Analysis and Discussion on Common Faults of Newspaper Printing Plates
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Split version
In the high-speed printing process of the newspaper industry, because the speed of the rotary machine is too fast, it is easy to cause the plate to break during the production process. There are two points to be concerned here: the purity of the aluminum base of one of the plates itself, the purity of the domestic brands is generally low, and there are many impurities, so it is possible to break when it is suitable for high-speed printing in the newspaper industry; the texture of the aluminum plate of the second plate material Be sure to select a vertical version with a grain direction perpendicular to the direction of the bite to avoid breakage.
Blank part on dirty
Since the newspaper version belongs to a photopolymerizable plate, the appearance of blanks on the blank portion is mainly caused by poor quality of the printing plate, insufficient development or blank portion oxidation, dampening solution concentration, and improper printing machine water roller and ink roller pressure.
Obviously, the plates of different brands will have different performances. If it is confirmed that there is no problem with the plates, it is recommended to try to replace the old developer and protective glue in the developing tank, and add a new developer (the normal pH of the developer should be In 12) and new protective glue to ensure normal development, uniform sizing; if there is any problem, it is recommended to adjust the concentration of the printing machine dampening solution or adjust the pressure of the printing machine water roller, ink roller.
Low print resistance
In the exposure process of the photopolymerization CTP plate, the image portion of the printing plate is formed after the light portion is polymerized, and the unexposed portion is removed by the development process to form a blank portion of the printing plate. The photopolymerization type CTP plate generally needs pre-heat treatment in the pre-development stage, and the preheating temperature is generally between 99 ° C and 121 ° C. The effect of the pre-heat treatment is to absorb the heat energy by the coating on the surface of the plate material, so that the exposure is formed. The text is more sturdy, which greatly improves the printing durability of the plate.
If there is occasional low printing durability of the printing plate in the printing, partial or full-page graphic loss occurs, commonly known as missing the plate, which is generally due to insufficient exposure or low preheating temperature, so that the graphic portion is not fully cured. Therefore, trying to increase the exposure energy of CTP or controlling the preheating temperature and reducing the flushing speed of the processor are some effective ways to solve the problem.
Graphic is too shallow or too deep
If the picture is too shallow, it will easily lead to the loss of highlights; if the picture is too deep, it will result in a dark tone. This requires that the laser exposure of CTP plate making equipment should not be insufficient or excessive, and a plate with high sensitivity, good stability and good dot reduction is also a decisive factor.
If the pre-washed brush pressure during development is too high, it may wear out the plate version of the Internet access point; if the preheating temperature is too high, the dot may be too deep and should be controlled within the normal range.