objects such as billboards and thick paper, such small holes that are not easy to observe are generally not a problem. However, for precision printing on aluminum, glass, and acrylic plates, pinholes are not allowed when post-processing and etching are required. In addition, pinholes are caused by a variety of reasons. Pinholes are printed products one of the most important inspection items in the inspection.
①If dust and foreign matter adhere to the screen, blocking the screen opening will cause pinholes. For example, when making a screen printing mesh plate, some sols are mixed in during washing and developing. In addition, when the emulsion is applied, dust is also mixed in, and pinholes are generated on the screen printing mesh. During the test, if you pay attention to inspection, you can find it and make timely repairs.
Before the official
printing, if the ink-absorbing paper is used for several sheets of printing, the dust can be removed from the plate.
② Cleaning the surface of substrates. Aluminium plates, glass plates, acrylic plates, etc. should be pre-treated before printing and printed immediately. In multi-color printing, the method of rubbing with alcohol before printing is generally used. In addition, semi-automatic and full-automatic ultrasonic cleaning machines can also be used. After the pretreatment, dirt such as grease can be removed, and at the same time, dust on the screen printing mesh surface can be removed.
This detergent stays in alcohol. When cleaning the surface of the substrate, a thin surfactant film will be formed, and pin holes will occur when printing ink on the film. So when using cleaning agents and alcohol. Pay special attention. When the substrate is carried by hand, the fingerprint of the hand will also adhere to the screen printing mesh surface, cause the forming pinholes during printing.
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