A ball mill is a type of grinder used to grind, blend, and sometimes for mixing of materials for use in mineral dressing processes, paints, pyrotechnics, ceramics, and selective laser sintering. It works on the principle of impact and attrition: size reduction is done by impact as the balls drop from near the top of the shell.The inner surface of the cylindrical shell is usually lined with an abrasion-resistant material such as manganese steel or rubber lining.