Relationship between Grinding Results in a Planetary Ball Mill with Liquid Media and the Distribution of Ball Impact Energy Calculated by DEM Simulation

Abstract

Ball motions in a planetary ball mill with liquid media were simulated using the DEM. The distributions of ball impact energy were calculated from the simulation. Then, the cumulative value of the impact energy (E) and median of the impact energy at one collision (e_1/2) were calculated. Grinding tests were examined and relationships between particle sizes and the specific impact energy multiplied by grinding time (E_wt) were evaluated. At higher acceleration, particle sizes of ground powders decreased faster. However, from the viewpoint of the impact energy, the energy efficiency got worse. With increase of ball sizes, e_1/2 increased but the number of collisions decreased. As results, using the smaller balls, particle sizes decreased faster and the energy efficiency was also better. The amount of E_wt required to obtain 0.5 μm mean diameter (E_wt*(0.5 μm)) was calculated for each test condition. The fitting curve was applied for the relation of E_wt*(0.5 μm) vs e_1/2.