Koç University
OPSM 301: Operations Management
Session 7:
Process analysis
Zeynep Aksin
zaksin@ku.edu.tr
Process Architecture is defined and
represented by a process flow chart:
Process = network of activities performed by
resources
1. Process Boundaries:
– input
– output
2. Flow unit: the unit of analysis
3. Network of Activities & Storage/Buffers
– activities with activity times
– routes: precedence relationships (solid lines)
4. Resources & Allocation
5. Information Structure & flow (dashed lines)
Flowchart Symbols
Tasks or operations
Examples: Giving an
admission ticket to a customer,
installing an engine in a car,
etc.
Decision Points
Examples: How much change
should be given to a customer,
which wrench should be used,
etc.
Flowchart Symbols
Storage areas or
queues
Examples: Lines of people or
cars waiting for a service, parts
waiting for assembly etc.
Flows of
materials or
customers
Examples: Customers moving
to a seat, mechanic getting a
tool, etc.
Recall:Terminology
Flow Time (T)
The flow time (also called variously throughput time, cycle time) of
a given routing is the average time from release of a job at the
beginning of the routing until it reaches an inventory point at the end
of the routing.
Flow time
1
2
3
4
Flow time in the House Game process?
Production Control
(color sheets, log sheets, scissors)
Base Cut
(scissors)
Roof
Base Form
(scissors)
Base Weld
(stapler)
Final Assembly
(tape)
Quality Control
Customer
Critical Path & Critical Activities
 Critical Path: A path with the longest total cycle
time.
A
B
D
C
 Critical Activity: An activity on the critical path.
Operational Measure: Flow Time
Driver: Activity Times, Critical Activity
 (Theoretical) Flow Time
 Critical Activity
 Flow Time efficiency
Theoretical Flow Time
=
Average Flow Time
X-Ray Service Process
 1. Patient walks to x-ray lab
 2. X-ray request travels to lab by messenger
 3. X-ray technician fills out standard form based on info. From
physician
 4. Receptionist receives insurance information, prepares and signs
form, sends to insurer
 5. Patient undresses in preparation of x-ray
 6. Lab technician takes x-ray
 7. Darkroom technician develops x-ray
 8. Lab technician checks for clarity-rework if necessary
 9. Patient puts on clothes, gets ready to leave lab
 10. Patient walks back to physicians office
 11. X-rays transferred to physician by messenger
Example
1
6
7
start
2
3
20
6
4
5
5
3
6
2
12
3
7
9
10
75%
7
8
25%
end
11
20
transport
support
Value added
decision
Measured actual flow time: 154 minutes
Consider all possible paths




Path1: 1-4-5-6-7-8-9-10
Path 2: 2-3-4-5-6-7-8-9-10
Path 3: 1-4-5-6-7-8-11
Path 4: 2-3-4-5-6-7-8-11
50
69
60
79
Levers for Reducing Flow Time
 Decrease the work content of critical activities
– work smarter
– work faster
– do it right the first time
– change product mix
 Move work content from critical to non-critical activities
– to non-critical path or to ``outer loop’’
 Reduce waiting time.
Most time inefficiency comes from waiting:
E.g.: Flow Times in White Collar Processes
Industry
Process
Average
Flow Time
Theoretical
Flow Time
Flow Time
Efficiency
Life Insurance
New Policy
Application
72 hrs.
7 min.
0.16%
Consumer
Packaging
New Graphic
Design
18 days
2 hrs.
0.14%
Commercial Bank
Consumer
Loan
24 hrs.
34 min.
2.36%
Hospital
Patient Billing
10 days
3 hrs.
3.75%
Automobile
Manufacture
Financial
Closing
11 days
5 hrs
5.60%
Flow rate (capacity) in the House Game
process?
Production Control
(color sheets, log sheets, scissors)
Base Cut
(scissors)
Roof
Base Form
(scissors)
Base Weld
(stapler)
Final Assembly
(tape)
Quality Control
Customer
Tools: Gantt Chart
Gantt charts show the time at which different
activities are performed, as well as the sequence of
activities
Resources
1
activities
2
3
4
time
Example of a two-stage production line
A
5 min
B
2 min
Gantt Chart
A
A
5
A
10
B
20
15
B
7
A
B
12
B
17
22
Example of a two-stage production line
A1
5 min
B
A2
5 min
2 min
Gantt Chart
A1
A1
A1
5
A1
15
10
A2
A2
A2
5
A2
17
12
B
B
7
B
9
20
B
12 14
B
B
17 19
22
B
22
B
24
Theoretical Capacity
 Theoretical capacity: The capacity (throughput
rate) of a process under ideal conditions (units /
time)
 Effective capacity: The capacity that one expects
of a process under normal working conditions
(units/time)
 Effective capacity < Theoretical capacity
Effective Capacity (scheduled availability)
 Effective capacity depends on the following
–
–
–
–
Number of shifts
Product variety
Maintenance
Idleness
Realized Capacity (net availability)
 Actual production or realized throughput rate
– Usually lower than effective capacity.
