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Unformatted text preview: Chapter 19 - Scheduling CHAPTER 19 SCHEDULING Review and Discussion Questions 1. What are the objectives of work-center scheduling? The objective can vary but include: meeting due dates, minimizing lead time, minimizing set- up times and cost, minimizing work-in-process inventory, and maximizing machine and/or worker utilization. 2. Distinguish between a work center, a GT cell, and a flow shop. A work center may have the flow of products going in any direction between departments. A GT cell is somewhere in between a work center and a flow shop in terms of product flow. A flow shop has the flow of products going in a specific sequence for all products. 3. What practical considerations are deterrents to using the SOT rule? Perhaps one will encounter a situation whereby those jobs with the shortest operations times are least urgent than those with long due-dates. Also long jobs will always be preempted in a dynamic shop so they may never be completed. A good example would be applying this rule to all student assignments (including term papers) for one semester. At the beginning of the semester, this works quite well, but it results in the term papers being postpone until immediately before their due-date, typically resulting in inadequate time to complete the term paper. 4. What priority rule do you use in scheduling your study time for midterm examinations? If you have 5 exams to study for, how many alternative schedules exists? Most students will probably respond that they use either FCFS (first things first) or SOT. After understanding the chapters material, they should use SOT and have one schedule, but many will respondtwo or more schedules. The are 5! possible schedules or 5 x 4 x 3 x 2 x 1 or 120 schedules. 5. The SOT rule provides an optimal solution in a number of evaluation criteria. Should the manager of a bank use the SOT rule as a priority rule? Why? Even though the SOT rule is optimal, the bank manager may still choose the FIFO rule for customer sequencing in order to keep the sense of fairness; whoever comes in first, gets served first. 2 Chapter 19 - Scheduling 6. Data integrity is a big deal in industry? Why? Data inaccuracy coupled with computer usage simply speeds up the mess and results in serious problems, such as excess inventory, stockouts, missed due dates, costing inaccuracies, etc. 7. Why does batching cause so much trouble in work centers? Batching can appear to improve efficiency and reduce setups. However, in some situations batching can lead to split lots, broken setups, lost parts, defects, late deliveries, large WIPs and the hockey stick phenomenon. 8. What job characteristics would lead you to schedule jobs according to longest processing time first?...
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- Spring '11