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Exam 15: Short-Term Scheduling

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Question 61

Multiple Choice

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Which of the following is not an effectiveness criterion for scheduling?

A) minimizing customer waiting time
B) minimizing completion time
C) minimizing WIP inventory
D) maximizing utilization
E) maximizing flow time

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Question 62

Multiple Choice

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The most appropriate sequencing rule to use if the goal is to dynamically track the progress of jobs and establish relative priority on a common basis is

A) shortest processing time.
B) earliest due date.
C) critical ratio.
D) longest processing time.
E) Johnson's rule.

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Question 63

Multiple Choice

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Which of the following statements regarding finite capacity scheduling (FCS) is false?

The jobs listed below needed to be completed. Assume that it is now day 140. If the jobs are sequenced according to shortest processing time rule, what is the average completion time? $\begin{array} { | c | c | c | } \hline \text { Job } & \begin{array} { c } \text { Processing } \\\text { Time (days) }\end{array} & \begin{array} { c } \text { Job due date } \\\text { (days) }\end{array} \\\hline \text { A } & 20 & 180 \\\hline \text { B } & 30 & 200 \\\hline \text { C } & 10 & 175 \\\hline \text { D } & 16 & 230 \\\hline \text { E } & 18 & 210 \\\hline\end{array}$

Some firms have developed arrangements to literally "swap" employees with each other during their respective peak demand times.

Forward scheduling

The first step in level material use is to combine orders into a few large batches in order to utilize economies of scale.

Find the sequence for the priority rules of a. LPT b. SPT c. EDD Given the table below and the fact that today is the 1st $\begin{array} { | l | l | l | } \hline \text { job } & \text { Process Time } & \text { Due Date } \\\hline \text { A } & 6 & 4 \\\hline \text { B } & 4 & 2 \\\hline \text { C } & 2 & 5 \\\hline \text { D } & 3 & 1 \\\hline\end{array}$

A work centre had planned outputs of 10,15,13, and 20 hours with actual outputs of 12, 14, 13, and 18 hours. The cumulative deviation in output is

Which of the following statements regarding scheduling at Air Canada is false?

Which critical ratio value implies that a job is already late?

Sequencing (or dispatching)

Lockport Marine Services, Inc. wishes to assign a set of jobs to a set of machines. The following table provides data on the cost of production of each job when performed on a specific machine. a. Determine the set of assignments that maximizes production value. b. What is the total production value of your assignments? $\begin{array} { | l | l | l | l | l | } \hline & { \text { Machine } } \\\hline \text { Job } & \text { A } & \text { B } & \text { C } & \text { D } \\1 & 27 & 29 & 28 & 30 \\2 & 30 & 29 & 27 & 26 \\3 & 31 & 25 & 29 & 26 \\4 & 29 & 31 & 25 & 28 \\\hline\end{array}$

A firm that specializes in desktop publishing for local charities has agreed to take on the following jobs. The firm has not decided which dispatching rule to apply in order to prioritize the jobs and fix them into the schedule. All dates are specified as days from Day 1. $\begin{array} { | r | r | r | r | } \hline \text { Start day } & 1 & & \\\hline \text { Data } & & & \\\hline & \text { Received } & \text { Time } & \text { Due Date } \\\hline \text { A } & 1 & 20 & 25 \\\hline \text { B } & 1 & 15 & 20 \\\hline \text { C } & 1 & 7 & 16 \\\hline \mathrm { D } & 1 & 25 & 50 \\\hline \text { E } & 1 & 17 & 7 \\\hline \text { F } & 1 & 13 & 32 \\\hline\end{array}$ 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? $\begin{array} { | l | l | l | l | l | } \hline \begin{array} { l } \text { Dispatching } \\\text { Rule }\end{array} & \begin{array} { l } \text { Average } \\\text { Flow Time }\end{array} & \begin{array} { l } \text { Average Number } \\\text { of Jobs }\end{array} & \begin{array} { l } \text { Number of } \\\text { Jobs Late }\end{array} & \begin{array} { l } \text { Average } \\\text { Lateness }\end{array} \\\hline \text { FCFS } & & & & \\\hline \text { SPT } & & & & \\\hline\text { LPT } & & & & \\\hline \text { EDD } & & & & \\\hline \text { SLACK } & & & & \\\hline \text { CR } & & & &\\\hline\end{array}$

Which file contains important information regarding an item's flow through the shop?

Bob Dresser operates a major appliance warranty service centre. His operation has two check stations that are required at the end of every repair task performed by his appliance repair staff. These are the Functionality Review (FR) and the Overall Scan (OS). The FR must be performed successfully before the OS is begun. On Friday morning, six repair jobs are completed, awaiting these two inspection activities. Processing times are given in minutes. $\begin{array} { | c | c | c | } \hline \text { Job } & \text { FR } & \text { OS } \\\hline \text { A } & 50 & 30 \\\hline \text { B } & 35 & 55 \\\hline \text { C } & 25 & 20 \\\hline \text { D } & 20 & 35 \\\hline \text { E } & 15 & 10 \\\hline \text { F } & 10 & 25 \\\hline\end{array}$ a. What is the optimal sequence of jobs for the objective of minimizing the total flow time? b. Show your work, and document the sequence. c. Chart the solution to this problem. d. What jobs are being processed at time period 90? e. What is the total flow time of this problem? $\begin{array} { | l | l | l | l | l | l | l | l | l | l | l | } \hline \mathrm { FR } & & & & & & & & & & \\\hline \mathrm { OS } & & & & & & & & & & \\\hline & 20 & 40 & 60 & 80 & 100 & 120 & 140 & 160 & 180 & 200 \\\hline\end{array}$

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

Which of the following best describes the strategic importance of short-term scheduling?

Identify the disadvantages of the Gantt load chart.

Use Johnson's rule to determine the optimal sequencing for the five jobs to be processed on two machines in a fixed order (Machine 1 before Machine 2). The processing times are given in the table below. a. What is the optimal sequence? b. What is the total flow time for this sequence? $\begin{array} { | c | c | c | } \hline \text { Job } & \text { Machine 1 } & \text { Machine 2 } \\\hline \text { L } & 10 & 11 \\\hline \text { M } & 8 & 17 \\\hline \mathrm { N } & 14 & 9 \\\hline \mathrm { O } & 13 & 7 \\\hline \mathrm { P } & 10 & 8 \\\hline\end{array}$