Chapter 05 essentials final

Slack, Brandon-Jones and Johnston, Essentials of Operations Management, 1st Edition, © Slack, Brandon-Jones and Johnston, 2011
Chapter 5
Process design

Design
Deliver
Direct
Develop
Operations
Management
Slack et al’s model of operations management
Location,
layout
and flow
Process
design
Product and
service
design

In Chapter 5 – Process design– Slack et. al. identify the
following key questions…….
What is process design?
How does volume and variety affect process design?
How are processes designed in detail?
What are the human implications of process design
Key operations questions

Delay (a wait, e.g. For materials)
Operation (an activity
that directly adds
value)
Inspection (a check of
some sort)
Transport (a movement
of some thing)
Storage ( deliberate
storage, as opposed to a
delay)
Process mapping symbols
derived from “Scientific
Management”
Decision (exercising discretion)
derived from Systems
Analysis
Direction of flow
Input or Output from the
process
Activity
Beginning or end of
process

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

High
VolumeLow High
Variety
Project
Low
Manufacturing process types
Process
tasks
Process
flow
Diverse/
complex
Repeated/
divided
Intermittent
Continuous
Jobbing
Batch
Mass
Contin-
uous

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
Project 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
Jobbing 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
Batch Processes

Higher volumes than batch
Standard, repeat products (“runners”)
No set-ups, or almost instantaneous ones
Low and/or narrow skills
Mass (Line) 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
Continuous Processes

VolumeLow High
VarietyLowHigh
Service process types
Process
tasks
Process
flow
Diverse/
complex
Repeated/
divided
Intermittent
Continuous
Professional
service
Service shop
Mass service

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

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
Service shops

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
Mass service

Variety
Volume
Deviating from the ‘natural’ diagonal on the product-
process matrix has consequences for cost and flexibility
None
None
The ‘natural’ line of fit of process to
volume/variety characteristics
Project
Jobbing
Batch
Mass
Continuous
Manufacturing
operations
process types
Professional
service
Service
Shop
Mass
service
Service
operations
process types
More process
flexibility than
is needed so
high cost
Less process
flexibility than
is needed so
high cost

Deviating from the ‘natural’ diagonal on the product-
process matrix has consequences for cost and flexibility
Variety
Volume
None
None
The ‘natural’ line of fit of process to
volume/variety characteristics
Old
process
Old
process
new
product
New
process
new
product

Standard sandwich process
Raw
Materials
Assembly Stored
Sandwiches
Move to
Outlets
Stored
Sandwiches
Customer
Request
Sell
Take
Payment
Customized sandwich - old process

Raw
Materials
Take
Payment
Customer
Request
Assembly
Customized sandwich - old process

The operation of
making and selling
customised
sandwiches
The outline process of
making and selling
customised sandwiches
Prepare
Assemble as
required
Take
payment
Bread and
Base filling
Stored
“Bases”
Fillings
Assemble whole
sandwich
Customer Request
Use standard
“base”?
Assemble from
standard “base”
No
Yes
The detailed process of
assembling customised
sandwiches
Sandwich
materials and
customers
Customers
“assembled” to
sandwiches
Higher level process map

Bread and
base filling
Assembly of
“sandwich
bases”
Assemble from
standard “base”
Take
payment
Assemble whole
sandwich
Customer Request
Use standard
“base”?
No
Yes
Fillings
Stored “Bases”
Customized sandwich - new process

Flow process charts for processing expenses
Send to accounts receivable
Reports to batch control
Reports filed
Confirm payment
Report arrives
Stamp and date report
Send cash to receipt desk
Wait for processing
Check expenses report
Wait for processing
Check employee record
Check advance payment
Send to account payable
Wait for processing
Attach payment voucher
Collect retorts into batch
Check against rules
Wait for processing
Batch control number
Check payment voucher
Log report
Batch to audit desk
Wait for batching
Batch of reports logged
Copy of reports to filing
Description of activity
Totals
8
1
2
4
5
6
7
9
10
3
18
11
12
14
15
16
17
19
20
13
26
22
23
24
25
21
7 8 5 5 1
Payment voucher to keying
Before
Reports to batch control
Reports filed
Payment voucher to keying
Confirm payment
Report arrives
Stamp and date report
Check expenses report
Wait for processing
Check reports and vouchers
Attach payment voucher
Collect retorts into batch
Batch control number
Batch to audit desk
Wait for batching
Copy of reports to filing
Description of activity
Totals
8
1
2
4
5
6
7
9
10
3
11
12
14
15
13
5 5 2 2 1
After

Throughput (TH) = Work In Process (WIP) x Cycle Time (CT)
Little’s law (a really quite useful law)
Cycle time
= 2 mins
Throughput time = ?
WIP = 10
Throughput time = 10 x 2 mins
Throughput time = 20 mins

Throughput (TH) = Work In Process (WIP) x Cycle Time (CT)
Throughput time = 5 days x 7 hours = 35 hours
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?
35 hours = 500 scripts x Cycle times
Cycle time = 35 hours
500 scripts
= 0.07 hours
Number of markers = Work content = 1 hour = 14.29
Cycle time 0.07
Little’s law (a really quite useful law)

Throughput efficiency =
Work content
Throughput time
X 100
Throughput efficiency is the work content of whatever is
being processed as a percentage of its throughput time
Throughput efficiency

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 4
Stage
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 4
Stage
Cycle time = 3.0 mins
3.5
Idle time

1 every 15
minutes
15 15 15 15
1 every 15
minutes
30 30
3030
‘Long & thin’ versus ‘short & fat’ arrangements
1 every 15
minutes
60
60
60
60
A 60 minute task with a required cycle time of 15 minutes.....

0 20% 40% 60% 80% 100%
Capacity Utilization
Low
X
X
X
High utilization but
long throughput times
Low utilization but
short throughput times
Reduce process
variability
High
10
mins
30
mins
Arrival
frequency
(demand)
Processing
time
Utilization = 33.33 % Q = 0
Averagelengthofqueue
X
Utilization = 50 % Q = 0
20
mins
X
10
mins
Utilization = 100 % Q = 0
X
Utilization = 100 % Q = infinity
9
mins
X
5-15
mins
5-15
mins
Arrival
frequency
(demand)
Processing
time
Utilization = <100% % Q = >0
Processthroughputtime
(orinventory)

10 20 30 40 50 60 70 80 90 1000
Utilization
Averagenumberofunits
waitingtobeprocessed
Decreasing
variability
10 20 30 40 50 60 70 80 90 1000
Utilization
Averagenumberofunits
waitingtobeprocessed
X
Y Z
High utilization
but long waiting
time
Reduction in
process
variability
Short waiting
time but low
utilization
(a) Decreasing variability allows higher
utilization without long waiting times
(b) Managing process capacity
and/or variability.
Process utilization, waiting time and variability

Chapter 05 essentials final

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Chapter 05 essentials final