discussed in detail in separate sections. The discussion includes situations in w hich elements of
lean have been successfully applied, as well as situations in which they may not be applicable
(e.g. smoothing the Master Production Schedule in services). The chapter concludes with
Teaching Notes
The lean systems chapter begins with a broad orientation to lean and its various elements
with an historical perspective of its development. Then each of the specific elements is
manage operations. Lean can also be broken down into its five main tenets, which serve as the
organizing scheme for the chapter. I then get specific about how lean is implemented by going
through a list of elements such as master production schedule, Kanban, set-up, layout, workers,
and suppliers. Interesting discussions can also be held on historical Japanese and U.S.
management practices.
Womack et al. describe lean production and lean thinking in their 1990, 1996 and 2003
Liker (2004), The Toyota Way, is a good current source of information. Several citations are also
provided for discussions of lean beyond manufacturing environments.
Answers to Questions
1. There is no unique answer to this question since it requires the student to conduct a field
project before responding. The purpose of the field project is to acquaint students with
repetitive manufacturing and possible applications of lean.
2. Repetitive manufacturing is when the master schedule is very similar on a daily or
– exposing and eliminating problems
– stabilizing the production time and the production levels
– reducing rework and scrap
– improving the production process
In the past, set-up times were long, primarily because they were not considered to be
waste. Long production runs and large lot sizes were used to compensate for inefficient
set-up times. Since managers were usually evaluated on the basis of unit production
costs, which decrease with larger lot sizes, they were indifferent to set-up times.
Utilizing a more contemporary lean philosophy, the supplier is commonly viewed as an
extension of the factory. Long-term relationships are encouraged and the supplier is
considered part of the team. This can lead in some cases to the use of single source
suppliers where prices and terms are negotiated well in advance of delivery. Lean views
the quality and the timeliness of deliveries with similar importance as price.
problems or parts shortages. They will be responsible for maintenance, machine set-up,
the inspection of the product, and the improvement of the production process. A new pay
system is usually implemented based on the worker’s flexibility, rather than seniority or
position.
9. Lean reduces costs by using value stream mapping and kaizen methods to take waste out
of the system. Lean also reduces inventory costs when using a pull system of production
control. Lean reduces material costs by adhering to strict quality control methods. For
example, when a production line is not functioning properly, it is stopped and repaired
these situations lean faces an increased risk of failure, and other manufacturing methods
should be considered.
12. Lean thinking can naturally be applied to accounting, finance or marketing processes. It
is a general approach that begins with asking what value the customer requires and then
determines how to best provide that value. Accounting, finance or marketing should ask
first who are their internal customers? Next, they should approach those customers to
find out what value they require and compare it to what is currently being provided.
equipment purchased (usually smaller), less emphasis on economies of scale, and the
investments required for inventory (less investment). Information systems are usually
simplified by less tracking of inventory and WIP and a more visual control system.
Transportation: movement of customers between several departments.
Processing: poor procedures (too many steps) for processing transactions.
Overproduction: idle time of staff due to imbalance in demand and staffing.
b. Some of the seven wastes in a doctor’s office:
Processing: non-value added steps in diagnosis and treatment.
Overproduction: having idle time in physicians or staff schedules.
15. a. Cafeteria value stream map:
Restaurant arrival departure
4 min 1 min 2 min 5 min 12 minutes wait time
get eat
5 minutes table 2 minutes 30 minutes rest 37 minutes process time
in aisles approval
Store arrival Store departure
9 minutes 10 minutes 2 mins 1 min 22 minutes wait time
*series of pick operations (e.g., 10 total minutes) and isle transfer times ( 9 minutes waiting)
Answers to Problems
1. a. Daily Requirements:
The sequence is determined by dividing each daily requirement by the largest
common multiple. In part a, it is 25. Therefore the sequence is:
A = 250/25 = 10
B = 125/25 = 5
required per day.
Daily Requirements:
A = 100/50 = 2
B = 150/50 = 3
C = 300/50 = 6
(3 × 100)/25 = 12 containers Note: 180 minutes = 3 hours
b. The maximum inventory is simply the container size times the number of
containers: 12 x 25 = 300 units
Number of containers (n) = D(T)/C = 125(4)/40 = 12.5 => 13 containers
b. Process takt time = 60 minutes/125 units/hour = 0.48 minutes/part
b. The effect of reducing container size would be to increase the number of
containers (n):
D(T)/C = 100,000(.012)/60 = 20.0
5. a. Scheduling the work centers on time lines provides a clear representation
of the situation:
Container 1
Move Set-up and Move
Use Parts at WC B Time Run Time – WC A Time
|___________________________________|________|_________________|_________|
0 50 60 90 100
we have: T = 30 + 10 + 50 + 10 = 100
The number of containers required is: (1)(100)/50 = 2
Time to complete the circuit = 49 minutes
(4 parts/min)(49 min) = 196 = 3.92 => 4 containers
50 parts/container 50
Time to complete the circuit = 42 minutes
(4 parts/min)(42 min) = 168 = 3.35 => 4 containers
50 parts/container 50
7. a. n = DT/C = (200/hour)(3 hrs)/(50 units/container) = 600/50 = 12
containers
b. Maximum inventory = nC = DT = (12 containers)(50 units/container) =
8. a. n = DT/C = 2(6)/12 = 1 truck
b. If the truck breaks down, the supplier will not be able to deliver the
necessary pallets on time. Thus one spare truck is probably needed to insure
delivery.
