Comparison and Selection of Several Grinding Instruments
There are many types of grinders, including planetary ball mills, mortar grinders, knife grinders, disc grinders, jaw crushers, and so on. Today we mainly introduce the selection of three types of grinding machines.
1. Planetary ball mill
Working principle: The grinding jar of the planetary ball mill is located at the eccentric position of the sun gear at the bottom. The grinding jar rotates on its axis, which is exactly opposite to the direction of rotation of the public sun gear. The ball in the grinding jar is affected by the superimposed rotation deflection force when it moves with the grinding jar. The difference between the moving speed of the grinding jar and the grinding ball produces strong friction and impact force, and the instrument releases a large amount of kinetic energy. This combination of impact and friction makes the planetary ball mill extremely pulverized during grinding.
Features: Suitable for fine grinding of neutral, hard, and brittle materials, such as minerals, metal oxides, ore, plant fiber groups, soil, etc., all can be ground with a planetary ball mill.
The final minimum sample size: generally less than 1 micron, the sample can be ground to sub-micron fineness (wet grinding + dispersant) if possible.
The grinding throughput depends on the volume of the grinding tank and the number and size of the grinding balls. The planetary ball mill with four grinding platforms can grind 4 samples at the same time. It takes about 20 minutes to grind a batch of samples, and 12 samples can be prepared in one hour. The more grinding tanks and grinding balls are equipped, the higher the efficiency and the price. If there are not many samples, of course, you can also choose a planetary ball mill with a single grinding platform, but you need to adjust the position of the counterweight to maintain the balance of motion. If it is equipped with a free force compensation base, it can better maintain balance while running at high speed.
Secondly, if you don’t want heavy metal pollution, avoid using stainless steel instead of agate or zirconia or tungsten carbide.
For soil grinding, it is generally recommended to have a hardness above the agate level. It is not cheap to match a set of grinder with corresponding agate tank and agate ball, depending on which model you choose. In addition, some consumables after long-term grinding, such as gaskets, also need to be replaced, but the price is very cheap.
2. Mortar grinder
Working principle: Put the sample to be processed into the mortar and mortar through the feed port on the top for grinding. The sample is crushed by squeezing and friction between the mortar and the wall of the mortar. The rotating mortar drives the rotation of the mortar, and the sample also rotates. Repeated grinding to achieve uniform mixing of the sample.
Features: Suitable for grinding hard and medium-hard materials, such as ash, cement clinker, soil samples, yeast cells (frozen processed), food, etc.
The final sample size: generally less than 10 microns.
Cost of use: It also depends on the configuration. In order to prevent contamination, stainless steel is not used for the material selection of mortar and mortar. Generally, agate material is used, and the price will be more expensive. However, only stainless steel can be selected for freezing.
3. Knife grinder
Working principle: The knife grinder has a two-blade cutter head, which is placed in the center of the bottom of the grinding cup, and the cutter heads are kept at a certain height between them, and they start to rotate under the drive of a motor. The cutting action of the sharp steel blade produces reliable crushing and homogenization effects. According to the direction of rotation, the blunt surface can be selected for coarse crushing of large samples, or the tough surface for fine crushing of samples.
Features: Suitable for soft, water-containing and oily materials, such as: food samples, fruits, meat, vegetables, etc. It is recommended to use a gravity top cover with overflow channels, and the separated liquid components can be completely retained and mixed with solid components More evenly. There are more acceleration modes, higher power and higher speed, and difficult-to-handle samples can also be homogenized.
The final minimum sample size: generally less than 300 microns.