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When the ore grinding machine are rotating in a certain rotate speed, the ore grinding medium in barrel will produce centrifugal force by rotating so that there will be certain friction between ore grinding medium and barrel. The friction will drive the ore grinding medium rotating with the barrel and reach a certain level. When its own gravity (centripetal force of gravity) are larger than centrifugal force, the ore grinding medium will leave the barrel then fall in projectile way. When the medium are falling down, impact force are produced and the grinding medium can crush the ores. At the same time, in the mill operation process, there are sliding phenomenon and extrusion phenomenon that is produced by lining medium to outer medium in the ore grinding medium, which can produce abrasive and extrusion action to ores. So the ores can be ground by combined effect of impact force, grinding force and extrusion pressure of ore grinding medium.
The ore grinding function of ore grinding machine are like the following picture:
Lifting height and motion trail of projectile action of ore grinding medium depend on rotating speed of grinding machine and the filled amount of ore grinding medium. Both the low speed and high speed will have direct influence on the performance of grinding machine. The grinding medium moving condition in three kinds of different working speed are:
1. Grinding machine running in a low speed(pic.a)
The rotating speed is not high so the lifting height of grinding medium is low and the grinding medium will fall to the bottom of barrel along to their own inclined plane for circulating. The medium is in spilling state and has smaller impact. The abrasive and extrusion action are formed by rolling action among mediums. Ball has less grinding action to materials.
2．Grinding machine running in a normal speed(pic.b)
The rotating speed is higher so the lifting height of grinding medium is high and the grinding medium will be up to a certain height with barrel circular motion, then leave the barrel in a certain velocity and do fall down movement along parabolic path. At this time, the grinding medium has high impact and the abrasive and extrusion action will get sufficient exertion. The materials are ground in the most intense level. Most of grinding machines are working in such a ore grinding condition.
3. Centrifugal operation(pic.c)
When the rotating speed of ore grinding machine is enhanced to a limit numerical value, all the grinding medium will do concentric rotation with the barrel and will not fall down, which will be called centrifugal operation. When the medium produces centrifugal operation, the ore grinding action will be lost in theory. So the grinding machine should work in the rotation speed which is below centrifugal operation. Get rotary kiln, ball mill, Mineral Processing From http://www.ballmill8.com
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