d. If the manufacturer shuts down for six hours, the supplier’s delivery cycle
will be disturbed. Delay could be announced by the customer when: a) the truck
is still at supplier’s plant, b) when the truck is on its way to the customer’s plant,
and c) when the truck is on its way back. In the first case the supplier has to keep
– exposing and eliminating problems
– stabilizing the production time and the production levels
– reducing rework and scrap
– improving the production process
In the past, set-up times were long, primarily because they were not considered to be
waste. Long production runs and large lot sizes were used to compensate for inefficient
set-up times. Since managers were usually evaluated on the basis of unit production
costs, which decrease with larger lot sizes, they were indifferent to set-up times.
Utilizing a more contemporary lean philosophy, the supplier is commonly viewed as an
extension of the factory. Long-term relationships are encouraged and the supplier is
considered part of the team. This can lead in some cases to the use of single source
suppliers where prices and terms are negotiated well in advance of delivery. Lean views
the quality and the timeliness of deliveries with similar importance as price.
problems or parts shortages. They will be responsible for maintenance, machine set-up,
the inspection of the product, and the improvement of the production process. A new pay
system is usually implemented based on the worker’s flexibility, rather than seniority or
position.
9. Lean reduces costs by using value stream mapping and kaizen methods to take waste out
of the system. Lean also reduces inventory costs when using a pull system of production
control. Lean reduces material costs by adhering to strict quality control methods. For
example, when a production line is not functioning properly, it is stopped and repaired
these situations lean faces an increased risk of failure, and other manufacturing methods
should be considered.
12. Lean thinking can naturally be applied to accounting, finance or marketing processes. It
is a general approach that begins with asking what value the customer requires and then
determines how to best provide that value. Accounting, finance or marketing should ask
first who are their internal customers? Next, they should approach those customers to
find out what value they require and compare it to what is currently being provided.
equipment purchased (usually smaller), less emphasis on economies of scale, and the
investments required for inventory (less investment). Information systems are usually
simplified by less tracking of inventory and WIP and a more visual control system.
Transportation: movement of customers between several departments.
Processing: poor procedures (too many steps) for processing transactions.
Overproduction: idle time of staff due to imbalance in demand and staffing.
b. Some of the seven wastes in a doctor’s office:
Processing: non-value added steps in diagnosis and treatment.
Overproduction: having idle time in physicians or staff schedules.
15. a. Cafeteria value stream map:
Restaurant arrival departure
4 min 1 min 2 min 5 min 12 minutes wait time
get eat
5 minutes table 2 minutes 30 minutes rest 37 minutes process time
in aisles approval
Store arrival Store departure
9 minutes 10 minutes 2 mins 1 min 22 minutes wait time
*series of pick operations (e.g., 10 total minutes) and isle transfer times ( 9 minutes waiting)
Answers to Problems
1. a. Daily Requirements:
The sequence is determined by dividing each daily requirement by the largest
common multiple. In part a, it is 25. Therefore the sequence is:
A = 250/25 = 10
B = 125/25 = 5
required per day.
Daily Requirements:
A = 100/50 = 2
B = 150/50 = 3
C = 300/50 = 6
(3 × 100)/25 = 12 containers Note: 180 minutes = 3 hours
b. The maximum inventory is simply the container size times the number of
containers: 12 x 25 = 300 units
Number of containers (n) = D(T)/C = 125(4)/40 = 12.5 => 13 containers
b. Process takt time = 60 minutes/125 units/hour = 0.48 minutes/part
b. The effect of reducing container size would be to increase the number of
containers (n):
D(T)/C = 100,000(.012)/60 = 20.0
5. a. Scheduling the work centers on time lines provides a clear representation
of the situation:
Container 1
Move Set-up and Move
Use Parts at WC B Time Run Time – WC A Time
|___________________________________|________|_________________|_________|
0 50 60 90 100
we have: T = 30 + 10 + 50 + 10 = 100
The number of containers required is: (1)(100)/50 = 2
Time to complete the circuit = 49 minutes
(4 parts/min)(49 min) = 196 = 3.92 => 4 containers
50 parts/container 50
Time to complete the circuit = 42 minutes
(4 parts/min)(42 min) = 168 = 3.35 => 4 containers
50 parts/container 50
7. a. n = DT/C = (200/hour)(3 hrs)/(50 units/container) = 600/50 = 12
containers
b. Maximum inventory = nC = DT = (12 containers)(50 units/container) =
8. a. n = DT/C = 2(6)/12 = 1 truck
b. If the truck breaks down, the supplier will not be able to deliver the
necessary pallets on time. Thus one spare truck is probably needed to insure
delivery.
d. If the manufacturer shuts down for six hours, the supplier’s delivery cycle
will be disturbed. Delay could be announced by the customer when: a) the truck
is still at supplier’s plant, b) when the truck is on its way to the customer’s plant,
and c) when the truck is on its way back. In the first case the supplier has to keep