Russell Ch.17 Scheduling Full Test Bank

CHAPTER 17

SCHEDULING

CHAPTER LEARNING OBJECTIVES

1. Describe scheduling techniques and list the objectives of scheduling. Scheduling techniques vary by type of production process. Scheduling in a job shop environment is difficult because jobs arrive at varying time intervals, require different resources and sequences of operations, and are due at different times. This lowest level of scheduling is referred to as shop floor control or production control. It involves assigning jobs to machines or workers (called loading), specifying the order in which operations are to be performed, and monitoring the work as it progresses. There are many objectives in constructing a schedule—some of which may conflict:

• Meeting customer due dates

• Minimizing job lateness

• Minimizing response time

• Minimizing completion time

• Minimizing time in the system

• Minimizing overtime

• Maximizing machine or labour use

• Minimizing idle time

• Minimizing work-in-process inventory

2. Explain what loading is and use the assignment method to load work on to limited resources. Loading is the process of assigning work to limited resources. The assignment method is a specialized linear programming solution procedure for deciding which worker to assign to a task, or which job to assign to a machine. The procedure creates an opportunity cost matrix and selects the best assignment in consideration of trade-offs among alternatives. See Section 17.2 for an example of the assignment method.

3. Explain what sequencing is and use rules and quantitative tools for optimizing the sequence of jobs processed through one or two workstations. Sequencing is the process of prioritizing jobs and determining the processing order. See Section 17.3 for examples of sequencing jobs through one or two workstations.

4. Use several methods to monitor the progress of jobs in a job shop environment. Gantt charts can be used to monitor a job’s progress against the plan, and input/output controls monitor the input to and output from each work centre.

5. Explain the basics of finite scheduling, and use the theory of constraints procedure to schedule multiple jobs through multiple workstations. Realistic schedules must reflect capacity limitations. Infinite scheduling initially assumes infinite capacity and then manually “levels the load” of resources that have exceeded capacity. Finite scheduling loads jobs in priority order and delays those jobs for which current capacity is exceeded. The theory of constraints is a finite scheduling approach that schedules bottleneck resources first and then schedules other resources to support the bottleneck schedule. It also allows items to be transferred between resources in lot sizes that differ from the lot size in which the item is produced. Other advanced planning and scheduling techniques include mathematical programming, genetic algorithms, and simulation.

6. Use a heuristic to schedule workers and explain the capabilities provided by employee scheduling software. Employee scheduling is often difficult because of the variety of options available and the special requirements for individual workers. Scheduling heuristics are typically used to develop patterns of worker assignment (see Example 17.2 for an example). Automated workforce scheduling systems are becoming more commonplace. Scheduling software:

• Assigns qualified workers to standardize shift patterns, taking into account leave requests and scheduling conflicts

• Allows workers to bid on certain shifts and post and trade schedules

• Creates demand-driven forecasts of labour requirements and assigns workers to variable schedules that change dynamically with demand

TRUE-FALSE STATEMENTS

1. Scheduling specifies when labour, equipment and facilities are needed to produce a product.

Answer: True

Difficulty: Easy

Learning Objective: Describe scheduling techniques and list the objectives of scheduling.

Section Reference: 17.1 Scheduling Techniques

2. Scheduling is considered the last stage of the planning process.

Answer: True

Difficulty: Easy

Learning Objective: Describe scheduling techniques and list the objectives of scheduling.

Section Reference: 17.1 Scheduling Techniques

3. The wide variety of jobs in a job shop makes scheduling difficult.

Answer: True

Difficulty: Easy

Learning Objective: Describe scheduling techniques and list the objectives of scheduling.

Section Reference: 17.1 Scheduling Techniques

4. Managers typically use multiple objectives when constructing a schedule.

Answer: True

Difficulty: Easy

Learning Objective: Describe scheduling techniques and list the objectives of scheduling.

Section Reference: 17.1 Scheduling Techniques

5. Minimizing overtime is one of several objectives that could be considered when constructing a schedule.

Answer: True

Difficulty: Easy

Learning Objective: Describe scheduling techniques and list the objectives of scheduling.

Section Reference: 17.1 Scheduling Techniques

6. Job-shop scheduling is usually performed by skilled machine operators.

Answer: False

Difficulty: Easy

Learning Objective: Describe scheduling techniques and list the objectives of scheduling.

