To produce a large number of different products in an efficient way, traditional industry production architectures have incorporated non-value-adding operations such as transporting, storing and inspecting to provide flexibility. These operations should be minimized, if not eliminated, to improve performance on automated manufacturing systems. Heuristic planning tools seem to offer a good methodology to deal with a sub-optimal scheduling policy of present flexible manufacturing systems. In this paper a simulation approach, based on Coloured Petri Nets, to evaluate and improve production planning policies will be presented.