Simulation of AMHS in transient manufacturing scenarios

Commonly applied simulations are focused on steady-state behavior of an AMHS (Automated Material Handling System) and are not suitable for the investigation of highly dynamic and variable manufacturing scenarios. As wafer fabs often are in a transient statte (factroy ramp-up, down events of resources, shifts in process flow, phase-in of new products etc.) new simulation approaches are required to evaluate the robustness of an AMHS during transient events. A model for transient simulations was implemented in AutoMod 10.0, based on a path-mover-system following the Aerotrak System of Brooks-PRI Automation. This model consists of 7 stockers and 10 turntables. In this paper we describe two simulation experiments with the AMHS-Simulation. In the first experiment we increase the lot start rate over time. The result analysis allows us to indicate various bottlenecks in the system. In a second step we apply Frequency Domain Experiments (FDEs) to the simulation. In Frequency Domain Experiments we vary input factors over time in a sinusoidal manner and look for the frequency response ot various parts of the system. The two main goals are to identify queuing behavior of vehicles and to identify critical turntables.