Section Reference: 17.1 Scheduling Techniques

7. Gantt charts show the planned and yet to be completed activities against total activities.

Answer: False

Difficulty: Medium

Learning Objective: Describe scheduling techniques and list the objectives of scheduling.

Section Reference: 17.1 Scheduling Techniques

8. The scheduling function for mass production and job shop production are basically the same.

Answer: False

Difficulty: Medium

Learning Objective: Describe scheduling techniques and list the objectives of scheduling.

Section Reference: 17.1 Scheduling Techniques

9. Job shop scheduling is also known as shop floor control.

Answer: True

Difficulty: Medium

Learning Objective: Describe scheduling techniques and list the objectives of scheduling.

Section Reference: 17.1 Scheduling Techniques

10. The process of assigning work to limited resources is known as scheduling.

Answer: False

Difficulty: Medium

Learning Objective: Explain what loading is and use the assignment method to load work on to limited resources.

Section Reference: 17.2 Loading

11. Sequencing involves determining the order in which jobs are released to the shop floor.

Answer: False

Difficulty: Hard

Learning Objective: Explain what sequencing is and use rules and quantitative tools for optimizing the sequence of jobs processed through one or two workstations.

Section Reference: 17.3 Sequencing

12. The sequence in which jobs should be processed is determined using linear programming.

Answer: False

Difficulty: Medium

Learning Objective: Explain what sequencing is and use rules and quantitative tools for optimizing the sequence of jobs processed through one or two workstations.

Section Reference: 17.3 Sequencing

13. Determining the optimal allocation of jobs to machines or workers can be solved using the assignment method of linear programming.

Answer: True

Difficulty: Medium

Learning Objective: Explain what sequencing is and use rules and quantitative tools for optimizing the sequence of jobs processed through one or two workstations.

Section Reference: 17.3 Sequencing

14. The process of prioritizing jobs that have been assigned to a resource is called sequencing.

Answer: True

Difficulty: Easy

Learning Objective: Explain what sequencing is and use rules and quantitative tools for optimizing the sequence of jobs processed through one or two workstations.

Section Reference: 17.3 Sequencing

15. The time required for a job to move through the system is referred to as flow time.

Answer: True

Difficulty: Medium

Learning Objective: Explain what sequencing is and use rules and quantitative tools for optimizing the sequence of jobs processed through one or two workstations.

Section Reference: 17.3 Sequencing

16. All sequencing rules strive to optimize both processing efficiency and due date performance.

Answer: False

Difficulty: Medium

Learning Objective: Explain what sequencing is and use rules and quantitative tools for optimizing the sequence of jobs processed through one or two workstations.

Section Reference: 17.3 Sequencing

17. Johnson’s rule gives an optimal sequence for jobs processed serially through a two step system.

Answer: True

Difficulty: Medium

Learning Objective: Explain what sequencing is and use rules and quantitative tools for optimizing the sequence of jobs processed through one or two workstations.

Section Reference: 17.3 Sequencing

18. The shortest processing time (SPT) rule is most useful when the job shop is not congested.

Answer: False

Difficulty: Medium

Learning Objective: Explain what sequencing is and use rules and quantitative tools for optimizing the sequence of jobs processed through one or two workstations.

Section Reference: 17.3 Sequencing

19. The longest processing time (LPT) rule tends to complete larger jobs in-house when subcontracting is anticipated.

Answer: True

Difficulty: Medium

Learning Objective: Explain what sequencing is and use rules and quantitative tools for optimizing the sequence of jobs processed through one or two workstations.

Section Reference: 17.3 Sequencing

20. The first-come, first-served (FCFS) sequencing rule should be only used when operating at high levels of capacity.

Answer: False

Difficulty: Medium

Learning Objective: Explain what sequencing is and use rules and quantitative tools for optimizing the sequence of jobs processed through one or two workstations.

Section Reference: 17.3 Sequencing

21. The dispatch list contains the order in which work is assigned to a productive resource.

Answer: False

Difficulty: Medium

Learning Objective: Explain what sequencing is and use rules and quantitative tools for optimizing the sequence of jobs processed through one or two workstations.

Section Reference: 17.3 Sequencing

22. In a job shop environment, the process of prioritizing jobs assigned to a productive resource is called sequencing.

Answer: True

Difficulty: Medium

Learning Objective: Explain what sequencing is and use rules and quantitative tools for optimizing the sequence of jobs processed through one or two workstations.

