On the role of a queueing network model in the design of a complex assembly system

Abstract

This paper describes the modeling, analysis and re-design of a complex assembly system consisting of many processes (assembly, testing and inspection) and resources (machines and operators) and an advanced material handling system with intricate routing logics. It presents a systematic approach using both analytical and simulation models for the evaluation and modification of the complex assembly system. It demonstrates the application of a queueing network model to quickly generate rough-cut solutions and provide qualitative information for the evaluation of design alternatives. Iteratively, processes and resources that affect the system performance are identified, one at a time, and the system modified accordingly, until a satisfactory performance is obtained. The preliminary analyses using the queueing network model help to identify bottleneck processes, estimate optimal pallets, and determine a more efficient system layout. The use of the analytical model significantly reduces the number of the lengthy simulation runs. A detailed simulation model is subsequently employed for fine-tuning and further improvement. Compared with the original design, significant improvements have been made: a higher throughput, a reduced cycle time with less operators, and lower WIP inventories.