Chapter
5 Constraint Management
DISCUSSION QUESTIONS
1. Examples of everyday bottlenecks include traffic lights, drive-thru windows at the
bank or fast food restaurants. On the highway merging lanes and speed zones.
Efficiency can be improved by maintaining constant speeds, setting traffic lights to
coordinate traffic patterns and only allowing highway construction after rush hour.
Fast food restaurants have two windows, pull over spots and new cash card options
to reduce time at the window.
2. A change in demand can easily shift bottlenecks. For instance, fast food restaurants
can provide promotional pricing on certain types of sandwiches or fries, which
would make their workstations take longer than normal and become capacity
constrained. Banks can provide incentives for new accounts to be opened, causing
bottlenecks at teller windows where none existed before.
3. There are many ways that process efficiency may be improved further. In the case
of our banking example, a manager might: (1) reduce processing time by providing
forms to be filled out by the customer before the customer reaches the teller
window, (2) reduce processing variability by restricting each customer to three
transactions, (3) reduce the arrival variability of customers by requiring that
customers make an appointment to see a teller, (4) add resource capacity by
increasing the number of tellers during busy periods, (5) improve resource
flexibility by ensuring that all tellers are cross trained and will help co-workers with
complex transactions, (6) improve resource availability by restricting lunch and
break time for tellers, (7) coordinate the movement of customers by making sure
that all teller windows are available to all arriving customers, (8) outsource non-
value-adding activities such as rework by rerouting difficult customers to branch
management, and (9) create standardized work procedures for routine, non-complex
processes.
PROBLEMS
Managing Bottlenecks in Service Processes
1. Bill’s Barbershop
a. 10 + 8 + (15+10)/2 + 9 = 39.5 minutes
b. Step B1 is the bottleneck, it can only handle 6 customers per hour while the rest of
the steps can handle 7.5, 10 (60/10 +60/15), and 6.67 customers per hour.
5-1
Copyright © 2016 Pearson Education, Inc.
,5-2 l PART 1 l Managing Processes
c. This process is limited by step B1, therefore the entire process can only serve 6
customers per hour.
2. Melissa’s Photo Studio
a. 5 + (5+7)2 + 20 + 7 = 38 min
b. Taking group portraits is the bottleneck for the entire process. Only 3 group
portraits can be taken per hour.
c. Groups bottleneck is taking the portrait the bottleneck time is 20 min which
yields a capacity of 60/20 or 3 per hour. Individuals bottleneck is taking the
portrait which has a processing time of 15 min, which yields a capacity of 60/15
or 4 per hour.
3. Barbara’s Boutique
a. 3 [the bottleneck is step T4 at 18 minutes – 3.33 customers per hour or 3]
b. Step T6 at 22 minutes limits Type B to 60/22 = 2.73 customers/hr.
c. 3.33(.3) + 2.73(.7) = 2.91 customers on average
With an arrival rate greater than 5 customers per hour into the process, then type A
customers may wait at step T1, T2 and T4. Waiting occurs at these steps because
the arrival rate of customers into their step is greater than that step’s processing rate.
Also assuming that the arrival rate is greater than 5 customers per hour, type B
customers may wait steps T1, T5, and T6 because these steps’ processing times are
slower than the processing time of their immediate preceding steps.
Managing Bottlenecks in Manufacturing Processes
4. CKC
Station X is the bottleneck – 2600 minutes
Work Station Product A Product B Total Load
W 10*90=900 14*85=1190 2090
X 10*90=900 20*85=1700 2600
Y 15*90=1350 11*85=935 2285
5. Super Fun Industries
a. Since the plant is open for (16 hours*5 days+8 hours)60 mins =5280 mins/week
A-148 takes 6 minutes at Processing Station 1: 5280/6 = 880 units
b. Station 1 is the bottleneck with a utilization of (4850/5280) = 91.9%.
A-148 B-356 B-457 C-843
Total
Weekly Demand 200 250 250 300 Load
Processing Time Station 1 6 5 0 8 4850
Processing Time Station 2 4 4 5 2 3650
Processing Time Station 3 5 7 4 2 4350
Processing Time Station 4 3 0 10 1 3400
Copyright © 2016 Pearson Education, Inc.
