Ball mills are a form of mills with grindingbodies. The drums can be opened at the front and loaded with the material to bemilled (limestone is recommended) and the milling balls. The drums are mountedon a drive roller and a loose roller with adjustable spacing between the axles.At low rotation speeds the comminution is effected by the balls rolling overthe material (cascade motion). At higher speeds, some balls are lifted up thewall, become detached and drop down onto the material (cataract motion). Abovethe critical speed, centrifugal forces ensure that no more comminution takesplace. These motion states can be observed through the transparent fronts ofthe drums. In order to compare the theoretical power demand with the actual,the power consumption of the drive motor is indicated on a digital display. Toassess the success of the comminution, an analytical screening machine isrecommended.