The Difference Structure between Overflow Rod Mill and Ball Mill

Overflow rod mill structure is similar to the overflow ball mill. The difference is that the cone end cover of the rod mill has a small curvature. The inside is the smooth liner plate. If the liner plate is rough, it will not be used in the barrel. The hollow shaft diameter for the ore discharge is large and make the steel bar avoid escaping and getting bent for hitting each other in the falling. The purpose of a large diameter of the ore discharge port is to install the steel bar conveniently and easy to maintain and check. Meanwhile, it will lower the pulp level and make the pulp to be discharged quickly.

The rotating speed and the medium charge ratio of the overflow rod mill are low. The particle size of the feeding ore is 25~30mm. If it is oversize, the steel bar will be skew and the make the steel bar bend and break in the operation. Meanwhile, the oversize material will make the gap between the bars big. The fine particle size will not be ground and the production will be reduced. Because of the line contact as the steel bars are falling, the material will be crushed and ground. Before the chunk being crushed, the fine particles will hardly get the impact of the bars, the over crushed product is small and the product particle size is even. Therefore, the rod mill is better to be used in the first section open circuit. It is applied for the fine crushing and primary grinding, especially for the fragile materials.

The application fields of the rod mill are:

1. The gravity plant or the magnetic plant of the tungsten-tin ore and the rare metal ore. To prevent the material to be crushed too much, in the primary grinding stage, it adopts the rod mill with shattered light particles. 

2. Sometimes it can replace the cone short-headed crusher to have fine crushing. When dealing with the soft, muddy and glutinous ores and adopt the cone short-headed crusher. The dust particle size is big and easy to block the fine crusher. If using the rod mill to replace the fine crushing, the ores between 20-30mm can be crushed and ground into 6-10mm. The cos will be lowered and the process for fine crushing and removing the dust will be simplified. If using the cone short-headed and the screen circuit to grind the ores, it will have a large investment and the blocking of fine crushing will be serious. 

3. When the rod mill is used for primary grinding, the product particle sizes are 3-1mm. The production capacity of rod mill is larger than that of the ball mill with the same specifications. While the rod mill is used for fine grinding, the ground and crushed particle sizes are 0.5mm.