, Constraint Management l CHAPTER 5 5-3
6. Super Fun Industries continued
Station 3 is the new bottleneck with a utilization of (4500/5280) = 85.2%.
A-148 B-356 B-457 C-843
Total
Weekly Demand 100 400 250 100 Load
Processing Time Station 1 6 5 0 8 3400
Processing Time Station 2 4 4 5 2 3450
Processing Time Station 3 5 7 4 2 4500
Processing Time Station 4 3 0 10 1 2900
While maximizing the production of C-843, note that station 1 has the longest processing
time at 8 mins/unit. Thus 5280 mins of capacity – 3400 mins used =1880 mins
remaining. Additional units of C-843 that could be produced = 1880/8 = 235 units or
335 units produced in total. This calculation is confirmed in the table below.
A-148 B-356 B-457 C-843
Total
Weekly Demand 100 400 250 335 Load
Processing Time Station 1 6 5 0 8 5280
Processing Time Station 2 4 4 5 2 3920
Processing Time Station 3 5 7 4 2 4970
Processing Time Station 4 3 0 10 1 3135
7. YPI Bottleneck
Station W is the bottleneck
Work Station A B C Total Load
W 12*60= 720 9*80= 720 20*60= 1200 2640
X 10*60= 600 0 10*60 = 600 1200
Y 0 15*80=1200 5*60 = 300 1500
Z 12*60= 720 10*80=800 0 1520
Applying the Theory of Constraints to Product Mix Decisions
8. CKC
a. Traditional Method: Product B has the higher contribution margin/unit
Product A Product B
Price 55.00 65.00
Raw and Purchased Parts 5.00 10.00
Contribution Margin 50.00 55.00
Work Station Minutes at Mins. Left after Mins. Left after Can Only Make
Start Making 85 Bs Making 90 As 70 As
W 2400 1210 310
X 2400 700 700/10 = 70
Y 2400 1465 115
Copyright © 2016 Pearson Education, Inc.
5 Constraint Management
DISCUSSION QUESTIONS
1. Examples of everyday bottlenecks include traffic lights, drive-thru windows at the
bank or fast food restaurants. On the highway merging lanes and speed zones.
Efficiency can be improved by maintaining constant speeds, setting traffic lights to
coordinate traffic patterns and only allowing highway construction after rush hour.
Fast food restaurants have two windows, pull over spots and new cash card options
to reduce time at the window.
2. A change in demand can easily shift bottlenecks. For instance, fast food restaurants
can provide promotional pricing on certain types of sandwiches or fries, which
would make their workstations take longer than normal and become capacity
constrained. Banks can provide incentives for new accounts to be opened, causing
bottlenecks at teller windows where none existed before.
3. There are many ways that process efficiency may be improved further. In the case
of our banking example, a manager might: (1) reduce processing time by providing
forms to be filled out by the customer before the customer reaches the teller
window, (2) reduce processing variability by restricting each customer to three
transactions, (3) reduce the arrival variability of customers by requiring that
customers make an appointment to see a teller, (4) add resource capacity by
increasing the number of tellers during busy periods, (5) improve resource
flexibility by ensuring that all tellers are cross trained and will help co-workers with
complex transactions, (6) improve resource availability by restricting lunch and
break time for tellers, (7) coordinate the movement of customers by making sure
that all teller windows are available to all arriving customers, (8) outsource non-
value-adding activities such as rework by rerouting difficult customers to branch
management, and (9) create standardized work procedures for routine, non-complex
processes.
PROBLEMS
Managing Bottlenecks in Service Processes
1. Bill’s Barbershop
a. 10 + 8 + (15+10)/2 + 9 = 39.5 minutes
b. Step B1 is the bottleneck, it can only handle 6 customers per hour while the rest of
the steps can handle 7.5, 10 (60/10 +60/15), and 6.67 customers per hour.
5-1
Copyright © 2016 Pearson Education, Inc.
,5-2 l PART 1 l Managing Processes
c. This process is limited by step B1, therefore the entire process can only serve 6
customers per hour.
