Complex systems such as the ball mill grinding circuit have been traditionally perceived by many researchers as MIMO systems due to the inherent existence of several I/O variables thereby producing interconnectivity among them. As it is well-known, variables involved in the system are strongly correlated each other, fact that is reflected at the influence of the set of manipulated variables on the output ones. This paper has paid attention on the evolution of the particle-size variable by analyzing its behavior when it is subject to disturbances during the mineral processing. Thus, a methodology in order to search the effect of implementing functions of random nature whose existence might be attained to the interaction among variables as normally occurs in a balls mill grinding circuit dynamics, is provided. In this short report, some simulations of the particle-size evolution are exposed by emphasizing the impact of those random functions which is supposed coexists together to the ones which traditionally are used. ©2010 IEEE.