Chapter 5 Process designcc.sspu.cn/download/5ab2d911-0d63-45bd-ada6-d8e2a… · ·...
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Slack, Brandon-Jones and Johnston, Essentials of Operations Management, 1st Edition, © Slack, Brandon-Jones and Johnston, 2011
Chapter 5
Process design
Slack, Brandon-Jones and Johnston, Essentials of Operations Management, 1st Edition, © Slack, Brandon-Jones and Johnston, 2011
Design
Deliver
Direct
Develop
Operations Management
Slack et al’s model of operations management
Location, layout
and flow
Process design
Product and service design
Slack, Brandon-Jones and Johnston, Essentials of Operations Management, 1st Edition, © Slack, Brandon-Jones and Johnston, 2011
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
Slack, Brandon-Jones and Johnston, Essentials of Operations Management, 1st Edition, © Slack, Brandon-Jones and Johnston, 2011
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)
Process mapping symbols derived from Systems
Analysis
Direction of flow
Input or Output from the process
Activity
Beginning or end of process
Process mapping symbols
Slack, Brandon-Jones and Johnston, Essentials of Operations Management, 1st Edition, © Slack, Brandon-Jones and Johnston, 2011
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
Slack, Brandon-Jones and Johnston, Essentials of Operations Management, 1st Edition, © Slack, Brandon-Jones and Johnston, 2011
Hig
h
VolumeLow High
Varie
ty
Project
Low
Manufacturing process types
Process tasks
Process flow
Diverse/ complex
Repeated/ divided
Intermittent
Continuous
Jobbing
Batch
Mass
Contin-uous
Slack, Brandon-Jones and Johnston, Essentials of Operations Management, 1st Edition, © Slack, Brandon-Jones and Johnston, 2011
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
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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
Slack, Brandon-Jones and Johnston, Essentials of Operations Management, 1st Edition, © Slack, Brandon-Jones and Johnston, 2011
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
Slack, Brandon-Jones and Johnston, Essentials of Operations Management, 1st Edition, © Slack, Brandon-Jones and Johnston, 2011
Higher volumes than batch
Standard, repeat products (“runners”)
No set-ups, or almost instantaneous ones
Low and/or narrow skills
Mass (Line) Processes
Slack, Brandon-Jones and Johnston, Essentials of Operations Management, 1st Edition, © Slack, Brandon-Jones and Johnston, 2011
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
Slack, Brandon-Jones and Johnston, Essentials of Operations Management, 1st Edition, © Slack, Brandon-Jones and Johnston, 2011
VolumeLow High
Varie
tyLo
wH
igh
Service process types
Process tasks
Process flow
Diverse/ complex
Repeated/ divided
Intermittent
Continuous
Professional service
Service shop
Mass service
Slack, Brandon-Jones and Johnston, Essentials of Operations Management, 1st Edition, © Slack, Brandon-Jones and Johnston, 2011
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
Slack, Brandon-Jones and Johnston, Essentials of Operations Management, 1st Edition, © Slack, Brandon-Jones and Johnston, 2011
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
Slack, Brandon-Jones and Johnston, Essentials of Operations Management, 1st Edition, © Slack, Brandon-Jones and Johnston, 2011
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
Slack, Brandon-Jones and Johnston, Essentials of Operations Management, 1st Edition, © Slack, Brandon-Jones and Johnston, 2011
VarietyVolume
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
Professionalservice
ServiceShop
Massservice
Service operations
process types
More process flexibility than is needed so
high cost
Less process flexibility than is needed so
high cost
Slack, Brandon-Jones and Johnston, Essentials of Operations Management, 1st Edition, © Slack, Brandon-Jones and Johnston, 2011
Deviating from the ‘natural’ diagonal on the product-process matrix has consequences for cost and flexibility
VarietyVolume
None
None
The ‘natural’ line of fit of process to volume/variety characteristics