Section Reference: 17.3 Sequencing

23. Tardiness is defined as the difference between a job’s flow time and makespan.

Answer: False

Difficulty: Medium

Learning Objective: Explain what sequencing is and use rules and quantitative tools for optimizing the sequence of jobs processed through one or two workstations.

Section Reference: 17.3 Sequencing

24. Input/output control provides the information necessary to regulate work flow in a job shop environment.

Answer: True

Difficulty: Medium

Learning Objective: Use several methods to monitor the progress of jobs in a job shop environment.

Section Reference: 17.4 Monitoring

25. Increasing the capacity of a work centre that is a bottleneck increases output.

Answer: True

Difficulty: Medium

Learning Objective: Explain the basics of finite scheduling, and use the theory of constraints procedure to schedule multiple jobs through multiple workstations.

Section Reference: 17.5 Advanced Planning and Scheduling Systems

26. Finite scheduling will not load a resource beyond its fixed capacity.

Answer: True

Difficulty: Medium

Learning Objective: Explain the basics of finite scheduling, and use the theory of constraints procedure to schedule multiple jobs through multiple workstations.

Section Reference: 17.5 Advanced Planning and Scheduling Systems

27. The theory of constraints (TOC) approach to scheduling concentrates on scheduling the bottleneck resources.

Answer: True

Difficulty: Medium

Learning Objective: Explain the basics of finite scheduling, and use the theory of constraints procedure to schedule multiple jobs through multiple workstations.

Section Reference: 17.5 Advanced Planning and Scheduling Systems

28. With drum-buffer-rope (DBR), the bottleneck resource is always the buffer.

Answer: False

Difficulty: Medium

Learning Objective: Explain the basics of finite scheduling, and use the theory of constraints procedure to schedule multiple jobs through multiple workstations.

Section Reference: 17.5 Advanced Planning and Scheduling Systems

29. Scheduling using the theory of constraints (TOC) requires that process batch sizes and transfer batch sizes always match.

Answer: False

Difficulty: Medium

Learning Objective: Explain the basics of finite scheduling, and use the theory of constraints procedure to schedule multiple jobs through multiple workstations.

Section Reference: 17.5 Advanced Planning and Scheduling Systems

30. Typically, there are more options available when scheduling employees because labour is a very flexible resource.

Answer: True

Difficulty: Medium

Learning Objective: Use a heuristic to schedule workers and explain the capabilities provided by employee scheduling software.

Section Reference: 17.6 Employee Scheduling

31. The assignment method of linear programming can be used for both loading and employee scheduling.

Answer: True

Difficulty: Medium

Learning Objective: Use a heuristic to schedule workers and explain the capabilities provided by employee scheduling software.

Section Reference: 17.6 Employee Scheduling

MULTIPLE CHOICE QUESTIONS

32. Which of the following is not typically considered an objective of scheduling?

a) minimizing job lateness

b) maximizing time in the system

c) minimizing overtime

d) maximizing machine utilization

Answer: b

Difficulty: Easy

Learning Objective: Describe scheduling techniques and list the objectives of scheduling.

Section Reference: 17.1 Scheduling Techniques

33. The process of assigning work to limited resources is known as

a) loading.

b) sequencing.

c) monitoring.

d) dispatching

Answer: a

Difficulty: Easy

Learning Objective: Explain what loading is and use the assignment method to load work on to limited resources.

Section Reference: 17.2 Loading

34. The process of prioritizing jobs that have been assigned to a resource is called

a) loading.

b) monitoring.

c) sequencing.

d) input/output analysis.

Answer: c

Difficulty: Easy

Learning Objective: Explain what sequencing is and use rules and quantitative tools for optimizing the sequence of jobs processed through one or two workstations.

Section Reference: 17.3 Sequencing

35. If a job is ahead of schedule, then its critical ratio (CR) will be

a) less than one.

b) greater than one.

c) equal to one.

d) none of the above.

Answer: b

Difficulty: Medium

Learning Objective: Explain what sequencing is and use rules and quantitative tools for optimizing the sequence of jobs processed through one or two workstations.