2. Melissa’s Photo Studio
a. 5 + (5+7)2 + 20 + 7 = 38 min
b. Taking group portraits is the bottleneck for the entire process. Only 3 group
portraits can be taken per hour.
c. Groups bottleneck is taking the portrait the bottleneck time is 20 min which
yields a capacity of 60/20 or 3 per hour. Individuals bottleneck is taking the
portrait which has a processing time of 15 min, which yields a capacity of 60/15
or 4 per hour.
3. Barbara’s Boutique
a. 3 [the bottleneck is step T4 at 18 minutes – 3.33 customers per hour or 3]
b. Step T6 at 22 minutes limits Type B to 60/22 = 2.73 customers/hr.
c. 3.33(.3) + 2.73(.7) = 2.91 customers on average
With an arrival rate greater than 5 customers per hour into the process, then type A
customers may wait at step T1, T2 and T4. Waiting occurs at these steps because
the arrival rate of customers into their step is greater than that step’s processing rate.
Also assuming that the arrival rate is greater than 5 customers per hour, type B
customers may wait steps T1, T5, and T6 because these steps’ processing times are
slower than the processing time of their immediate preceding steps.
Managing Bottlenecks in Manufacturing Processes
4. CKC
Station X is the bottleneck – 2600 minutes
Work Station Product A Product B Total Load
W 10*90=900 14*85=1190 2090
X 10*90=900 20*85=1700 2600
Y 15*90=1350 11*85=935 2285
5. Super Fun Industries
a. Since the plant is open for (16 hours*5 days+8 hours)60 mins =5280 mins/week
A-148 takes 6 minutes at Processing Station 1: 5280/6 = 880 units
b. Station 1 is the bottleneck with a utilization of (4850/5280) = 91.9%.
A-148 B-356 B-457 C-843
Total
Weekly Demand 200 250 250 300 Load
Processing Time Station 1 6 5 0 8 4850
Processing Time Station 2 4 4 5 2 3650
Processing Time Station 3 5 7 4 2 4350
Processing Time Station 4 3 0 10 1 3400
Copyright © 2016 Pearson Education, Inc.
, Constraint Management l CHAPTER 5 5-3
6. Super Fun Industries continued
Station 3 is the new bottleneck with a utilization of (4500/5280) = 85.2%.
A-148 B-356 B-457 C-843
Total
Weekly Demand 100 400 250 100 Load
Processing Time Station 1 6 5 0 8 3400
Processing Time Station 2 4 4 5 2 3450
Processing Time Station 3 5 7 4 2 4500
Processing Time Station 4 3 0 10 1 2900
While maximizing the production of C-843, note that station 1 has the longest processing
time at 8 mins/unit. Thus 5280 mins of capacity – 3400 mins used =1880 mins
remaining. Additional units of C-843 that could be produced = 1880/8 = 235 units or
335 units produced in total. This calculation is confirmed in the table below.
A-148 B-356 B-457 C-843
Total
Weekly Demand 100 400 250 335 Load
Processing Time Station 1 6 5 0 8 5280
Processing Time Station 2 4 4 5 2 3920
Processing Time Station 3 5 7 4 2 4970
Processing Time Station 4 3 0 10 1 3135
7. YPI Bottleneck
Station W is the bottleneck
Work Station A B C Total Load
W 12*60= 720 9*80= 720 20*60= 1200 2640
X 10*60= 600 0 10*60 = 600 1200
Y 0 15*80=1200 5*60 = 300 1500
Z 12*60= 720 10*80=800 0 1520
Applying the Theory of Constraints to Product Mix Decisions
8. CKC
a. Traditional Method: Product B has the higher contribution margin/unit
Product A Product B
Price 55.00 65.00
Raw and Purchased Parts 5.00 10.00
Contribution Margin 50.00 55.00
Work Station Minutes at Mins. Left after Mins. Left after Can Only Make
Start Making 85 Bs Making 90 As 70 As
W 2400 1210 310
X 2400 700 700/10 = 70
Y 2400 1465 115
Copyright © 2016 Pearson Education, Inc.
