Process practice shows that there are many reasons that affect the printing quality. The abnormal moisture content of the paper is also the reason that affects the quality of the product. Therefore, the correct understanding of the relationship between the moisture content of the paper and the printing, and the accurate control of the moisture content of the paper are Printing quality plays a crucial role.
We know that paper is made up of fibers, fillers, and rubber. When the temperature and humidity of the environment cause the moisture content of the paper to be excessive, the binding force between fibers, fillers, and rubber in the paper is easily reduced. Will affect paper surface strength. In this printing process, it is easier to generate de-powdering and off-paper dust defects, thereby reducing the hardness and stiffness of the paper edge. When paper is transported, it is easy to cause instability in the front gauge positioning and cause overprinting inaccuracies. Conversely, paper with low water content on the paper has poor paper elasticity, and the printing dot and imprint expansion rate are large. In the printing process, the paper is prone to hygroscopic variation, resulting in misregistration.
If the moisture content of the paper is not uniform, there will also be various printing defects. If the water content around the paper is higher than about 1.4% in the middle, the overprinting rule line of the back drawing part of the paper will be 1 mm longer than the opening; if the water content is higher than 2.5%, the paper will be pulled Printing wrinkles will occur, and the trailing thread printing guideline will be 2mm longer than the mouthline. The overprinting inaccuracies will also appear in the printed sheets. If the water content is higher than 3%, the paper will appear lotus leaf. Edge phenomenon, will cause serious wrinkles when printing; if the paper has a high moisture content, the relative humidity of the printing site is lower on the paper, the paper will easily release moisture on all four sides, so that the central part of the paper moisture than the four sides of the water content Above 2.5%, the paper will have a tight edge. When printing, it will easily cause image ghosting in the middle.
All the circumstances clearly indicate that the normal moisture content of the paper has a great influence on the printing quality. Therefore, when the paper is hung, the water content of the base paper should be grasped first, so that the moisture content of the center and the four sides of the paper after hanging can be maintained evenly. To do this, we should control the thickness of each paper clip. The graphic paper-hanging machine used by our factory hangs about 70 g/m2 of paper, and each folder has about 70 sheets. Basically, the air volume can be blown through the gaps of the paper to the center. Achieve uniform blowing through to ensure that the paper surface water content is basically the same, to ensure print quality.
In summary, the moisture content of the paper has a significant effect on the printing quality. Controlling the moisture content of the paper is a necessary measure to check the quality of the printing. It guarantees normal printing, reduces the occurrence of printing failures and reduces paper loss. Very important significance. If this is the case, then to what extent is the water content of the paper controlled? In general, the moisture content of the paper is controlled at 7Â±1%, and the difference between the center of paper and the moisture content on the four sides does not exceed 1%, basically ensuring normal printing and avoiding failures.
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