Section Reference: 17.3 Sequencing

36. If the work remaining is greater than the time remaining, the critical ratio (CR) will be

a) less than one.

b) greater than one.

c) equal to one.

d) none of the above.

Answer: a

Difficulty: Medium

Learning Objective: Explain what sequencing is and use rules and quantitative tools for optimizing the sequence of jobs processed through one or two workstations.

Section Reference: 17.3 Sequencing

37. The time required to complete a group of jobs is referred to as

a) flow time.

b) makespan.

c) completion time.

d) none of the above.

Answer: b

Difficulty: Easy

Learning Objective: Explain what sequencing is and use rules and quantitative tools for optimizing the sequence of jobs processed through one or two workstations.

Section Reference: 17.3 Sequencing

38. The sequencing rule that will minimize average job completion time for a set number of jobs to be processed on one machine is

a) first-come-first served (FCFS).

b) longest processing time (LPT).

c) shortest process time (SPT).

d) due date (DDATE).

Answer: c

Difficulty: Medium

Learning Objective: Explain what sequencing is and use rules and quantitative tools for optimizing the sequence of jobs processed through one or two workstations.

Section Reference: 17.3 Sequencing

39. The sequencing rule that minimizes average tardiness for a set of jobs to be processed on one machine is

a) first-come-first served (FCFS).

b) longest processing time (LPT).

c) shortest process time (SPT).

d) due date (DDATE).

Answer: c

Difficulty: Medium

Learning Objective: Explain what sequencing is and use rules and quantitative tools for optimizing the sequence of jobs processed through one or two workstations.

Section Reference: 17.3 Sequencing

40. If the following jobs are sequenced according to the first-come-first-served (FCFS) rule, then the mean completion time in days for all jobs is (assume zero for today’s date)

a) 33 days.

b) 22 days.

c) 6.6 days.

d) 4.4 days.

Answer: b

Difficulty: Medium

Learning Objective: Explain what sequencing is and use rules and quantitative tools for optimizing the sequence of jobs processed through one or two workstations.

Section Reference: 17.3 Sequencing

41. If the following jobs are sequenced according to the FCFS rule, then the mean tardiness (in days) for all jobs would be (assume zero for today’s date)

a) 5 days.

b) 8.33 days.

c) 10.6 days.

d) 25 days

Answer: c

Difficulty: Medium

Learning Objective: Explain what sequencing is and use rules and quantitative tools for optimizing the sequence of jobs processed through one or two workstations.

Section Reference: 17.3 Sequencing

42. If the following jobs are sequenced according to the FCFS rule, then the maximum job tardiness (in days) is (assume zero for today’s date)

a) 0 days.

b) 8 days.

c) 20 days.

d) 25 days.

Answer: d

Difficulty: Medium

Learning Objective: Explain what sequencing is and use rules and quantitative tools for optimizing the sequence of jobs processed through one or two workstations.

Section Reference: 17.3 Sequencing

43. If the following jobs are sequenced according to the FCFS rule, then the total number of jobs that would be late is (assume zero for today’s date)

a) 4.

b) 3.

c) 2.

d) 1.

Answer: b

Difficulty: Medium

Learning Objective: Explain what sequencing is and use rules and quantitative tools for optimizing the sequence of jobs processed through one or two workstations.

Section Reference: 17.3 Sequencing

44. If the following jobs are sequenced according to the FCFS rule, then job C is completed on day (assume zero for today’s date)

a) 11.

b) 17.

c) 25.

d) 30.

Answer: c

Difficulty: Medium

Learning Objective: Explain what sequencing is and use rules and quantitative tools for optimizing the sequence of jobs processed through one or two workstations.

Section Reference: 17.3 Sequencing

45. If the following jobs are sequenced according to the SPT rule, then the mean completion time (in days) for all jobs is (assume zero for today’s date)

a) 6.6 days.

b) 16 days.

c) 22 days.

d) 33 days.

Answer: b

Difficulty: Medium

Learning Objective: Explain what sequencing is and use rules and quantitative tools for optimizing the sequence of jobs processed through one or two workstations.

Section Reference: 17.3 Sequencing

46. If the following jobs are sequenced according to the SPT rule, then the mean tardiness (in days) for all jobs is (assume zero for today’s date)

a) 16 days.

b) 13 days.

c) 5.2 days.

d) 3.2 days.

