Planetary ball mill is a necessary device for mixing, fine grinding, sample preparation, nano-material dispersion, new product development and small batch production of high-tech materials. The pre-treatment of solid samples in the laboratory is usually done by means of a ball mill. So how to choose a suitable laboratory planetary ball mill? The following are several aspects that need to be paid attention to when purchasing a laboratory planetary ball mill.
 
1. Determine the sample particle diameter, which usually includes the feeding particle diameter and the outgoing particle diameter. The feeding particle diameter refers to the particle diameter of the sample when it is filled in the tank before grinding, and the outgoing particle diameter refers to the average particle diameter of the sample after grinding, generally taking the value of D50 (median diameter), namely the particle diameter reached by 50% of the sample. It should be noted that the sample feed should be controlled below 10mm, and the fragile sample (such as soil) below 15mm. In addition, the external shape of the sample is also one of the factors affecting the grinding effect. For example, needle-shaped samples are easy to be ground after being cut into segments with scissors.
 
2. Determine the sample size that needs to be ground for an experiment. The sample size  refers to the amount that needs to be used in an experiment. Since the sample amount is based on the volume of the ball mill tank (usually one-third to two-thirds of the volume of the ball mill tank), and the weight of the same volume of samples is also inconsistent due to their different density, so it is better to calculate the sample size by volume. In addition, the planetary ball mill can run two or four ball milling tanks at the same time, and the sample grinding repeatability is good, so the sample can be dispersed in four ball milling tanks for grinding. Based on this, a ball milling tank with a suitable volume can be selected to help determine the mill model.
 
3. Determine the characteristics of the sample and the relevant grinding conditions. The characteristics of the sample can be considered from the aspects of hardness, toughness, viscosity, water content, temperature influence, etc., and the grinding conditions can be considered in terms of dry grinding or wet grinding, normal temperature or low temperature, as well as whether you mind pollution or whether it needs to be vacuumed.
 
4. Determine the source of the sample and subsequent use. The source of the sample can be divided into self-made, collected and sent for inspection, which will affect the selection of supporting tools for the planetary ball mill and facilitate the processing of samples. The use of samples after grinding can be divided into two types. One is used as a raw material for the preparation and synthesis of other substances, and the other is used to detect and analyze their internal components.
 
5. Contamination requirements: the samples of the laboratory ball mill are in direct contact with the ball mill tank and the grinding ball, so the sample may be mixed with the small particles from the tank and the ball during the grinding process, especially the stainless steel tank and the grinding ball. Therefore, if the follow-up testing experiment has requirements in this respect, it is necessary to avoid the secondary contamination of the sample caused by ball mill. For example, for soil heavy metal testing, stainless steel balls and tanks cannot be used, but agate or zirconia materials are acceptable.