Operations Management Processes And Supply Chains 12th Edition – Test Bank

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Operations Management: Processes and Supply Chains, 12e (Krajewski)

Chapter 5  Constraint Management

 

5.1  The Theory of Constraints

 

1) A bottleneck is an operation that has the lowest effective capacity of any operation in the process.

Answer:  TRUE

Difficulty:  Easy

Keywords:  bottleneck, effective capacity

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Explain the theory of constraints.

 

2) The process with the least capacity is called a bottleneck if its output is less than market demand.

Answer:  TRUE

Difficulty:  Moderate

Keywords:  bottleneck, capacity

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Explain the theory of constraints.

 

3) Constraints at any step causes imbalance in the capacity of a process. As a result, the overall performance of a system is affected which in turn leads to low customer satisfaction and loss of money even with high sales level.

Answer:  TRUE

Difficulty:  Moderate

Keywords:  capacity, customer satisfaction

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Explain the theory of constraints.

 

4) The Theory of Constraints method is also referred to as the drum-buffer-rope method.

Answer:  FALSE

Difficulty:  Easy

Keywords:  TOC, theory of constraints, drum-buffer-rope

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Explain the theory of constraints.

 

 

5) Any system composed of resources that are operating at maximum output will, by definition, have maximum output for the entire system.

Answer:  FALSE

Difficulty:  Moderate

Keywords:  constraint, bottleneck, TOC

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Explain the theory of constraints.

6) The first step in applying the Theory of Constraints is to identify the constraint.

Answer:  TRUE

Difficulty:  Moderate

Keywords:  constraint, bottleneck, TOC

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Explain the theory of constraints.

 

7) Lanny discovers that the bottleneck is the riveting machine so he schedules all production around when that machine is available. This is an example of elevating the constraint in the five-step constraint management process.

Answer:  FALSE

Difficulty:  Moderate

Keywords:  elevate bottleneck, TOC

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Explain the theory of constraints.

 

8) The focus for a process improvement exercise should be on balancing:

  1. A) flow.
  2. B) capacity.
  3. C) workload.
  4. D) time.

Answer:  A

Difficulty:  Moderate

Keywords:  TOC, theory of constraints, flow

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Explain the theory of constraints.

 

 

9) Consider consecutive processes A-B-C, where process A has a capacity of 20 units per hour, process B has a capacity of 25 units per hour, and process C has a capacity of 30 units per hour. Where would an operations manager want any inventory?

  1. A) in front of process A
  2. B) in front of process B
  3. C) in front of process C
  4. D) Inventory should not exist anywhere.

Answer:  A

Difficulty:  Moderate

Keywords:  TOC, theory of constraints, inventory

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Explain the theory of constraints.

10) Use the process flow diagram to determine which of these events has the greatest net benefit.

 

 

  1. A) reducing the flow time at Station A from 8 to 7 minutes
  2. B) increasing the capacity at Station B to 8 units per hour
  3. C) increasing the capacity at Station C to 7 units per hour
  4. D) reducing the flow time at Station D from 9 to 8 minutes

Answer:  C

Difficulty:  Moderate

Keywords:  TOC, theory of constraints, bottleneck

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Explain the theory of constraints.

 

 

11) Use the process flow diagram to determine which of these events has the greatest net benefit.

 

 

  1. A) reducing the flow time at Station A from 10 to 8 minutes
  2. B) increasing the capacity at Station B to 12 units per hour
  3. C) increasing the capacity at Station C to 10 units per hour
  4. D) reducing the flow time at Station D from 12 to 10 minutes

Answer:  D

Difficulty:  Moderate

Keywords:  TOC, theory of constraints, bottleneck

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Explain the theory of constraints.

12) Use the process flow diagram to determine which of these events has the greatest net benefit.

 

 

  1. A) reducing the flow time at Station A from 8 to 7 minutes
  2. B) increasing the capacity at Station B to 12 units per hour
  3. C) increasing the capacity at Station C to 9 units per hour
  4. D) reducing the flow time at Station D from 6 to 5 minutes

Answer:  A

Difficulty:  Moderate

Keywords:  TOC, theory of constraints, bottleneck

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Explain the theory of constraints.

 

 

13) Work should be released into the system when:

  1. A) a customer order is received.
  2. B) the first step in the process is idle.
  3. C) a customer order is completed.
  4. D) the bottlenecks need work.

Answer:  D

Difficulty:  Moderate

Keywords:  TOC, theory of constraints, bottleneck

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Explain the theory of constraints.

 

14) The second step in Theory of Constraints application, “exploit the bottleneck(s),” means that the analyst should:

  1. A) create a schedule that maximizes the throughput of the bottlenecks.
  2. B) repeat the analysis process to look for other bottlenecks.
  3. C) consider increasing capacity of the bottleneck.
  4. D) schedule non-bottleneck resources to support the bottleneck.

Answer:  A

Difficulty:  Moderate

Keywords:  bottleneck, TOC, theory of constraints

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Explain the theory of constraints.

15) The third step in Theory of Constraints application, “subordinate all other decisions to Step 2,” means that the analyst should:

  1. A) wait for authorization before proceeding with any system-wide changes.
  2. B) schedule non-bottleneck resources to support the bottleneck schedule.
  3. C) seek to increase capacity of only the bottleneck resources.
  4. D) seek to increase capacity of both the bottleneck and non-bottleneck resources.

Answer:  B

Difficulty:  Moderate

Keywords:  bottleneck, TOC, theory of constraints

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Explain the theory of constraints.

 

 

16) The fourth step in Theory of Constraints application, “elevate the bottleneck(s),” means that the analyst should:

  1. A) create a schedule that maximizes the throughput of the bottlenecks.
  2. B) repeat the analysis process to look for other bottlenecks.
  3. C) consider increasing capacity of the bottleneck.
  4. D) schedule non-bottleneck resources to support the bottleneck.

Answer:  C

Difficulty:  Moderate

Keywords:  bottleneck, TOC, theory of constraints

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Explain the theory of constraints.

 

17) The fifth step in Theory of Constraints application, “do not let inertia set in,” means that the analyst should:

  1. A) create a schedule that maximizes the throughput of the bottlenecks.
  2. B) repeat the analysis to identify and manage new set of constraints.
  3. C) consider increasing capacity of the bottleneck.
  4. D) schedule non-bottleneck resources to support the bottleneck.

Answer:  B

Difficulty:  Moderate

Keywords:  bottleneck, TOC, theory of constraints

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Explain the theory of constraints.

 

18) Any factor that limits the performance of a system and restricts its output is a(n) ________.

Answer:  constraint

Difficulty:  Easy

Keywords:  constraint

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Explain the theory of constraints.

19) ________ is the maximum rate of output of a process or a system.

Answer:  Capacity

Difficulty:  Easy

Keywords:  capacity

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Explain the theory of constraints.

 

 

20) A(n) ________ is an operation that has the lowest effective capacity of any operation in the process, and thus limits the system’s output.

Answer:  bottleneck

Difficulty:  Easy

Keywords:  bottleneck, TOC, output

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Explain the theory of constraints.

 

21) According to the Theory of Constraints, all the money invested in a system in purchasing things that it intends to sell is ________.

Answer:  inventory

Difficulty:  Easy

Keywords:  inventory, TOC

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Explain the theory of constraints.

 

22) The wages paid to workers on the line are categorized as ________ in the Theory of Constraints.

Answer:  operational expense

Difficulty:  Easy

Keywords:  operating expense

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Explain the theory of constraints.

 

23) Explain why a bottleneck limits system output.

Answer:  A bottleneck, by definition, is a process that has less capacity than all other processes in the system. Just as a chain is as strong as its weakest link, the rest of a production system can produce only as much as the slowest process. The bottleneck limits capacity by serving to slow the rest of the system down. Running all other processes at their maximum capacity will result in inventory buildup in front of the bottleneck.

Difficulty:  Moderate

Keywords:  bottleneck, output, TOC

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Explain the theory of constraints.

 

24) What are five of the seven key principles of the Theory of Constraints?

Answer:  The principles of TOC are:

The focus should be on balancing flow, not on balancing capacity.

Maximizing the output and efficiency of every resource may not maximize the throughput of the entire system.