Answer: c

Difficulty: Medium

Learning Objective: Explain what sequencing is and use rules and quantitative tools for optimizing the sequence of jobs processed through one or two workstations.

Section Reference: 17.3 Sequencing

47. If the following jobs are sequenced according to the SPT rule, then the maximum job tardiness (in days) is (assume zero for today’s date)

a) 26 days.

b) 16 days.

c) 10 days.

d) 5.2 days.

Answer: b

Difficulty: Medium

Learning Objective: Explain what sequencing is and use rules and quantitative tools for optimizing the sequence of jobs processed through one or two workstations.

Section Reference: 17.3 Sequencing

48. If the following jobs are sequenced according to the SPT rule, then the total number of jobs that would be late is (assume zero for today’s date)

a) 0 jobs.

b) 1 job.

c) 2 jobs.

d) 3 jobs.

Answer: c

Difficulty: Medium

Learning Objective: Explain what sequencing is and use rules and quantitative tools for optimizing the sequence of jobs processed through one or two workstations.

Section Reference: 17.3 Sequencing

49. If the following jobs are sequenced according to the SPT rule, then job B is completed on day (assume zero for today’s date)

a) 6.

b) 14.

c) 15.

d) 22.

Answer: b

Difficulty: Medium

Learning Objective: Explain what sequencing is and use rules and quantitative tools for optimizing the sequence of jobs processed through one or two workstations.

Section Reference: 17.3 Sequencing

50. If the following jobs are sequenced according to the LPT rule, then the mean completion time (in days) for all jobs is (assume zero for today’s date)

a) 118 days.

b) 6.6 days.

c) 33 days.

d) 23.6 days.

Answer: d

Difficulty: Medium

Learning Objective: Explain what sequencing is and use rules and quantitative tools for optimizing the sequence of jobs processed through one or two workstations.

Section Reference: 17.3 Sequencing

51. If the following jobs are sequenced according to the LPT rule, then the mean tardiness (in days) for all jobs is (assume zero for today’s date)

a) 62 days.

b) 12.4 days.

c) 15.5 days.

d) 25 days.

Answer: b

Difficulty: Medium

Learning Objective: Explain what sequencing is and use rules and quantitative tools for optimizing the sequence of jobs processed through one or two workstations.

Section Reference: 17.3 Sequencing

52. If the following jobs are sequenced according to the LPT rule, then the maximum job tardiness (in days) is (assume zero for today’s date)

a) 7 days.

b) 10 days.

c) 20 days.

d) 25 days.

Answer: d

Difficulty: Medium

Learning Objective: Explain what sequencing is and use rules and quantitative tools for optimizing the sequence of jobs processed through one or two workstations.

Section Reference: 17.3 Sequencing

53. If the following jobs are sequenced according to the LPT rule, then the total number of jobs that would be late is (assume zero for today’s date)

a) 5 jobs.

b) 4 jobs.

c) 3 jobs.

d) 2 jobs.

Answer: b

Difficulty: Medium

Learning Objective: Explain what sequencing is and use rules and quantitative tools for optimizing the sequence of jobs processed through one or two workstations.

Section Reference: 17.3 Sequencing

54. If the following jobs are sequenced according to the LPT rule, then job D would be completed on day (assume zero for to day’s date)

a) 5.

b) 25.

c) 30.

d) 33.

Answer: c

Difficulty: Medium

Learning Objective: Explain what sequencing is and use rules and quantitative tools for optimizing the sequence of jobs processed through one or two workstations.

Section Reference: 17.3 Sequencing

55. If the following jobs are sequenced according to the SLACK rule, then the mean completion time (in days) for all jobs is (assume zero for today’s date)

a) 35 days.

b) 20.8 days.

c) 18.4 days.

d) 7 days.

Answer: b

Difficulty: Hard

Learning Objective: Explain what sequencing is and use rules and quantitative tools for optimizing the sequence of jobs processed through one or two workstations.

Section Reference: 17.3 Sequencing

56. If the following jobs are sequenced according to the SLACK rule, then the mean tardiness (in days) for all jobs is (assume zero for today’s date)

a) 11.25 days.

b) 9 days.

c) 20 days.

d) 12.5 days.

Answer: b

Difficulty: Hard

Learning Objective: Explain what sequencing is and use rules and quantitative tools for optimizing the sequence of jobs processed through one or two workstations.

