Transcript Document

7.1
Layout and Flow
© Nigel Slack, Stuart Chambers & Robert Johnston, 2004
Operations Management, 4E: Chapter 7
7.2
Chapter coverage
• Basic layout types
• Selecting a layout type
• Detailed design of a layout
© Nigel Slack, Stuart Chambers & Robert Johnston, 2004
Operations Management, 4E: Chapter 7
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
© Nigel Slack, Stuart Chambers & Robert Johnston, 2004
Operations Management, 4E: Chapter 7
7.4
Fixed position layout
1)
2)
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:
i. Too large
ii. Too delicate or
iii. Objects being moved
© Nigel Slack, Stuart Chambers & Robert Johnston, 2004
Operations Management, 4E: Chapter 7
7.5
Process layout
1)
In a process layout, similar processes or processes
with similar needs are located together because:
i.
ii.
2)
3)
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.
© Nigel Slack, Stuart Chambers & Robert Johnston, 2004
Operations Management, 4E: Chapter 7
7.6
An example of a process layout in a library
showing the path of just one customer
Loan books in subject order
On-line and
CD-ROM
access room
Study desks
Enquiries
Company reports
To
journal
sack
Current
journals
Reference
section
Reserve
collection
Store
room
Counter staff
Entrance
© Nigel Slack, Stuart Chambers & Robert Johnston, 2004
Copying area
Exit
Operations Management, 4E: Chapter 7
7.7
Cell layout
1)
2)
3)
4)
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.
© Nigel Slack, Stuart Chambers & Robert Johnston, 2004
Operations Management, 4E: Chapter 7
7.8
The ground floor plan of a department store
showing the sports goods shop-within-a-shop
retail ‘cell’
Books
and
videos
Footwear
Sports shop
Menswear
Perfume
& jewellery
Elevators
Confectionery,
newspaper,
magazines and
stationery
Women’s clothes
Luggage
and gifts
Entrance
© Nigel Slack, Stuart Chambers & Robert Johnston, 2004
Operations Management, 4E: Chapter 7
7.9
Product layout
1)
2)
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.
© Nigel Slack, Stuart Chambers & Robert Johnston, 2004
Operations Management, 4E: Chapter 7
7.10
An army induction centre with uses
product layout
Waiting
area
Lecture theatre
Doctor
Waiting
area
Doctor
Blood
test
X-ray
Uniform
issuing
area
Doctor
Doctor
Blood
test
Record
personal
history and
medical
details
X-ray
Uniform
store
Doctor
© Nigel Slack, Stuart Chambers & Robert Johnston, 2004
Blood
Doctor test
X-ray
Operations Management, 4E: Chapter 7
7.11
A restaurant complex with all four basic
layout types
Line layout cafeteria
Cell layout buffet
Starter
buffet
Desert
buffet
Fixed-position layout
service restaurant
Main course
buffet
Service line
Oven
Preparation
Process layout kitchen
Cool room
Freezer
© Nigel Slack, Stuart Chambers & Robert Johnston, 2004
Vegetable prep
Grill
Operations Management, 4E: Chapter 7
Volume-variety relationship
High
Flow is
intermittent
Low
High
Volume
Fixed-position
layout
Variety
Process
layout
Cell layout
Product
layout
Regular flow more feasible
7.12
Low
Flow
becomes
continuous
Regular flow more important
© Nigel Slack, Stuart Chambers & Robert Johnston, 2004
Operations Management, 4E: Chapter 7
7.13
Volume and
variety
Layout selection steps
Decision 1
Process type
Strategic
performance
objectives
Decision 2
Basic layout type
Project process
Professional services
Jobbing process
Service shops
Batch process
Mass services
Mass process
Continuous process
Fixed position layout
Process layout
Cell layout
Product layout
Decision 3
Detailed design of
layout
The physical position
of all transforming
resources
The flow of the
operation’s
transformed resources
© Nigel Slack, Stuart Chambers & Robert Johnston, 2004
Operations Management, 4E: Chapter 7
7.14
Selecting a layout type
© Nigel Slack, Stuart Chambers & Robert Johnston, 2004
Operations Management, 4E: Chapter 7
7.15
1) The nature of the basic layout types
Manufacturing
process types
Basic layout
types
Service
process types
Project processes
processes
Project
Fixed
position layout
Professional
services
Jobbing processes
Process layout
Service shops
Batch processes
Cell layout
Mass processes
Product layout
Mass services
Continuous processes
© Nigel Slack, Stuart Chambers & Robert Johnston, 2004
Operations Management, 4E: Chapter 7
7.16
2) Advantages and disadvantages
Fixed
Advantages
Process
Product
- Very high mix
position
and product
layout
flexibility
- High mix and
product
flexibility
layout
- Good compromise
between
cost and
layout
flexibility
Lo- w unit costs for high
volume
layout
- Product/customer
not moved or
disturbed.
