Industry Reports

What is an overflow ball mill?

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  • Apr 12, 2019  UTC+8
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  • Tags: overflow ball mill ball grinding mill

The overflow ball mill is a widely used one in the ball mill. Its structure is basically the same as that of the ball mill. It mainly includes the cylinder, the end cover, the main bearing, the hollow journal, the transmission gear and the inlet and outlet parts. The overflow ball mill has a slower discharge rate, and the large density of the ore is not easily discharged, which is prone to over-grinding. The cylinder is welded with a steel plate with a thickness of 15~36mm. The flange made of cast steel is welded to both ends of the cylinder, and the end cover and the flange are welded together by bolts. Both need precision machining and Cooperate. The hollow shaft bearing the quality of the grinding medium is welded on the end cover, and there are 1~2 personal opening doors on the cylinder for maintenance and replacement of the liner. The inside of the cylinder and the end cap are lined with a lining to reduce the impact of the grinding medium on the cylinder wall during the turning motion.

When the cylinder is in operation, it is supported by the main bearings at both ends. In the manufacture and assembly of the ball mill, the main bearing is mostly selected from sliding bearings according to the production requirements, and its characteristic is that the aspect ratio is small. The bearing bush is made of babbitt. Sliding bearings used in ball mills differ from other types of plain bearings in that they only have bushings in the lower half of the bearing. Except for the Babbitt material used for the bearing bush, the other parts of the bearing are made of cast iron. Because the span of the ball mill and the load are relatively large, the cylinder will bend to a certain extent during operation, and it will be produced during the manufacture and assembly of the machine. The error is also difficult to guarantee accurate concentricity. Therefore, the main bearing is designed as a self-aligning sliding bearing, and a cylindrical pin is placed between the bearing seat and the spherical surface of the bearing bush to prevent the bearing bush from being excessively pulled out of the bearing seat.

The main bearing plays an important role in the work of the ball mill, so the lubrication of the bearing should be given full attention. In actual production, large-scale mills generally use the lubrication mode of concentrated oil circulation. The oil is pressed into the main bearing and the sliding bearing through the oil pump, and then flows back to the fuel tank through the oil drain pipe at the bottom of the bearing to complete the lubrication. For medium and small ball mills, oil ring automatic lubrication, oil cup drip lubrication and moving solid lubricants are used. Some concentrators also have an automatic alarm device for lubricating oil cut-off to ensure continuous lubrication of the bearings.

The hollow shaft at both ends of the ball mill cylinder is supported on the main bearing, one end of which is fixed, and the other end is freely expandable and contractible in the axial direction of the main bearing. Since the large gear generates a certain axial force during transmission, when the structure is designed, two shoulders are added on the hollow shaft at one end, and the distance between the shoulders is just the length of the bearing bush, so that the shaft can be prevented from occurring. Sliding in. The hollow shaft of the other end does not have a shoulder on the shaft diameter, and the length of the shaft diameter is slightly larger than the width of the bearing bush. When the working heated cylinder is elongated or the load is too large, the cylinder has a certain deformation space. Generally, a hollow shaft having a shaft diameter close to the end of the transmission large gear is selected. Inside the hollow shaft, a tapered bushing and a bearing bushing are provided, and the requirements between the hollow shaft and the inner bushing are tightly matched, and the necessary seal is added. In order to produce a certain inclination of the inner pulp medium surface of the ball mill, the inner diameter of the hollow shaft at the discharge end is slightly larger than the inner diameter of the hollow shaft of the feed end. The inner surface of the hollow shaft may be smooth or have spiral blades, and the forward spiral blades in the hollow journal of the ore end are used to transport the material; the reverse spiral blades in the hollow shaft diameter of the discharge end can make the coarse material Return and prevent the grinding steel ball from running out.