Lot size optimisation under pooled and unpooled scenarios in batch production system

Abstract

The lot-sizing problem in batch manufacturing systems with capacity constraints is studied using queueing relationships and optimisation techniques. In this research, the effect of lot sizes when there are parallel machines and multiple part types is considered. Furthermore, the issue of whether or not to use pooled queues, based on part types, to feed the machines is examined. Different scenarios are evaluated using GI/G/n queueing approximations to predict performance and optimise lot sizes. Optimisation is based on minimising the mean flowtimes, which include queue and lot service times. The results show that if part types are very different, there are situations in which pooling is not advantageous.

Keywords:

• batch production
• flowtime
• lot-sizing
• resource pooling
• queueing
• simulation
• optimisation

Acknowledgements

This research was supported in part by a grant from the National Science and Engineering Research Council (NSERC) of Canada. The authors also acknowledge the helpful comments provided by several reviewers.