A line-balancing strategy for designing flexible assembly systems

The authors present a rough-cut analysis tool that quickly determines a few potential cost-effective designs at the initial design stage of flexible assembly (FASs) prior to a detailed analysis such as simulation. It uses quantitative methods for selecting and configuring the components of an FAS suitable for medium to high volumes of several similar products. The system is organized as a series of assembly stations linked with an automated material-handling system moving parts in a unidirectional flow. Each station consists of a single machine or of identical parallel machines. The methods exploit the ability of flexible hardware to switch almost instantaneously from product to product. The present approach is particularly suitable where the product mix is expected to be stable, since the hardware-configuration phase is combined with the task-allocation phase. For the required volume of products, the authors use integer programming to select the number of stations and the number of machines at each station and to allocate tasks to stations. They use queueing network analysis, which takes into account the mean and variance of processing times among different products to determine the necessary capacity of the material-handling system. The authors iterate between the two analyses to find the combined solution with the lowest costs. Work-in-process costs are also included in the analysis. Computational results are presented.