First, the screen screen mesh number of choice:
Need to consider three factors
1. Ink used:
① general water-based ink for thicker screen (125-180 head / inch) (inches is the length of the unit 1inch = 1000mil = 2.54cm = 25.4mm);
② solvent-based ink in the print ads, electrical appliances, etc., the choice of medium mesh screen (196-420 head / inch);
③ UV ink selection of high mesh screen (355-457 head / inch);
④ the general ink pigment particles are relatively fine, the ink through the good, this ink can be used when the high mesh wire mesh is very low pass; and high pigment concentration of ink, despite the fine particles, but its permeability will be Relatively poor.
2. Type of substrate:
① the surface of the rough absorption of the substrate, to achieve the best ink cover, need more ink, and therefore the choice of thicker screen;
② smooth surface of the non-absorbent substrates need less ink, so choose a higher mesh mesh.
3. Mesh mesh matches the original image: The mesh size is chosen to be sufficient for the image on the film, that is, to ensure that the finest image area has sufficient screen support. (The number of mesh screen can be printed out of the thinnest line width is equal to the mesh aperture and the diameter of the screen plus the screen weaving when about 7% of the expansion (such as: 180 mesh / inch screen, Mesh diameter of 23μm, wire diameter of 30μm, printed out of the thinnest line width = 23 +30 + (23 +30) × 7% ≈ 57μm. That the smallest screen can only print 57 micron lines, there is a Formula is the screen can be completely printed out the smallest point (or line) of the roughness = √2 * (1 + mesh mesh * wire diameter) ÷ mesh mesh).
Second, the choice of wire diameter: to consider two aspects, ① wire mesh tensile strength. ② the fine degree of the original.
1. The same number of mesh, the greater the wire diameter, tensile strength, wear resistance, corrosion resistance are stronger, the greater the thickness of hope, opening area (opening rate) smaller. When the origin of the original image size 2 times the wire diameter, the network may fall on the screen, the high light area of the network loss is heavy. When the network 3 times the wire diameter when any part of the network can get enough support, dark point network can also get enough hole area.
Third, the choice of screen should pay attention to the problem:
Unevenness in weaving;
2. The thickness of the screen is uneven;
3. Choose the cost of the screen;
4. Note the moire:
In the halftone screen, the screen will also affect the level of the level of moire.