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Which one is the best, ball mill or rod mill?

The milling equipment which are widely used in the mineral processing plant are the ball mills and the rod mills. The two have similarities in shape and grinding principle, but there are also differences in structure, performance, use and so on.

First, when the barrel rotating, the grinding medium (ball or rod) installed in the barrel body would be left to the certain height under the action of friction and centrifugal force, thus making a certain line speed drop. At last, the material will be crushed in the barrel impact, grinding and squeezing.

shape structure analysis of the ball mill and rod mill

The shape ratio of the two barrels is different, the ratio of the length to diameter of the rod mill barrel is generally 1.5-2.0, and the lining surface on the end cover is vertical plane.

The ratio of barrel length to diameter of the ball mill is small, and in most cases the ratio is only slightly greater than 1. In addition, according to the China Fote Machinery the barrel speed of the rod mill is lower than the operating speed of the ball mill of the same specification, so that the medium inside the machine is in a drop-off state.

Type analysis (different methods of mining)

In the ball mill, commonly used have the lattice ball mill and overflow ball mill (named from different drainage structure), and the rod mill does not use the grid plate drainore, only overflow type and opening type two kinds, the diameter of the hollow shaft at the drainage and  end is generally larger than the same specification ball mill.

Grinding media analysis

 rod grinders are commonly used as grinding media with steel rods with a diameter of 50-100mm, while ball mills use steel balls as grinding mediums, and the differences in grinding bodies are the main differences between the two.

The steel ball between the ball grinder is point contact, the rod grinder’s steel rod is the line contact, so there is a clear difference in the working characteristics of the two.

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The media filling rate refers to the percentage of grinding medium’s total volume of the mill. For different grinding methods, grinding structure, operating conditions and media shape, the media filling rate has a suitable range, too high or too low to affect the grinding effect. Usually the filling rate of the ball mill is 40%-50%, the rod mill is 35%-45%, and here, the filling rate of the self-grinder is 25%-40%, and the filling rate of the grafter is about 43%.

Performance analysis

The process characteristics of the rod mill are the rougher product, but the grain size is uniform, the coarse particles and the mineral mud are less, the over-crushing is lighter, and the particle size characteristics of the rod mill product are related to the condition of the rod grinding ore.

The performance of the ball mill is characterized by high production capacity, strong adaptability to the material, high fineness of the material, fine grain of the material, easy to fine grinding, energy saving is more significant, but its over-crushing phenomenon is serious.

Stability analysis

In the operation of the ball mill has no inertial impact, to ensure that the equipment can be normal and efficient operation, reduce the equipment downtime, improve the efficiency of production.

the use of analysis

When re-selecting or magnetically selecting tungsten tin ore and other rare metal mines, a rod mill is often used to prevent over-crushing, and in the second-stage grinding process, a rod mill is generally used as the first grinding equipment, with a large revaluation capacity and high efficiency.

When handling softer or less hard ore, a rod mill can be used instead of a short-head conical crusher to finebreak, which is not only simple to configure, but also less costly, and can simplify dust removal in the workshop. And ball mill because of the fine grinding material, it is easy to appear the phenomenon of crushing, but is not suitable for metal ore re-selection production line.

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In general, users can choose according to their raw materials, finished product granularity and effect, production methods, etc.

According to raw material processing selection

If the raw material stoic in operation is tungsten tin ore, the rod mill is a better choice, and if the material that needs to be ground is aluminum ash, lime, slag, tantalum ore, etc., the ball mill has a stronger processing power.

According to the grain size of the finished product selection

In the rough grinding, the product particle size of 1-3mm, the processing capacity of the rod mill is greater than the same specificationof ball mill, when used for fine grinding, the product granularity is less than 0.5mm, the grinding effect of the ball mill is greater than the same specification of the rod mill.

That is, the product of the ball mill is more refined, the rod mill’s product is rougher, but more uniform.

According to the mode of production selection

In rare metal ore re-selection or magnetic selection, in order to prevent the hazards caused by over-powder in the operation, the grinding of materials is often used for production and processing of rod grinders, while the production and processing of cement plants are mostly selected ball grinders.

About RJ Frometa

Head Honcho, Editor in Chief and writer here on VENTS. I don't like walking on the beach, but I love playing the guitar and geeking out about music. I am also a movie maniac and 6 hours sleeper.

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