Inner diameter of sieve (μm) ≈14832.4 / mesh number of sieve:

The unit size of the unit of measurement refers to the size of the raw material particles, which is generally expressed by the maximum length of the particles. The mesh is the size of the standard mesh. In the Taylor standard sieve, the so-called mesh is the number of sieve holes in a length of 2.54 cm (1 inch), and is simply referred to as mesh.

Taylor standard sieve system:

The indexing of the Taylor sieve is based on the 200 mesh screen size 0.074mm, multiplied or divided by the nth power of the square root of the main module (1.141) (n = 1, 2, 3 ...), you get a 200 For coarse or fine mesh sizes, if you multiply or divide 0.074mm by the fourth power of the number 2 (1.1892) to the nth power, you can obtain a series of finer screen sizes. The larger the mesh size, Means finer particles. Similar to the magnification of the metallographic structure.

The plus or minus sign before the mesh number indicates whether the mesh of the mesh number can be missed. A negative number indicates that the mesh that can pass through the mesh number, that is, the particle size is smaller than the mesh size; and a positive number indicates that the mesh that cannot pass through the mesh number, that is, the particle size is larger than the mesh size. For example, the particles are -100 mesh-+200 mesh, which means that these particles can leak through the mesh of 100 mesh but not through the mesh of 200 mesh. When filtering particles of this mesh size, the mesh size should be large (200) is placed under the mesh with a small mesh (100), and the particles left in the mesh with a large mesh (200) are -100-200 mesh.

The mesh number is the number of holes, which is the number of holes per square inch. The larger the mesh, the smaller the aperture. In general, mesh number × aperture (micron number) = 15000. For example, the pore size of a 400 mesh screen is about 38 microns; the pore size of a 500 mesh screen is about 30 microns. Due to the problem of the opening rate, that is, because of the different thickness of the wire used in weaving the mesh, the standards of different countries are also different. At present, there are three types of American standards, British standards and Japanese standards. , Japan is quite different. Our country uses the American standard, which is calculated using the formula given above. A comparison table of mesh sizes of American Taylor standard screens. Details can be seen in the picture.

It can be seen from this definition that the size of the mesh determines the size of the screen aperture. The size of the screen pore size determines the maximum particle Dmax of the sieved powder. Therefore, we can see that the 400-mesh polishing powder is very likely to be very fine, for example, only 1-2 microns, it is also possible to be 10 microns, 20 microns. Because the pore size of the screen is about 38 microns. The D50 of our 400 mesh polishing powder is 20 microns. The picture shows the photo of this polishing powder. Note that the scale is 50 microns.

Therefore, it is not appropriate to use the mesh number to constant the particle size of the polishing powder. The correct approach should be to use the particle size (D10, median diameter D50, D90) to express the particle size, and use the mesh number to convert the maximum particle size. If you have read the Japanese JIS standard on abrasives, you will find it very scientific. Each of their abrasives is given the requirements of D3, D50, D97, and the data is different when using a particle size analyzer with different principles. The requirements are very strict. For example, D50 is a 2 micron powder, D3 is roughly 0.9 micron, and D97 is 4 micron. What does that mean? The so-called 2 micron powder cannot exceed 3% for less than 0.9 microns and 3% for powders larger than 4 microns. This is very strict, and the vast majority of polishing powders (including foreign ones) seen on the market cannot meet this requirement, especially fine powders exceeding the standard.

There are reasons to use mesh to characterize the particle size of the polishing powder. The old polishing powder factory used the process of dry ball milling and dry sieving, so the D50 of the 300-mesh powder is about 9 microns, and the 500-purpose D50 is about 2 microns. Everyone has been using it in this way, and can basically guide production and use. However, with the emergence of new production processes and the need for higher precision polishing, this method should also advance.

Explanation (2)

1. The mesh refers to the number of empty eyes per square inch of mesh. 50 mesh means 50 holes per square inch, and 500 mesh means 500. The higher the mesh number, the more holes. In addition to indicating the perforation of the screen, it is also used to indicate the particle size of particles that can pass through the screen. The higher the mesh size, the smaller the particle size.

2. Powder particle size is called particle size. Since the shape of the particles is very complicated, there are usually several expression methods such as sieving particle size, sedimentation particle size, equivalent volume particle size, and equivalent surface area particle size. The sieving size is the size of the mesh that the particles can pass through the screen. It is expressed as the number of meshes in the screen with a width of 1 inch (25.4mm), so it is called "mesh number". At present, there is no unified technical standard for powder particle size at home and abroad, and each enterprise has its own definition and representation method of particle size index. There are different standards for screen specifications in different countries and different industries, so the meaning of "mesh" is also difficult to unify.