Section Reference: 17.3 Sequencing

57. If the following jobs are sequenced according to the SLACK rule, then the maximum job tardiness (in days) is (assume zero for today’s date)

a) 20 days.

b) 12 days.

c) 10 days.

d) 7 days.

Answer: a

Difficulty: Hard

Learning Objective: Explain what sequencing is and use rules and quantitative tools for optimizing the sequence of jobs processed through one or two workstations.

Section Reference: 17.3 Sequencing

58. If the following jobs are sequenced according to the SLACK rule, then the total number of jobs that would be late is (assume zero for today’s date)

a) 1 jobs.

b) 2 jobs.

c) 3 jobs.

d) 4 jobs.

Answer: d

Difficulty: Hard

Learning Objective: Explain what sequencing is and use rules and quantitative tools for optimizing the sequence of jobs processed through one or two workstations.

Section Reference: 17.3 Sequencing

59. If the following jobs are sequenced according to the SLACK rule, then job A would be completed on day (assume zero for today’s date)

a) 8.

b) 7.

c) 15.

d) 12.

Answer: c

Difficulty: Hard

Learning Objective: Explain what sequencing is and use rules and quantitative tools for optimizing the sequence of jobs processed through one or two workstations.

Section Reference: 17.3 Sequencing

60. If the following jobs are sequenced according to the DDATE rule, then the mean completion time (in days) for all jobs is (assume zero for today’s date)

a) 16.4 days.

b) 22.6 days.

c) 28.7 days.

d) 33.0 days

Answer: a

Difficulty: Medium

Learning Objective: Explain what sequencing is and use rules and quantitative tools for optimizing the sequence of jobs processed through one or two workstations.

Section Reference: 17.3 Sequencing

61. If the following jobs are sequenced according to the DDATE rule, then the mean tardiness (in days) for all jobs is (assume zero for today’s date)

a) 9.0 days.

b) 5.4 days.

c) 3.2 days.

d) 2.8 days

Answer: b

Difficulty: Medium

Learning Objective: Explain what sequencing is and use rules and quantitative tools for optimizing the sequence of jobs processed through one or two workstations.

Section Reference: 17.3 Sequencing

62. If the following jobs are sequenced according to the DDATE rule, then the maximum job tardiness (in days) is (assume zero for today’s date)

a) 12 days.

b) 15 days.

c) 16 days.

d) 27 days.

Answer: c

Difficulty: Medium

Learning Objective: Explain what sequencing is and use rules and quantitative tools for optimizing the sequence of jobs processed through one or two workstations.

Section Reference: 17.3 Sequencing

63. If the following jobs are sequenced according to the DDATE rule, then the total number of jobs that would be late is (assume zero for today’s date)

a) 5 jobs.

b) 4 jobs.

c) 3 jobs.

d) 2 jobs.

Answer: c

Difficulty: Medium

Learning Objective: Explain what sequencing is and use rules and quantitative tools for optimizing the sequence of jobs processed through one or two workstations.

Section Reference: 17.3 Sequencing

64. If the following jobs are sequenced according to the DDATE rule, then job A would be completed on day (assume zero for today’s date)

a) 8.

b) 12.

c) 16.

d) 22.

Answer: c

Difficulty: Medium

Learning Objective: Explain what sequencing is and use rules and quantitative tools for optimizing the sequence of jobs processed through one or two workstations.

Section Reference: 17.3 Sequencing

65. Four products (1, 2, 3, and 4) must be processed on one of four machines (A, B, C, and D). The times required in minutes for each product on each machine are shown below:

If management wishes to assign products to machines so that the total time to complete all the products is minimized, then Product 1 is assigned to

a) machine A

b) machine B

c) machine C

d) machine D

Answer: b

Difficulty: Hard

Learning Objective: Explain what sequencing is and use rules and quantitative tools for optimizing the sequence of jobs processed through one or two workstations.

Section Reference: 17.3 Sequencing

66. Four products (1, 2, 3, and 4) must be processed on one of four machines (A, B, C, and D). The times required in minutes for each product on each machine are shown below:

If management wishes to assign products to machines so that the total time to complete all the products is minimized, then Product 3 is assigned to

a) machine A.

b) machine B.

c) machine C.

d) machine D.

Answer: d

Difficulty: Hard

Learning Objective: Explain what sequencing is and use rules and quantitative tools for optimizing the sequence of jobs processed through one or two workstations.

