Performance evaluation and capacity planning in a metallurgical job-shop system using open queueing network models

Abstract

In this paper, we apply performance evaluation and capacity allocation models to support decisions in the design (or redesign) and planning of a job-shop queueing network of a metallurgical plant. Approximate parametric decomposition methods are used to evaluate system performance measures, such as the expected work-in-process (WIP) and production leadtimes. Based on these methods, optimisation models are then applied for the allocation (or reallocation) of capacity to the stations of the job-shop network. These models are also used to generate approximate trade-off curves between capacity investment and WIP or leadtime, which are valuable for a production manager to estimate how much capacity should be allocated to the stations to reach some targeted performance measures. These curves are also useful for the sensitivity analysis of the solutions to changes in the input parameters, such as the variability of the product demands, the mix of the production and the throughput rate of the network.

Keywords:

• job-shop systems
• capacity planning
• performance evaluation methods
• open queueing network models
• trade-off curves

Acknowledgements

The authors would like to thank the anonymous reviewers for their useful comments and suggestions, and Nelson Marrara for the collaboration with this study. This research was partially supported by FAPESP and CNPq (grants 00/00973-9 and 522973/95-4).