CHAPTER-15 : Discussion Questions
1. What is the overall objective of scheduling?
The goal of scheduling is to allocate and organize request (produced by either conjectures or client orders) to accessible offices.
2. List the four criteria for determining the effectiveness of a scheduling decision. How do these criteria relate to the four criteria for sequencing decisions?
Minimize completion time: Evaluated by determining the average completion time.
Maximize utilization: Evaluated by determining the percent of the time the facility is utilized.
Minimize work-in-process (WIP) inventory: Evaluated by determining the average number of jobs in the system. The relationship between the number of jobs in the system and WIP inventory will be high. Therefore, the fewer the number of jobs that are in the system, the lower the inventory.
Minimize customer waiting time: Evaluated by determining the average number of late periods (e.g., days or hours).
3. Describe what is meant by “loading” work centers. What are the two ways work centers can be loaded? What are two techniques used in loading?
Loading work centers is when operations managers assign jobs to work centers so that costs, idle time, or completion times are kept to a minimum. It takes two forms— one is oriented to capacity; the second is related to assigning specific jobs to work centers.
Two techniques used in loading:
Gantt schedule chart—The Gantt schedule chart is used to monitor jobs in progress (and is also used for project scheduling). It indicates which jobs are on schedule and which are ahead of or behind schedule.
Assignment method —A special class of linear programming models that involves assigning tasks or jobs to resources.
4. Name five priority sequencing rules. Explain how each works to assign jobs.
First come, first served (FCFS) — Jobs are completed in the order in which they arrived.
Shortest processing time (SPT) — Jobs with the shortest processing times are assigned first.
Earliest due date — earliest due date jobs are performed first.
Longest processing time (LPT) — Jobs with the longest processing time are completed first.
Performance Criteria — the choice of which priority rule to choose depends in part on how each rule performs on four criteria: the priority rules try to minimize completion time, maximize facility utilization, minimize number of jobs in the system, and minimize job lateness.
5. What are the advantages and disadvantages of the shortest processing time (SPT) rule?
Short processing time is by and large the best procedure for limiting occupation stream and limiting the normal number of employments in the framework. Its main weakness is that long-term employments might be persistently pushed back in need for brief span occupations. Clients may see this faintly, and an intermittent change for longer occupations must be made
6. What is a due date?
It is the date on which something falls due. A due date may range from a (meaningless) promise to a contractual obligation. It is a target with or without penalties.
7. Explain the terms flow time and lateness.
Flow time is the period required to finish a particular employment or a characterized measure of work. The flow time measures the time each activity invests holding up in addition to the energy it takes to be prepared. Lateness alludes to coming, happening, or staying after the right, normal, or expected time.
8. Which shop-floor scheduling rule would you prefer to apply if you were the leader of the only team of experts charged with defusing several time bombs scattered throughout your building? You can see the bombs; they are of different types. You can tell how long each one will take to defuse. Discuss.
Given this circumstance I would most certainly utilize a shop-floor booking decide that obliges the significant issues confronting this circumstance. The reality we can see the bombs however they are of various assortment plays a central point. We are additionally looked with a course of events to work with which will figure out what planning standard is chosen. EDD would be select for a few reasons; this would organize what bombs should be defused first. From that point, specialists can be doled out to completing that work.
9. When is Johnson’s rule best applied in job-shop scheduling?
Johnson’s lead can be utilized to limit the ideal opportunity for sequencing a gathering of employments through two work focuses. It additionally limits add up to idle time on the machines.
10. State the four effectiveness measures for dispatching rules.
Four effectiveness measures for dispatching rules:
Average completion time, average number of jobs in the system, average job lateness, and utilization.
11. What are the steps of the assignment method of linear programming?
First, subtract the smallest number in each row from every number in that row and then, from the resulting matrix, subtract the smallest number in each column from every number in that column. This step has the effect of reducing the numbers in the table until a series of zeros, meaning zero opportunity costs, appear. Even though the numbers change, this reduced problem is equivalent to the original one, and the same solution will be optimal.
Second, draw the minimum number of vertical and horizontal straight lines necessary to cover all zeros in the table. If the number of lines equals either the number of rows or the number of columns in the table, then we can make an optimal assignment (see Step 4). If the number of lines is less than the number of rows or columns, we proceed to Step 3.
Third, subtract the smallest number not covered by a line from every other uncovered number. Add the same number to any number(s) lying at the intersection of any two lines. Do not change the value of the numbers that are covered by only one line. Return to Step 2 and continue until an optimal assignment is possible.
Lastly, optimal assignments will always be at zero locations in the table. One systematic way of making a valid assignment is first to select a row or column that contains only one zero square. We can make an assignment to that square and then draw lines through its row and column. From the uncovered rows and columns, we choose another row or column in which there is only one zero square. We make that assignment and continue the procedure until we have assigned each person or machine to one task.
12. What are the advantages to finite capacity scheduling?
It overcomes disadvantages of rule-based systems by providing the user with graphical interaction computing.
13. What is input–output control?
It is a system that allows operations personnel to manage facility work flows by tracking work added to a work center and its work completed.