Section Reference: 17.3 Sequencing

67. Four products (1, 2, 3, and 4) must be processed on one of four machines (A, B, C, and D). The times required in minutes for each product on each machine are shown below.

If management wishes to assign products to machines so that the total time to complete all the products is minimized, then Product 4 is assigned to

a) machine A.

b) machine B.

c) machine C.

d) machine D.

Answer: c

Difficulty: Hard

Learning Objective: Explain what sequencing is and use rules and quantitative tools for optimizing the sequence of jobs processed through one or two workstations.

Section Reference: 17.3 Sequencing

68. Four products (1, 2, 3, and 4) must be processed on one of four machines (A, B, C, and D). The times required in minutes for each product on each machine are shown below:

If management assigns products to machines so that the total time to complete all jobs is minimized, then the time to complete Product 1 is

a) 10 minutes.

b) 9 minutes.

c) 16 minutes.

d) 12 minutes

Answer: b

Difficulty: Hard

Learning Objective: Explain what sequencing is and use rules and quantitative tools for optimizing the sequence of jobs processed through one or two workstations.

Section Reference: 17.3 Sequencing

69. Four products (1, 2, 3, and 4) must be processed on one of four machines (A, B, C, and D). The times required in minutes for each product on each machine are shown below:

The minimum time required to complete all the products is

a) 29 minutes.

b) 27 minutes.

c) 33 minutes.

d) 36 minutes.

Answer: a

Difficulty: Hard

Learning Objective: Explain what sequencing is and use rules and quantitative tools for optimizing the sequence of jobs processed through one or two workstations.

Section Reference: 17.3 Sequencing

70. The scheduling rule that minimizes the makespan time for a set of jobs that must be processed through a two-step system where every job follows the same sequence through the two processes is

a) the shortest processing time (SPT).

b) Johnson’s Rule.

c) the assignment method.

d) the minimal slack rule.

Answer: b

Difficulty: Easy

Learning Objective: Explain what sequencing is and use rules and quantitative tools for optimizing the sequence of jobs processed through one or two workstations.

Section Reference: 17.3 Sequencing

71. The following set of jobs must be processed serially through a two-step system. If Johnson’s Rule is used to sequence the jobs, then the order in which the jobs would be performed is

a) A-B-C-D-E

b) C-B-E-D-A

c) E-B-D-A-C

d) D-E-B-A-C

Answer: c

Difficulty: Hard

Learning Objective: Explain what sequencing is and use rules and quantitative tools for optimizing the sequence of jobs processed through one or two workstations.

Section Reference: 17.3 Sequencing

72. The following set of jobs must be processed serially through a two-step system. The times at each process are in hours. If Johnson’s Rule is used to sequence the jobs then the makespan time (in hours) for all jobs is

a) 42 hours.

b) 53 hours.

c) 90 hours.

d) 95 hours.

Answer: b

Difficulty: Hard

Learning Objective: Explain what sequencing is and use rules and quantitative tools for optimizing the sequence of jobs processed through one or two workstations.

Section Reference: 17.3 Sequencing

73. The following set of jobs must be processed serially through a two-step system. The times at each process are in hours. If Johnson’s Rule is used to sequence the jobs then Job C would start processing on operation 2 at

a) hour 13.

b) hour 26.

c) hour 47.

d) hour 53.

Answer: c

Difficulty: Hard

Learning Objective: Explain what sequencing is and use rules and quantitative tools for optimizing the sequence of jobs processed through one or two workstations.

Section Reference: 17.3 Sequencing

74. The following set of jobs must be processed serially through a two-step system. The times at each process are in hours. If Johnson’s Rule is used to sequence the jobs, then Job A would complete processing on operation 2 at

a) hour 21.

b) hour 35.

c) hour 38.

d) hour 47.

Answer: d

Difficulty: Hard

Learning Objective: Explain what sequencing is and use rules and quantitative tools for optimizing the sequence of jobs processed through one or two workstations.

Section Reference: 17.3 Sequencing

75. A ___ chart is used to show both planned and completed activities against a time scale.

a) Gantt

b) Dispatch

c) Sequencing

d) None of the above.

Answer: a

Difficulty: Easy

Learning Objective: Use several methods to monitor the progress of jobs in a job shop environment.

