4.1
Chapter 4
Process design
Shenval. Alamy
4.1
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
4.2
Process design
Operations
strategy
Design
Supply network design
Layout
and flow
Process
technology
Operations
management
Improvement
Planning and
control
People, jobs
and
organization
Product/ service
design
4.2
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
4.3
Key operations questions
In Chapter 4 – Process design – Slack et al. identify the
following key questions:
• What is process design?
• What objectives should process design have?
• How does volume and variety affect process design?
• How are processes designed in detail?
4.3
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
4.4
Nature and purpose of the design activity
Products, services and the processes which produce
them all have to be designed.
Decisions taken during the design of a product or
service will have an impact on the decisions taken
during the design of the process which produces those
products or services and vice versa.
4.4
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
4.5
The design of products/services and processes are interrelated
and should be treated together
• Products and services should be designed in
such a way that they can be created effectively.
• Product/service design has an impact on the
process design and vice versa.
• Processes should be designed so they can
create all products and services which the
operation is likely to introduce.
4.5
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
4.6
The overlap of activities is greater in service design
• In manufacturing operations overlapping the
activities of product and process design is
beneficial.
• In most service operations the overlap between
service and process design is implicit in the nature
of service.
4.6
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
4.7
4.7
The Smart car uses environmentally friendly design principles
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
4.8
Process mapping symbols
Process mapping symbols
derived from ‘Scientific
Management’
Process mapping symbols
derived from Systems
Analysis
Operation (an activity
that directly adds
value)
Beginning or end of
process
Inspection (a check of
some sort)
Activity
Transport (a movement
of something)
Input or Output from the
process
Delay (a wait, e.g. for materials)
Direction of flow
Storage (deliberate
storage, as opposed to a
delay)
4.8
Decision (exercising discretion)
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
4.9
Designing processes
• There are different ‘process types’.
• Process types are defined by the volume and
variety of ‘items’ they process.
• Process types go by different names depending
on whether they produce products or services.
4.9
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
Manufacturing process types
Process
tasks
Process
flow
Diverse/
complex
Intermittent
High
4.10
Project
Variety
Jobbing
Batch
Mass
Continuous
Low
Repeated/
divided
Continuous
Low
4.10
Volume
High
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
4.11
Project processes
One-off, complex, large scale, high work content
‘products’
Specially made, every one customized
Defined start and finish: time, quality and cost objectives
Many different skills have to be coordinated.
4.11
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
4.12
Jobbing processes
Very small quantities: ‘one-offs’, or only a few required
Specially made. High variety, low repetition. ‘Strangers’
every one customized
Skill requirements are usually very broad
Skilled jobber, or team, complete whole product.
4.12
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
4.13
Batch Processes
Higher volumes and lower variety than for jobbing
Standard products, repeating demand. But can make
specials
Specialized, narrower skills
Set-ups (changeovers) at each stage of production.
4.13
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
4.14
Mass (line) processes
Higher volumes than batch
Standard, repeat products (‘runners’)
Low and/or narrow skills
No set-ups, or almost instantaneous ones.
4.14
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
4.15
Continuous processes
Extremely high volumes and low variety: often single
product
Standard, repeat products (‘runners’)
Highly capital-intensive and automated
Few changeovers required
Difficult and expensive to start and stop the process.
4.15
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
Process
tasks
Process
flow
Diverse/
complex
Intermittent
High
Service process types
Professional
service
Service shop
Variety
4.16
Repeated/
divided
Continuous
Low
Mass service
Low
4.16
Volume
High
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
4.17
Professional service
High levels of customer (client) contact.
Clients spend a considerable time in the service process.
High levels of customization with service processes being
highly adaptable.
Contact staff are given high levels of discretion in
servicing customers.
People-based rather than equipment-based.
4.17
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
4.18
Service shops
Medium levels of volumes of customers
Medium, or mixed, levels of customer contact
Medium, or mixed, levels of customization
Medium, or mixed, levels of staff discretion.
4.18
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
4.19
Mass service
High levels of volumes of customers
Low to medium levels of customer contact
Low, or mixed, levels of customization
Low, or mixed, levels of staff discretion.