An hour lost at a bottleneck or a constrained resource is an hour lost for the whole system. In contrast, an hour saved at a nonbottleneck resource is a mirage because it does not make the whole system more productive.

Inventory is needed only in front of the bottlenecks in order to prevent them from sitting idle, and in front of assembly and shipping points in order to protect customer schedules. Building inventories elsewhere should be avoided.

Work, which can be materials, information to be processed, documents, or customers, should be released into the system only as frequently as the bottlenecks need it. Bottleneck flows should be equal to the market demand. Pacing everything to the slowest resource minimizes inventory and operating expenses.

Activating a nonbottleneck resource (using it for improved efficiency that does not increase throughput) is not the same as utilizing a bottleneck resource (that does lead to increased throughput). Activation of nonbottleneck resources cannot increase throughput, nor promote better performance on financial measures outlined in Table 5.1.

Every capital investment must be viewed from the perspective of its global impact on overall throughput (T), inventory (I), and operating expense (OE).

Difficulty:  Moderate

Keywords:  TOC, steps

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Explain the theory of constraints.

 

25) Describe a process from your own personal experience at home or work that suffers from a lack of sufficient throughput. Apply the first four TOC steps to address the situation, assuming you have complete authority to do so.

Answer:  Examples will vary. The steps of TOC are (1) identify the system bottleneck(s); (2) exploit the bottlenecks; (3) subordinate all other decisions to step 2; (4) elevate the bottleneck(s); and (5) do not let inertia set in.

Difficulty:  Moderate

Keywords:  TOC, steps

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Explain the theory of constraints.

 

5.2  Managing Bottlenecks in Service Processes

 

1) There are three consecutive steps in a customer service process. The first two steps are each capable of serving 25 customers per hour while the third step can process only 20 customers per hour. Which of the following statements regarding this system is true?

  1. A) The entire system is capable of processing 25 customers per hour.
  2. B) There are floating bottlenecks in the system.
  3. C) If the first two steps are run at full capacity, then the third step has a waiting line.
  4. D) The first and second steps are bottlenecks for the system.

Answer:  C

Difficulty:  Moderate

Keywords:  capacity, bottleneck

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Identify and manage bottlenecks in service processes.

 

Figure 5.1

 

The figure above shows the process for paying tuition at a major university. Students receive their bill, for the next term, for review. They are directed to different tables for clarifications, before being asked to pay their tuition at E. The numbers in parentheses are the time in minutes for each step of the process.

 

2) Use the information in Figure 5.1. What is the throughput time for the A-B-C-E process route?

  1. A) 17 minutes
  2. B) 27 minutes
  3. C) 21 minutes
  4. D) 19 minutes

Answer:  A

Difficulty:  Easy

Keywords:  bottleneck, throughput time

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Identify and manage bottlenecks in service processes.

 

3) Use the information in Figure 5.1. What is the throughput time for the A-B-D-E process route?

  1. A) 17 minutes
  2. B) 27 minutes
  3. C) 21 minutes
  4. D) 19 minutes

Answer:  C

Difficulty:  Easy

Keywords:  bottleneck, throughput time

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Identify and manage bottlenecks in service processes.

 

4) Use the information in Figure 5.1. What is the capacity for the A-B-C-E process route?

  1. A) 10 students per hour
  2. B) 6 student per hour
  3. C) 3.5 students per hour
  4. D) 2.9 students per hour

Answer:  A

Difficulty:  Moderate

Keywords:  bottleneck, throughput time

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Identify and manage bottlenecks in service processes.

 

5) Use the information in Figure 5.1. What is the capacity for the A-B-D-E process route?

  1. A) 10 students per hour
  2. B) 6 student per hour
  3. C) 3.5 students per hour
  4. D) 2.9 students per hour

Answer:  B

Difficulty:  Moderate

Keywords:  capacity

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Identify and manage bottlenecks in service processes.

 

 

6) Use the information in Figure 5.1. If 60% of the students are routed to C and 40% are routed to D, what is the average capacity per hour for the process?

  1. A) 10 students per hour
  2. B) 6.5 student per hour
  3. C) 8 students per hour
  4. D) 8.4 students per hour

Answer:  D

Difficulty:  Challenging

Keywords:  bottleneck, capacity

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Identify and manage bottlenecks in service processes.

7) Use the information in Figure 5.1. Where would you expect student wait times to occur?

  1. A) D only
  2. B) B, C and D
  3. C) A only
  4. D) E only

Answer:  B

Difficulty:  Challenging

Keywords:  bottleneck, capacity, customer wait times

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Identify and manage bottlenecks in service processes.

 

 

Figure 5.2

 

The figure above shows the process for customers arriving at Pierre’s Spa and Salon. After signing in, customers are routed to different locations in the Spa for the two different services provided. The numbers in parentheses are the time in minutes for each step of the process.

 

8) Use the information in Figure 5.2. What is the throughput time for the A-B-C-D-H routing?

  1. A) 48 minutes
  2. B) 30 minutes
  3. C) 53 minutes
  4. D) 23 minutes

Answer:  C

Difficulty:  Easy

Keywords:  bottleneck, throughput time

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Identify and manage bottlenecks in service processes.

 

9) Use the information in Figure 5.2. What is the throughput time for the A-B-E-F-G-H routing?

  1. A) 48 minutes
  2. B) 30 minutes
  3. C) 53 minutes
  4. D) 23 minutes

Answer:  A

Difficulty:  Easy

Keywords:  bottleneck, throughput time

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Identify and manage bottlenecks in service processes.

 

10) Use the information in Figure 5.2. What is the process bottleneck?

  1. A) H
  2. B) B
  3. C) C
  4. D) D

Answer:  D

Difficulty:  Moderate

Keywords:  bottleneck

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Identify and manage bottlenecks in service processes.

 

Figure 5.3

 

The figure above shows the process for customers arriving at Hobbies Unlimited for several advertised crafts demonstrations. After signing in, customers are routed to different locations in the store for the two different programs provided. The numbers in parentheses are the time in minutes for each step of the process.

 

11) Use the information in Figure 5.3 What is the throughput time for the A-B-C-D-G routing?

  1. A) 25 minutes
  2. B) 70 minutes
  3. C) 105 minutes
  4. D) 60 minutes

Answer:  D

Difficulty:  Easy

Keywords:  bottleneck, throughput time

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Identify and manage bottlenecks in service processes.

 

 

12) Use the information in Figure 5.3. What is the throughput time for the A-B-E-F-G routing?

  1. A) 25 minutes
  2. B) 70 minutes
  3. C) 105 minutes
  4. D) 60 minutes

Answer:  B

Difficulty:  Easy

Keywords:  bottleneck, throughput time

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Identify and manage bottlenecks in service processes.

13) Use the information in Figure 5.3. How many customers can be processed through the A-B-C-D-G routing during a 4-hour evening session?

  1. A) 48
  2. B) 24
  3. C) 32
  4. D) 12

Answer:  D

Difficulty:  Moderate

Keywords:  bottleneck, throughput time

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Identify and manage bottlenecks in service processes.

 

14) Use the information in Figure 5.3. How many customers can be processed through the A-B-E-F-G routing during a 4-hour evening session?

  1. A) 8
  2. B) 24
  3. C) 12
  4. D) 32

Answer:  A

Difficulty:  Moderate

Keywords:  bottleneck, throughput time

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Identify and manage bottlenecks in service processes.

 

15) ________ is the total time taken from the start to the finish of a process.

Answer:  Throughput time

Difficulty:  Easy

Keywords:  throughput time

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Identify and manage bottlenecks in service processes.

 

 

16) Variability of a firm’s workload may create ________.

Answer:  floating bottlenecks

Difficulty:  Challenging

Keywords:  workload, variability, floating bottleneck

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Identify and manage bottlenecks in service processes.

17) What are two ways a process manager can identify a bottleneck in a service or manufacturing process? If you were in a manufacturing firm, what physical cues would signal a bottleneck?

Answer:  A workstation in a process is a bottleneck if 1) it has the highest total time per unit processed, or 2) it has the highest average utilization and total workload. Generally, the bottleneck has a pile of materials in front of it waiting to be processed.

Difficulty:  Moderate

Keywords:  bottleneck

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Identify and manage bottlenecks in service processes.

