Test-Bank-for-Heizer-Operations-Management-9e

95.Rerouting work, changing work sequence, and accepting idleness at other workstations are some techniques for dealing with a _____________.

bottleneck (Theory of constraints, moderate)

96.In "drum, buffer, rope,"__________ is the resource, usually inventory, necessary to keep the constraint operating at capacity.

buffer (Theory of constraints, moderate)

97.______________ means frequent, high-quality, small lot sizes that contribute to just-in-time production.

Level material use (Repetitive facilities, moderate)

98.In “drum, buffer, rope,” the __________ acts like kanban signals.

rope (Theory of constraints, moderate)

SHORT ANSWERS

99.Briefly describe how "the unexpected" makes short-term scheduling at Delta Airlines a challenge. Also describe how Delta meets that challenge, and achieves competitive advantage through shortterm scheduling.

The unexpected refers to delays and cancellations that are largely weather-related. These events require rapid rescheduling in order to keep operations going and to keep passengers from becoming too inconvenienced. Delta's solution involves a high-tech nerve center of computers and communications gear, and uses mathematical models to reroute and reschedule as quickly as possible. (Global company profile, easy)

100.What makes short-term scheduling of strategic importance?

Effective scheduling lowers cost by making greater use of facilities. Faster throughput leads to faster delivery to customers. Good scheduling contributes to realistic schedules and therefore to more dependable delivery. These three elements can create competitive advantage, and therefore make short-term scheduling of strategic importance. (The strategic importance of short-term scheduling, moderate)

101.Explain, in your own words, how backward scheduling and forward scheduling differ.

Forward scheduling starts the schedule as soon as the requirements are known. Backward scheduling begins with the due date, scheduling the final operation first and proceeding in the reverse order. (Scheduling issues, moderate)

102.How does short-term scheduling vary among the different process choices? Specifically, compare short-term scheduling at process-oriented, work cells, repetitive, and product-focused facilities.

All three process choices produce forward-looking schedules. Process-focused facilities and work cells use MRP; their scheduling problems are ongoing because their product mix is so variable. Repetitive facilities schedule with line balancing and pull techniques; their scheduling problems are most challenging when assembly lines are new or when models change. Continuous processes have rather straightforward scheduling because they make relatively few products, and facility capacity and setup times and run times are usually known. (Scheduling issues, moderate)

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103.Identify the types of planning files used in scheduling decisions. Which are used in manual systems, and which are used in automated systems?

The three types are item master files, routing files, and work center master files. All three are used in both manual and in automated systems. (Scheduling issues, moderate)

104.What is input-output control?

Input-output control is a technique that allows operations personnel to manage facility work flow by tracking work added to a work center and its completed work. (Loading jobs, moderate)

105.What are the options available to operations personnel to manage facility work flow?

Options available to manage facility work flow include correcting performances, increasing capacity, and increasing or reducing input to the work center by routing work to or from other work centers, increasing or decreasing subcontracting, and producing less or more. (Loading jobs, moderate)

106.What is the assignment method?

The assignment method is a special class of linear programming models that involves assigning tasks or jobs to resources. (Loading jobs, moderate)

107.Identify the disadvantages of the Gantt load chart.

It does not account for production variability, such as unexpected breakdowns or human errors that require reworking a job, and it must be updated regularly to account for new jobs and revised time estimates. (Loading jobs, moderate)

108.What is the difference between a Gantt load chart and a Gantt scheduling chart?

The Gantt load chart indicates a planned allocation of capacity—the allocation of the capacity of a department or work center to a particular job or order. The Gantt schedule chart indicates, for each job or order, the relative adherence to the particular time schedule, i.e., what fraction of total time to be expended on an order has been expended. (Loading jobs, moderate)

109.What does Johnson's rule do?

Johnson's rule is an approach that minimizes processing time for sequencing a group of jobs through two work centers while minimizing total idle time in the work centers. (Sequencing jobs, moderate)

110.In retail outlets, customers are usually processed on a first come, first served basis. Why? Is the express lane in the supermarket an exception? Craft a sequencing rule to explain express lane behavior.

All customers are considered equally important, and not one should be given a higher priority than another. Most students will write a rule like "FCFS, except for very short processing times"; "8 items or less" is a proxy for processing time. (Sequencing jobs, moderate) {AACSB: Reflective Thinking}

111.What is the primary disadvantage of the shortest processing time dispatch rule? Is this a problem if there can be no new jobs arriving after the sequence is set?

