How Can Determine the Working Speed of Ball Mill?

When ball mills work, they mainly rely on the frictional force and impact force of the grinding media inside the grinding chamber to crush materials. The higher the rotating speed is, the greater the effect of the frictional force and the impact force will be. For this reason, on the condition that ball mill is working normally, the discharging granularity is in direct proportion to the rotating speed of the ball mills, which shows the great importance of determining the working speed of this grinding balls.

When the rotating speed of the cylinder of the milling equipment reaches a value, the centrifugal force produced by the grinding media will be equal to their gravity, and the grinding media will be lifted to that the release angle become 0°, and the grinding media will tightly press on the cylinder wall and will not fall off with the rotation of the cylinder, and this rotating speed will be the critical speed of rotation.

When the cylinder of the ball making equipment reaches the critical speed of rotation, as the grinding media tightly press on the cylinder wall and cannot crush the materials, the crushing work on the materials is zero. When the rotating speed of the cylinder slows down, the grinding media will fall down, but the crushing effect on the materials is still weak, which means the crushing work is still small, for this reason, the work consumed by the crushing of the grinding media on the materials is the function of the rotating speed of the cylinder. For this reason, the rotating speed of the cylinder that can make the grinding media produce the highest crushing work is the theoretically most suitable working speed of ball mill. To get the highest crushing work, the grinding media must have the highest falling speed. According to the calculation formula of critical speed of rotation, the theoretically most suitable working speed will be 76% of the critical speed of rotation.

In practical production, the working speed of the ball grinding mill does not only consider getting the highest crushing work, as the material grinding has not only impact crushing, but grinding. For this reason, we should start from the optimum economic index, which means that the production capacity of the milling equipment should be the highest, the power consumption for unit output should be the smallest and the abrasion consumption of the grinding media and the lining board should be the lowest. So that the determination of the working speed should consider the property of the grinding materials, feeding granularity and grinding fineness, other than the diameter of the milling equipment, production method, the shape of the lining boards, filling coefficient of the grinding media and the types of the grinding media.