 

5.3  Managing Bottlenecks in Manufacturing Processes

 

1) A bottleneck process has the lowest capacity and the longest total time from the start to the finish.

Answer:  TRUE

Difficulty:  Moderate

Keywords:  bottleneck process, lowest capacity, longest total time

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Identify and manage bottlenecks in manufacturing processes.

 

2) A competent operations manager should first eliminate all of the bottlenecks from the process.

Answer:  FALSE

Difficulty:  Moderate

Keywords:  bottleneck process

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Identify and manage bottlenecks in manufacturing processes.

 

3) Short term capacity planning should be driven by identification and management of bottlenecks.

Answer:  TRUE

Difficulty:  Moderate

Keywords:  capacity planning, bottleneck

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Identify and manage bottlenecks in manufacturing processes.

 

 

4) The key to preserving bottleneck capacity is to watch them carefully and keep them as busy as practical.

Answer:  TRUE

Difficulty:  Easy

Keywords:  bottleneck

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Identify and manage bottlenecks in manufacturing processes.

5) In a drum-buffer-rope system, the lot size that moves from one work center to another for additional processing is a(n):

  1. A) process batch.
  2. B) operations batch.
  3. C) transfer batch.
  4. D) rope batch.

Answer:  C

Difficulty:  Easy

Keywords:  DBR, drum-buffer-rope, transfer batch

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Identify and manage bottlenecks in manufacturing processes.

 

6) The process batch at the constraint in a drum-buffer-rope system should be:

  1. A) the same size as that at any non-constraint.
  2. B) the same size as the transfer batch.
  3. C) of such a size as to maximize the number of setups for the constraint.
  4. D) of such a size as to improve utilization of the constraint.

Answer:  D

Difficulty:  Easy

Keywords:  DBR, drum-buffer-rope, process, batch, size

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Identify and manage bottlenecks in manufacturing processes.

 

7) Which statement about transfer batch sizes is best?

  1. A) Transfer batches are the same size as process batches when arriving at a bottleneck.
  2. B) Transfer batches are the same size as process batches when departing from a bottleneck.
  3. C) Transfer batches are a convenient way to increase lead time.
  4. D) Transfer batches can be as small as one unit.

Answer:  D

Difficulty:  Moderate

Keywords:  transfer batch, process batch

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Identify and manage bottlenecks in manufacturing processes.

 

 

8) Which statement about process batches is best?

  1. A) One or more transfer batches may combine at the constrain buffer to form a process batch.
  2. B) A process batch is used to maximize setups at the bottleneck.
  3. C) A process batch must be greater than or equal to market demand.
  4. D) Process batches are used to increase lead time.

Answer:  A

Difficulty:  Moderate

Keywords:  transfer batch, process batch

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Identify and manage bottlenecks in manufacturing processes.

9) ________ is a planning and control system that regulates the flow of work-in-process materials at the bottleneck or the capacity constrained resource in a productive system.

Answer:  Drum-buffer-rope (DBR)

Difficulty:  Easy

Keywords:  drum-buffer-rope, DBR, CCR, capacity constrained resource, bottleneck

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Identify and manage bottlenecks in manufacturing processes.

 

10) Every time a manufacturer uses one resource, they make a lot size of 300. Once a group of 30 units are completed, they are taken to the next step in the process. The lot of 300 is the ________ and the group of 30 is the ________.

Answer:  production batch, transfer batch

Difficulty:  Moderate

Keywords:  production batch, transfer batch

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Identify and manage bottlenecks in manufacturing processes.

 

 

11) What is a Drum-Buffer-Rope system for planning and control?

Answer:  Drum-Buffer-Rope (DBR) is a planning and control system based on the theory of constraints that is often used in manufacturing firms to plan and schedule production. It works by regulating the flow of work-in-process materials at the bottleneck or the capacity constrained resource (CCR). The bottleneck schedule is the drum because it sets the beat or the production rate for the entire plant and is linked to the market demand. The buffer is a time buffer that plans early flows to the bottleneck and thus protects it from disruption. It also ensures that the bottleneck is never starved for work. A finished-goods inventory buffer can also be placed in front of the shipping point in order to protect customer shipping schedules. Finally, the rope represents the tying of material release to the drum beat, which is the rate at which the bottleneck controls the throughput of the entire plant. It is thus a communication device to ensure that raw material is not introduced into the system at a rate faster than what the bottleneck can handle. Completing the loop, buffer management constantly monitors the execution of incoming bottleneck work. Working together, the drum, the buffer, and the rope can help managers create a production schedule that reduces lead times and inventories while simultaneously increasing throughput and on-time delivery.

Difficulty:  Moderate

Keywords:  bottleneck

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Identify and manage bottlenecks in manufacturing processes.

5.4  Applying the Theory of Constraints to Product Mix Decisions

 

1) Managers should produce products with the highest contribution margins or unit sales, provided they have market demand for them.

Answer:  FALSE

Difficulty:  Moderate

Keywords:  contribution margin

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Apply the theory of constraints to product mix decisions.

 

2) A firm’s actual throughput and profit depend more on the contribution margin generated at the bottleneck than by the contribution margin of each individual product produced.

Answer:  TRUE

Difficulty:  Moderate

Keywords:  contribution margin

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Apply the theory of constraints to product mix decisions.

 

Table 5.1

A company makes four products that have the following characteristics: Product A sells for $50 but needs $10 of materials and $15 of labor to produce; Product B sells for $75 but needs $30 of materials and $15 of labor to produce; Product C sells for $100 but needs $50 of materials and $30 of labor to produce; Product D sells for $150 but needs $75 of materials and $40 of labor to produce. The processing requirements for each product on each of the four machines are shown in the table.

 

 

Work centers W, X, Y, and Z are available for 40 hours per week and have no setup time when switching between products. Market demand for each product is 80 units per week. In the questions that follow, the traditional method refers to maximizing the contribution margin per unit for each product, and the bottleneck method refers to maximizing the contribution margin per minute at the bottleneck for each product.

 

3) Use the information in Table 5.1. Which work center is of greatest concern to the operations manager?

  1. A) Work Center W
  2. B) Work Center X
  3. C) Work Center Y
  4. D) Work Center Z

Answer:  B

Difficulty:  Moderate

Keywords:  TOC, bottleneck

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Apply the theory of constraints to product mix decisions.

 

4) Use the information in Table 5.1. Using the traditional method, which product should be scheduled first?

  1. A) Product A
  2. B) Product B
  3. C) Product C
  4. D) Product D

Answer:  D

Difficulty:  Moderate

Keywords:  TOC, bottleneck, profit per minute at bottleneck

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Apply the theory of constraints to product mix decisions.

 

5) Use the information in Table 5.1. Using the traditional method, in what sequence should products be scheduled for production?

  1. A) D, C, B, A
  2. B) D, B, A, C
  3. C) C, D, A, B
  4. D) C, D, B, A

Answer:  B

Difficulty:  Moderate

Keywords:  TOC, bottleneck, sequence, profit per minute at bottleneck

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Apply the theory of constraints to product mix decisions.

 

6) Use the information in Table 5.1. Using the traditional method, what is the optimal product mix (consider variable costs only—overhead is not included in this profit calculation)?

  1. A) 71 A, 80B, 80C, 80 D
  2. B) 80A, 72B, 80C, 80D
  3. C) 80A, 80B, 60C, 80D
  4. D) 80A, 80B, 80C, 70D

Answer:  C

Difficulty:  Challenging

Keywords:  TOC, bottleneck, profit per minute at bottleneck, mix

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Apply the theory of constraints to product mix decisions.

 

7) Use the information in Table 5.1. Using the traditional method, what is the profit if the company manufactures the optimal product mix (consider variable costs only—overhead is not included in this profit calculation)?

  1. A) less than or equal to $8,100
  2. B) greater than $8,100 but less than or equal to $8,300
  3. C) greater than $8,300 but less than or equal to $8,500
  4. D) greater than $8,500

Answer:  C

Difficulty:  Challenging

Keywords:  TOC, bottleneck, profit per minute at bottleneck, mix

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Apply the theory of constraints to product mix decisions.

 

8) Use the information in Table 5.1. Using the bottleneck method, which product should be scheduled first?

