Chapter 7 Layout and Flow

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

Chapter 7

Layout and flow

Source: Alamy/AG Stock USA Inc.


Operations strategy

Design Improvement

Planning and control

Operations management

Functional design

Supply network design

Layout and flow

Functional technology

Job design

Product/service design

Layout and flow


Relative positioning of transforming resources

Layout involves the relative positioning of transformed resources within operations and functions and the allocation of tasks to the resources, which together dictate the flow of

transformed resources through the operation or function

Allocation of tasks to transforming resources

Flow of transformed resources

Source: J Sainsbury plc



Detailed design techniques

Fixed position – resource location analysis

Functional layout – flow charts and relationship charts

Cell layout – product flow analysis

Product layout – assembly line balancing techniques


Example of a functional layout in a library,showing the path of just one customer

Entrance Exit

To journal stack

Study desks

Online andCD-ROM access room

Loan books in subject order

Enq

uirie

s

Store room

Counter staffCopying area

Com

pan

y re

port

s

Current journals

Reserve collection

Reference section


Ground-floor plan of a department store, showing the sports goods shop-within-a-shop retail ‘cell’

Sports shop Menswear

Women’s clothing

Luggage and gifts

Confectionery, newspapers, magazines, stationery

Books and

videos Footwear

Perfumes& jewellery

Elevators

Entrance

Entrance


An army induction centre which 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

Records: personal

history and medical details


A product layout in a paper manufacturing operation


A restaurant complex with all four basic layout types

Fixed-position layout service restaurant

Cell layout buffet

Line layout

cafeteria

Cool room

Freezer Vegetable preparationGrill

Preparation

Ove

n

Functional layout kitchen

Main course buffet

Sta

rte

r b

uff

et

De

sse

rt

bu

ffe

t

Service line


Advantages and disadvantages

Fixed-position layout

Disadvantages

Advantages

Very high product and mix flexibility

Product/customer not moved

High variety of tasks for staff

Very high unit costs

Scheduling space and activities can be difficult


Functional layout

Disadvantages

Advantages

High product and mix flexibility

Relatively robust in the case of disruptions

Easy to supervise

Low utilization

Can have very high WIP


Complex flow


Cell layout

Disadvantages

Advantages

Can give good compromise

Fast throughput

Group work can result in good motivation

Can be costly to rearrange existing layout


Can need more plant


Product layout

Disadvantages

Advantages

Low unit costs for high volume

Opportunities for specialization of equipment

Can have low mix flexibility

Not very robust in the case of disruptions


Work can be very repetitive



Functional layout

VolumeLow High

Var

iety

Low

High

Flow is intermittent

Regular flow more important

Flow becomes

continuous

Reg

ular

flow

mor

e fe

asib

le

Cell layout

Product layout


Service functional types

Mass services

Service shops

Manufacturing functional types

Continuous processes

Mass processes

Batch processes

Basic layout types


Functional layout

Cell layout

Product layout

Relationship between functional types and basic layout types

Jobbing processes

Professional services

Project processes


The basic layout types have different fixed and variable cost characteristics that seem to determine which one to use

Volume

Co

sts

Use productUsecell

Use functionalUse fixed-

position


In practice, uncertainty about the exact fixed and variable costs of each layout means the decision can rarely be made on cost alone

Volume

Co

sts Fixed-position

Functional

Cell

Product

Use fixed-position

Use functionalUse fixed-position or functional

?

Use functional or cell

?

Use functional or cell or product

?

Use cell or product

?

Use product


A B C D E

A 17 - 30 10

B 13 20 20

C 10 - 70

D 30 - - 30

E 10 10 10 10

A B C D E

A 30 - 60 20

B 30 - 30

C - 80

D 40

E

(b) Loads per day

Collecting information in functional layout

To

From

(a) Loads per day

If direction is not important, collapses to


A B C D E

A 30 - 60 20

B 30 - 30

C - 80

D 40

E


(b) Loads per day

Or alternatively

30

30

40

60

3020

80-

-

-

A

E

D

C

B

(c) Loads per day


A B C D E

A 17 - 30 10

B 13 20 20

C 10 - 70

D 30 - - 30

E 10 10 10 10

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

(d) Unit cost per distancetravelled


To

From

(a)Loads per day

If cost of flow differs between work centres, combine with

To

From


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

To

From

(d) Unit cost per distancetravelled


A B C D E

A 34 60 20

B 39 60 60

C 20 140

D 300 - 300

E 20 20 20 20

(e) Daily cost per distancetravelled

To

From

To give


A B C D E

A 34 60 20

B 39 60 60

C 20 140

D 300 - 300

E 20 20 20 20

To

From

(e) Daily cost per distancetravelled


A B C D E

A 73 - 360 40

B 80 80

C - 160

D 320

E

(f) Daily cost per distancetravelled

If direction is not important,

collapses to


DEPARTMENT

Metrology

Electronic testing

Analysis

Ultrasonic testing

Fatigue testing

Impact testing

E

I

I

I

E

A

U

O

O

O

U

UU

XX

A relationship chart

Absolutely necessaryEspecially importantImportantOrdinary closenessUnimportantUndesirable

CLOSENESSCODEAEIOUX


Types of cell

High

Low

Amount of indirect resources included in the cell

HighLow

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

Specialist functionalmanufacturing cell

Internal audit groupin a bank

e.g. Plant-within-a-plantmanufacturingoperation

Maternity unitin a hospital

e.g.

