Modelling of the screening performance for classification processes is important to obtain a first estimate for a new process in the planning phase. In this work especially the grade efficiency curves of sieve classifications with vibrating screens were examined. A sensitivity study was performed by changing the operating parameters of the sieving machine and the parameters of the charging material (i.e. mass flow, particle size, etc.). The aim was to correlate the input parameters with the grade efficiency curve of the classification process. The main aspect of the presented work is to find an appropriate method to adjust four screening parameters in a way that the measured grade efficiency curve is modelled correctly. Several methods for this adjustment step are reviewed. A sensitivity study using a tumbling screen was performed previously. It is apparent that for that study, different methods and models for the parameter adjustment need to be used. Furthermore it is shown that data reconciliation is necessary, since the mass balance of the particle streams may not be closed correctly. In summary this work is the first step to predict the screening performance of a sieving machine without material- and time-consuming experiments.