  1. A) Product A
  2. B) Product B
  3. C) Product C
  4. D) Product D

Answer:  C

Difficulty:  Challenging

Keywords:  TOC, bottleneck, profit per minute at bottleneck

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Apply the theory of constraints to product mix decisions.

 

9) Use the information in Table 5.1. Using the bottleneck method, in what sequence should products be scheduled for production?

  1. A) D, C, B, A
  2. B) D, C, A, B
  3. C) C, D, A, B
  4. D) C, D, B, A

Answer:  D

Difficulty:  Challenging

Keywords:  TOC, bottleneck, sequence, profit per minute at bottleneck

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Apply the theory of constraints to product mix decisions.

 

10) Use the information in Table 5.1. Using the bottleneck method, what is the optimal product mix (consider variable costs only—overhead is not included in this profit calculation)?

  1. A) 71 A, 80B, 80C, 80 D
  2. B) 80A, 72B, 80C, 80D
  3. C) 80A, 80B, 60C, 80D
  4. D) 80A, 80B, 80C, 70D

Answer:  A

Difficulty:  Challenging

Keywords:  TOC, bottleneck, profit per minute at bottleneck, mix

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Apply the theory of constraints to product mix decisions.

 

11) Use the information in Table 5.1. Using the bottleneck method, what is the profit if the company manufactures the optimal product mix (consider variable costs only—overhead is not included in this profit calculation)?

  1. A) less than or equal to $8,100
  2. B) greater than $8,100 but less than or equal to $8,300
  3. C) greater than $8,300 but less than or equal to $8,500
  4. D) greater than $8,500

Answer:  D

Difficulty:  Challenging

Keywords:  TOC, bottleneck, profit per minute at bottleneck, mix

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Apply the theory of constraints to product mix decisions.

 

Table 5.2

A company makes four products that have the following characteristics: Product A sells for $75 but needs $20 of materials and $20 of labor to produce; Product B sells for $90 but needs $45 of materials and $20 of labor to produce; Product C sells for $110 but needs $50 of materials and $30 of labor to produce; Product D sells for $135 but needs $75 of materials and $40 of labor to produce. The processing requirements for each product on each of the four machines are shown in the table.

 

 

Work centers W, X, Y, and Z are available for 40 hours per week and have no setup time when switching between products. Market demand is 50 As, 60 Bs, 70 Cs, and 80 Ds per week. In the questions that follow, the traditional method refers to maximizing the contribution margin per unit for each product, and the bottleneck method refers to maximizing the contribution margin per minute at the bottleneck for each product.

 

12) Use the information in Table 5.2. Which work center is the bottleneck operation?

  1. A) Work Center W
  2. B) Work Center X
  3. C) Work Center Y
  4. D) Work Center Z

Answer:  C

Difficulty:  Moderate

Keywords:  TOC, bottleneck

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Apply the theory of constraints to product mix decisions.

13) Use the information in Table 5.2. Using the traditional method, which product should be scheduled first?

  1. A) Product A
  2. B) Product B
  3. C) Product C
  4. D) Product D

Answer:  A

Difficulty:  Moderate

Keywords:  TOC, bottleneck

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Apply the theory of constraints to product mix decisions.

 

14) Use the information in Table 5.2. Using the traditional method, in what sequence should products be scheduled for production?

  1. A) A, B, C, D
  2. B) A, C, B, D
  3. C) A, D, B, C
  4. D) D, B, C, A

Answer:  B

Difficulty:  Moderate

Keywords:  TOC, bottleneck

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Apply the theory of constraints to product mix decisions.

 

15) Use the information in Table 5.2. Using the traditional method, what is the optimal product mix?

  1. A) 37 A, 60 B, 70 C, 80 D
  2. B) 50 A, 51 B, 70 C, 80 D
  3. C) 50 A, 60 B, 62 C, 80 D
  4. D) 50 A, 60 B, 70 C, 60 D

Answer:  D

Difficulty:  Challenging

Keywords:  TOC, bottleneck

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Apply the theory of constraints to product mix decisions.

 

16) Use the information in Table 5.2. Using the traditional method, what is the profit if the company manufactures the optimal product mix (consider variable costs only—overhead is not included in this profit calculation)?

  1. A) less than or equal to $6,500
  2. B) greater than $6,500 but less than or equal to $6,700
  3. C) greater than $6,700 but less than or equal to $6,900
  4. D) greater than $6,900

Answer:  B

Difficulty:  Challenging

Keywords:  TOC, bottleneck, profit per minute at bottleneck, mix

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Apply the theory of constraints to product mix decisions.

 

17) Use the information in Table 5.2. Using the bottleneck method, which product should be scheduled first?

  1. A) Product A
  2. B) Product B
  3. C) Product C
  4. D) Product D

Answer:  A

Difficulty:  Challenging

Keywords:  TOC, bottleneck

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Apply the theory of constraints to product mix decisions.

 

18) Use the information in Table 5.2. Using the bottleneck method, in what sequence should products be scheduled for production?

  1. A) A, D, B, C
  2. B) D, A, B, C
  3. C) A, D, C, B
  4. D) D, A, C, B

Answer:  C

Difficulty:  Challenging

Keywords:  TOC, bottleneck

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Apply the theory of constraints to product mix decisions.

 

19) Use the information in Table 5.2. Using the bottleneck method, what is the optimal product mix?

  1. A) 37 A, 60 B, 70 C, 80 D
  2. B) 50 A, 51 B, 70 C, 80 D
  3. C) 50 A, 60 B, 62 C, 80 D
  4. D) 50 A, 60 B, 70 C, 60 D

Answer:  B

Difficulty:  Challenging

Keywords:  TOC, bottleneck

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Apply the theory of constraints to product mix decisions.

 

20) Use the information in Table 5.2. Using the bottleneck method, what is the profit if the company manufactures the optimal product mix (consider variable costs only—overhead is not included in this profit calculation)?

  1. A) less than or equal to $6,500
  2. B) greater than $6,500 but less than or equal to $6,700
  3. C) greater than $6,700 but less than or equal to $6,900
  4. D) greater than $6,900

Answer:  C

Difficulty:  Challenging

Keywords:  TOC, bottleneck

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Apply the theory of constraints to product mix decisions.

 

Table 5.3

King Supply makes four different types of plumbing fixtures: W, X, Y and Z. The contribution margins for these products are: $70 for Product W, $60 for Product X, $90 for Product Y and $100 for Product Z. Fixed overhead is estimated at $5,500 per week. The manufacture of each fixture requires four machines, Machines #1, 2, 3 and 4. Each of the machines is available for 40 hours a week and there is no setup time required when shifting from the production of one product to any other. The processing requirements to make one unit of each product are shown in the table. Weekly product demand for the next planning period has been forecasted as follows: 70 Ws, 60 Xs, 50 Ys and 30 Zs.

 

 

In the questions that follow, the traditional method refers to maximizing the contribution margin per unit for each product, and the bottleneck method refers to maximizing the contribution margin per minute at the bottleneck for each product.

 

21) Use the information in Table 5.3. Which machine is the bottleneck operation?

  1. A) Machine 1
  2. B) Machine 2
  3. C) Machine 3
  4. D) Machine 4

Answer:  A

Difficulty:  Moderate

Keywords:  TOC, bottleneck

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Apply the theory of constraints to product mix decisions.

 

22) Use the information in Table 5.3. Using the traditional method, which product should be scheduled first?

  1. A) Fixture W
  2. B) Fixture X
  3. C) Fixture Y
  4. D) Fixture Z

Answer:  D

Difficulty:  Moderate

Keywords:  TOC, bottleneck

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Apply the theory of constraints to product mix decisions.

 

23) Use the information in Table 5.3. Using the traditional method, in what sequence should the fixtures be scheduled for production?

  1. A) Z, Y, X, W
  2. B) X, W, Z, Y
  3. C) Z, Y, W, X
  4. D) W, X, Y, Z

Answer:  C

Difficulty:  Moderate

Keywords:  TOC, bottleneck

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Apply the theory of constraints to product mix decisions.

 

24) Use the information in Table 5.3. Using the traditional method, what is the optimal product mix?