Small multi-machinemanufacturing cell

Joint reference andcopying room in alibrary

e.g. Completecomponentmanufacturing cell

Lunch and snackproduce area in supermarket

e.g.


X X

X X X

X X X

X X X

X X X

X X

X X

X X X

1

2

3

4

5

6

7

8

Mac

hine

s

Component families1 2 3 4 5 6 7 8

(a)

Using production flow analysis to allocate machines to cells

X X X

X X

X X

X X X

X X X

X X X

X X X

X X

Component families3 6 8 5 2 4 1 8

(b)

4

1

6

3

8

2

5

7M

achi

nes


Balancing loss is that proportion of the time invested in processing the product or service which is not used productively

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

Load

0

0.5

1

1.5

2

2.5

3

1 2 3 4Stage

Cycle time = 2.5 mins Work allocated to stage


Balancing loss is that proportion of the time invested in processing the product or service which is not used productively

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

Work allocated to stage

Load

0

0.5

1

1.5

2

2.5

3

1 2 3 4Stage

Cycle time = 3.0 mins

3.5

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 =

2.0

4 × 3.0

= 0.1667

= 16.67%


Element listing for Karlstad Cakes

Element

Element

Element

Element

Element

Element

Element

Element

Element

De-tin and trim

Reshape with offcuts

Clad in almond fondant

Clad in white fondant

Decorate, red icing

Decorate, green icing

Decorate, blue icing

Affix transfers

Transfer to base and pack

0.12 mins

0.30 mins

0.36 mins

0.25 mins

0.17 mins

0.05 mins

0.10 mins

0.08 mins

0.25 mins

Total work content = 1.68 mins

a

b

c

d

e

f

g

h

i


Precedence diagram for Karlstad Cakes

a b c d

e

f g

h

i

0.12 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


Allocation of elements to stages and balancing lossfor Karlstad Cakes

a b c d

e

f g

h

i

0.12 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

Cycle time = 0.48 mins

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 mins

= 12.5%

Proportion of idle time per cycle

0.24

4 × 0.48=


1 every 15 minutes

15 15 15 15

1 every 15 minutes

30 30

3030

Long and thin versus short and fat layouts

1 every 15 minutes

60

60

60

60

Short fat process

Long thin process

A 60-minute task with a required cycle time of 15 minutes


Long and thin versus short and fat

Long or short describes the number of stages

Fat or thin describes the amount of work at each stage

Advantages of long-thin processescontrolled flowsimple materials handlinglower capital requirement (no duplication)

greater efficiency

higher space utilization

Advantages of short-fat processeshigher mix flexibilityhigher volume flexibility greater robustness

less monotonoushigher ownership


Calculating the required cycle time

Forecast demands during the period (A)

Availability of productive time (B)

Cycle time (C = B/A)

Deciding how many staff are needed

Work content of the task (D)

Cycle time required (C)

Number of staff (D/C)

100

480 mins

4.8 mins

55 mins

4.8 mins

11.46 (12)


Key Terms Test

Fixed-position layoutLocating the position of a product or service such that it remains

largely stationary, while transforming resources are moved to and from it.

Cell layoutLocating transforming resources with a common purpose such

as processing the same types of product, serving similar types of customer, etc., together in close proximity (a cell).

Product layoutLocating transforming resources in a sequence defined by the

processing needs of a product or service.


Key Terms TestShop-within-a-shopAn operations layout which groups together facilities that have a

common purpose; the term was originally used in retail operations but is now sometimes used in other industries, very similar to the idea of a cell layout.

Line layoutA more descriptive term for what is technically a product layout.

Combinatorial complexityThe idea that many different ways of processing products and services

at many different locations or points in time combine to result in an exceptionally large number of feasible options; the term is often used in facilities layout and scheduling to justify non-optimal solutions (because there are too many options to explore).


Key Terms TestFlow record chartA diagram used in layout to record the flow of products or

services between facilities.

Relationship chartA diagram used in layout to summarize the relative

desirability of facilities to be close to each other.

Heuristic procedures‘Rules of thumb’ or simple reasoning short-cuts that are

developed to provide good but non-optimal solutions, usually to operations decisions that involve combinatorial complexity.


Key Terms TestCRAFTComputerized Relative Allocation of Facilities Technique, a

heuristic technique for developing good, but non-optimal, solutions.

Cluster analysisA technique used in the design of cell layouts to find which

process groups fit naturally together.

Production flow analysis (PFA)A technique that examines product requirements and

process grouping simultaneously to allocate tasks and machines to cells in cell layout.


Key Terms Test

Remainder cellThe cell that has to cope with all the products that do

not conveniently fit into other cells.

Cycle timeThe average time between units of output emerging

from a process.

Total work contentThe total amount of work required to produce a unit of

output, usually measured in standard times.


Key Terms Test

Line balancingThe activity of attempting to equalize the load on each

station or part of a line layout or mass process.

Balancing lossThe quantification of the lack of balance in a production

line, defined as the time that is not used for productive purposes expressed as a percentage of the total time invested in making a product.


Key Terms Test

Long thinA process designed to have many sequential stages,

each performing a relatively small part of the total task; the opposite of a short fat process.

Short fatA process designed to have relatively few sequential

stages, each of which performs a relatively large part of the total task; the opposite of a long thin process.

Chapter 7 Layout and Flow

Documents

robert johnston

stuart chambers

edition nigel slack

control slack

repetitive slack

existing layout

continuous low slack

difficult disadvantages