serviceprocess types

Fixedposition layout

Project processes

Process layout

Cell layout

Product layout

Jobbing processes

Batch processes

Mass processes

Continuous processes

Professionalservices

Service shops

Mass services

Project processes


7.162) Advantages and disadvantages

Fixed

positionlayout

Process

layout

Cell

layout

Product

layout

Disadvantages

Advantages

- Very high mix and product flexibility

- Product/customer not moved or disturbed.

- Very high unit cost.

- Scheduling space and activities can be difficult.

- High mix and product flexibility

- Relatively robust if in the case of disruptions

Low utilization of resources.

Can have very high WIP

Complex flow.

- Good compromise between cost and flexibility

- Fast throughput.

- Group work can result in good motivation

Can be costly to rearrange existing layoutCan need more plant and equipment

Lo- w unit costs for high volume

- Gives Opportunities for specialization of equipment

Can have low mix and flexibilityNot very robust to disruption

Work can be very repetitive.

- High variety of tasks for staff

- Easy supervision of equipment of plant

- Gives Opportunities for specialization of equipment


7.17 (a) The basic layout types have different fixed and variable cost characteristics which seem to determine which one to use. (b) In practice the uncertainty about

the exact fixed and variable costs of each layout means the decision can rarely be made on cost alone

Use fixed-positionUse fixed-position or process

Use processUse process or cell

Use process or cell or productUse cell or product

Use product

Volume

Co

sts Fixed-position

Process

Cell

Product

Volume

Co

sts

Use product

Usecell

Use process

Use fixed-

position

(a) (b)

? ? ? ?

3) Consider total cost


7.18

Detailed design of a layout


7.19

Fixed position layout design:• The location of resources for each project is unique

and it will be determined on the convenience of transforming resources themselves.

• Although there are techniques which held to locate resources on fixed position layouts, they are not widely used because this layout can be very complex and planned schedules do change frequently.


7.20

Process layout design:• When cost of traveling is important:

– Collecting information such as:• number of loads per day• cost per distance traveled

• When process relationship is important– Relationship chart


7.21 Collecting information in process layout

If direction is not important, collapses

to

A B C D E

A 30 60 20

B 30 30

C 80

D 40

E

LOADS/DAY(b)

ToFrom

A B C D E

A 17 30 10

B 13 20 20

C 10 70

D 30 30

E 10 10 10 10

LOADS/DAY(a)



Or alternatively

A B C D E

A 30 60 20

B 30 30

C 80

D 40

E

LOADS/DAY(c)

LOADS/DAY(d)A

B

C

D

E

30

30

-

40

-

-

80

60

3020



ToFrom

A B C D E

A 17 30 10

B 13 20 20

C 10 70

D 30 30

E 10 10 10 10

If cost of flow differs between work

centers, combine with

LOADS/DAY

ToFrom

A B C D E

A 2 2 2 2

B 3 3 3 4

C 2 2 2 2

D 10 10 10 10

E 2 2 2 2

UNIT COST/DISTANCE TRAVELLED(e) (f)



To give

ToFrom

A B C D E

A 34 60 20

B 39 60 60

C 20 140

D 300 300

E 20 20 20 20

DAILY COST/DISTANCE TRAVELLED(g)



If direction is not important, collapses

to

ToFrom

A B C D E

A 34 60 20

B 39 60 60

C 20 140

D 300 300

E 20 20 20 20

DAILY COST/DISTANCE TRAVELLED(h)

A B C D E

A 73 360 40

B 80 80

C 160

D 320

E

DAILY COST/DISTANCE TRAVELLED(i)


7.26 A relationship chart

CODE CLOSENESSA Absolutely necessaryE Especially importantI Important

O Ordinary closenessU UnimportantX Undesirable

X

Metrology

Electronic testing

Analysis

Ultrasonic testing

Fatigue testing

E

I

I

I

A

U

O

O

UX

DEPARTMENT

Impact testingE

OU

UX


7.27

Cell layout design1) Cells in an operation can be created based on two

interrelated decisions: 1) What is the extent and nature of the cell i.e. the

amount of direct and indirect resources the cell has as shown in Fig 7.28

2) Which resources to allocate to which cell using:i. Cluster analysis – which process group naturally togetherii. Parts and family coding – based on similar characteristics

of parts of productsOR2) Production Flow Analysis (PFA)

Examines both product requirement and process grouping(See Fig. 7.31)


7.28 Types of cell

High

HighLow

Low

Completecomponentmanufacturing cell

Lunch and snackproduce area insupermarket

Small multi-machinemanufacturing cell

Joint reference andcopying room in alibrary

Plant-within-a-plantmanufacturingoperation

Maternity unitin a hospital

Specialist processmanufacturing cell

Internal audit groupin a bank

Amount of indirect resources included in the cell

Proportion of the resources needed to complete the transformation included in the cell

e.g. e.g.

e.g. e.g.


7.29

1 2 3 4 5 6 7 8

1 X X

2 X X X

3 X X X

4 X X X

5 X X X

6 X X

7 X X

8 X X X

(a) and (b) Using production flow analysis to allocate machines to cells

Product

Mac

hin

es

3 6 8 5 2 4 1 8

4 X X X

1 X X

6 X X

3 X X X

8 X X

2 X X X

5 X X X

7 X X

Product

Mac

hin

es

Cell A

Cell B

Cell C

(a) (b)


7.30

Product layout design1) Product type layout is designed based on a

technique called line balancing. The technique consist of the following steps:

1) Calculating the required cycle time.

