For a drug synthesis plant will be considered approaches for estimations of capacity. Here will be illustrated for a particularly case, that by using a system data model of PPS the capacity will be obtained with 17 batches per month, while the experienced foremen supposes a capacity of 8 batches per month. Through the simulation of the machine allocation plan by using a detailed data model will be able to involve technological aspects (stable stages) in the thoughts, to obtain representative results. Further will be evaluated several sets of orders concerning the influence of the capacity of the plant.