Plant supply logistics : balancing delivery and stockout costs

Jennifer A. Pope, J. A. Pope
{"title":"Plant supply logistics : balancing delivery and stockout costs","authors":"Jennifer A. Pope, J. A. Pope","doi":"10.22237/JOTM/1143849900","DOIUrl":null,"url":null,"abstract":"INTRODUCTION Transporting raw materials to a production facility would seem to be almost trivial when the final product requires only one primary raw material. While the process is not as involved as a multi-level bill of materials system, there are still a number of variables with which one must deal, particularly in the logistics system. In this case, the raw material, peanuts, are transported from a sheller near Columbus, Georgia, to Portsmouth, Virginia, to be converted into peanut butter. The transportation is via railroad--a distance of about 700 miles. The manufacturer is currently required to lease rail cars, which are then moved from Georgia to Virginia full of raw, shelled peanuts, and returned to Georgia empty. The question the plant manager faces on a regular basis is how many rail cars to lease? Analytically, the system faced by the plant manager is a circular queueing system. As explained in Appendix A, this is a special case of a Jackson network (see Figure 1). In the usual queueing process, customers enter the system, are served and leave the system. In our case, the rail cars leased by the company moved in a continuous loop. The rail cars are \"served\"' in Georgia when they were loaded with peanuts, in Virginia when they are unloaded at the plant and en route in both directions. Appendix A describes briefly the analytical construction of the problem. [FIGURE 1 OMITTED] There are numerous examples in the literature of analytic solutions to rail car scheduling (Cordeau, Soumis, and Derosiers, 2000; Luub-becke and Zimmermann, 2003; and Sherali and Maguire, 2000). Although the objective here was to solve for the optimal number of rail cars, an analytical solution was not a practical option for several reasons. The first is the limitation of Jackson networks for predictive purposes (see Appendix A); the second is the nature of the data. The probability distributions of service times were empirical distributions. Using theoretical distributions would have made the problem computationally more attractive, but less realistic. Third, the company did not want to release cost figures. Therefore, results could only be stated as trade-offs in terms of numbers of rail cars and number of days the plant would be shut down. Given the results, however, the company could easily calculate the corresponding total costs. Finally, the company wanted the flexibility to test easily a variety of scenarios. For these reasons, it was decided to use simulation as the method of dealing with The travel time between the sheller and the plant (and the return trip) varied widely. The rail cars were sent from the sheller to a rail yard, where they waited until a northbound the problem. It was also easier to explain the process and results to the plant manager. Further, the plant manager could watch the outcomes develop as the simulation was running and could run the simulation with various scenarios. THE PROBLEM The peanut butter manufacturer in Virginia (VA) required an average of 180,000 pounds of peanuts per day to keep the line running. Rail cars carrying 190,000 pounds of peanuts each supplied the plant. The rail cars queued up at the plant waiting to be unloaded. Any time the queue was empty, the plant had to be shut down at a corresponding substantial cost. If there were too many rail cars in the queue, it could cause a problem, especially in the summer. Peanuts are a live organic product and could spoil if left sitting in the sun too long. Although the com-pany could provide no specific data for this problem, management asked that the solution tell them the length of the queue at the plant and the mean number of days in the queue. The peanuts are purchased from a sheller in Georgia (GA). The sheller buys raw peanuts from the farmers, shells them, and loads them in the hopper cars. Since the sheller maintains an inventory of peanuts, there is virtually no queue at the sheller except on weekends. …","PeriodicalId":242296,"journal":{"name":"Journal of Transportation Management","volume":"82 1","pages":"0"},"PeriodicalIF":0.0000,"publicationDate":"2006-03-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Transportation Management","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.22237/JOTM/1143849900","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
引用次数: 0