•
•
•
•
Machine and equipment failures
Quality problems
Workforce losses
Other uncertainties
Operational Measure: Capacity
Drivers: Resource Loads
 (Theoretical) Capacity of a Resource
 Bottleneck Resource
 (Theoretical) Capacity of the Process
 Capacity Utilization of a Resource/Process =
Realized throughput [units/hr]
Theoretical capacity [units/hr]
X-ray revisited
1
6
7
start
2
3
20
6
4
5
5
3
6
2
12
3
7
9
10
75%
7
8
25%
end
11
20
transport
support
Value added
decision
Measured actual flow time: 154 minutes
X-Ray revisited
Resource
Pool
Res. Unit
Load
Load
Batch
Theoretical No of units Theoretical
Capacity of in pool
capacity of
Res. unit
pool
Messenger
20+20
1
min/patient
60/40=1.5
patients/hr
6
1.5(6)=9
Patient/hr
Receptionist
5
1
60/5=12
1
12
X-ray
technician
6+7.5+2.5
1
60/16=3.75
4
15
X-ray lab
6+0.25(6)= 1
7.5
60/7.5=8
2
16
Darkroom
technician
12+0.25(12)
=15
1
60/15=4
3
12
Darkroom
12+0.25(1
2)=15
1
60/15=4
2
8
Changing
room
3+3
1
60/6=10
2
20
Utilizations given an observed throughput of
5.5 patients/hr
Resource pool
Theoretical capacity
Patients/hr
Capacity utilization
Messenger
9
61.11
Receptionist
12
45.83
X-ray technician
15
36.67
X-ray lab
16
34.38
Darkroom technician
12
45.83
Darkroom
8
68.75
Changing room
20
27.50
A Recipe for Capacity Measurements
Resource Unit Load
Resource Capacity
(time/job) Unit Capacity # of units Total
* assuming system is processing at full capacity
Process Resource
Capacity Utilization*
Effect of Product Mix- Example
Resource
pool
Unit Load
(Physician)
Unit Load
(Hospital)
Mailroom
clerk
0.6
1.0
Unit Load
(60%-40%
mix)
0.76
Data-entry
clerk
4.2
5.2
4.60
Claims
processor
6.6
7.5
6.96
Claims
supervisor
2.2
3.2
2.60
Theoretical capacity for hospital claims
Resource
Sch.
Unit Load
availability min/claim
Th.
Capacity
resource
Number in Th.
pool
Capacity
pool
Mailroom
clerk
450
1.0
450/1=450
1
450
Data entry 450
clerk
5.2
450/5.2=86.5
8
692
Claims
360
processor
7.5
360/7.5=48
12
576
Claims
240
supervisor
3.2
240/3.2=75
5
375
Theoretical capacity for 60%-40% mix
Resource
Sch.
Unit Load
availability min/claim
Th.
Capacity
resource
Number in Th.
pool
Capacity
pool
Mailroom
clerk
450
0.76
592
1
592
Data entry 450
clerk
4.60
98
8
784
Claims
360
processor
6.96
51.7
12
621
Claims
240
supervisor
2.60
92
5
460
In summary

 Throughput Process Capacity
Theoretical Capacity
 Effective Capacity 
Levers for Increasing Process Capacity
 Decrease the work content of bottleneck activities
–
–
–
–
work smarter
work faster
do it right the first time
change product mix
 Move work content from bottlenecks to non-bottlenecks
– to non-critical resource or to third party
 Increase Net Availability
–
–
–
–
work longer
increase scale (invest)
increase size of load batches
eliminate availability waste
Announcements
 Read and be prepared to analyze Kristen’s
Cookie for next class (Mon 17/10)
 Second Assignment: Read the Universal Pulp
and Paper case-due next Wednesday 19/10!
– Draw a process flowchart
– Find the bottleneck for this process. Show all analysis
in detail.
– To produce the projected 3.68 million tons per year of
newsprint, where should an investment in capacity
occur?
– Do you have any further recommendations for
management?