In screen printing, the ink is transferred through the screen printing plate through a moving squeegee under a certain pressure and transferred to the substrate to form an image. Therefore, various indicators of the squeegee affect the printing effect. Since the substrate materials are various and the shapes are different, they can be roughly divided into plane and curved surfaces. Therefore, the following factors should be considered when selecting the squeegee according to different substrates and the surface shape of the substrate.
â‘ Scraper hardness The amount of ink transfer and the reproducibility of graphics are related to the hardness of the squeegee. Generally, when printing on a hard substrate, a soft squeegee can be used, so that the pressure applied during the squeegee can make Full contact between the layout and the substrate to improve the printing effect. On the contrary, when printing soft substrates, it is necessary to use a hard squeegee to make the plate contact with the substrate well. The reason for the two is the same. Due to the wide variety of substrates and the different substrates, the harder scrapers are generally used for smoother substrates. Conversely, the softer scraper printing effect will be more ideal. When the squeegee exerts a certain pressure on it during squeegee printing, the squeegee will bend to a certain extent. Therefore, when using the squeegee, the bending fatigue and mechanical strength of the squeegee must be considered, and the squeegee must have a certain elasticity. The scraper will generate heat due to friction at the same time of scraping, and the hardness will change after the temperature rises. When choosing the scraper material, please pay attention to the material that is not easily deformed by heat. Generally, the hardness of the scraper material should be selected at Shore hardness 60 to 90 degrees is better.
â‘¡The wear resistance of the scraper, because the scraper and the screen printing plate are in direct contact, there is friction every time the scraper is printed, and the number of prints in the screen printing can reach tens of thousands. Therefore, the scraper is required to have good wear resistance, lubricity and certain mechanical strength, so that the friction can be reduced as much as possible to ensure the service life of the scraper.
â‘¢ The solvent-resistant gender board of the scraper should be in contact with various inks and solvents, such as ethanol and gasoline. Various types of rubber materials have different affinity for solvents, and the scraper will change to different degrees after contact with ink or solvent. Commonly, the hardness of the scraper changes, and the volume expansion will deform after contact with the solvent. If the squeegee swells, the edge accuracy of the squeegee will be reduced, and ink leakage will be uneven during printing, which will affect the printing quality. It is generally believed that rubbers with high hardness have high cross-linking density, and the molecules of ink and solvent are difficult to immerse in the molecules of rubber, so the coefficient of expansion is small. When selecting the scraper, consider to meet the printing requirements as much as possible, in order to reduce the deformation to a minimum, you can choose a rubber blade with higher hardness.
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