2) Calculating the number of stages.

3) Producing a precedence diagram.

4) Finally allocating activities to the stages.


7.31

Cycle time:It is the time between completed products emerging from the process.

Example: Suppose the regional back-office operation of a large bank is designing an operation which will process its mortgage applications. The number of applications to be processed is 160 per week and the time available to process the applications is 40 hours per week.Cycle time = 40 = 1/4 hours = 15 minutes

1601 product every 15 minutes


7.32

Number of stagesRequired no. of stages = total work content

required cycle time

Where the total work content is the total quantity of work involved in producing the product given in time.

Example: Suppose that the bank in the previous example calculated that the average total work content of processing a mortgage application is 60 minutes. The number of stages needed to produce a processed application every 15 minutes can be calculated

Required no. of stages = 60 minutes = 4 stages 15 minutes

If you get a fraction round it up to the higher whole number.


7.33

Precedence diagramThis is a diagram representing the ordering of the elements which comprise the total work content of the product or service.

Two rules when constructing the diagram:

1. The circles which represent the elements are drawn as far to the left as possible.

2. None of the arrows which shows the precedence of the elements should be vertical.

a b c d

e

f g

h

i0.12 mins

0.30 mins

0.36 mins

0.25 mins 0.05 mins

0.17 mins

0.10 mins

0.08 mins

0.25 mins


7.34

Allocating activities to the stagesThe general approach is to allocate elements from the precedence

diagram to the first stage, starting from the left, until the work allocated to the stage is as close to, but less than, the cycle time.

When the stage is full of work without exceeding the cycle time, move to the next stage.

Two rules help to decide which activities to allocate to a stage:1. Choose the largest that will fit into the time remaining at

the stage

2. Choose the element with the most ‘followers’.


7.35

Balancing lossThe effectiveness of the line balancing activity is measured by the balancing loss.

This is the time wasted through the unequal allocation of work as a percentage of the total time invested in processing the product or service.

Balancing loss = Total idle time

No. of stages x Cycle time


7.36 Balancing loss is that proportion of the time invested in processing the product or service

which is not used productively

0

0.5

1

1.5

2

2.5

3

1 2 3 4

Lo

ad

Stage

Cycle time = 2.5 mins

0

0.5

1

1.5

2

2.5

3

3.5

1 2 3 4

Lo

ad

Stage


2.32.5

2.2

3.0

An ideal ‘balance’ where work is allocated equally between the stages

But if work is not equally allocated the cycle time will increase and ‘balancing losses’ will occur

Work allocated to stage

Idle time

Calculating balancing loss:Idle time every cycle =(3.0 - 2.3) +

(3.0 - 2.5) + (3.0 - 2.2) = 2.0 mins

Balancing loss = 2 4 x 3.0= 0.1667= 16.67%


7.37

Worked ExampleConsider Karlstad Kakes, a manufacturer of specialty cakes, which has recently obtained contract to supply a major supermarket chain with a specialty cake in the shape of a space rocket. It has been decided that the volumes required by the supermarket warrant a special production line to perform the finishing, decorating and packing of the cake. This line would have to carry out the elements shown in the next slide, which also shows the precedence diagram for the total job. The initial order from the supermarket is for 5000 cakes a week and the number of hours worked by the factory is 40 per week. From this:

The required cycle time = 40 hrs x 60 mins = 0.48 mins5000

The required number of stages = 1.68 mins (total work content) 0.48 mins (required cycle time)= 3.5 stages


7.38 Element listing and precedence diagram for Karlstad Kates

Element - - De-tin and trim 0.12 minsaElement - Reshape with off-cuts 0.30 minsb

Element - Clad in almond fondant 0.36 minscElement - Clad in white fondant 0.25 minsdElement - Decorate, red icing 0.17 minseElement - Decorate, green icing 0.05 minsfElement - Decorate, blue icing 0.10 minsgElement - Affix transfers 0.08 minshElement - Transfer to base and pack 0.25 minsi

Total work content = 1.68 mins

a b c d

e

f g

h

i0.12 mins

0.30 mins

0.36 mins

0.25 mins 0.05 mins

0.17 mins

0.10 mins

0.08 mins

0.25 mins


7.39 Allocation of elements to stages and balancing loss for Karlstad Kates

a b c d

e

f g

h

i0.12 mins

0.30 mins

0.36 mins

0.25 mins 0.05 mins

0.17 mins

0.10 mins

0.08 mins

0.25 mins

Stage 1 Stage 2 Stage 3 Stage 4

0

0.1

0.2

0.3

0.4

0.5

0.6

1 2 3 4


Idle time every cycle = (0.48 - 0.42) + (0.48 - 0.36) + (0.48 - 0.42) = 0.24 minsProportion of idle time per cycle = 0.24 = 12.5%

4 x 0.48

© Nigel Slack, Stuart Chambers & Robert Johnston, 2004 Operations Management, 4E: Chapter 7 7.1 Layout and Flow.

Documents

product layout slide

layout type slide

fixed position layout

cell type layout attempts

operations management

layout selection steps

nigel slack

flow slide