Development of Drum-Buffer-Rope scheduling software to support a “what if” approach to scheduling job shops
Thesis (MScEng (Industrial Engineering))--University of Stellenbosch, 2006.
The Theory of Constraints is a management philosophy based on the underlying assumption that only a few constraining factors limit the throughput of the entire system. Drum-Buffer-Rope is the production logistical solution of the Theory of Constraints. It is the implementation of Constraints Management on the manufacturing shop floor, to manage physical resource constraints. Drum-Buffer-Rope was designed with the purpose of increasing Throughput, while simultaneously decreasing Inventory, and minimising Operating Expense. It aims to accomplish these goals by focusing on simplifying and therefore reducing variability in the production process, and ultimately protecting order due dates against disruptions. The dynamic conditions under which typical job shops operate can make Constraints Management of the resource constraints a cumbersome task. By following a “What If” approach to the scheduling process, the scheduler can play an interactive role in developing practical shop floor schedules. In this way the scheduler can see the results of his/her ideas on the shop floor situation quickly as immediate feedback is provided. The Drum-Buffer-Rope methodology only finite schedules certain points in the manufacturing process therefore scheduling calculations can be performed quickly if done in software. This makes it possible for the scheduler to analyse various scenarios in a short period of time and allowing the development of near optimal shop floor schedules by following a “What If” approach to scheduling. In this project, new developments in the field of Drum-Buffer-Rope were investigated, and the newly developed Simplified Drum-Buffer-Rope methodology was researched. The methodologies were incorporated in a fully developed software package that uses Drum-Buffer- Rope or Simplified Drum-Buffer-Rope to marry the intrinsic knowledge of the shop-floor worker with modern day computer technology to create production schedules that can be released to the shop floor. Schedules are created rapidly enough by the software to enable the scheduler to follow a “What If” approach to create near optimal shop floor schedules. The developed software was used with live data from a South African job shop to illustrate the “What If” approach to Simplified Drum-Buffer-Rope scheduling. The results show that throughput can be increased and operating expense decreased, therefore increasing bottom line results, by analysing various scenarios.