Why do planetary ball mills use different sizes of grinding balls?

Experimental results show that different sized balls grind better and more efficiently than a single size ball.
The grinding balls play a vital role in the grinding process of a planetary ball mill. The ball mill drives the material and the grinding balls to operate, and through the movement of the grinding balls energy is constantly applied to the material, thus crushing or mixing the material to the desired state.
Many users of planetary ball mills receive grinding balls from planetary ball mill manufacturers, a set of grinding balls is always available in various sizes, why should planetary ball mills use different sizes of grinding balls?
Experimental results show that different sized balls are more effective and efficient in grinding than a single size of ball. By using only small balls, it is clear that too little energy and low efficiency will occur. Using only large balls, although the large balls have high energy, the number of actions in the same mass and time is less, and according to Davis’ grinding ball wear hypothesis, the wear rate of the balls is proportional to their mass.
The planetary ball mill uses different sizes of grinding balls, with the large balls having high energy and strong effects on large materials, and the small balls filling in the gaps between the large balls, corresponding to the different coarse and fine materials to enhance the grinding efficiency. The two complement each other, in order to make the planetary ball mill efficiency and effect into a layer.