With the development of the printing industry, people have higher requirements for packaging decoration, and they are required to be bright in color. Increase the level of three-dimensional sense.
Bump printing is a special printing process that does not use ink in the range of plate printing. On the printed matter printed with pictures and texts, two concave-convex plates are made according to the pictures and texts, and then pressed with a flat press to make the surface of the printed matter like reliefs, producing unique artistic effects. So it is also called "rolling bump", this method is similar to "arch flower".
The process flow of bump printing is as follows: the production of bump printing plate → stamping of bump printing plate.
1. Production of bump printing plate
First of all, distinguish the primary and secondary levels of the drawing. We should use the main body as the theme, use the deep and shallow levels to reach a certain depth, and then consider the secondary level. The prominent main part should make the height of the protrusion higher. The printing plate is first made into a gravure plate, which is engraved using a carving process, which can be wood engraving, copper engraving, steel engraving, and corrosion; secondly, determining the representation method of graphics and lines, the main body should be coordinated with the general level, the layout is deep and shallow Coordinate everywhere, the outline of a picture should be from shallow to deep, and have a certain slope. The engraving drawing uses the perspective principle and the near, far, far and shallow expression methods. Finally, after the contour carving is completed, the elaborate work is done to make the entire layout smooth and even. Run.
Stick the engraved gravure to the center of the metal base plate of the flattening press, and level the printing plate to prevent unbalanced pressure, false pressure or plate shifting, and paste yellow paper on the platen To correct the pressure, for parts with many levels of uneven contours, press the size of the printing surface with yellow paper to cut and paste into paper sheets to form the same trapezoidal punch as the intaglio. At this time, the details of the trapezoidal punch are not the same as The gravure is consistent. A layer of gypsum slurry is spread on the trapezoidal convex mold. The gypsum slurry is mixed with fine clean gypsum powder and mixed with glue. The consistency should be suitable. A thin piece of paper is used to cover the gypsum slurry. For uneven pressure test, in order to prevent gypsum from sticking, a layer of kerosene can be applied on the intaglio plate. It is used to lightly shake the machine during the pressure test, and the speed should be slow at the beginning to avoid the rapid spreading of the gypsum layer and the inconsistency between the intaglio and the relief. After the gypsum is dry and hard, it can be embossed at normal speed. If the graphics pressed for the first time do not meet the quality requirements, the gypsum layer needs to be repaired, and when the gypsum is not yet dry, the excess gypsum on the non-imprinted surface is scraped off with a knife.
2. Embossing
When printing, the printed matter is placed between the intaglio and relief plate, and a large pressure is applied to roll out the concave and convex pattern. If the paper is damaged due to excessive pressure or too deep unevenness during the imprinting process, you can use sandpaper to grind evenly on the gypsum surface. In the imprinting process, the uneven surface should be brushed frequently to prevent dirt from being pressed into the damaged printing surface. The printing paper is hard in nature, and when the product quality requirements are very high, hot pressing can be used, that is, adding a resistance wire in the middle of the metal base plate, and passing a current during work to heat the printing plate, which can press out high-quality products.
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