- Relatively robust
if in the case of
disruptions
- Fast throughput.
- Gives Opportunities
for specialization of
equipment
- High variety of
tasks for staff
- Easy supervision
of equipment of
plant
- Group work can
result in good
motivation
- Gives Opportunities
for specialization of
equipment
Low utilization of
resources.
- Very high unit cost.
Disadvantages
Cell
Can have very high
WIP
- Scheduling space
and activities can be
Complex flow.
difficult.
© Nigel Slack, Stuart Chambers & Robert Johnston, 2004
Can be costly to
rearrange existing
layout
Can need more plant
and equipment
Can have low mix and
flexibility
Not very robust to
disruption
Work can be very
repetitive.
Operations Management, 4E: Chapter 7
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
(b)
Costs
Costs
(a)
Fixed-position
Process
Cell
Product
Use
Use
fixed- process
position
Use
cell
Use
product
Volume
3) Consider total cost
© Nigel Slack, Stuart Chambers & Robert Johnston, 2004
?
?
?
?
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
Operations Management, 4E: Chapter 7
7.18
Detailed design of a layout
© Nigel Slack, Stuart Chambers & Robert Johnston, 2004
Operations Management, 4E: Chapter 7
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.
© Nigel Slack, Stuart Chambers & Robert Johnston, 2004
Operations Management, 4E: Chapter 7
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
© Nigel Slack, Stuart Chambers & Robert Johnston, 2004
Operations Management, 4E: Chapter 7
Collecting information in process layout
7.21
(a)
LOADS/DAY
To
From
A
A
B
B
C
17
13
C
(b)
30
E
10
E
30
10
A
20
B
20
70
30
10
10
A
D
10
D
LOADS/DAY
If direction is not
important, collapses
to
10
© Nigel Slack, Stuart Chambers & Robert Johnston, 2004
B
C
30
30
D
E
60
20
30
C
80
D
40
E
Operations Management, 4E: Chapter 7
Collecting information in process layout
7.22
(c)
LOADS/DAY
A
A
B
B
C
30
30
D
E
60
20
(d)
LOADS/DAY
A
B
30
C
C
D
80
Or alternatively
40
D
E
30
30
40
80
60
30
20
E
© Nigel Slack, Stuart Chambers & Robert Johnston, 2004
Operations Management, 4E: Chapter 7
7.23
Collecting information in process layout
(e)
LOADS/DAY
To
From
A
A
B
B
C
17
13
C
(f) UNIT COST/DISTANCE TRAVELLED
D
E
To
From
30
10
A
20
B
3
C
2
2
D
10
10
10
E
2
2
2
20
10
D
30
E
10
70
30
10
10
If cost of flow differs
between work
centers, combine
with
10
© Nigel Slack, Stuart Chambers & Robert Johnston, 2004
A
B
C
D
E
2
2
2
2
3
3
4
2
2
10
2
Operations Management, 4E: Chapter 7
7.24
Collecting information in process layout
(g) DAILY COST/DISTANCE TRAVELLED
To
From
A
A
B
To give
B
C
34
39
C
D
E
60
20
60
60
20
D
300
E
20
© Nigel Slack, Stuart Chambers & Robert Johnston, 2004
140
300
20
20
20
Operations Management, 4E: Chapter 7
Collecting information in process layout
7.25
(h) DAILY COST/DISTANCE TRAVELLED
To
From
A
A
B
B
C
34
39
C
300
E
20
E
60
20
A
60
B
60
140
300
20
20
A
D
20
D
(i) DAILY COST/DISTANCE TRAVELLED
If direction is not
important, collapses
to
20
© Nigel Slack, Stuart Chambers & Robert Johnston, 2004
B
C
73
80
D
E
360
40
80
C
160
D
320
E
Operations Management, 4E: Chapter 7
A relationship chart
7.26
DEPARTMENT
X
Metrology
CODE
A
E
I
O
U
X
CLOSENESS
Absolutely necessary
Especially important
Important
Ordinary closeness
Unimportant
Undesirable
E
Electronic testing
A
I
Analysis
O
U
I
Ultrasonic testing
X
U
O
I
Fatigue testing
X
U
U
O
E
Impact testing
© Nigel Slack, Stuart Chambers & Robert Johnston, 2004
Operations Management, 4E: Chapter 7
7.27
Cell layout design
1)
Cells in an operation can be created based on two
interrelated decisions:
1)
2)
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:
i.
ii.
