Lithographic offset printing is based on the principle that oil and water are immiscible. Therefore, after printing, the paper generally stretches, and shrinkage becomes shorter. In order to eliminate such failures, the related printing process is now discussed: 1. Use horizontal thread locks when printing. The paper is divided into horizontal threads and longitudinal threads. In the papermaking part of the papermaking process, because the pulp (vegetable fiber) flows vertically to the moving wire mesh, the fibers are suddenly accelerated, and most of them will be connected along the direction of the wire mesh, forming what we call Dreadlocks. The plant fibers in the paper are hollow and translucent tubes. We can vividly say that the length direction of the fiber itself is what we call the longitudinal thread lock, and the direction of the gap between the fiber and the fiber is the horizontal thread lock. The experimental results show that the cohesive force of the fiber itself is greater than the bonding force between the fibers (mainly hydrogen bonding force). After the paper is damp, the expansion and contraction in the direction of the longitudinal threads is smaller than that in the direction of the horizontal threads. The two are roughly 1: 2. Therefore, products with more accurate overprinting must consider the deformation relationship of the horizontal and vertical threads of the paper. Therefore, when printing, make the longitudinal thread direction of the paper parallel to the cylinder axis, and the thread direction of the same batch of printing paper should be consistent. 2. Overprint clear water (commonly known as pressurized water). In the case that the printing paper is not easy to master, in order to prevent the paper from stretching during printing, you can use the method of overprinting once to make the paper adapt to the printing requirements, and then start printing the color, this method is not accurate Has a certain role. 3. Control the moisture of the printing plate. The moisture content of the printing plate is the key factor to control the expansion and contraction of the paper. The moisture of the plate is transferred to the paper through the blanket. The larger the moisture of the plate, the greater the expansion and contraction. Therefore, the smaller the moisture control of the plate, the better, especially when printing 80 grams of double-coated paper. 4. The printing plate is elongated by a plate-drawing machine. Generally, the single-color machine is in the third and four-color printing process, and the two-color machine is in the second printing process, and the image on the paper may be elongated, resulting in inaccurate overprinting. This is because the PS plate material has better ductility, and can be elongated by a plate-drawing machine to make the plate image and the image on the paper stretch evenly, so that the overprinting is accurate. At present, most domestic small and medium-sized enterprises generally do not have air-conditioning equipment. Most of the practice is to spray some water around the machine to increase the air humidity. For products with low requirements for non-dot printing, you can use a spray cylinder to sprinkle water on the edge of the paper and then print on the machine; for high air humidity in the workshop, the cut paper is best covered with a plastic cover to prevent moisture from becoming longer ; If it is a secondary printing, you can use the method of borrowing lines to make up for the shrinkage of the image. In general, there are many process treatment methods to solve the inaccurate overprint caused by the expansion and contraction of paper. As long as the discussion and management of the printing process are strengthened, it can generally be solved. Electric Eyebrow Trimmer,Eyebrow Trimmer,Eyebrow Razor Trimmer,Eyebrow Razor Yangjiang Yangdong Kartier Beauty Tools Product Factory , https://www.kartierbeauty.com
Paper is a material containing variable plant fibrous tissue. It has the function of absorbing moisture and releasing moisture. When the moisture in the air is constantly changing, it will adjust the balance with the air humidity. When the humidity of the air is higher than the moisture content of the paper, it will absorb the moisture in the air and expand and stretch; otherwise it will release the moisture and shrink to shorten to achieve a relative balance with the humidity of the environment.