Section Reference: 17.4 Monitoring

SHORT-ANSWER ESSAY QUESTIONS

76. What makes scheduling so difficult in a job shop?

Answer: Job shop scheduling is difficult because of the variety of jobs (or customers) that are processed, each with distinctive routing and processing requirements. In addition, although the volume of each customer order may be small, there are probably a great number of different orders in the shop at any one time. This necessitates planning for the production of each job as it arrives, scheduling its use of limited resources, and monitoring its progress through the system.

Difficulty: Easy

Learning Objective: Describe scheduling techniques and list the objectives of scheduling.

Section Reference: 17.1 Scheduling Techniques

77. List some of the objectives in scheduling.

Answer: There are many different possible objectives in constructing a schedule, including: meeting customer due dates, minimizing job lateness, minimizing response time, minimizing completion time, minimizing time in the system, minimizing overtime, maximizing machine or labour utilization, minimizing idle time, and minimizing work-in-process inventory.

Difficulty: Medium

Learning Objective: Describe scheduling techniques and list the objectives of scheduling.

Section Reference: 17.1 Scheduling Techniques

78. Why is monitoring an important component of job-shop scheduling?

Answer: In a job-shop environment, where jobs follow different paths through the shop, visit many different machine centres, and compete for similar resources, it is not always easy to keep track of the status of a job. When jobs are first released to the shop, it is relatively easy to observe the queue that they join and predict when their initial operations might be completed. As the job progresses, however, or the shop becomes more congested, it becomes increasingly difficult to follow the job through the system. Competition for resources (resulting in long queues), machine breakdowns, quality programs, and setup requirements are just a few of the things that can delay a job’s progress. Monitoring develops progress reports on each job until it is completed and helps maintain reliable schedules in the system.

Difficulty: Medium

Learning Objective: Use several methods to monitor the progress of jobs in a job shop environment.

Section Reference: 17.4 Monitoring

79. What is the difference between infinite scheduling and finite scheduling?

Answer: Infinite scheduling loads work without regard to capacity and then levels the load and sequences the jobs. Thus, levelling and sequencing decisions are made after overloads and underloads have been identified. This iterative process is very time consuming and not efficient. Finite scheduling assumes a fixed maximum capacity and will not load the resource beyond its capacity. Loading and sequencing decisions are made at the same time, so that the first jobs loaded onto a work centre are of highest priority. Any jobs remaining after the capacity of the work centre or resource has been reached are of lower priority and are scheduled for later time periods. This approach is easier than the infinite scheduling approach, but it will be successful only if the criteria for choosing the work to be performed, as well as capacity limitations, can be expressed accurately and concisely.

Difficulty: Medium

Learning Objective: Explain the basics of finite scheduling, and use the theory of constraints procedure to schedule multiple jobs through multiple workstations.

Section Reference: 17.5 Advanced Planning and Scheduling Systems

80. Who developed the theory of constraints (TOC) and what is its approach to scheduling?

Answer: The theory of constraints (TOC) was developed by an Israeli physicist named Eliyahu Goldratt. Because he did not have a business or manufacturing background, Dr. Goldratt took a commonsense, intuitive approach to scheduling. He developed a software system that used mathematical programming and simulation to create a schedule that realistically considered the constraints of the manufacturing system. Dr. Goldratt’s first insight into the scheduling problem led him to simplify the number of variables considered. Instead of trying to balance the capacity of the manufacturing system, he thought it best to balance the flow of work through the system. He identified resources as bottleneck or non-bottleneck and noted that the system’s flow is controlled by the bottleneck resources. These resources should always have material to work on, should spend little time on nonproductive activities, should be fully staffed, and should be the focus of continuous improvement activities. Goldratt pointed out that an hour’s worth of production lost at a bottleneck reduces the output of the system by the same amount of time, whereas an hour lost at a non-bottleneck resource may have no effect at all. Consequently, Goldratt simplified the scheduling problem by initially scheduling the bottleneck resources and then the non-bottleneck ones. In this way production could be synchronized with the needs of the bottleneck and the system as a whole.

Difficulty: Hard

Learning Objective: Explain the basics of finite scheduling, and use the theory of constraints procedure to schedule multiple jobs through multiple workstations.

Section Reference: 17.5 Advanced Planning and Scheduling Systems

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