OPSM 405 Service Operations Management Class 17: Wrap-up of process game Process Analysis Koç University Zeynep Aksin [email protected]
Jan 03, 2016
OPSM 405 Service Operations Management
Class 17:
Wrap-up of process game
Process Analysis
Koç University
Zeynep [email protected]
Original process flowchart
M M P C P M M C
Task times?Bottleneck?
Resource utilization? Cycle time? (Flow time)
Value adding time? (theoretical)
Terminology
Flow Time (CT or 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.
1 2 3 4
Flow time
Throughput Rate (TH or R)The average output of a production process per unit time. At the firm level, it is defined as the production per unit time that is sold.
1 2 3 4
Terminology
Critical Path & Critical Activities
Critical Path: A path with the longest total cycle time.
Critical Activity: An activity on the critical path.
A B
C
D
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: X-Ray
32
1
4 765
11
109
start end
25%
75%7
20 6
5 3
6 12 2
20
3 7
transport
support
Value added
decisionMeasured actual flow time: 154 minutes
8
Consider all possible paths
Path1: 1-4-5-6-7-8-9-10 50 Path 2: 2-3-4-5-6-7-8-9-10
69 Path 3: 1-4-5-6-7-8-11
60 Path 4: 2-3-4-5-6-7-8-11 79
Levers for Reducing Flow Time
Decrease the work content of critical activities
– work smarter
– work faster
– do it right the first time
Move work content from critical to non-critical activities
– to non-critical path or to ``outer loop’’
Reduce waiting time.
X-Ray revisitedResource Pool
Res. Unit Load
Load Batch
Theoretical Capacity of Res. unit
No of units in pool
Theoretical capacity of pool
Messenger 40 min/patient
1 1.5 patients/hr
6 9 Patient/hr
Receptionist 5 1 12 1 12
X-ray technician
16 1 3.75 4 15
X-ray lab 7.5 1 8 2 16
Darkroom technician
15 1 4 3 12
Darkroom 15 1 4 2 8
Changing room
6 1 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
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
Structuring The Service Enterprise
Example: Automobile’s Driver’s License Office
License Renewal TimesActivity Description Time (Sec) 1 Review application for correctness 15 2 Process and record payment 30
3 Check for violations and restrictions 60 4 Conduct eye test 40 5 Photograph applicant 20
6 Issue temporary license 30
3 60
60
Present Flow Diagram
1 240
15
2 120
30
4 90
40
5 180
20
6 120
30
Activity
flow rate per hour
time (sec)
Flow time: sec
Throughput rate: per hour
What happens if you hire one more employee?
sec sec sec sec sec sec/hr /hr /hr /hr /hr /hr
Activity Activity Activity Activity Activity Activity
Proposed Flow Diagram
Flow time: sec
Throughput rate: per hour
2 120
30sec/hr
Activity
5 180
20
6 120
30sec sec/hr /hr
Activity Activity
1,4 65
55sec/hr
Activity
3 60
60 sec/hr
Activity
1,4 65
55sec/hr
Activity
3 60
60 sec/hr
Activity
Another Design
Flow time: sec
Throughput rate: per hour
1-5 22
165sec/hr
Activity
1-5 22
165sec/hr
Activity
1-5 22
165sec/hr
Activity
1-5 22
165sec/hr
Activity
1-5 22
165sec/hr
Activity
1-5 22
165sec/hr
Activity
6 120
30 sec/hr
Activity
The role of task times: a balanced line
if task times are similar will have a balanced line
• in the absence of variability (deterministic) complete synchronization is possible
• in a balanced line idleness is minimized, though in the presence of variability full synchronization cannot be achieved
The role of task times: an unbalanced line
if average task times are different will have an unbalanced line• will have idleness
in unbalanced case, slowest task determines output rate• bottleneck is busy
• idleness in other stages
The role of variability
6/hr 6/hr
4 or 8/hr 4 or 8/hr
2 or 10 2 or 10
0 or 120 or 12
As variability increases, throughput (rate) decreases
Compounding effect of variability and unbalanced task times
6/hr 4/hr
4 or 8/hr 2 or 6/hr
2 or 10 0 or 8
4/hr
3.5/hr
2.5/hr
Resource interaction effects
6/hr 6/hr
4 or 8/hr 4 or 8/hr
2 or 10 2 or 10
0 or 120 or 12
6/hr
6/hr
6/hr
6/hr
6/hr
4 or 8/hr
2 or 10
0 or 12
6/hr
4.5/hr
3/hr
1.5/hr
In a serial process downstream resources depend on upstreamresources: can have temporary starvation (idleness)
As variability increases, the impact of resource interaction increases
Want to eliminate as much variability as possible from your processes: how?
specialization in tasks can reduce task time variability standardization of offer can reduce job type variability automation of certain tasks IT support: templates, prompts, etc. incentives
Want to reduce resource interference in your processes: how?
smaller lotsizes (smaller batches) better balanced line
• by speeding-up bottleneck (adding staff, changing procedure, different incentives, change technology)
• through cross-training eliminate steps buffers integrate work (pooling)
The impact of task integration (pooling)
balances utilization... reduces resource interference... ...therefore reduces the impact of temporary
bottlenecks there is more benefit from pooling in a high utilization
and high variability process pooling is beneficial as long as
• it does not introduce excessive variability in a low variability system
• the benefits exceed the task time reductions due to specialization
Examples of pooling in business
Consolidating back office work Call centers Single line versus separate queues
Summary of fundamental process principles
identify and eliminate bottlenecks reduce as much variability as possible eliminate handoffs, improve communication to minimize
resource interference for high utilization processes build-in more slack