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Layout and Flow. Chapter coverage Basic layout types Selecting a layout type Detailed design of a layout. Layout:

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Presentation Transcript
slide2
Chapter coverage

Basic layout types

Selecting a layout type

Detailed design of a layout

slide3
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:

Fixed position layout

Process layout

Cell layout

Product layout

slide4
Fixed position layout

In a fixed position layout, the transformed resource does not move between its transforming resources.

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

Too large

Too delicate or

Objects being moved

slide5
Process layout

In a process layout, similar processes or processes with similar needs are located together because:

It is convenient to group them together or

The utilization of the transforming resource is improved

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

The flow in a process layout can be very complex.

slide6

Loan books in subject order

On-line and CD-ROM access room

Study desks

To journal sack

Company reports

Current journals

Enquiries

Reference section

Reserve collection

Store room

Counter staff

Copying area

Entrance

Exit

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

slide7
Cell layout

In a cell layout, the transformed resources entering the operation move into a cell in which all the transforming resources it requires in located.

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.

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

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

slide8

Books and videos

Sports shop

Menswear

Footwear

Entrance

Perfume

& jewellery

Elevators

Confectionery, newspaper, magazines and stationery

Women’s clothes

Luggage and gifts

Entrance

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

slide9
Product layout

In a product layout, the transformed resource flow a long a line of processes that has been prearranged.

Flow is clear, predictable and easy to control.

slide10

An army induction centre with uses product layout

Waiting area

Waiting area

Lecture theatre

Blood

test

Doctor

Doctor

Record personal history and medical details

X-ray

Uniform issuing area

Blood

test

Doctor

Doctor

X-ray

Blood

test

Doctor

Doctor

Uniform store

X-ray

slide11

Line layout cafeteria

Cell layout buffet

Fixed-position layout service restaurant

Desert buffet

Starter buffet

Main course buffet

Service line

Preparation

Oven

Process layout kitchen

Cool room

Freezer

Grill

Vegetable prep

A restaurant complex with all four basic layout types

slide12

Low

High

Flow is intermittent

Volume

Fixed-position layout

High

Process layout

Regular flow more feasible

Cell layout

Variety

Product layout

Flow becomes continuous

Low

Regular flow more important

Volume-variety relationship

slide13

Volume and variety

Project process

Jobbing process

Batch process

Mass process

Continuous process

Professional services

Service shops

Mass services

Decision 1

Process type

Strategic performance objectives

Fixed position layout

Process layout

Cell layout

Product layout

Decision 2

Basic layout type

Decision 3

The physical position of all transforming resources

Detailed design of layout

The flow of the operation’s transformed resources

Layout selection steps

slide15

1) The nature of the basic layout types

Manufacturing

B

asic layout

Service

process types

types

process types

Fixed

Project processes

Project processes

Professional

position layout

services

Jobbing processes

Process layout

Service shops

Batch pro

cesses

Cell layout

Mass services

Mass

processes

Product layout

Continuous

processes

slide16

2) Advantages and disadvantages

Fixed

Process

Cell

Product

- Very high mix and product flexibility

- High mix and product flexibility

- Good compromise between cost and flexibility

position

Lo- w unit costs for high volume

layout

layout

layout

layout

- Gives Opportunities for specialization of equipment

- Product/customer not moved or disturbed.

- Relatively robust if in the case of disruptions

- Fast throughput.

- Group work can result in good motivation

Advantages

- Easy supervision of equipment of plant

- Gives Opportunities for specialization of equipment

- High variety of tasks for staff

Low utilization of resources.

Can be costly to rearrange existing layout

Can have low mix and flexibility

- Very high unit cost.

Can have very high WIP

Not very robust to disruption

Can need more plant and equipment

Disadvantages

- Scheduling space and activities can be difficult.

Complex flow.

Work can be very

repetitive.

slide17

(a)

(b)

Fixed-position

Costs

Costs

Process

Cell

Product

?

?

?

?

