The ball mill works mainly under the force of impacting and grinding. The movement of grinding media in the cylinder body takes several different forms. Some media make upward movement by attaching onto the surface of cylinder;

some slide downward; some make projectile motion. In order to further know the motion law of grinding media in the ball mill and simplify the problem, the following hypothesis are made in the research:

When the ball mill operates at normal speed, the grinding medium in cylinder makes circular motion according to its position;

2. The motion trajectory of the grinding body comes in only two kinds: one is ascending motion along with rotating barrel according to the concentric circular track centering the cross-sectional geometry center; another is downward motion along the parabolic trajectory.

The sliding movement between the grinding media and the cylinder and that between the layers of the grinding media is too subtle to be counted. The effect exerted by material to the cylinder body can be neglected.

The rotation speed and the filling rate of the cylinder have a big effect on the grinding effect. According to the different factors, the motion types can be summarized as follows,

Purging fall type

When the cylinder speed is too low and ball mill media are too few, there will only be rolling and sliding and basically no impact can be produced, so the grinding efficiency is not so ideal.

Tossing down type

When the cylinder speed is proper, the grinding media can attach themselves to the cylinder wall under the effect of centrifugal force. The grinding media will make upward circular movement along with the cylinder and will be taken to the appropriate height, and then land like projectiles. The grinding media will be in a waterfall state and crush material with the maximum impact force, and meanwhile the rolling and sliding of the grinding media will play a role in the whole process of material grinding.