Pressure, paste, vignetting and other processes
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First, the pressure problem
Printing pressure has a great influence on print quality. Maintaining a uniform and constant printing pressure in the effective printing area not only makes the ink color uniform, but also has a small chromatic aberration, and can also stabilize the size of the print. Flat presses are able to achieve maximum printing pressure. However, due to the problem of the flatness of the manufacturing precision plate and the thickness of the self-adhesive substrate, it is impossible to achieve complete uniformity, resulting in uneven pressure, which affects the printing quality. One measure to deal with uneven pressure is to make a liner. Where the pressure is small, the lower part of the workbench is padded; one is to appropriately reduce the hardness of the flexographic plate. However, reducing the hardness of the flexographic plate is limited. If the flexural hardness is too low, the geometrical dimensions of the graphic will be expanded outward, making the small font easy to blur. When printing large-area, the problem of printing pressure is not easy to solve. For this reason, we borrow the method used in bronzing, that is, a silicone rubber plate with a 175-line netting and a hardness of 90° on the workbench. This can solve the problem of insufficient exhaust and partial pressure.
Second, the paste problem
Small texts such as the font below the eighth grade are often too small, and the phenomenon of ink drying on the top is often caused, so that the adhesion between the images cannot be discerned, mainly because the ink is dried too fast. Our company now uses the resin offset ink produced by Shenzhen Ink Co., Ltd., which has high viscosity, high temperature, fast ink drying, and printed products are very fine self-adhesive printed matter. . In this case, you should first look for problems from the flexible resin version. Generally, the resin version has a smooth feel on the bottom of the font, and should not be sticky. However, due to insufficient exposure, the bottom of the font is in a soft state, and it is easy to stick to the ink, and the ink accumulates more and dry in the thin line. If it is not used, it will waste the plate. At this time, the resin plate post-treatment liquid can be used, and the post-treatment liquid contains sodium hypochlorite and hydrochloric acid, which can harden the bottom of the word and eliminate the problem of stickiness. The most fundamental way is to find out the exact exposure time and make a standard resin version. The font is particularly fine. It is recommended to use the copper-zinc plate. The copper-zinc version of the font is not easy to dry, and the font is hard, it is easier to print clear strokes. In terms of the operating environment, care should be taken to reduce the air flow rate. If it is not working, add a suitable slow drying agent to the ink to reduce the drying speed. A relatively appropriate increase in printing speed can prevent excessive drying of the ink.
Third, the vignette problem
Sometimes there will be a cloud-like shadow on the self-adhesive product, which is mainly caused by uneven ink distribution. The leveling roller of the flat-pressing self-adhesive printing machine is a chrome-plated iron roller with a diameter of 150mm and can be axially linked. Its function is to receive the ink from the ink fountain roller and the transfer roller and uniformly distribute the ink. When the ink roller is given to the ink roller, the ink roller loses the ink repellency and easily forms a halo. In addition, the inking roller is made of soft nitrile rubber. If the maintenance is not paid attention to, the effect of the ink is lowered, and the vignette is also caused. The problem of uneven shading is solved by solving the halo, and the amount of ink can be appropriately increased.