What is the unit for the mesh size of a filter screen? What is the relationship between the mesh size of a sieve filter and particle size (μm)?

Thread Content

What is the unit of measure for ‘me?’ How do you convert between eyes and micrometers? Explanation (1): The inner diameter of the sieve (μm) ≈ 14832.4 / number of sieve mesh. The unit used to measure mesh size is the dimension of the raw material particles, which is generally expressed as the maximum length of those particles. The mesh size indicates the dimension of the sieve holes in a standard sieve. In Taylor standard sieves, the term \"mesh\" refers to the number of sieve pores per 2.54 centimeters (1 inch) in length, and is abbreviated as mesh. Taylor standard sieving: The grading in Taylor sieving is based on a sieve mesh size of 0.074 mm for 200 mesh; by multiplying or dividing this value by n raised to the power of the square root of the primary modulus (1.141), where n = 1, 2, 3..., sieve mesh sizes that are coarser or finer than 200 mesh are obtained. If 0.074 mm is multiplied or divided by n raised to the power of the square root of 4 (1.1892), a series of sieve mesh sizes with even finer gradations can be obtained. The higher the mesh number, the finer the particles. Similar to the magnification of metallographic structures. Adding a plus or minus sign in front of the mesh number indicates whether to skip that mesh size. Negative values indicate mesh sizes through which particles can pass, that is, particle sizes smaller than the mesh size ； A positive value indicates that the mesh with that mesh size must not be missed, meaning the particle size is larger than the mesh size. For example, if the particles are between -100 mesh and +200 mesh, this means that they can pass through a 100-mesh sieve but not through a 200-mesh sieve. When screening particles of such mesh sizes, the sieve with the higher mesh number (200) should be placed below the sieve with the lower mesh number (100); the particles that remain on the sieve with the higher mesh number (200) are those with a size of -100 to 200 mesh. Tensile count refers to the number of holes, that is, the number of holes per square inch. The larger the mesh size, the smaller the pore size. Generally, the mesh number × pore size (in micrometers) = 15,000. For example, the pore size of a 400-mesh sieve is approximately 38 micrometers ； The pore size of a 500-mesh sieve is around 30 microns. Due to the issue of porosity, which is caused by the varying thicknesses of the wires used in weaving the mesh, different **standards exist. Currently, there are three standards: the American standard, the British standard, and the Japanese standard. The British and American standards are similar to each other, while the Japanese standard differs significantly. Our country uses American standards, so the formulas given above can be used for calculations. The mesh size chart for Taylor standard sieves in the United States is available for detailed information on the following webpage. As defined by this system, the mesh number determines the size of the sieve pores. The size of the sieve pores determines the maximum particle size Dmax of the powder being screened. Therefore, we can see that 400-mesh polishing powder can be extremely fine, for example only 1–2 microns in size, but it can also be 10 microns or 20 microns in size. Because the pore size of the sieve mesh is around 38 microns. The D50 of the 400-mesh polishing powder we produce is 20 microns. The attached figure shows a photo of this polishing powder; note that the scale is 50 micrometers. Therefore, it is inappropriate to use mesh number to determine the particle size of polishing powder; the correct approach is to use particle size parameters such as D10, median diameter D50, and D90, with the mesh number being used to estimate the maximum particle size. If you have seen Japan’s JIS standards for abrasives, you will find them to be very scientific. The abrasives for each of their grades have specified requirements for D3, D50, and D97, and the data obtained using particle size analyzers based on different principles vary. The requirements in it are very strict. For example, D50 refers to powder with a size of 2 microns, D3 is approximately 0.9 microns, and D97 is 4 microns. What does that mean? In powder claimed to be 2 microns in size, those smaller than 0.9 microns must not exceed 3%, and those larger than 4 microns must also not exceed 3%. This requirement is very strict; the vast majority of polishing powders available on the market (including those from abroad) fail to meet it, especially when it comes to the level of fine particles. There is a reason for using mesh number to represent the particle size of polishing powder. Old polishing powder factories use dry ball milling and dry screening processes; as a result, the D50 value for powder with a particle size of 300 mesh is around 9 microns, while for powder with 500 mesh, the D50 is approximately 2 microns. Everyone has been using it this way, and it generally serves as a guide for production and usage. However, with the emergence of new manufacturing processes and the need for polishing with higher precision, this method should also evolve. Explanation (II): 1. The mesh count refers to the number of openings per square inch of the screen; 50 mesh means there are 50 openings per square inch, while 500 mesh means 500 openings. The higher the mesh count, the more openings there are. In addition to indicating the mesh size of the sieve, it is also used to represent the particle size of particles that can pass through the sieve; the higher the mesh number, the smaller the particle size. 2. The size of powder particles is referred to as particle size. Due to the complex shape of particles, there are usually several ways to represent them, such as sieve particle size, sedimentation particle size, equivalent volume particle size, and equivalent surface area particle size. The screening size refers to the size of the openings in a sieve through which particles can pass. It is expressed as the number of openings per 1 inch (25.4 mm) width of the sieve; hence, it is called “mesh size”. Currently, there are no unified technical standards for powder particle size at either the domestic or international level; each company has its own definitions and methods for expressing particle size. There are different standards for screen specifications in various ** and different industries; therefore, the meaning of “mesh size” is also difficult to standardize. Currently, in the international community, the calculated diameter of the allowable equivalent volume particle is commonly used to represent particle size. Expressed in μm or mm.