What is the unit of order? How to convert eye and micron

Explanation (1)

Sieve diameter (μm)≈14832.4/ mesh number of sieve

Unit size refers to the size of raw material particles, generally expressed by the maximum length of particles. Mesh is the size of the mesh size of a standard screen. In the Taylor standard sieve, the mesh is the number of screens in the 2.54 cm (1 inch) length, and is simply referred to as the mesh.

Taylor standard sieve system: Taylor sieve system classification is based on the 200 mesh size of 0.074mm, multiplied or divided by the main modulus root (1.141) to the power of n (n = 1,2,3...) If the fourth root of the number 2 (1.1892) is multiplied or divided by the power of n by 0.074mm, a finer range of sieve sizes can be obtained.

The larger the mesh number, the finer the grain. Similar to the magnification of metallographic structure.

A plus or minus sign before the mesh number indicates whether the mesh number can be missed. A negative number indicates the mesh that can leak through the mesh number, i.e. the particle size is smaller than the mesh size; The positive number indicates that the mesh number cannot be missed, that is, the particle size is larger than the mesh size. For example, if the particle size ranges from -100 mesh to +200 mesh, it means that the particles can leak through the mesh size of 100 mesh but cannot leak through the mesh size of 200 mesh size. When screening the particles with such mesh size, the ones with large mesh size (200) should be placed under the screen size with small mesh size (100). The particles left in the screen size with large mesh size (200) are -100 to 200 mesh size.

The mesh, that's the number of holes, that's the number of holes per square inch. The larger the number of eyes, the smaller the aperture. In general, mesh number x aperture (microns) = 15000. For example, 400-mesh screens have a diameter of about 38 microns; The aperture of the 500 mesh screen is about 30 microns. Because of the problem of opening rate, that is, because of the difference in the thickness of the silk used in the weaving net, the standards of different countries are not the same. At present, there are three kinds of American standards, British standards and Japanese standards, among which the United Kingdom and the United States are similar, and the difference is larger in Japan. We use the American standard, which can be calculated by the formula given above. American Taylor standard screen size comparison table. You can see the details in the figure.

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 aperture determines the maximum particle Dmax of the sifted powder. So, we can see that 400 mesh polishing powder is completely possible to be very fine, such as only 1-2 microns, is also completely possible to be 10 microns, 20 microns. Because the aperture of the screen is about 38 microns. Our D50, which produces 400 TBS of polishing powder, has 20 microns. The picture attached shows a picture of this polishing powder. Note that the scale is 50 microns.

Therefore, it is inappropriate to use the mesh number to measure the particle size of polishing powder. The correct way should be to use the particle size (D10, median diameter D50, D90) to express the particle size, and convert the maximum particle size with the mesh number. If you look at JIS, the Japanese standard for abrasives, it's very scientific. The requirements of D3, D50 and D97 are given for each size of their abrasives, and the data is different when using different principles of particle size tester. The requirements are very strict. For example, D50 is 2 microns of powder, D3 is roughly 0.9 microns, and D97 is 4 microns. What does that mean? Of the powder that claims to be 2 microns, no more than 3% is smaller than 0.9 microns, and no more than 3% is larger than 4 microns. This is very strict, the vast majority of polishing powder seen on the market (including foreign) can not meet this requirement, especially the fine powder exceed the serious.

The mesh number is used to characterize the particle size of polishing powder for a reason. The old polishing powder factory adopts the process of dry ball milling and dry screening, so the D50 of 300 purpose powder is about 9 microns, and the D50 of 500 purpose is about 2 microns. We have been so used down, but also basic guidance for production and use. However, with the advent of new production processes and the need for higher precision finishes, this method should also advance.

Explanation (2)

1. Mesh refers to the number of empty holes in the screen per square inch. 50 mesh refers to the number of holes in the screen per square inch, and 500 mesh refers to the number of holes in the screen. In addition to representing the holes in the screen, it is also used to represent the size of the particles that can pass through the screen. The higher the mesh, the smaller the size.

2. The particle size of powder is called particle size. Because the particle shape is very complex, there are usually several expressions, such as screening size, settling size, equivalent volume size and equivalent surface size. Screen size is the size of the screen through which the particles can pass, expressed as the number of screens in a 1 inch (25.4mm) wide screen, and thus called "mesh size". At present, there is no unified technical standard for powder size at home and abroad, and each enterprise has its own definition and representation of particle size indicators. In different countries, different industries screen specifications have different standards, so the meaning of "purpose" is difficult to unify.