Cluster analysis – which process group naturally together
Parts and family coding – based on similar characteristics
of parts of products
OR
2) Production Flow Analysis (PFA)
Examines both product requirement and process grouping
(See Fig. 7.31)
© Nigel Slack, Stuart Chambers & Robert Johnston, 2004
Operations Management, 4E: Chapter 7
7.28
Types of cell
High
e.g. Specialist process
manufacturing cell
Internal audit group
in a bank
Amount of indirect
resources included
in the cell
e.g. Plant-within-a-plant
manufacturing
operation
Maternity unit
in a hospital
Low
e.g. Small multi-machine
manufacturing cell
Joint reference and
copying room in a
library
e.g. Complete
component
manufacturing cell
Proportion of
the resources
needed to
complete the
High transformation
included in the
cell
Lunch and snack
produce area in
supermarket
Low
© Nigel Slack, Stuart Chambers & Robert Johnston, 2004
Operations Management, 4E: Chapter 7
(a) and (b) Using production flow analysis
to allocate machines to cells
(a)
1
2
3
4
5
1
Machines
2
X
X
X
4
7
X
X
X
X
X
X
X
X
6
3
6
8
X
X
X
X
X Cell A
© Nigel Slack, Stuart Chambers & Robert Johnston, 2004
X
5
2
4
1
8
X
X
X
X
Cell B
8
X
X
2
5
X
Product
3
1
X
X
X
4
X
X
X
7
8
X
X
6
8
6
X
3
5
(b)
Product
Machines
7.29
7
Cell C
X
X
X
X
X
X
X
X
Operations Management, 4E: Chapter 7
7.30
Product layout design
1)
Product type layout is designed based on a
technique called line balancing. The technique
consist of the following steps:
1)
2)
3)
4)
Calculating the required cycle time.
Calculating the number of stages.
Producing a precedence diagram.
Finally allocating activities to the stages.
© Nigel Slack, Stuart Chambers & Robert Johnston, 2004
Operations Management, 4E: Chapter 7
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
160
1 product every 15 minutes
© Nigel Slack, Stuart Chambers & Robert Johnston, 2004
Operations Management, 4E: Chapter 7
7.32
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.
© Nigel Slack, Stuart Chambers & Robert Johnston, 2004
Operations Management, 4E: Chapter 7
7.33
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:
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.
0.17 mins
e
0.25 mins
0.30 mins
a
0.12 mins
b
c
d
0.36 mins
0.05 mins
f
0.25 mins
g
i
0.10 mins
h
0.08 mins
© Nigel Slack, Stuart Chambers & Robert Johnston, 2004
Operations Management, 4E: Chapter 7
7.34
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:
1.
2.
Choose the largest that will fit into the time remaining at
the stage
Choose the element with the most ‘followers’.
© Nigel Slack, Stuart Chambers & Robert Johnston, 2004
Operations Management, 4E: Chapter 7
7.35
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
© Nigel Slack, Stuart Chambers & Robert Johnston, 2004
Operations Management, 4E: Chapter 7
Balancing loss is that proportion of the time
invested in processing the product or service
which is not used productively
7.36
An ideal ‘balance’ where work is
allocated equally between the stages
3
But if work is not equally allocated the
cycle time will increase and
‘balancing losses’ will occur
3.5
Cycle time = 3.0 mins
Cycle time = 2.5 mins
3
3.0
2.5
2
Load
Load
2.5
1.5
1
2.5
2
2.2
2.3
1.5
1
0.5
0.5
0
0
1
2
3
Stage
4
Work allocated to stage
Idle time
© Nigel Slack, Stuart Chambers & Robert Johnston, 2004
1
2
3
Stage
4
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%
Operations Management, 4E: Chapter 7
7.37
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
© Nigel Slack, Stuart Chambers & Robert Johnston, 2004
Operations Management, 4E: Chapter 7
Element listing and precedence diagram
for Karlstad Kates
7.38
Element
Element
Element
Element
Element
Element
Element
Element
Element
ab
- De-tin and trim
0.12 mins
- Reshape with off-cuts
0.30 mins
c
d
- Clad in almond fondant
0.36 mins
- Clad in white fondant
0.25 mins
- Decorate, red icing
0.17 mins
- Decorate, green icing
0.05 mins
- Decorate, blue icing
0.10 mins
- Affix transfers
0.08 mins
- Transfer to base and pack
0.25 mins
e
f
g
h
i
Total work content = 1.68 mins
0.17 mins
e
0.25 mins
0.30 mins
a
0.12 mins
b
c
d
0.05 mins
f
0.36 mins
0.25 mins
g
i
0.10 mins
h
0.08 mins
© Nigel Slack, Stuart Chambers & Robert Johnston, 2004
Operations Management, 4E: Chapter 7
Allocation of elements to stages and
balancing loss for Karlstad Kates
7.39
Stage 1
Stage 2
Stage 3
0.17 mins
Stage 4
e
0.25 mins
0.30 mins
a
b
c
0.12 mins
d
0.36 mins
0.05 mins
f
0.25 mins
g
i
0.10 mins
h
0.08 mins
0.6
0.5
Cycle time = 0.48 mins
0.4
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
0.3
0.2
0.1
0
1
2
3
4
© Nigel Slack, Stuart Chambers & Robert Johnston, 2004
Operations Management, 4E: Chapter 7