Why initial conditions are important

Most simulation textbooks assume that a model can be started in an empty state and the final output will not be affected, so long as the "warm-up period" is excluded from the analysis. In this paper we test this assumption, using a discrete-event model of a existing manufacturing facility. Using a series of model runs with no initial Work in Progress (WIP) and another series of simulation runs with a realistic initial level of WIP, the results can be compared and contrasted. While the results show similar shaped profiles in terms of throughput and lead time, the differences between the curves has important practical implications.

Using bottlenecks to control production inventory

In this paper, we investigate how to best optimise the level of Production Inventory or Work In Progress (WIP) in a factory. Using a simulation model of the factory, we show that a level of inventory can be optimised by controlling the buffer levels of the key bottleneck workcenters. By firstly identifying the key bottlenecks, and then systematically reducing the maximum buffer level for each bottleneck, results show that the throughput does not drop rapidly from it's high levels until the WIP is halved. Conversely, the production lead time decreases rapidly and levels out around the point of the optimum WIP level.

On work in progress optimisation

In this paper, we investigate how to best optimise the level of work in progress (WIP) in a real world factory. Using a simulation model of the factory, we show that an optimum level of WIP can be attained. By systematically varying the maximum allowable level of WIP within different model runs, results show that the throughput reaches a high level very quickly and then tapers off. The production lead times, in contrast, begin at relatively low levels and increase after the optimum WIP level has been reached.

Development of an optimum factory model for a manufacturing operation through computer simulation

Often manufacturing enterprises will maintain high levels of Work In Progress (WIP) to maximise production throughput. Using computer simulation, this thesis investigates a manufacturing facility and identifies an optimal level of WIP. At this optimum throughput is maximised, manufacturing lead times are minimised, and the WIP level is significantly reduced.