Ink mixing
When the screen printer is printing, the method to judge the degree of ink concentration is: the concentration is when the ink passes through the screen and there is no screen pattern or drawing on the printed surface. The dilution is when the ink can pass through the mesh holes by its own weight without dripping. When the printed lines are thin, the ink should be diluted, otherwise, it should be concentrated.
Screen selection
When the screen printer is printing, the quality of the screen cloth is stable when the wire diameter is uniform and the mesh number is accurate and consistent. The mesh number generally selected is 450~500 mesh. For substrates with fine lines, high ink fineness and poor absorption, a screen with a high mesh number should be selected, otherwise, a screen with a low mesh number should be selected. When making the plate, the position of the image on the screen and the size of the screen should be determined according to the structure, size and position of the image on the substrate. If the design is not good, it will affect the quality of the screen printing, or even make it impossible to print. In addition, it is best to use one screen to print the image on the same printed object. If the screen printing is divided into two or more, the number of processes will reduce the screen printing pass rate.
Squeegee selection
When the screen printer is printing, the material used for the squeegee is mostly polyurethane. Polyurethane rubber scrapers have good wear resistance, solvent resistance and resilience. Its hardness is selected to be 60~80 Shore. For substrates with large screen tension and good surface flatness, a squeegee with high hardness should be selected. On the contrary, a squeegee with low hardness should be selected. When printing on curved surfaces, low-degree spherical surfaces or substrates with poor flatness (local protrusions), the squeegee width should be narrow rather than wide.
Screen positioning
Generally, the clamp materials used in factories include metal, wood, plywood, PVC transparent sheets, etc. If positioning is difficult and the substrate size is small, metal clamps should be used. If the image and text are close to the edge of the substrate, a flat piece of wood with the same height as the edge of the substrate should be fixed next to the substrate to prevent the image and text from being easily blurred. The distance between the screen and the substrate is generally 1.0~2.5mm. If the printed pattern is still easy to blur or there are reticulations, the distance between the screen and the substrate should be increased.
Screen printing process
If the scraping pressure is large, the amount of ink will be large, but the screen is easy to deform, so the scraping pressure should not be too large. The scraping speed is usually 60~200mm/s. The scraping speed is fast, the amount of ink is small, but it is not easy to block the screen. Therefore, the scraping speed should be faster for ink that is easy to block the screen. There are three types of scraping routes: straight line, oblique line and curve. It should be selected according to the flatness of the substrate and the distribution of the image on the substrate. When the scraping route is long and the ink consumption is large, the scraping amount of ink should be more, or even ink should be applied first and then scraped.