The Mechanism and Grinding Limit of Planetary Ball Milling [Translated]†

Abstract

To clarify the mechanism and characteristics of planetary ball milling, batch grinding experiments were carried out under various conditions. The motion of the balls in the mill was observed and analyzed by using multi stroboscope photography connected to an image analyzer, and the contact force on the mill wall by the balls was measured using a pressure sensor. The surging phenomenon of the balls in the mill was confirmed by the photographic analysis. Based on this result, it is predicted that the grinding mechanism in the planetary ball mill consists of compressive, abrasive and shear stress of the balls, which is believed to be effective in producing very fine particles. About thirty percent of ball filling of the mill was found to be the optimum. This was explained by an analysis of the motion of the balls and the measurement of the contact force. It was found that the grinding limit is greatly dependent on ball size. An experimental equation expressing the relationship between the finest average size of the ground product and the ball size is also given in this article.† This report was originally printed in J. Soc. Powder Technology, Japan, 25(5), 297-302 (1988) in Japanese, before being translated into English by KONA Editorial Committee with the permission of the editorial committee of the Soc. Powder Technology, Japan.