A ball mill consists of a hollow cylindrical shell rotating about its axis. The axis of the shell may be either horizontal or at a small angle to the horizontal. It is partially filled with balls. The grinding media are the balls, which may be made of steel (chrome steel), stainless steel, ceramic, or rubber. The inner surface of the cylindrical shell is usually lined with an abrasion-resistant material such as manganese steel or rubber lining. Less wear takes place in rubber lined mills. The length of the mill is approximately equal to its diameter.
The general idea behind the ball mill is an ancient one, but it was not until the industrial revolution and the invention of steam power that an effective ball milling machine could be built.
Advantages of the ball mill
Ceramic ball mill before 1945 Thiem&Towe Halle. Property of Faculty of Chemistry, Gdańsk University of Technology
Ball milling boasts several advantages over other systems: the cost of installation and grinding medium is low; the capacity and fineness can be adjusted by adjusting the diameter of the ball; it is suitable for both batch and continuous operation, similarly it is suitable for open as well as closed circuit grinding and is applicable for materials of all degrees of hardness.