Use

cell

Use process

Use product

Use fixed-position

Volume

Volume

Use product

Use cell or product

Use process or cell or product

Use process or cell

Use process

Use fixed-position or process

Use fixed-position

(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

3) Consider total cost

slide19
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.

slide20
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

slide21

(a)

LOADS/DAY

Collecting information in process layout

(b)

LOADS/DAY

If direction is not important, collapses to

slide22

A

30

B

-

30

60

C

-

20

-

30

D

80

40

E

Collecting information in process layout

(c)

LOADS/DAY

(d)

LOADS/DAY

Or alternatively

slide23

UNIT COST/DISTANCE TRAVELLED

Collecting information in process layout

(e)

(f)

LOADS/DAY

If cost of flow differs between work centers, combine with

slide24

Collecting information in process layout

(g)

DAILY COST/DISTANCE TRAVELLED

To give

slide25

Collecting information in process layout

(h)

(i)

DAILY COST/DISTANCE TRAVELLED

DAILY COST/DISTANCE TRAVELLED

If direction is not important, collapses to

slide26

DEPARTMENT

Metrology

E

Electronic testing

A

I

O

Analysis

U

X

I

U

X

Ultrasonic testing

O

U

I

U

Fatigue testing

O

E

Impact testing

A relationship chart

slide27
Cell layout design

Cells in an operation can be created based on two interrelated decisions:

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

Which resources to allocate to which cell using:

Cluster analysis – which process group naturally together

Parts and family coding – based on similar characteristics of parts of products

OR

Production Flow Analysis (PFA)

Examines both product requirement and process grouping

(See Fig. 7.31)

slide28

Amount of indirect resources included in the cell

High

e.g.

e.g.

Plant-within-a-plant

manufacturing

operation

Maternity unit

in a hospital

Specialist process

manufacturing cell

Internal audit group

in a bank

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

Low

High

e.g.

Complete

component

manufacturing cell

Lunch and snack

produce area in

supermarket

e.g.

Small multi-machine

manufacturing cell

Joint reference and

copying room in a

library

Low

Types of cell

slide29

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

(a)

(b)

Product

Product

Cell A

Machines

Machines

Cell B

Cell C

slide30
Product layout design

Product type layout is designed based on a technique called line balancing. The technique consist of the following steps:

Calculating the required cycle time.

Calculating the number of stages.

Producing a precedence diagram.

Finally allocating activities to the stages.

slide31
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

160

1 product every 15 minutes

slide32
Number of stages

Required 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.

slide33
Precedence diagram

This 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:

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

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

0.17 mins

e

0.25 mins

0.30 mins

0.05 mins

0.25 mins

a

b

c

d

f

g

i

0.12 mins

0.36 mins

0.10 mins

h

0.08 mins

slide34
Allocating activities to the stages

The 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:

Choose the largest that will fit into the time remaining at the stage

Choose the element with the most ‘followers’.

slide35
Balancing loss

The 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

slide36

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

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

Cycle time = 3.0 mins

Cycle time = 2.5 mins

3.0

2.5

2.2

2.3

Load

Load

Stage

Stage

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%

Work allocated to stage

Idle time

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

slide37
Worked Example

Consider 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 mins

5000

The required number of stages = 1.68 mins (total work content)

0.48 mins (required cycle time)

= 3.5 stages

slide38

Element - -De-tin and trim 0.12 mins

a

Element - Reshape with off-cuts 0.30 mins

b

c

Element - Clad in almond fondant 0.36 mins

Element - Clad in white fondant 0.25 mins

d

Element - Decorate, red icing 0.17 mins

e

Element - Decorate, green icing 0.05 mins

f

Element - Decorate, blue icing 0.10 mins

g

Element - Affix transfers 0.08 mins

h

Element - Transfer to base and pack 0.25 mins

i

Total work content = 1.68 mins

0.17 mins

e

0.25 mins

0.30 mins

0.05 mins

0.25 mins

a

b

c

d

f

g

i

0.12 mins

0.36 mins

0.10 mins

0.08 mins

h

Element listing and precedence diagram for Karlstad Kates

slide39

0.17 mins

e

Stage 1

Stage 2

Stage 3

Stage 4

0.25 mins

0.30 mins

0.05 mins

0.25 mins

a

b

c

d

f

g

i

0.12 mins

0.36 mins

0.10 mins

h

0.08 mins

Cycle time = 0.48 mins

Idle time every cycle= (0.48 - 0.42) + (0.48 - 0.36) + (0.48 - 0.42)= 0.24 mins

Proportion of idle time per cycle = 0.24 = 12.5%

4 x 0.48

Allocation of elements to stages and balancing loss for Karlstad Kates