Simply put, a ball mill is machine for grinding, mixing or blending different elements. A ball mill is seen as one of the most effective and cost-effective technologies in milling. This sustainable technology is fast becoming extremely popular. Ball mills are used in paints, pyrotechnics, mineral dressing processes, selective laser sintering and ceramics industries. The since behind the ball mill is simple. It uses impact force to reduce size of materials.
One of the advantages of a ball mill is its simple design and operation. It is really one of the oldest designs in milling. Balls are used in a hollow cylindrical chamber to continuously pound the material. The balls, in continuous motion, keep moving over the material inside, milling it. Ball mill manufacturers received a technological boost during the industrial revolution when steam energy was used to make the mill movement smooth and efficient.
Construction of the ball mill
The ball milling consists of a cylindrical vessel which is mounted on its two ends. The vessel rotates around its central axis. The vessel contains a grinding medium, which are the balls which give this mill its name. The balls can be made of different types of materials, such as steel, pebbles, rubber or ceramic. Industrial ball mills are made to operate continuously, ensuring that the balls keep going inside the vessel. It is an efficient system where the relentless action of the balls produces a fine effect.
The shell of the vessel has a girth gear and a pinion shaft, which move the vessel. The vessel is filled partially with the material along with the grinding media (the balls). As the mill rotates, the heavy grinding media keeps moving with the motion. Its weight and kinetic energy breaks down the material. High-end ball mills are capable of grinding to a very fine product.
Factors to keep in mind when making a ball mill
There are some essential factors that ball mill manufacturers have to keep in mind:
The lining of the cylindrical vessel is an important criteria. The unceasing action of the balls combined with the materials that go from bulky to coarse to fine texture, can take a toll on the lining. This is constant abrasion, which can cause serious wear and tear. Hence, we have to minimize the effect of sharp edges and impact force. Popular choices are abrasion-resistant materials like rubber or manganese steel. Rubber is one of the most effective materials in this regard. Rubber-lined walls are among the most wear-resistant mill lining.
- Ball media
The balls do all the job here. This is the most important piece of equipment in the ball mill, used for crushing and grinding the material. The ball mill processes a whole range of materials, from silicates, glass ceramics to ore dressing ferrous and non-ferrous material. The mill can grind materials wet or dry. There are many kind of ball media used in these mills. It’s important that we select these carefully. There are three important factors that one must keep in mind when selecting the ball media:
- Density: The ball media must be heavier than the material being grounded. Otherwise, it would simply stay or float on top of the material. A lighter material will not have enough force to make any meaningful impact on the material.
- Hardness: The ball media must be hard enough to withstand the constant grinding action. However, we also have to consider the wear and tear on the mill lining.
- Size: The size of the ball media must be substantially bigger than the largest of the materials to be grounded. But keep in mind, that you cannot have very large-sized media. The smaller the ball size, the smaller will be the resultant grounded material.
- Composition: The composition or the material of the ball media is itself important. If the material of the media is to be part of the finished product, we have to see that it achieves the objective. But if that is not the case, the media’s reaction to the material being grounded must be evaluated carefully. The balls media’s impact and reactivity can occur in many forms. The color of the balls can bleed into the material or dust or particles from the ball can contaminate the final product. Ferrous metals can react with certain media. Flammable materials must be handled carefully.