Compared with offset printing , gravure does not require high technical experience of operators. However, in actual production, there are always various sudden technical problems. If these problems cannot be solved in time, they will be produced. Efficiency and yield have a greater impact.
Solving the problem of ink and whitening when gravure black ink
Sudden problems: Since any package needs to print barcodes, black ink becomes an indispensable ink in packaging printing , but it is easy to appear ink and whitening when gravure black ink.
Black ink soluble ink means that the ink or varnish of the same system will cause the blur of the edge of the black ink printed image when it is overprinted with the black ink, and the blurring phenomenon will be elongated under the action of the scraper. Therefore, waste products are generated, especially when varnish and black ink are overprinted, which is more likely to cause black ink solution, because the same solvent as black ink in varnish will have a certain dissolution effect on black ink.
There are three main reasons for the formation of whitening phenomenon: one is that the ink itself is not black enough; the other is that the proportion of the base color used by the ink manufacturer in the production of black ink has certain problems, such as the use of yellow, The magenta and cyan base color materials add 50% of the finished black ink when modulating the black ink; the third is that the black ink is printed too much, and the ink is reused too many times.
Solution: Change the black ink system to change with the ink generation system overlaid on it, such as ester-soluble varnish and ester-soluble black ink, in a ratio of 2:1 in the ester-soluble black ink. The non-phenyl alcohol soluble black ink is added, so that the black ink and the varnish system are different, thereby eliminating the black ink solution. This method is equally applicable to whitening, and the effect is very good.
Cleverly mention the printing tolerance of large-area intaglio
Sudden problem: the biggest feature of gravure printing is that the large-area solid printing hue is stable and the color is saturated. The printing durability of the gravure mainly depends on the graphic structure and distribution ratio of the solid block, usually the square block, the round shape and other solid blocks. When the basic consistency is the same, the gravure printing resistance is higher; the upper and lower ratios are larger (such as the middle solid block is larger, the two sides are smaller); the two solid blocks are larger, the middle solid block is smaller; When the size is large, the other side is small, etc.), the gravure resistance is low.
This is mainly because when the upper and lower ratios are large, the scraper portion corresponding to the large solid block is worn more, and the rest is less worn, which causes the uneven force of the scraper, so that the scraper pressure needs to be continuously increased. As a result, the gravure wear is large, and the gravure resistance of the gravure is reduced.
Solution: Add several real strips with the same length and small width of 6~7mm in the vertical front and vertical rear non-image parts of the smaller part of the solid block to support the wear area, so as to achieve uniform scraping The purpose of the force, and thus to some extent, improve the gravure resistance of the gravure. According to the author's actual operation statistics, this method can increase the printing durability of the gravure by 50%.
Accurate overprinting accuracy of special gravure
Sudden problems: In recent years, the development and application of a large number of new materials (such as laser paper, glittering gold sand, silver sand ink, etc.) and new technology in the gravure field have changed the tradition of gravure printing only white cardboard and film.
We know that web gravure is a method of detecting overprint marks by a cursor probe to achieve precise overprinting between color groups. Conventional white cardboard, film and conventional gravure inks are not reflective, and new types of Laser paper (especially laser beam paper), flashing gold sand, silver sand ink have strong reflective, and most of the domestic gravure printing machine cursor detection system is difficult to effectively detect it.
Solution: When using laser paper as the printing material, it usually needs to print white ink. It has been proved that the conventional gravure white ink has strong reflective property under the laser paper, which will cause the accuracy of the tracking of the cursor probe to fluctuate. This makes the overprinting accuracy of the gravure machine fluctuate and even stops.
The solution is to add a small amount of blue ink to the gravure white ink. This is because, under the perception of the human eye, these blue inks will not only make the white ink blue, but will increase the whiteness of the white ink and even reduce the reflectiveness of the white ink. This allows the cursor probe on the gravure to easily identify the overprint mark. For inks with strong reflectivity such as glittering gold sand and silver sand ink, the angle of the cursor probe is changed to reduce the influence of the reflective property on the cursor probe. Usually, the cursor probe is used to detect the angle of 5° with the paper.
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