Abstract

INTRODUCTION Transporting raw materials to a production facility would seem to be almost trivial when the final product requires only one primary raw material. While the process is not as involved as a multi-level bill of materials system, there are still a number of variables with which one must deal, particularly in the logistics system. In this case, the raw material, peanuts, are transported from a sheller near Columbus, Georgia, to Portsmouth, Virginia, to be converted into peanut butter. The transportation is via railroad--a distance of about 700 miles. The manufacturer is currently required to lease rail cars, which are then moved from Georgia to Virginia full of raw, shelled peanuts, and returned to Georgia empty. The question the plant manager faces on a regular basis is how many rail cars to lease? Analytically, the system faced by the plant manager is a circular queueing system. As explained in Appendix A, this is a special case of a Jackson network (see Figure 1). In the usual queueing process, customers enter the system, are served and leave the system. In our case, the rail cars leased by the company moved in a continuous loop. The rail cars are "served"' in Georgia when they were loaded with peanuts, in Virginia when they are unloaded at the plant and en route in both directions. Appendix A describes briefly the analytical construction of the problem. [FIGURE 1 OMITTED] There are numerous examples in the literature of analytic solutions to rail car scheduling (Cordeau, Soumis, and Derosiers, 2000; Luub-becke and Zimmermann, 2003; and Sherali and Maguire, 2000). Although the objective here was to solve for the optimal number of rail cars, an analytical solution was not a practical option for several reasons. The first is the limitation of Jackson networks for predictive purposes (see Appendix A); the second is the nature of the data. The probability distributions of service times were empirical distributions. Using theoretical distributions would have made the problem computationally more attractive, but less realistic. Third, the company did not want to release cost figures. Therefore, results could only be stated as trade-offs in terms of numbers of rail cars and number of days the plant would be shut down. Given the results, however, the company could easily calculate the corresponding total costs. Finally, the company wanted the flexibility to test easily a variety of scenarios. For these reasons, it was decided to use simulation as the method of dealing with The travel time between the sheller and the plant (and the return trip) varied widely. The rail cars were sent from the sheller to a rail yard, where they waited until a northbound the problem. It was also easier to explain the process and results to the plant manager. Further, the plant manager could watch the outcomes develop as the simulation was running and could run the simulation with various scenarios. THE PROBLEM The peanut butter manufacturer in Virginia (VA) required an average of 180,000 pounds of peanuts per day to keep the line running. Rail cars carrying 190,000 pounds of peanuts each supplied the plant. The rail cars queued up at the plant waiting to be unloaded. Any time the queue was empty, the plant had to be shut down at a corresponding substantial cost. If there were too many rail cars in the queue, it could cause a problem, especially in the summer. Peanuts are a live organic product and could spoil if left sitting in the sun too long. Although the com-pany could provide no specific data for this problem, management asked that the solution tell them the length of the queue at the plant and the mean number of days in the queue. The peanuts are purchased from a sheller in Georgia (GA). The sheller buys raw peanuts from the farmers, shells them, and loads them in the hopper cars. Since the sheller maintains an inventory of peanuts, there is virtually no queue at the sheller except on weekends. …
工厂供应物流:平衡交货和库存成本
当最终产品只需要一种主要原材料时,将原材料运输到生产设施似乎几乎微不足道。虽然这个过程不像多层次的物料清单系统那样复杂,但仍然有许多必须处理的变量,特别是在物流系统中。在这种情况下,原料花生从佐治亚州哥伦布附近的脱壳机运送到弗吉尼亚州的朴茨茅斯,然后转化为花生酱。运输是通过铁路——距离大约700英里。制造商目前被要求租用火车车厢,然后将满载生花生、剥了壳的花生从乔治亚州运到弗吉尼亚,然后空车返回乔治亚州。工厂经理经常面临的问题是要租用多少轨道车辆?解析地说,工厂经理所面临的系统是一个循环排队系统。如附录A所述,这是Jackson网络的一个特例(见图1)。在通常的排队过程中,客户进入系统,得到服务,然后离开系统。在我们的例子中,公司租赁的轨道车辆在一个连续的循环中移动。火车车厢在佐治亚州装载花生时是“服务”的,在弗吉尼亚州,当它们在工厂卸货时,在两个方向上都是“服务”的。附录A简要描述了问题的分析结构。[图1省略]文献中有许多关于轨道车辆调度解析解的例子(Cordeau, Soumis, and Derosiers, 2000;Luub-becke and Zimmermann, 2003;Sherali and Maguire, 2000)。虽然这里的目标是求解轨道车辆的最佳数量,但由于几个原因,分析解决方案不是一个实际的选择。首先是Jackson网络用于预测目的的局限性(见附录A);其次是数据的性质。服务时间的概率分布为经验分布。使用理论分布会使这个问题在计算上更有吸引力,但不太现实。第三,公司不想公布成本数据。因此,结果只能用铁路车辆的数量和工厂关闭的天数来权衡。然而,根据结果,公司可以很容易地计算出相应的总成本。最后,该公司希望能够灵活地测试各种场景。由于这些原因,决定采用模拟的方法来处理脱壳机和工厂之间的行程时间(以及回程时间)变化很大。这些火车车厢被从脱壳厂送到一个铁路调车场,在那里他们等待着向北行驶的问题。向工厂经理解释过程和结果也更容易。此外,工厂经理可以在模拟运行时观察结果的发展,并可以在各种场景下运行模拟。问题:维吉尼亚州的花生酱制造商平均每天需要18万磅花生来维持生产线的运转。每节载有19万磅花生的火车车厢为工厂供应花生。火车车厢在工厂里排队等待卸货。只要队列空了,工厂就必须以相应的巨额成本关闭。如果有太多的火车在排队,这可能会造成问题,特别是在夏天。花生是一种活的有机产品,如果在阳光下放置太久可能会变质。虽然该公司无法提供这个问题的具体数据,但管理层要求解决方案告诉他们工厂排队的长度和平均排队的天数。这些花生是从乔治亚州的剥壳商那里购买的。剥壳工从农民那里购买生花生,剥壳,然后装进料车里。由于剥壳机保持着花生的库存,除了周末,几乎没有人在剥壳机前排队。…
本文章由计算机程序翻译,如有差异,请以英文原文为准。
求助全文
约1分钟内获得全文 求助全文
来源期刊
自引率
0.00%
发文量
0
×
引用
GB/T 7714-2015
复制
MLA
复制
APA
复制
导出至
BibTeX EndNote RefMan NoteFirst NoteExpress
×
提示
您的信息不完整,为了账户安全,请先补充。
现在去补充
×
提示
您因"违规操作"
具体请查看互助需知
我知道了
×
提示
确定
请完成安全验证×
copy
已复制链接
快去分享给好友吧!
我知道了
右上角分享
点击右上角分享
0
联系我们:info@booksci.cn Book学术提供免费学术资源搜索服务,方便国内外学者检索中英文文献。致力于提供最便捷和优质的服务体验。 Copyright © 2023 布克学术 All rights reserved.
京ICP备2023020795号-1
ghs 京公网安备 11010802042870号
Book学术文献互助
Book学术文献互助群
群 号:481959085
Book学术官方微信