4.19
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
4.20
Deviating from the ‘natural’ diagonal on the product–process
matrix has consequences for cost and flexibility
Manufacturing
operations
process types
None Professional
service
Project
More process
flexibility than
is needed so
high cost
Jobbing
Batch
Mass
Service
operations
process types
Volume
Variety
Less process
flexibility than
is needed so
high cost
Continuous None
Service
shop
Mass
service
The ‘natural’ line of fit of process to
volume/variety characteristics
4.20
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
4.21
Deviating from the ‘natural’ diagonal on the product–process
matrix has consequences for cost and flexibility (Continued)
Volume
Variety
None
Old
process
Old
process
new
product
New
process
new
product
None
The ‘natural’ line of fit of process to
volume/variety characteristics
4.21
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
4.22
Customized sandwich – old process
Raw
materials
Assembly
Stored
sandwiches
Standard sandwich process
4.22
Move to
outlets
Stored
sandwiches
Sell
Take
payment
Customer
request
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
4.23
Customized sandwich – old process (Continued)
Raw
materials
Assembly
Take
payment
Customer
request
4.23
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
4.24
Higher level process map
Prepare
The operation of
making and selling
customized
sandwiches
Sandwich
materials and
customers
Bread and
base filling
Assemble whole
sandwich
Use standard
‘base’?
Assemble as
required
Take
payment
Customers
‘assembled’ to
sandwiches
The outline process of
making and selling
customized sandwiches
No
Yes
Fillings
Customer request
Assemble from
standard ‘base’
The detailed process of
assembling customized
sandwiches
Stored
‘bases’
4.24
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
4.25
Customized sandwich - new process
Assemble whole
sandwich
Assembly of
‘sandwich
bases’
Use standard
‘base’?
Take
payment
No
Fillings
Yes
Bread and
base filling
Customer request
Stored ‘bases’
4.25
Assemble from
standard ‘base’
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
4.26
Flow process charts for processing expense
1
2
3
4
5
6
Description of activity
Report arrives
1
Wait for processing
Check expenses report
Stamp and date report
2
3
4
Send cash to receipt desk
Wait for processing
5
6
Check advance payment
7
8 Send to accounts receivable
9
Wait for processing
10
Check employee record
11
Send to account payable
Attach payment voucher
12
13
14
15
16
17
18
19
20
21
22
23
7
8
9
Description of activity
Report arrives
Stamp and date report
Check expenses report
Attach payment voucher
Wait for batching
Collect retorts into batch
Batch to audit desk
Wait for processing
Check reports and vouchers
Reports to batch control
10
11
Batch control number
Copy of reports to filing
12
Reports filed
13
14 Payment voucher to keying
Log report
Check against rules
Wait for batching
Collect retorts into batch
15
Confirm payment
Totals
Batch to audit desk
Wait for processing
5 5 2 2 1
Batch of reports logged
Check payment voucher
Before
Reports to batch control
Batch control number
After
Copy of reports to filing
24
Reports filed
25 Payment voucher to keying
26
Confirm payment
Totals
4.26
7 8 5 5 1
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
4.27
Little’s law (a really quite useful law)
Throughput (TH) = Work In Process (WIP) x Cycle Time (CT)
Cycle time
= 2 mins
WIP = 10
Throughput time = ?
Throughput time = 10 × 2 mins
Throughput time = 20 mins
4.27
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
4.28
Little’s law (a really quite useful law) (Continued)
Throughput (TH) = Work In Process (WIP) x Cycle Time (CT)
Need to mark 500 exam scripts in 5 days (working 7 hours a day). Takes 1 hour
to mark a script. How many markers are needed?
Throughput time = 5 days × 7 hours = 35 hours
35 hours = 500 scripts × Cycle times
Cycle time =
35 hours
500 scripts
= 0.07 hours
Number of markers = Work content = 1 hour = 14.29
Cycle time
0.07
4.28
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
4.29
Throughput efficiency
Throughput efficiency is the work content of whatever is
being processed as a percentage of its throughput time
Throughput efficiency =
4.29
Work content
Throughput time
× 100
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
4.30
Throughput time
and capacity
utilisation
Arrival
Arrival
30
9 5–15 105–15
Processing
10
Processing
frequency
frequency 20
time
time
mins mins
mins
(demand)
(demand) mins
X
Utilization
Utilization
33.33
50
100
%
%
%%% QQ
Q
0>0
Utilization===100
<100%
Q====0infinity
time
Process
length of queue
Average throughput
(or inventory)
High
High utilization but
long throughput times
X
Low utilization but
short throughput times
X
Reduce process
variability
X
Low
0
20%
X
40%
X
60%
80%
X
100%
Capacity utilization
4.30
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010
4.31
Average number of units
waiting to be processed
Average number of units
waiting to be processed
Process utilization, waiting time and variability
Decreasing
variability
High utilization
but long waiting
time
Reduction in
process
variability
Short waiting
time but low
utilization
Y
0
10 20 30 40 50 60 70 80 90 100
Utilization
(a) Decreasing variability allows higher
utilization without long waiting times.
4.31
0
X
Z
10 20 30 40 50 60 70 80 90 100
Utilization
(b) Managing process capacity
and/or variability.
Slack, Chambers and Johnston, Operations Management, 6th Edition,
© Nigel Slack, Stuart Chambers, and Robert Johnston 2010