Koç University
OPSM 301 Operations Management
Class 5:
Business process flows
House Building Game
Zeynep Aksin
zaksin@ku.edu.tr
Example: Hospital Emergency Room
A hospital emergency room is currently organized so that all patients register through
an initial check-in process. At his or her turn, each patient is seen by a doctor and
then exits the process, either with a prescription or with admission to the hospital.
Currently, 55 people per hour arrive at the ER, 10% of who are admitted to the
hospital. On average, 7 people are waiting to be registered and 34 are registered
and waiting to see a doctor. The registration process takes, on average, 2 minutes
per patient. Among patients who receive prescriptions, average time spent with a
doctor is 5 minutes. Among those admitted to the hospital, average time is 30
minutes.



On average, how long does a patient spend in the ER?
On average, how many patients are being examined by doctors?
On average, how many patients are there in the ER?
Assume the process to be stable; that is, average inflow rate equals average outflow
rate.
Example: Emergency Room
Potential admits
10%
Buffer 1
R =55/hr
I=7
Registration
Doctor
I = 34
T = 2 min
Flow units?
Buffer 2
T1 = 5min
T2 = 30min
90%
Simple Prescription
Little’s Law
Potential admits
10%
Buffer 1
R =55/hr
I=7
T = I/R = 7/55 hr
= 0.127 hrs = 7.6 min
Registration
Buffer 2
Doctor
I = 34
T = 2 min
I = RT = 55*2/60
= 1.83 patients.
T1 = 5min
= 0.62 hrs = 37.1 min T2 = 30min
T = I/R = 34/55 hr
90%
Simple Prescription
On average how long does a patient spend
in the ER?
 Two types of flow units:
– Potential admits
– Simple prescriptions
 Potential admits flow time=7.6 + 2 + 37.1 +
30 = 76.7 minutes
 Simple prescriptions flow time= 7.6 + 2 +
37.1 + 5 = 51.7 minutes.
 Average
– T = 10% * 76.7 + 90%*51.7 = 54.2 minutes.
On average how many patients are being
examined by doctors?
 Potential admits:
– R = 5.5 patients/hr,
– T = 30 min = 0.5 hr
– I = RT = 5.5/hr*0.5 hr = 2.75 patients
 Simple prescription:
– R = 49.5 patients/hr,
– T = 5 min = (5/60) hr
– I = RT = 49.5*(5/60) = 4.125 patients
On average how many patients are there in
the ER?
 total inventory in ER
 = inventory in buffer 1 + inventory in
registration + inventory in buffer 2 +
inventory with doctors
 = 7 + 1.83 + 34 + 6.865 = 49.695 patients.
Relating operational measures (flow time T,
throughput R & inventory I) with Little’s Law
Inventory I
...
... ...
Flow rate/Throughput R
[units]
Flow Time T [hrs]
 Inventory = Throughput x Flow Time
I = RxT
 Inventory Turns = 1/ T
[units/hr]
... ...
Inventory Turns examples (source Cachon and Terwiesch)
Key learnings: Little’s Law
 Relates three leading performance measures based on
process flows: throughput, inventory, flow time
 Applies to processes in steady state
 Important to
– First determine process boundaries for analysis
– Then identify appropriate flow unit for your analysis
From measurement to analysis
 So far we have considered
– Measuring process flows-R, T, I
– Relating these measures through Little’s Law:
I=RxT
 Next: understand what drives each
measure
– What drives flow time?
– What drives throughput rate?
– What drives inventory?
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.
House Building Game-Introduction
KEEP DESKS CLEAR!
 Only need a pen or pencil.
 Please keep desks and aisles
clear of notebooks, PCs,
backpacks etc.
 Please do not disturb
materials!
HouseBuilding.com:
Manufacturing Operations
Production Control
(color sheets, log sheets, scissors)
Base Punch
(scissors)
Roof
Base Form
(scissors)
Base Weld
(stapler)
Final Assembly
(tape)
Quality Control
Customer
Production Control Operating Procedures
 Prepare a batch of 4 units.
– Cut each sheet (one at a time) into two: roof and base.
– Write the batch number on the roof and the base. All items in the same
batch have the same number. The numbers have to match in assembly.
– Repeat
– 4 times, which yields one batch
 When 4 units (one batch) are complete, “release” the batch.
– Put the batch in your out-basket: it’s ready for pickup by the trucker.
– Record release time for each batch.
 Release one batch each minute.
Truckers Operating Procedures
 Truckers are
responsible for
transporting work
in process
inventory between
production steps.
 You can carry only
one batch of 4
roofs or 4 bases at
a time. Not both!
Production Control
(color sheets, log sheets, scissors)
Base Punch
(scissors)
Roof
Base Form
(scissors)
(scissors)
Base Weld
(stapler)
Final Assembly
(tape)
Quality Control
Customer
Roof Operating Procedures
 Cut the roof along double lines, one at a
time.
 Fold roof along dotted line at top. Think
quality!
 Work in batches of 4 units.
 When a batch is ready, call the trucker and
Base Cut Operating Procedures
 Cut the base along double lines, one at a time.
Think quality!
 Work in batches of 4 units
 When a batch is ready, call the trucker and send
to Base Form.
 Ask trucker for inputs when needed.
Base Form Operating Procedures
 Fold the lines on the base (4 folds).
 Work in batches of 4 units
 When a batch is ready, call the trucker to
send them to Base Weld.
 Ask trucker for inputs when needed
Base Weld Operating Procedures
 Staple base on top and bottom about 0.5 cm
from the edge.
 Work in batches of 4 units.
 When a batch is ready, call the trucker to send
them to Final Assembly.
 Ask trucker for inputs when needed.
Final Assembly Operating Procedures
 Tape the roof to the base (2 tapes).
 Work in batches of 4 units.
 When a batch is ready, send them to QA.
(No trucker required.)
 Ask trucker for inputs when needed.
Quality Assurance Operating Procedures
 Check each batch if they
conform to quality standards!
 If the house conforms to
quality standards, put it on the
market. Once on the market no
more rework!
 Customers can reject houses
Quality Standards
 Batch numbers must match.
 Folds and cuts should be
along appropriate lines.
– Folds should be crisp and cuts
should be straight.
 Roof should be centered and
door should be visible.
– Top of base should be flush
with roof.
 Staples and tape should be
centered and parallel to the
ground.
– Not too much tape. About 1
cm
– Staples about 0.5 cm from
edge.
House Game Overview
Production Control
 Quality Standards
(color sheets, log sheets, scissors)
Base Punch
(scissors)
Roof
Base Form
(scissors)
(scissors)
Base Weld
(stapler)
Final Assembly
(tape)
Quality Control
Customer
 Batch numbers must match.
 Folds and cuts should be
along appropriate lines.
– Folds should be crisp and cuts
should be straight.
 Roof should be centered and
door should be visible.
– Top of base should be flush
with roof.
 Staples and tape should be
centered and parallel to the
ground.
– Not too much tape. About 1
cm.
– Staples about 0.5 cm from
edge.
HouseBuilding.com:
Operational Performance
Flow time T
Team House # 1
(color) To - Ti = T
House # 16
To - Ti = T
Input
Ri
Output Inventory Sales Quality
Ro
I
R Q = R/ Ro