Pinhole phenomenon for screen printing staff, is the most headache problem.If it is the printing of billboards and opaque things such as thick paper, this is not easy to observe holes, generally not a problem.But in the aluminum plate, glass, propylene plate precision printing, after processing and corrosion processing, do not allow to produce pinholes.In addition, the pinhole is also a variety of reasons, many are currently unexplained reasons, or quality management problems.Pinhole is one of the most important inspection items in the inspection of printed products.
① dust and foreign matter attached to the plate.When making plate, washing development will have some sol mixed in.In addition, in the emulsion coating, there is also dust mixed, attached to the screen will produce pinholes.These can be found and repaired in time if carefully checked during testing.If dust and foreign bodies are attached to the screen, blocking the screen opening will also cause pinhole phenomenon.This dust can be removed from the plate after several sheets of printing on paper with strong ink absorbent before formal printing.
② substrate surface cleaning.Aluminum plate, glass plate, propylene plate, etc., should be printed immediately after the pre-treatment before printing.In multicolor printing, the method of rubbing with alcohol before printing is generally adopted.In addition, can also use semi-automatic and automatic ultrasonic cleaning machine.After pretreatment, it can remove grease and other dirt, and also remove dust attached to the surface.
The detergent of cleaning machine is often mixed with broken fiber, this detergent is dissolved in alcohol, when cleaning the substrate surface, often form a thin surfactant film, in the film printing ink will occur pinhole.So be careful when using cleaning agents and alcohol.When carrying the substrate by hand, the fingerprint of the hand will also be attached to the printing surface, forming pinholes during printing.