Ball mill is an essential equipment for grinding materials. A certain number of steel balls are loaded into the cylinder of this type of grinding machine as the grinding medium. It is suitable for grinding various ores and other materials in cement, beneficiation, silicate products, new construction materials, refractories, glass ceramics and other production industries. It can be divided into dry and wet grinding methods. According to different ore discharging methods, it can be divided into grid type and overflow type.

Wet overflow ball mill is often used to grind fine ores and used for second-stage and third-stage grinding in multi-stage grinding operation. It is mainly consisted of feeding part, main bearing part, cylinder part, transmission part, discharge part and main motor. 

Ball Mill Working Principle：

The main component of overflow ball mill is a cylinder with small diameter and large length, which is supported by sliding (or rolling) bearings and rotates slowly through transmission machinery. The materials are fed from the feeding end of the cylinder and crushed due to the throwing impact and self grinding of steel balls and ore itself. Because of the continuous feeding of stones, the pressure causes the materials in the cylinder to move from the feeding end to the discharge end, and the ore pulp flows out when it is higher than the lower edge of the hollow shaft

at the discharge end. The hollow shaft is equipped with counter spiral blades, which can return the overflow steel balls and coarse ore blocks to the chamber.

Grid type ball mill is often used to grind ores with coarse particle size and used for first-stage grinding it multi-stage grinding is adopted. The difference of its working principle and overflow ball mill is that there are grids in the discharge end and through these grids to forced ore discharge and prevent steel balls discharge.

Characteristics of these two kinds ball mill are as shown below:

1. With jacking device for convenient maintenance.

2. With slow transmission, it is convenient for maintenance and start-up.

3. The large and small gears are lubricated by oil mist to ensure reliable lubrication and prolong the service life of the large and small gears.

4. It is equipped with air clutch and adopts flexible start to reduce the impact of ball mill start on the power grid of the beneficiation plants.

5. Hybrid bearing makes it run smoothly and reliably.

The dry-type ball mill is a horizontal cylindrical rotating device, driven by gears on the outside, with two bins and lattice ball mill. It is mainly used for grinding finished products and raw materials in cement plant.

The materials are spirally and evenly entered into the first bin of the mill through the feeding hollow shaft by the feeding device. The bin is with stepped lining plate or corrugated lining plate, which is filled with steel balls of different specifications. The rotation of the cylinder generates centrifugal force to bring the steel balls to a certain height and then fall down, which has a heavy impact and grinding effect on the materials. Then the stone enters the second bin through a single-layer compartment plate which is inlaid with flat lining plate and steel balls to further grind the material. The finished product will be discharged through the grid plate.

The dry ball milling machine has strong adaptability to materials, it can work continuously and it is easy to adjust the fineness of grinding products. The straight cylindrical design is adopted at the discharge outlet, and an induced draft device is set which has good dust removal effect. The hollow shaft is made of steel castings which makes it easier to disassemble and replace the liners.