  1. A) 70 W, 60 X, 90 Y, 100 Z
  2. B) 70 W, 50 X, 50 Y, 30 Z
  3. C) 70 W, 60 X, 47 Y, 30 Z
  4. D) 70 W, 47 X, 50 Y, 30 Z

Answer:  B

Difficulty:  Challenging

Keywords:  TOC, theory of constraints

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Apply the theory of constraints to product mix decisions.

 

25) Use the information in Table 5.3. Using the traditional method, what is the profit if King Supply manufactures the optimal product mix?

  1. A) less than or equal to $10,000
  2. B) greater than $10,000 but less than or equal to $11,000
  3. C) greater than $11,000 but less than or equal to $12,000
  4. D) greater than $12,000

Answer:  A

Difficulty:  Challenging

Keywords:  TOC, theory of constraints

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Apply the theory of constraints to product mix decisions.

 

26) Use the information in Table 5.3. Using the bottleneck method, which product should be scheduled first?

  1. A) Fixture W
  2. B) Fixture X
  3. C) Fixture Y
  4. D) Fixture Z

Answer:  B

Difficulty:  Challenging

Keywords:  TOC, theory of constraints

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Apply the theory of constraints to product mix decisions.

 

27) Use the information in Table 5.3. Using the bottleneck method, in what sequence should products be scheduled for production?

  1. A) Z, Y, X, W
  2. B) X, W, Z, Y
  3. C) Z, Y, W, X
  4. D) X, Y, Z, W

Answer:  B

Difficulty:  Challenging

Keywords:  TOC, theory of constraints

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Apply the theory of constraints to product mix decisions.

 

28) Use the information in Table 5.3. Using the bottleneck method, what is the optimal product mix?

  1. A) 70 W, 60 X, 90 Y, 100 Z
  2. B) 70 W, 50 X, 50 Y, 30 Z
  3. C) 70 W, 60 X, 47 Y, 30 Z
  4. D) 70 W, 47 X, 50 Y, 30 Z

Answer:  C

Difficulty:  Challenging

Keywords:  TOC, theory of constraints

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Apply the theory of constraints to product mix decisions.

 

29) Use the information in Table 5.3. Using the bottleneck method, what is the profit if Burdell manufactures the optimal product mix?

  1. A) less than or equal to $10,000
  2. B) greater than $10,000 but less than or equal to $11,000
  3. C) greater than $11,000 but less than or equal to $12,000
  4. D) greater than $12,000

Answer:  B

Difficulty:  Challenging

Keywords:  TOC, bottleneck, profit per minute at bottleneck, mix, profit

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Apply the theory of constraints to product mix decisions.

 

30) Instead of producing products with the highest profit margins, operations managers should focus on the ________ generated at the ________.

Answer:  profit (margin), bottleneck

Difficulty:  Moderate

Keywords:  TOC, bottleneck, profit, profit margin

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Apply the theory of constraints to product mix decisions.

 

31) The traditional method of determining contribution margin does not consider ________ costs.

Answer:  fixed

Difficulty:  Moderate

Keywords:  contribution margin

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Apply the theory of constraints to product mix decisions.

 

32) What is contribution margin for a product? How might it be used to manage the productive resources on a shop floor?

Answer:  Contribution margin is the amount each product contributes to profits and overhead. Determining which product has the highest contribution margin and producing it at the expense of other products is the traditional method of shop floor management. The Theory of Constraints instead studies product’s contribution margin based on bottleneck usage, which may be entirely different.

Difficulty:  Moderate

Keywords:  bottleneck

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Apply the theory of constraints to product mix decisions.

 

 

33) Schmidt Industries makes four different snake traps; the Harlan, the Gaylen, the Leah and the Matthew. The Harlan sells for $200 and has $40 in parts and $40 in labor; the Gaylen sells for $150 and requires $30 in parts and $30 in labor; the Leah sells for $100 and has $20 in parts and $20 in labor; and the Matthew sells for $75 but requires only $10 of parts and $10 of labor. Schmidt Industries has four machines (we’ll call them A, B, C, and D for convenience) that are used in the production of each of these products. Each of these machines is available for 40 hours a week and there is no setup time required when shifting from the production of one product to any other. The processing requirements to make one unit of each product are shown in the table.

 

 

Schmidt Industries has monthly fixed costs of $5,000 and has a demand forecast of 80 Harlans, 60 Gaylens, 40 Leahs and 20 Matthews for the coming month. How many of each of the four models should Susan, the operations manager, schedule for production this month?

Answer:  The processing requirements for the demand forecast result in a need for:

 

Machine A: 80 × 10 + 60 × 10 + 40 × 5 + 20 × 5 = 1,700 ≤ 2,400

Machine B: 80 × 15 + 60 × 10 + 40 × 10 + 20 × 10 = 2,400 ≤ 2,400

Machine C: 80 × 15 + 60 × 10 + 40 × 15 + 20 × 10 = 2,600 ≰ 2,400 Bottleneck

Machine D: 80 × 5 + 60 × 10 + 40 × 10 + 20 × 10 = 1,600 ≤ 2,400

 

The contribution margin per bottleneck minute is:

 

Harlan: (200 – 40 – 40)/15 = $8/min

Gaylen: (150 – 30 – 30)/10 = $9/min

Leah: (100 – 20 – 20)/15 = $4/min

Matthew: (75 – 10 – 10)/5 = $11/min

 

Products should be produced in Matthew, Gaylen, Harlan, and Leah order. The product mix is 20 Matthews (using 100 minutes of Machine C); 60 Gaylens (using 600 minutes of Machine C); 80 Harlans (using 1,200 minutes of Machine C); and 33 Leahs (using up the remaining 500 minutes of Machine C time).

Difficulty:  Challenging

Keywords:  capacity, bottleneck

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Apply the theory of constraints to product mix decisions.

 

 

5.5  Managing Contraints in Line Processes

 

1) Line balancing is the assignment of work to stations in a line to achieve the desired output rate with the smallest number of workstations.

Answer:  TRUE

Difficulty:  Moderate

Keywords:  line balance, workstations, line

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Describe how to manage constraints in line processes and balance assembly lines.

2) Line balancing strives to create workstations so that the capacity utilization for the bottleneck is much higher than for the other workstations in the line.

Answer:  FALSE

Difficulty:  Moderate

Keywords:  line balance, workstations, line, bottleneck

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Describe how to manage constraints in line processes and balance assembly lines.

 

3) Line balancing applies only to line processes that do assembly work, or to work that can be bundled in many ways to create the jobs for each workstation in the line.

Answer:  TRUE

Difficulty:  Moderate

Keywords:  line balance, workstations, line

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Describe how to manage constraints in line processes and balance assembly lines.

 

4) The balance delay is the amount by which efficiency falls short of 100 percent.

Answer:  TRUE

Difficulty:  Moderate

Keywords:  balance delay, efficiency

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Describe how to manage constraints in line processes and balance assembly lines.

 

5) To generate the maximum output, the cycle time should be set as the longest elemental task time.

Answer:  TRUE

Difficulty:  Moderate

Keywords:  cycle time, output, task

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Describe how to manage constraints in line processes and balance assembly lines.

 

 

6) Paced lines require that inventory storage areas be placed between stations.

Answer:  FALSE

Difficulty:  Moderate

Keywords:  paced line, inventory

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Describe how to manage constraints in line processes and balance assembly lines.

7) A mixed-model line produces several items belonging to the same family.

Answer:  TRUE

Difficulty:  Moderate

Keywords:  mixed model line, family

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Describe how to manage constraints in line processes and balance assembly lines.

 

8) Which of the following statements concerning line balancing is true?

  1. A) The theoretical minimum number of stations must always be fewer than the actual number.
  2. B) The largest number of followers rule assigns (as quickly as possible) those work elements most difficult to fit into a station.
  3. C) Selecting the cycle time can never have an effect on line efficiency.
  4. D) Increasing the output rate may increase the theoretical minimum number of stations.

Answer:  B

Difficulty:  Moderate

Keywords:  line balancing, output rate, theoretical minimum number of work stations

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Describe how to manage constraints in line processes and balance assembly lines.

 

9) What is the definition of “theoretical maximum efficiency”?

  1. A) It is the amount by which efficiency falls short of 100 percent.
  2. B) It is the efficiency that could be obtained by a solution that achieves the theoretical minimum number of stations.
  3. C) It is the maximum time allowed for work on a unit at each station.
  4. D) It is alternatively called the desired output rate.