As new jobs arrive, new short-duration jobs will push back existing long-duration jobs in priority in favor of short-duration jobs. If newly arriving jobs must wait for a new sequence to be built, this is less problematic. (Sequencing jobs, moderate)

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112.Consider the arrival of patients into a public health clinic. Some patients are ill; some are injured; some are elderly; and some are very young. Some cases may be life-threatening, while others are inconsequential. How do the basic dispatch rules fall short in this situation? Design a dispatch rule for scheduling these patients.

First come, first served is inappropriate because it ignores the urgency of treating the most serious cases. There is no "due date" on which to base lateness or critical ratio sequences. Most students will write a "priority" rule that behaves like triage—assigning an urgency code to each patient, and taking highest urgency cases first. Student rules may have more than one part; for example, patients may be sorted by urgency code, and by treatment time within urgency code. They may also create a separate code for contagious cases. (Sequencing jobs, moderate) {AACSB: Reflective Thinking}

113.What are the criteria by which we evaluate sequencing rules?

There are a number of criteria for evaluating job sequencing rules. Criteria discussed in the text include average job completion time, average number of jobs in the system, and average job lateness. Additional criteria include: average wait time, average total completion time, and variance in completion times. (Sequencing jobs, moderate)

114.What are some limitations of rule-based scheduling systems? What alternatives are there to rulesbased scheduling systems?

Three limitations are (1) Rules need to be revised to adjust to changes in process, equipment, product mix, etc.; (2) Rules do not look at upstream or downstream, and (3) Rules do not look beyond due dates. Finite capacity scheduling is one recently developed option. (Sequencing jobs, easy)

115.Describe finite capacity scheduling in a sentence or two. What is its role in short-term scheduling?

Finite capacity scheduling (FCS) removes a shortcoming of MRP, which is that it ignores the capacity of time buckets. FCS makes short-term scheduling more realistic because it accounts for the finite capacity of time buckets. FCS can allow almost instantaneous change, and may involve an expert system or simulation system as planning tools. Short-term scheduling is evolving into finite capacity scheduling. (Finite capacity scheduling (FCS), moderate) {AACSB: Use of IT}

116.Describe the theory of constraints in a sentence.

The theory of constraints is the body of knowledge that deals with anything that limits an organization's ability to achieve its goals. (Theory of constraints, easy)

117.Identify, in proper sequence, the steps in the process of recognizing and managing constraints.

The five-step process of the theory of constraints includes: Step 1: Identify the constraints.

Step 2: Develop a plan for overcoming them. Step 3: Focus resources on accomplishing step 2.

Step 4: Off-load work from the constraint or expand capability at the constraint. Step 5: Once one set of constraints is overcome, go back to step 1 and identify new constraints. (Theory of constraints, moderate)

118.Explain the importance of a bottleneck operation in a production sequence.

A bottleneck operation is one that limits output in the production sequence. Consequently, to increase throughput of the facility, the bottleneck operations must be maximized. (Theory of constraints, moderate)

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119.What techniques exist for dealing with bottlenecks? Which of these leads to increased capacity? Which of these leads to more throughput without adding capacity? Do any of these techniques fail to increase throughput?

Five techniques are available to deal with the constraint. They are:

1.Increase the capacity of the constraint. This obviously increases capacity.

2.Have well-trained and cross-trained employees keep the bottleneck at full operation. This increases capacity.

3.Develop alternate routings. This makes better use of existing capacity.

4.Move inspection and testing points to positions that precede the bottleneck, to avoid wasting bottleneck capacity on bad items. This makes better use of existing capacity.

5.Schedule throughput to match the bottleneck's capacity. There's no more throughput, but there may be lower costs at other work centers. (Theory of constraints, difficult)

120.In repetitive manufacturing, what are the advantages of level material use? Does level material use have any role in intermittent process facilities?

The five advantages are:

1.Lower inventory levels to release capital for other uses.

2.Increase the rate of product throughput.

3.Improve component quality and hence improve product quality.

4.Reduce floor-space requirements.

5.Move employees closer together to improve communication.

6.The production process is smoothed because large lots have not "hidden" the problems. Intermittent (job shop) facilities have so many additional sources of variation (materials, requirements, work center order, etc.) that there is little role for level material use. (Repetitive facilities, moderate)

121.Explain, in your own words, what is meant by "level material use." In what types of facilities is it appropriate? Explain.

It means frequent, high quality, small lot sizes that contribute to just-in-time production. It is appropriate in repetitive processing, not in intermittent processing, because repetitive processing has much more predictable material and processing needs. (Repetitive facilities, moderate)

122.In what ways does the problem of scheduling service systems differ from that of scheduling manufacturing systems?

