Generally, we can’t notice the motion of the steel ball of beneficiation mill at the scene. Studies have shown that there are three motions of steel ball, namely, the fall-diarrhea, thrown & fallen and centrifugal. In the cylinder of ball mill, with the rotation of the rotary cylinder and friction, grinding medium along the side of the cylinder is raised until power reaches the equilibrium point. Now let’s have a rough idea about the three motions.
When the cylinder of beneficiation ball mill rotates with low speed, the whole ball angled deflection along the direction of cylinder’s rotation. Now each ball rotating around its own axis, and the ball that located in the top are constantly rolling along the ball’s surface. It’s said to be the fall-diarrhea, grinding is the main mining function that the medium affect to ore.
With the increase of cylinder’s rotating speed, the ball bearing overall deflection rises gradually. When the cylinder rotation speeds to a certain extent, the steel ball along the top of ball bearing will fall at the parabolic trajectory. This motion is called thrown & fallen. The mining effect of medium to the ore is mainly impact and crushing effect.
The point of ball from the tube wall starts falling is known as departure points. The angle between cylinder radius and vertical diameter is called the separate corner. With the increase of rotating speed, the separate point rises gradually, and the separate corner reduces gradually. When the separate point reaches the highest point, and the separate corner becomes zero, the steel ball starts move and rotate along with the cylinder. This motion is called centrifugal. Now, there is no relative motion and ground effect between ball and ball room and liner.
When the steel ball is at the centrifugal motion, the ball mill is in non-working state. When it is at the other motions, the ball mill is working. The mining effect of media is the combination of grinding and impact.