What should I pay attention to when selecting the screen?

1 dark adjustment area, in the actual production, in order to ensure that the minimum photosensitive glue point of the image dark adjustment area is supported by the mesh of the screen, it is necessary to select the appropriate mesh with the mesh diameter for printing. In order to select the correct screen printing mesh, we need to accurately calculate the diameter of the smallest dot to be printed. For the calculation of the minimum dot diameter, we should based on the number of screen lines and the percentage of image dot area, if we print on glass. The image has a screen line of 75 lines/in (2a5 lines/cn). The tonal range of the image is 20%~80%, which means that the minimum dot area percentage in the brightness area is 20%. We can pass the formula. :d=(L1284t)1/2/L, d is the diameter of the minimum dot to be printed, t is the percentage of the dot area, L is the number of screen lines of the image, and the minimum dot diameter in the image brightness area is calculated to be 0ll7cm. After the diameter of the minimum dot to be printed is determined, in order to ensure that the minimum dot can be printed, the diameter of the minimum dot is not less than three times the diameter of the wire diameter of the wire used, and the wire diameter of the wire mesh used should be no more than 57 mm. In addition, the surface of the glass is a non-absorbent surface, so the dot gain is more serious than paper printing. In fact, the wire diameter of the wire is lower than the theoretical value.

2 Secondly, it is necessary to avoid interference between the dot of the tone image and the wire mesh. Moiré is a potential problem for halftone screen printing. It is generated because the two lines or two objects are constant. The visual result of interference between angle and frequency. When the human eye cannot distinguish the two lines or two objects, only the interference pattern can be seen, and the mesh and the screen can form another form of moiré. The distribution of moiré stripes on the screen can produce patterns that are illegible and significantly different from the original. In screen printing, it is very difficult to completely eliminate the moire fringe. We can only avoid the appearance of full moire fringe in the whole image. The ratio of the high mesh mesh number to the image screening line will be very helpful. The elimination of the fringe, in general, the ratio of the mesh number of the screen to the number of screen lines of the image is 5:1, which greatly improves the moire fringe, for example, when we need to print an image with a line number of 7 lines/inch, At this time, it is necessary to use a mesh with a mesh size of 350 mesh/inch. If the ratio of the number of screen meshes to the number of screen lines of the image is less than 5, it will easily lead to the overall tension of the printed image. After 72 hours, the two wires are placed. The screen of the net is again measuring the tension, and suddenly the attenuation of the two tensions is compared. The smaller the attenuation, the more stable the tension of the screen is, and the more favorable the printing is, especially for products with higher precision requirements. Be sure to use a screen that maintains a constant tension.

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