Answer:  B

Difficulty:  Moderate

Keywords:  efficiency, line process

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Describe how to manage constraints in line processes and balance assembly lines.

 

 

10) Balance delay could be described as the:

  1. A) amount by which efficiency falls short of 100 percent.
  2. B) efficiency that could be obtained by a solution that achieves the theoretical minimum number of stations.
  3. C) maximum time allowed for work on a unit at each station.
  4. D) desired output rate.

Answer:  A

Difficulty:  Moderate

Keywords:  balance delay, line process

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Describe how to manage constraints in line processes and balance assembly lines.

11) A line balance that is 100% efficient must:

  1. A) be using the minimum cycle time.
  2. B) be using the theoretical minimum number of work stations.
  3. C) also achieve 100% balance delay.
  4. D) be producing the theoretical maximum output.

Answer:  B

Difficulty:  Moderate

Keywords:  efficiency, line process

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Describe how to manage constraints in line processes and balance assembly lines.

 

12) Instead of dividing the total standard time required to assemble each unit by nc to determine the efficiency of a line balance, you could divide by:

  1. A) the number of workers times the number of stations.
  2. B) the number of tasks plus the number of stations.
  3. C) the sum of the task times plus the sum of the idle times.
  4. D) (1-balance delay).

Answer:  C

Difficulty:  Moderate

Keywords:  efficiency, line process

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Describe how to manage constraints in line processes and balance assembly lines.

 

 

13) The most controversial aspect of line-flow layout is:

  1. A) the heuristic decision rules in assigning the next work element.
  2. B) the number of models produced.
  3. C) the cycle time.
  4. D) behavioral response.

Answer:  D

Difficulty:  Moderate

Keywords:  behavioral response, line process

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Describe how to manage constraints in line processes and balance assembly lines.

 

14) A line that produces several items belonging to the same family is called a:

  1. A) mixed-model line.
  2. B) part family line.
  3. C) group technology line.
  4. D) cellular line.

Answer:  A

Difficulty:  Moderate

Keywords:  mixed-model, line process

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Describe how to manage constraints in line processes and balance assembly lines.

15) Which one of the following statements about line balancing is best?

  1. A) If a precedence relationship exists between A and B, they cannot be assigned to the same station.
  2. B) If the desired output rate increases, the cycle time also tends to increase.
  3. C) The theoretical minimum number of stations can never be achieved, hence the name “theoretical.”
  4. D) If a line’s balance delay is minimized, its efficiency is maximized.

Answer:  D

Difficulty:  Moderate

Keywords:  line balancing, flow, balance delay, efficiency

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Describe how to manage constraints in line processes and balance assembly lines.

 

 

Figure 5.4

 

 

16) Use the information in Figure 5.4. What are the required predecessors of activity H?

  1. A) E & G
  2. B) A through F, including E
  3. C) Activity H has no required predecessors.
  4. D) D

Answer:  A

Difficulty:  Easy

Keywords:  predecessor, line process, flow

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Describe how to manage constraints in line processes and balance assembly lines.

17) Use the information in Figure 5.4. If each task has a work time of one minute, what is the theoretical minimum cycle time?

  1. A) There is no minimum cycle time.
  2. B) 1 minute
  3. C) 8 minutes
  4. D) The cycle time cannot be determined with the information given.

Answer:  B

Difficulty:  Moderate

Keywords:  cycle time, line process, flow

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Describe how to manage constraints in line processes and balance assembly lines.

 

 

18) Use the information in Figure 5.4. If each task has a work time of one minute and there are 480 work minutes in a day, what is the task assignment at the fourth workstation if maximum output is desired?

  1. A) A
  2. B) B
  3. C) C
  4. D) D

Answer:  D

Difficulty:  Moderate

Keywords:  cycle, line process, flow, task

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Describe how to manage constraints in line processes and balance assembly lines.

 

19) Use the information in Figure 5.4. If each task has a work time of one minute and there are 8 hours in a day, what is the task assignment at the first station if 160 units should be produced each day?

  1. A) A, B, C, D
  2. B) H, G, F, E
  3. C) A, B, C
  4. D) H, G, F

Answer:  C

Difficulty:  Moderate

Keywords:  line process, flow, task, station

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Describe how to manage constraints in line processes and balance assembly lines.

20) Use the information in Figure 5.4. If each task has a work time of one minute and there are 8 hours in a day, what is the minimum number of stations if 240 units should be produced each day?

  1. A) one
  2. B) two
  3. C) three
  4. D) four

Answer:  D

Difficulty:  Moderate

Keywords:  station, minimum number of stations

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Describe how to manage constraints in line processes and balance assembly lines.

 

 

Table 5.4

 

The Superior Management Company assembles muffalettas in The Big Easy. The steps to making a world class sandwich and the time required (in seconds) for each step are shown in the table.

 

Work

Element

Time

(sec)

Immediate

Predecessor(s)

A 45
B 120 A
C 70 A
D 95 B
E 20 C
F 40 B
G 60 D,E
H 55 F
I 100 G
J 150 H, I

 

21) Customers demand muffalettas at the rate of 20 sandwiches per hour. Use the information in Table 5.4 to determine the cycle time that will meet this level of demand.

  1. A) 100 seconds
  2. B) 120 seconds
  3. C) 180 seconds
  4. D) 240 seconds

Answer:  C

Difficulty:  Easy

Keywords:  line balancing

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Describe how to manage constraints in line processes and balance assembly lines.

22) Customers demand muffalettas at the rate of 20 sandwiches per hour. Use the information in Table 5.4 to determine how many workstations are needed to balance this line to maximum efficiency.

  1. A) 4
  2. B) 5
  3. C) 6
  4. D) 7

Answer:  B

Difficulty:  Moderate

Keywords:  line balancing

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Describe how to manage constraints in line processes and balance assembly lines.

 

 

23) Customers demand muffalettas at the rate of 20 sandwiches per hour. Use the information in Table 5.4 to determine the maximum efficiency you can achieve balancing this line with an output rate that meets demand.

  1. A) 84%
  2. B) 100%
  3. C) 76%
  4. D) 92%

Answer:  A

Difficulty:  Moderate

Keywords:  line balancing

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Describe how to manage constraints in line processes and balance assembly lines.

 

24) Customers demand muffalettas at the rate of 20 sandwiches per hour. Use the information in Table 5.4 to determine which tasks are assigned to station 3 in the most efficient balance that meets the desired output rate exactly.

  1. A) EGIJ
  2. B) EGI
  3. C) CFHE
  4. D) FHEG

Answer:  D

Difficulty:  Moderate

Keywords:  line balancing

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Describe how to manage constraints in line processes and balance assembly lines.

25) Customers demand muffalettas at the rate of 24 sandwiches per hour. Use the information in Table 5.4 to determine the minimum number of work stations needed to achieve exactly the output rate of customer demand.

  1. A) 4
  2. B) 5
  3. C) 6
  4. D) 7

Answer:  C

Difficulty:  Moderate

Keywords:  line balancing

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Describe how to manage constraints in line processes and balance assembly lines.

 

 

Table 5.5

 

Balance the following line for an output rate of 3 units per minute.

 

Work

Element

Time

(sec)

Immediate

Predecessor(s)

A 12
B 6 A
C 12 A
D 4 B
E 14 B, C
F 10 E
G 6 D, F

 

26) Use the information in Table 5.5. How many stations are required?

  1. A) 3
  2. B) 4
  3. C) 5
  4. D) 6

Answer:  B

Difficulty:  Moderate

Keywords:  stations, flow, line process

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Describe how to manage constraints in line processes and balance assembly lines.

27) Use the information in Table 5.5. What is the balance delay for your solution?

  1. A) less than or equal to 15%
  2. B) more than 15% but less than or equal to 25%
  3. C) more than 25% but less than or equal to 35%
  4. D) more than 35%

Answer:  B

Difficulty:  Moderate

Keywords:  balance delay, line process, flow

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Describe how to manage constraints in line processes and balance assembly lines.

 

 

Table 5.6

 

Balance the following line for an output rate of five pieces per hour. The times are in minutes (not seconds).