Scheduling services differs from scheduling manufacturing systems in five ways:

1.In manufacturing, emphasis is on materials, whereas in services it is on staffing levels.

2.Service systems do not store inventories of services.

3.Services are labor intensive, and demand for this labor can be highly variable.

4.Legal considerations constrain scheduling decisions.

5.Behavioral, social, seniority, and status issues occur in service scheduling.

(Scheduling services, moderate)

123.Identify some scheduling optimization systems that are used at retail stores. Describe what these systems do.

Workbrain, Cybershift, and Kronos. These systems track individual store sales, transactions, units sold, and customer traffic in 15-minute increments to create work schedules. (Scheduling services, difficult) {AACSB: Use of IT}

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PROBLEMS

124.A practitioner of family medicine begins her day with five patients needing urgent care. She does a very brief assessment of what each patient appears to need and estimates the time required of each. None of the cases is life-threatening, and so she determines to take the five in the order that they arrived at the clinic. The data for these patients, in the order they arrived, is Patient A, 30 minutes; Patient B, 40 minutes; Patient C; 10 minutes; Patient D, 50 minutes; and Patient E, 15 minutes.

a.If it is now 8:00 a.m., at what time will the doctor be finished with all five of these emergencies?

b.How much time will the five patients have collectively spent waiting?

c.How much less time would have been spent waiting if the doctor had taken the patients according to shortest processing time?

(a)Using first come, first served, all five patients will be finished in 145 minutes, or at 10:25 a.m. (b)Total flow time is 455 minutes, of which 145 is for processing, and the remaining 310 is waiting time. (c) If the doctor had used shortest processing time, the total flow time would have been 330 minutes, of which 185 is waiting time. In both cases, the doctor finished all patients at 10:25 a.m. A supporting table for each rule appears below.

(Sequencing jobs, moderate) {AACSB: Analytic Skills}

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125.The emergency room at a hospital estimates the following requirements for registered nurses (RNs) for the late night shift each week. Nurses work four consecutive days, then have off three days.

Perform cyclical scheduling on the data. (Note that you must identify three-day patterns of minimum requirements). How many RNs are required? How much extra capacity is required?

Days off are shaded. Seven full-time RNs are needed; an eighth works Friday only. A total of 29 shifts are used, while only 24 are required; thus 5 shifts represent excess capacity. This solution is not unique, as there are two instances where an arbitrary set of days was selected for minimum sum. (Scheduling services, moderate) {AACSB: Analytic Skills}

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126.Jack's Refrigeration Repair is under contract to repair, recondition, and/or refurbish commercial and industrial icemakers from restaurants, seafood processors, and similar organizations. Jack currently has five jobs to be scheduled, shown in the order in which they arrived.

a.Complete the following table. (Show your supporting calculations below).

b.Which dispatching rule has the best score for flow time?

c.Which dispatching rule has the best score for work-in-process (jobs in the system)?

d.Which dispatching rule has the best score for lateness?

e.What dispatching rule would you select? Support your decision.

(a) A summary of calculations appears in the table below.

(b,c,d) SPT is best on all three criteria: flow time, work-in-process, and lateness. (e) Most students will select SPT as quite obvious, but EDD is a close second in all criteria. Supporting calculations for each priority rule appear in the tables below.

Average # jobs in system = 3.80

(Sequencing jobs, moderate) {AACSB: Analytic Skills}

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127.The operations manager of a body and paint shop has five cars to schedule for repair. He would like to minimize the throughput time (makespan) to complete all work on these cars. Each car requires body work prior to painting. The estimates of the times required to do the body and paint work on each are as follows:

a.Chart the progress of these five jobs through the two centers on the basis of the arbitrary order A ÆBÆCÆDÆE.

b.After how many hours will all jobs be completed?

Body Work

Paint

c.Use Johnson's rule to sequence these five jobs for minimum total duration. Show your work in determining the job sequence.

d.The optimal sequence is ________________________.

e.Chart the progress of the five jobs in this optimal sequence.

f.After how many hours will all jobs be completed?

SEE NEXT PAGE FOR SOLUTION.

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(a,b) Arbitrary order:

(c,d) The sequence of jobs is Car E, Car D, Car A, Car C, Car B. Makespan = 43 as per the POM for Windows solution below.

(c) Johnson's method sequence of steps

(e,f)

(Sequencing jobs, moderate) {AACSB: Analytic Skills}

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