Measurement and evaluation of the grinding bodies’ motions in a vibratory disc mill filled with viscous fluids

Abstract The grinding bodies’ motions (grinding disc and grinding ring) in the mill chamber of a vibratory disc mill have been experimentally studied and subsequently evaluated as well as interpreted in detail. The horizontal movements have been recorded by means of a high-speed camera positioned perpendicularly above the mill and the vertical movements using a measurement sensor, which enables a sensitive measurement of the grinding disc’s variation in height. Simultaneously, the influence of the fluid viscosity and the fluid’s filling quantity on these movements have been determined. Both parameters distinctly influence the grinding bodies’ motions. An increasing viscosity shows initially no visible influence on the grinding bodies’ centre velocities. In the case high viscosities are reached, a significant decrease in the grinding bodies’ velocities appears due to the higher flow resistance or more specifically, higher fluid’s resistance or lower fluid’s flowability counteracting the motions. Due to increased sliding of the grinding bodies on a highly viscous fluid, an inversion of the grinding bodies’ direction of rotation develops additionally. A larger fluid’s filling quantity causes a reduction of the sliding friction between the elements, wherefore the grinding bodies’ velocities increase accordingly. The vertical analysis of the grinding disc’s variation in height clearly reveals that the grinding bodies slide on a viscous fluid during operational mode. At the same time, a small vertical gap between the respective grinding body and the mill chamber bottom appears.