 

Work

Element

Time

(min)

Immediate

Predecessor(s)

A 7
B 5
C 3
D 4
E 2 A, B
F 5 C
G 6 D
H 7 E, F
I 11 F, G
J 4 H, I

 

28) Use the information from Table 5.6. The theoretical minimum number of stations is:

  1. A) fewer than three stations.
  2. B) three stations.
  3. C) four stations.
  4. D) more than four stations.

Answer:  D

Difficulty:  Moderate

Keywords:  line process, flow, stations

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Describe how to manage constraints in line processes and balance assembly lines.

29) Use the information from Table 5.6. The highest efficiency for a balanced line is:

  1. A) less than 89%.
  2. B) more than 89% and less than 91%.
  3. C) more than 91% and less than 93%.
  4. D) more than 93%.

Answer:  B

Difficulty:  Moderate

Keywords:  line process, flow, efficiency

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Describe how to manage constraints in line processes and balance assembly lines.

 

 

30) An assembly line has to perform 10 work elements, whose time requirements follow. An operations analyst has found a solution using some heuristics, as shown in the table. If the cycle time of the line is 90 seconds, what is the efficiency of the assembly line?

 

 

  1. A) less than 85%
  2. B) greater than 85% but less than 90%
  3. C) greater than 90% but less than 95%
  4. D) greater than 95%

Answer:  C

Difficulty:  Moderate

Keywords:  efficiency, line process, flow

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Describe how to manage constraints in line processes and balance assembly lines.

 

31) Given the following data about an assembly line and the knowledge that we are trying to attain an output rate of 40 units per hour, what is the theoretical minimum number of stations?

 

Work

Element

Time (sec)
1 90
2 80
3 75
4 70
5 90
6 85

 

  1. A) four or fewer stations
  2. B) five stations
  3. C) six stations
  4. D) seven or more stations

Answer:  C

Difficulty:  Moderate

Keywords:  line process, flow, minimum number of stations

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Describe how to manage constraints in line processes and balance assembly lines.

 

 

32) The production of a particular product consists of the following work elements. If the cycle time is 4 minutes and the work-element times are as follows, what is the theoretical minimum number of stations?

 

Work

Element

Time (min)
1 2.4
2 0.5
3 2.1
4 2.0
5 2.7
6 1.1
7 2.0
8 2.7
9 1.6
10 1.4

 

  1. A) fewer than or equal to three stations
  2. B) four stations
  3. C) five stations
  4. D) more than five stations

Answer:  C

Difficulty:  Moderate

Keywords:  line process, flow, minimum number of stations

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Describe how to manage constraints in line processes and balance assembly lines.

33) Fun Vehicles, Inc. makes beach buggies on an assembly line. The total productive time to make one buggy is 300 seconds. The current line has a 90-second cycle time and consists of four workstations. The balance delay of this line must be:

  1. A) 0%.
  2. B) greater than 0% but less than 6%.
  3. C) greater than 6% but less than 12%.
  4. D) greater than 12% but less than 18%.

Answer:  D

Difficulty:  Moderate

Keywords:  balance delay, line process, flow

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Describe how to manage constraints in line processes and balance assembly lines.

 

 

Table 5.7

 

The Terminal Company is attempting to balance its assembly line of high-voltage electrical connectors. The desired output for the line is 50 connectors per hour, and the information on the work elements for this assembly line is as follows.

 

Work

Elements

Time (sec) Immediate Predecessor(s)
A 40
B 36 A
C 20 A
D 25 A
E 30 B, C
F 34 D
G 35 E
H   5 F
I 15 E, H
J 40 H
K 38 G, I, J

 

34) Use the information from Table 5.7 to balance this line. What is the most efficient solution?

  1. A) more than 90%
  2. B) 80 – 90%
  3. C) 70 – 79%
  4. D) less than 70%

Answer:  C

Difficulty:  Challenging

Keywords:  efficiency, line balance, flow

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Describe how to manage constraints in line processes and balance assembly lines.

35) Use the information from Table 5.7 and the most efficient line balance possible. What work elements are included in the first station?

  1. A) A only
  2. B) A and B only
  3. C) A and E only
  4. D) A and D only

Answer:  D

Difficulty:  Moderate

Keywords:  tasks, station, line balance, flow

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Describe how to manage constraints in line processes and balance assembly lines.

 

 

36) Use the information from Table 5.7, and assume that the most efficient line balance possible has been achieved. What is the total idle time for an eight hour work day?

  1. A) less than an hour and a half
  2. B) more than 1:30 but less than or equal to 1:45
  3. C) more than 1:45 but less than or equal to 2 hours
  4. D) more than 2 hours

Answer:  D

Difficulty:  Moderate

Keywords:  idle time, line balance, flow

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Describe how to manage constraints in line processes and balance assembly lines.

 

37) ________ is the maximum time allowed for work on a unit at each station.

Answer:  Cycle time

Difficulty:  Moderate

Keywords:  cycle time, work, line process, flow

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Describe how to manage constraints in line processes and balance assembly lines.

 

38) ________ is the amount by which efficiency falls short of 100 percent.

Answer:  Balance delay

Difficulty:  Moderate

Keywords:  balance delay, efficiency, line process, flow

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Describe how to manage constraints in line processes and balance assembly lines.

39) Regardless of the number of tasks or their lengths, a line balance efficiency of 100% is possible if the number of stations is ________.

Answer:  one

Difficulty:  Moderate

Keywords:  line balance, efficiency

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Describe how to manage constraints in line processes and balance assembly lines.

 

40) A(n) ________ line is a product line that produces several items belonging to the same family.

Answer:  mixed-model

Difficulty:  Moderate

Keywords:  mixed-model line, family

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Describe how to manage constraints in line processes and balance assembly lines.

 

 

41) Describe three ways that line balancing and line flow layouts are similar to project management and three ways that they are different from project management.

Answer:  Answers may vary. Line balancing and project management both rely on the completion of predefined activities in the proper sequence. A line flow may have multiple feeder lines that supply subassemblies to the main line, similar to subcontractors working on the project in state of partial completion. Both have anticipated completion times that may not be reached if things don’t go smoothly.

 

The time scale is radically different between line balancing and project management; projects tend to take much longer. Projects also tend to be one of a kind endeavors; line balancing is performed with the anticipation of high volumes of fairly standardized output. Line flows are created for more routine, process-oriented work that can be composed of standardized tasks. Projects are typically anything but routine and far from process-focused.

Difficulty:  Moderate

Keywords:  line balancing, flow layout

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Describe how to manage constraints in line processes and balance assembly lines.

42) You have been assigned a line balancing task and given a list of tasks, their precedence requirements, and the time needed to accomplish them. As you begin to balance the line, you realize that you must make some assumptions. What are these assumptions and which of them has the greatest impact on the success of your balance?

Answer:  One assumption that is being made is that the task times are invariant, unless a mean and standard deviation have both been provided. You must also assume that the task durations will stay roughly the same, i.e., that learning effects are not significantly different amongst the tasks. You are also assuming that the tasks will stay somewhat static, or the line would require rearrangement and possibly rebalancing with some frequency. You also assume that the precedence is static. Among these, the last assumption is probably the least tenuous.

Difficulty:  Moderate

Keywords:  line balancing, flow layout

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Describe how to manage constraints in line processes and balance assembly lines.

 

 

43) How can Theory of Constraints principles be reconciled with line balancing?

Answer:  Line balancing strives to assign work to stations such that the amount of work at each station is equal. Work flows from station to station based on a cycle time that is determined based on the number of units to be produced per unit time. Theory of Constraints stresses the need to balance flow with demand and is concerned with preserving flow through the bottleneck, or lowest capacity station. Flow can be preserved by protecting the bottleneck with protective WIP and making sure that market demand is sufficient to support continuous bottleneck operation. Line balancing, as explained in the text, assumes that all task times are constant. So the person performing the balance can try to allocate capacity as evenly as possible. If task times were stochastic, then flow would not be preserved with classic line balancing techniques because the lowest capacity work station would occasionally fall idle.

Difficulty:  Moderate

Keywords:  line balancing, TOC, theory of constraints

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Application of Knowledge

Learning Obj.:  Describe how to manage constraints in line processes and balance assembly lines.

44) Consider the following production process. It is trying to meet a market demand of 500 units per week.

