The speed of rotation of the mill. At low speeds of rotation, the balls simply roll over one another and little crushing action is obtained. At slightly higher speeds, the balls are projected short distances across the mill, and at still higher speeds they are thrown greater distances and considerable wear of the lining of the mill takes place.
Retsch visualises the features and strengths of each ball bill model in a diagram to help finding the right model for a specific application. In the example shown it is easy to see that the Planetary Ball Mill PM 300 offers advantages in terms of power, final fineness and maximum jar volume compared to the Mixer Mill MM 500 control.