Old process
Old process
new product
New process
new product
Slack, Brandon-Jones and Johnston, Essentials of Operations Management, 1st Edition, © Slack, Brandon-Jones and Johnston, 2011
Standard sandwich process
Raw Materials Assembly Stored
SandwichesMove to Outlets
Stored Sandwiches
Customer Request
Sell Take Payment
Customized sandwich - old process
Slack, Brandon-Jones and Johnston, Essentials of Operations Management, 1st Edition, © Slack, Brandon-Jones and Johnston, 2011
Raw Materials
Take Payment
Customer Request
Assembly
Customized sandwich - old process
Slack, Brandon-Jones and Johnston, Essentials of Operations Management, 1st Edition, © Slack, Brandon-Jones and Johnston, 2011
The operation of making and selling
customised sandwiches
The outline process of making and selling
customised sandwiches
PrepareAssemble as
requiredTake
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
Slack, Brandon-Jones and Johnston, Essentials of Operations Management, 1st Edition, © Slack, Brandon-Jones and Johnston, 2011
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
Slack, Brandon-Jones and Johnston, Essentials of Operations Management, 1st Edition, © Slack, Brandon-Jones and Johnston, 2011
Flow process charts for processing expenses
Send to accounts receivable
Reports to batch control
Reports filed
Confirm payment
Report arrives
Stamp and date reportSend cash to receipt desk
Wait for processingCheck 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
12
4567
910
3
18
1112
14151617
1920
13
26
22232425
21
7 8 5 5 1
Payment voucher to keying
Before
Reports to batch control
Reports filed Payment voucher to keying
Confirm payment
Report arrivesStamp and date report
Check expenses report
Wait for processingCheck 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
12
4567
910
3
1112
1415
13
5 5 2 2 1
After
Slack, Brandon-Jones and Johnston, Essentials of Operations Management, 1st Edition, © Slack, Brandon-Jones and Johnston, 2011
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
Slack, Brandon-Jones and Johnston, Essentials of Operations Management, 1st Edition, © Slack, Brandon-Jones and Johnston, 2011
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 hours500 scripts
= 0.07 hours
Number of markers = Work content = 1 hour = 14.29Cycle time 0.07
Little’s law (a really quite useful law)
Slack, Brandon-Jones and Johnston, Essentials of Operations Management, 1st Edition, © Slack, Brandon-Jones and Johnston, 2011
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
Slack, Brandon-Jones and Johnston, Essentials of Operations Management, 1st Edition, © Slack, Brandon-Jones and Johnston, 2011
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 4Stage
Cycle time = 2.5 mins Work allocated to stage
Slack, Brandon-Jones and Johnston, Essentials of Operations Management, 1st Edition, © Slack, Brandon-Jones and Johnston, 2011
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 4Stage
Cycle time = 3.0 mins3.5
Idle time
Slack, Brandon-Jones and Johnston, Essentials of Operations Management, 1st Edition, © Slack, Brandon-Jones and Johnston, 2011
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.....
Slack, Brandon-Jones and Johnston, Essentials of Operations Management, 1st Edition, © Slack, Brandon-Jones and Johnston, 2011
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 = 0Av
erag
e le
ngth
of q
ueue
X
Utilization = 50 % Q = 0
20 mins
X
10 mins
Utilization = 100 % Q = 0X
Utilization = 100 % Q = infinity
9 mins
X
5-15 mins
5-15 mins
Arrival frequency (demand)
Processing time
Utilization = <100% % Q = >0
Proc
ess
thro
ughp
ut ti
me
(or i
nven
tory
)
Slack, Brandon-Jones and Johnston, Essentials of Operations Management, 1st Edition, © Slack, Brandon-Jones and Johnston, 2011
10 20 30 40 50 60 70 80 90 1000Utilization
Aver
age
num
ber o
f uni
ts
wai
ting
to b
e pr
oces
sed
Decreasing variability
10 20 30 40 50 60 70 80 90 1000Utilization
Aver
age
num
ber o
f uni
ts
wai
ting
to b
e pr
oces
sed
X
Y Z
High utilization but long waiting
timeReduction 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