Compared with offset printing, gravure printing does not have high requirements for the operator's technical experience, but in actual production, there will always be a variety of sudden technical problems. If these problems cannot be resolved in time, it will Efficiency and yield rate have a greater impact.
Ingeniously Solve the Dissolution and Whitening Phenomenon of Black Ink in Gravure Printing
Sudden problem: Since any packaging needs to print barcodes, black ink has become an indispensable ink in packaging printing, but it is easy to dissolve and blush when black ink is gravure printed.
Black ink soluble ink refers to the same system of ink or varnish when overprinted with black ink, which will cause the edge of the image printed by the black ink to be blurred, and this blurred phenomenon will be elongated under the action of the scraper. As a result, waste products, especially when the varnish and black ink are overprinted, are more prone to black ink dissolution, because the same solvent as the black ink in the varnish will have a certain dissolution effect on the black ink.
There are three main reasons for the whitening phenomenon: first, the blackness of the ink itself is not enough; second, there is a certain problem with the proportion of basic colorants used by ink manufacturers when producing black ink, such as the use of yellow, The magenta and cyan basic colors are added with 50% of the finished black ink when the black ink is modulated; the third is that the black ink printing volume is too large, and the number of repeated ink reuse is too many.
Solution technique: Properly change the black ink system to make a system change with the ink superimposed on it. For example, when using ester-soluble varnish and ester-soluble black ink, the ratio of ester-soluble black ink can be 2: 1 Add phenol-free soluble black ink, so that the system of black ink and varnish are different, thus eliminating the phenomenon of black ink dissolving. This method is also suitable for whitening, and the effect is very good.
Cleverly improve the printing resistance of large-area gravure
Sudden problem: The biggest feature of gravure printing is that the hue of large-area solid printing is stable and the color is saturated, and the printing resistance of gravure mainly depends on the graphic structure and distribution ratio of solid blocks, usually square and round, etc. When they are basically the same, the intaglio printing resistance is higher; the difference between the upper and lower ratios is larger (such as the middle solid block is larger and the solid blocks on both sides are smaller; the solid block on both sides is larger and the middle solid block is smaller; the solid block on one side Large, small solid land on the other side, etc.), the intaglio printing resistance is low.
This is mainly because when the gap between the upper and lower ratios is large, the scraper parts corresponding to the large solid block are worn more, and the other parts are less worn, which causes the uneven force of the scraper, so that the pressure of the scraper needs to be continuously increased. In the future, the greater the wear on the gravure, the lower the gravure durability.
Solution: Add a few solid strips with the same length as the small solid block and a width of 6-7mm in the non-graphic part of the vertical front and vertical back of the smaller part of the solid block to support the wear area, so as to achieve uniform scraper The purpose of the force is to improve the gravure durability to a certain extent. According to the author's actual operation statistics, this method can increase the durability of gravure by 50%.
Cleverly mention the overprint precision of special gravure printing
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 technologies in the field of gravure printing have changed the tradition of only printing white cardboard and film in gravure printing.
We know that roll paper gravure printing uses a cursor probe to detect overprint marks to achieve accurate overprinting between color groups. Traditional white cardboard, film and conventional gravure inks are not very reflective, but the new type Laser paper (especially laser beam paper), flashing gold sand and silver sand inks are highly reflective, and it is difficult for them to be effectively detected by the cursor detection system on most gravure printing machines in China.
Solution: When using laser paper as the printing material, it is usually necessary to print white ink. Practice has proved that conventional gravure white ink has strong reflectivity under the background of laser paper, which will cause the accuracy of the cursor probe tracking overprint to fluctuate. As a result, the overprinting accuracy of the gravure printing machine also fluctuated and even stopped.
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 reflectivity of the white ink. In this way, the cursor probe on the gravure printing machine can easily recognize the overprint mark. For flashing gold sand, silver sand ink, and other highly reflective inks, the method of changing the angle of the cursor probe is used to reduce the impact of the reflective probe on the cursor probe. Usually, the detection angle between the cursor probe and the paper is 5 °.
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