 

 

Step 1: Material release schedule

Step 2: Drilling (capacity is 500 units/week)

Step 3: Tapping (capacity is 450 units/week)

Step 4: Grinding (capacity is 600 units/week)

Step 5: Coating (capacity is 400 units/week)

Step 6: Inspection (capacity is 1,000 units/week)

 

  1. Where should buffers be placed?
  2. Which resource is the drum?
  3. Where should the rope be placed?
  4. Which resource is the bottleneck?
  5. Which resource is the CCR?

Answer:

  1. A constraint buffer should be placed between steps 4 and 5 to protect the bottleneck which is Step 5 (Coating). A shipping buffer should be placed at the end of the line, after Step 6, (Inspection).
  2. The resource functioning as the drum is the bottleneck, Step 5.
  3. The rope should connect Step 1 and Step 5.
  4. The bottleneck is Step 5.
  5. A CCR exists if the process with the least capacity can still meet market demand, which is not the case in this scenario.

Difficulty:  Moderate

Keywords:  drum-buffer-rope, DBR, CCR, capacity constrained resource, bottleneck

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Describe how to manage constraints in line processes and balance assembly lines.

45) Consider the following production process. It is trying to meet a market demand of 250 units per week.

 

 

Step 1: Material release schedule

Step 2: Drilling (capacity is 300 units/week)

Step 3: Tapping (capacity is 150 units/week)

Step 4: Grinding (capacity is 300 units/week)

Step 5: Coating (capacity is 200 units/week)

Step 6: Inspection (capacity is 500 units/week)

 

  1. Where should buffers be placed?
  2. Which resource is the drum?
  3. Where should the rope be placed?
  4. Which resource is the bottleneck?
  5. Which resource is the CCR?

Answer:

  1. A constraint buffer should be placed between steps 2 and 3 to protect the bottleneck which is Step 3 (Tapping). A shipping buffer should be placed at the end of the line, after Step 6, (Inspection).
  2. The resource functioning as the drum is the bottleneck, Step 3.
  3. The rope should connect Step 1 and Step 3.
  4. The bottleneck is Step 3.
  5. A CCR exists if the process with the least capacity can still meet market demand, which is not the case in this scenario.

Difficulty:  Moderate

Keywords:  drum-buffer-rope, DBR, CCR, capacity constrained resource, bottleneck

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Describe how to manage constraints in line processes and balance assembly lines.

 

46) Balance the assembly line for the tasks contained in the table. The desired output is 240 units per day. Available production time per day is 480 minutes. What is the efficiency for the balanced assembly line?

 

Work Element Time (Sec.) Immediate Predecessor(s)
A 40
B 45
C 55 A
D 55 B
E 65 B
F 40 C, D
G 25 D, E

 

Answer:  For 240 units/day with available time of 480 minutes per day, the cycle time is 2.00 minutes or 120 seconds.

One line balance is:

 

Station 1 2 3 Totals
Task(s) B, E D, A C, F, G  
Work Time 45, 65 55, 40 55, 40, 25 325
Idle Time 10 25 0 35

 

Efficiency =  =  = 90.28%

 

There are four other legal assignments possible at the first work station, AB, BA, AC, and BD. There are a large number of possible legal balances since the longest two task times sum to 120, which is within the desired cycle time. A number of possible balances will achieve the three station balance that yields 90.28% efficiency.

Difficulty:  Moderate

Keywords:  line balance, efficiency

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Describe how to manage constraints in line processes and balance assembly lines.

 

47) Balance the assembly line for the tasks contained in the table. The desired output is three units per hour. Available production time per day is eight hours. What is the theoretical minimum number of stations? What is the efficiency for the balanced assembly line?

 

Work Element Time (Min.) Immediate Predecessor(s)
A 5
B 8 A
C 12 A
D 11 B
E 5 C
F 6 D
G 4 D
H 12 E
I 14 G, H
J 9 F
K 8 I
L 3 K, J

 

Answer:  For 3 units/hour the cycle time is 20 minutes.

The theoretical minimum number of stations is 97/20 = 4.85→5

One line balance is:

 

Station 1 2 3 4 5 6 Totals
Task(s) A, C B, D F, J, E H, G I K, L  
Work Time 5, 12 8, 11 6, 9, 5 12, 4 14 8, 3 97
Idle Time 3 1 0 4 6 9 23

 

Efficiency =  =  = 80.8%

Difficulty:  Moderate

Keywords:  line balance, efficiency

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Describe how to manage constraints in line processes and balance assembly lines.

 

48) Balance the assembly line using the following task information contained in the table. The desired output is 360 units per day. Available production time per day is 480 minutes. What is the efficiency for the balanced assembly line?

 

Work Element Time (Sec.) Immediate Predecessor(s)
A 30
B 20 A
C 50 A
D 45 B
E 30 B
F 55 C, D
G 35 D, E
H 40 F

 

Answer:  Cycle time for 360 units in a 480 minute day is 480/360 = 1.33 minutes = 80 seconds

The theoretical minimum number of stations is 4; this balance is one of the 5-station solutions.

 

Station 1 2 3 4 5 Totals
Task(s) A, C B, D F H, E G  
Work Time 30, 50 20, 45 55 40, 30 35 305
Idle Time 0 15 25 10 45 95

 

Efficiency =  =  = 76.25%

Difficulty:  Moderate

Keywords:  line balance, efficiency

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Describe how to manage constraints in line processes and balance assembly lines.

 

 

49) Balance the line in order to achieve maximum output for this ten activity product. Determine the number of units produced in a seven hour work day and the total idle time in hours.

 

Task Time (sec) Predecessor
Z 40
Y 30 Z
X 80 Z
W 75 X, Y
V 15 W
T 55 W
S 35 V
R 40 T
Q 10 R
M 40 S, R

 

Answer:  Cycle time for maximum output is 80 seconds and the theoretical minimum number of stations is

 

Station 1 2 3 4 5 6 7 Totals
Task(s) Z, Y X W V, T S R, M Q  
Work Time 40, 30 80 75 15, 55 70 40, 40 60 420
Idle Time 10 0 5 10 10 0 20 55

 

Efficiency =  =  = 88.42%

 

There are 315 units produced in a day.

 

The total idle time per day at this level of production is 4.8125 hours. (4:48:45 to be precise)

 

300 units/day × 55 seconds idle/unit = 17,325 seconds

 

 = 4.8125 hours

Difficulty:  Moderate

Keywords:  line balance, efficiency

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Describe how to manage constraints in line processes and balance assembly lines.

 

 

50) Balance the line in order to achieve maximum output for this eight-activity product. Then balance the line to maximize the efficiency of the operation. How do the levels of output (assume an eight-hour day) and line efficiencies compare?

 

Task Time (min) Predecessor
1 10
2 8 Task 1
3 9 Task 1
4 2 Task 2
5 6 Task 3
6 12 Task 4, Task 5
7 7 Task 5
8 5 Task 6, Task 7

 

Answer:  The cycle time for maximum output is 12 minutes. One balance is shown below; it has 6 stations, an increase of one from the theoretical minimum of five stations. It produces at 81.9% efficiency. It produces a unit every twelve minutes, so over the course of a day it can produce 40 units using six people.

 

Station 1 2 3 4 5 6 Totals
Task(s) 1 3 2, 4 5 6 7, 8  
Work Time 10 9 8, 2 6 12 7, 5 59
Idle Time 2 3 2 6 0 0 13

 

Efficiency =  =  = 81.94%

 

The cycle time for maximum efficiency is 59 minutes. One balance is shown below; it has one station and produces at 100% efficiency. It produces a unit every 59 minutes, so over the course of an eight-hour day it can produce eight complete units plus get started on a ninth unit using just one person. If the line was replicated and six workers perfectly cross trained, they could produce 54 units and start on the first task for units 55-60.

 

Station 1 Totals
Task(s) 1, 3, 2, 4, 5, 6, 7, 8  
Work Time 10, 9, 8, 2, 6, 12, 7, 5 59
Idle Time 0 0

 

Efficiency =  =  = 100%

Difficulty:  Moderate

Keywords:  line balance, efficiency

Learning Outcome:  Explain options for managing bottlenecks and managing capacity in service and manufacturing processes

AACSB:  Analytical Thinking

Learning Obj.:  Describe how to manage constraints in line processes and balance assembly lines.

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