Rod - ball mill consists of a metal cylinder and a ball. Its working principle is that when the cylinder is rotated, the grinding body (ball) attached to the cylinder and the object to be polished (material) are rotated by the cylinder under the action of friction and centrifugal force. At a certain height, it will automatically fall and hit and grind the material in the cylinder to grind the material. In addition, the agitation of the ball will mix the materials evenly.