Chapter 7 Layout and Flow

(1)

C

hapter 7

L

ayout

and flow

(2)

Operations

strategy

Design

Improvement

Planning and

control

Operations

management

Functional design

Supply network design

Layout

and flow

Functional

technology

Job

design

Product/service

design

(3)

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

(4)

(5)

Detailed design techniques

Fixed position – resource location analysis

Functional layout – flow charts and relationship charts

Cell layout – product flow analysis

(6)

Example of a functional layout in a library,

showing the path of just one customer

To

journal

stack

Study desks

Online and

CD-ROM access

room

Loan books in subject order

E

nq

ui

rie

s

C

om

pa

ny

r

ep

or

ts

Current

journals

Reserve

collection

Reference

section

(7)

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

E

ntr

an

ce

(8)

An army induction centre which uses product layout

Lecture theatre

Uniform

issuing

area

Uniform

Waiting

area

Waiting

area

Doctor

Blood

test

Blood

test

Blood

test

X-ray

Records:

personal

history and

medical

details

(9)

(10)

A restaurant complex with all four basic layout types

Fixed-position layout

service restaurant

Cell layout buffet

Line

layout

cafeteria

Cool room

Freezer

Vegetable preparation

Grill

Preparation

O

ve

n

Functional layout kitchen

Main course

buffet

S

ta

rt

e

r

bu

ff

e

t

D

e

ss

e

rt

bu

ff

e

t

Service line

(11)

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

(12)

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

Advantages and disadvantages

(13)

Cell layout

Disadvantages

Advantages

Can give good compromise

Fast throughput

Group work can result in good

motivation

Can be costly to rearrange

existing layout

Advantages and disadvantages

(14)

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

Advantages and disadvantages

(15)

Fixed-position

layout

Functional

layout

Volume

Low

High

V

ar

ie

ty

Lo

w

H

ig

h

Flow is

intermittent

Regular flow more important

Flow

becomes

continuous

R

eg

ul

ar

fl

ow

m

or

e

fe

as

ib

le

Cell layout

Product

layout

(16)

Service functional

types

Mass services

Service shops

Manufacturing

functional types

Mass processes

Batch processes

Basic layout

types

Fixed-position layout

Functional layout

Cell layout

Product layout

Relationship between functional types and basic layout types

Jobbing processes

Professional services

Project processes

(17)

The basic layout types have different fixed and variable cost

characteristics that seem to determine which one to use

Volume

C

o

st

s

Use product

Use

cell

Use

functional

Use

fixed-position

(18)

In practice, uncertainty about the exact fixed and variable costs of

each layout means the decision can rarely be made on cost alone

Volume

C

o

st

s

_{Fixed-position}

Functional

Cell

Product

Use fixed-position

?

Use cell or product

?

(19)

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,

(20)

A

B

C

D

E

A

30 _-

60 20

B

30 _-

30 C

_-

80 D

40 E

Collecting information in functional layout

(b)

_{Loads per day}

Or alternatively

30

40

60

30

20

80 -

-A

E

D

C

B

(21)

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 B

3

4 C

2

2 D

10 10 10

10 E

2

2 (d)

_{Unit cost per distance}

travelled

Collecting information in functional layout

To

From

(a)

Loads per day

If cost of flow

differs between

work centres,

combine with

To

From

(22)

A

B

C

D

E

A

2

2 B

3

4 C

2

2 D

10 10 10

10 E

2

2 To

From

(d)

_{Unit cost per distance}

travelled

Collecting information in functional layout

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 distance}

travelled

To

From

(23)

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 distance}

travelled

Collecting information in functional layout

A

B

C

D

E

A

73 _-

360 40

B

80

80 C

_-

160 D

320 E

(f)

_{Daily cost per distance}

travelled

If direction is not

important,

collapses to

(24)

DEPARTMENT

Metrology

Electronic testing

Analysis

Ultrasonic testing

Fatigue testing

E

I

E

A

U

O

U

X

A relationship chart

Absolutely necessary

Especially important

Important

Ordinary closeness

Unimportant

Undesirable

CLOSENESS

CODE

A

E

I

O

U

X

(25)

Types of cell

High

Low

Amount of indirect resources included in the cell

High

Low

Proportion of

the resources

needed to

complete the

transformation

included in the

cell

Specialist functional

manufacturing cell

Internal audit group

in a bank

e.g.

Plant-within-a-plant

manufacturing

operation

Maternity unit

in a hospital

e.g.

Small multi-machine

manufacturing cell

Joint reference and

copying room in a

library

e.g.

Complete

component

manufacturing cell

Lunch and snack

produce area in

supermarket

e.g.

(26)

X

1

2

3

4

5

6

7

8 M

ac

hi

ne

s

Component families

1

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

Component families

3

6

8

5

2

4

1

8 (b)

4

1

6

3

8

2

5

7 M

ac

hi

ne

s

(27)

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

Lo

ad

0

0.5

1

1.5

2

2.5

3

1

2

3

4 Stage

(28)

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

Lo

ad

0

0.5

1

1.5

2

2.5

3 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%

(29)

Element listing for Karlstad Cakes

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

(30)

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

(31)

Allocation of elements to stages and balancing loss

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

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

=

(32)

1 every 15

minutes

15

15 1 every 15

minutes

30

30 Long and thin versus short and fat layouts

1 every 15

minutes

60

60 cess

Long

thin p

roces

s

(33)

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 processes

controlled flow

simple materials handling

lower capital requirement

(no duplication)

greater efficiency

higher space utilization

Advantages of short-fat processes

higher mix flexibility

higher volume flexibility

greater robustness

less monotonous

higher ownership

(34)

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)

(35)

Key Terms Test

Fixed-position layout

Locating the position of a product or service such that it remains

largely stationary, while transforming resources are moved to

and from it.

Cell layout

Locating 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 layout

Locating transforming resources in a sequence defined by the

processing needs of a product or service.

(36)

Key Terms Test

Shop-within-a-shop

An 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 layout

A more descriptive term for what is technically a product layout.

Combinatorial complexity

The 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).

(37)

Key Terms Test

Flow record chart

A diagram used in layout to record the flow of products or

services between facilities.

Relationship chart

A 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.

(38)

Key Terms Test

CRAFT

Computerized Relative Allocation of Facilities Technique, a

heuristic technique for developing good, but non-optimal,

solutions.

Cluster analysis

A 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.

(39)

Key Terms Test

Remainder cell

The cell that has to cope with all the products that do

not conveniently fit into other cells.

Cycle time

The average time between units of output emerging

from a process.

Total work content

The total amount of work required to produce a unit of

output, usually measured in standard times.

(40)

Key Terms Test

Line balancing

The activity of attempting to equalize the load on each

station or part of a line layout or mass process.

Balancing loss

The 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.

(41)

Key Terms Test

Long thin

A 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 fat

A 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.