The ball mill is a key equipment to grind the crushed materials, and the ball mill is widely used in powder-making production line including cement, silicate, new-type building material, refractory material, fertilizer, ore dressing of ferrous metal and non-ferrous metal, glass ceramics, etc, and the ball mill can grind various ores and other materials with dry type and wet type. There are two kinds of ball mill, grate type and overfall type due to different ways of discharging material.