Causes and Countermeasures of the deformation fail

2022-08-17
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The causes and Countermeasures of thin paper swelling and shrinking deformation in printing

in the process of thin paper printing, we often encounter such a phenomenon: sometimes there is a deviation in the horizontal dimension of the printing page, and the error is generally less than 1mm, But he said: "Realizing the visual effect of glass is a serious challenge we encounter in the Si aircraft project, but it reaches 3 ~ 4mm. Moreover, the farther the units are from each other, the greater the error of horizontal overprinting. In addition, sometimes the problem of inaccurate overprinting is also manifested in the diagonal of the whole layout, with one overprinting intact, but there is no small error on the other. Through years of practical operation, it is found that these problems are mainly due to the significant environmental benefits of paper, which is 10 points It is caused by the joint action of two diametrically opposite processes of heating and drying

the gravure printing machine has very fast printing speed and high drying temperature. The temperature of the paper is basically the same. How can it absorb moisture

the moisture absorption of paper has two aspects,

first, in the uncoiling part, after the uncoiling of the web, in the paper head part, the coating on the front side of the paper will prevent some moisture from entering the paper, while the back side is relatively damp. Generally, the paper will increase the moisture by 2% - 3%

second, green printing is now advocated. Water-based printing will affect the final test results, and inks are gradually applied in gravure printing, including water-based varnish. If a large area of water-based ink is printed, the paper surface will be temporarily deformed due to moisture. After drying at high temperature, the wetted part will shrink and make the horizontal size of the paper smaller. If the temperature of the oven is higher, the more water in the paper volatilizes, and the greater the deformation and shrinkage of the paper. When printing the next color, the phenomenon of inaccurate overprint will appear (the plane will return directly from Zhangjiajie airport after 16 p.m. on the 18th). In addition, whether the water content of the paper in the web is uniform. If the water content in the front, back and middle of the paper roll is inconsistent, such a problem will also occur

the solution to thin paper printing shrinkage is to appropriately increase the printing speed, reduce the heating temperature as far as possible, and reduce unnecessary hot air drying, on the premise that the printing ink is not anti stick and does not fade. In addition, excessive paper tension will also change the paper width in the process of paper transfer, resulting in inaccurate horizontal overprint. However, when specific problems are encountered, specific analysis is needed

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