An Analysis on the Effects of Dispatching Rules on Overtime Models
Date Issued
2005
Date
2005
Author(s)
Lin, Yi-Chien
DOI
zh-TW
Abstract
Due to the rapidly changing demand, corporations now put more emphasis on improving their workflow in order to provide better products and services with lower prices. The production scheduling problem is especially complicated and difficult to manage. Although current software and information systems, such as ERP, are designed to solve this kind of problem, they neglect the limitations of capacity, and usually produce infeasible planning results.
At present, most scheduling problems are job shop related. Dispatching rules, which are easy to understand and efficient, are one of the most common approaches to solving job shop scheduling problems. Nevertheless, the results generated by dispatching rules do not necessarily meet the goals of production scheduling. For instance, the due date of products may not be satisfied. In this case, having employees work overtime has been commonly used as a way to meet the delivery schedules, which is different from previous research where the scheduling problem was only solved by dispatching rules. In this study, the effects of different initial solutions resulting from different dispatching rules on overtime models are explored. The shortcomings of previous overtime models are also identified and a modified overtime model is proposed in this work. The experimental setting takes five experimental factors into account: the number of machines, the number of jobs, the maximum processing time, the due date allowance factor, and the maximum daily overtime. Fifty-five dispatching rules are evaluated both before and after overtime by three performance metrics: total tardiness, number of tardy jobs, and mean flow time.
The experimental results show that most dispatching rules that outperform others before overtime usually also perform well after overtime. On the other hand, by using more overtime, some of the dispatching rules that perform poorly before overtime can catch up with those performing well before overtime. However, the cost of overtime cannot be neglected. In the case of tighter due date settings, we observe that SPT.TWK and SPT.TWKR outperform other dispatching rules both before and after overtime in terms of the three performance metrics. In future implementations, our model could be extended to different production systems, such as flow shops. In addition, the cost and efficiency of overtime compared to normal working hours could be considered.
Subjects
零工式生產排程
派工法則
加班模式
job shop scheduling
dispatching rule
overtime model
Type
other
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