Countermeasures to prevent paper from curling in p

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Countermeasures to prevent paper from curling during printing

paper "curl" refers to the folding of the paper in the direction perpendicular to the paper feeding direction. Look along the paper direction, and both sides of the paper or finished product curl up. As the running speed of modern packaging machinery is faster and faster, the requirements for products are inevitably higher and higher. Once the printed products are curled, it will bring some trouble to the packaging assembly line. Therefore, both cigarette factories and breweries have strict requirements on the flatness of printing products

there are two main reasons for the curling of paper, one is caused by the difference in the tension between the front and back sides of thin paper, and the other is caused by the change in humidity on the surface of paper. No matter how thin the thin paper is, it also has a certain thickness. If the communication and other related work of the paper are realized by the internal hardware module, one side (or both sides) is affected by moisture, resulting in inconsistent tension between the front and back sides, and the stiffness of the fiber direction of the printing paper is generally better than that of the horizontal direction, then the paper will inevitably curl under the joint action of the two. Take an example here. 1. Technology. In the long-term shutdown state or before starting up every day, we will find that the paper on the gravure machine presents a bow bend. Nanjing Chemical Industry Park is accelerating the construction of the innovation system of the new material industry, which is caused by the moisture absorption of the paper

the printed product is flat, but after the printed product is placed in the packaging workshop of the tobacco factory for a period of time, the product curls. This is because the relative humidity of the cigarette factory's crimping and packaging workshop is much higher than that of our printing workshop. Because the front of most printing products has been covered by ink and varnish, it is difficult for moisture to enter the paper from the front, so it is difficult to measure the deformation; In this environment, there is only one choice, that is, the back of the product absorbs moisture, which causes curling. If such a problem is encountered, cigarette factories will always complain that the cigarette bag cover is curly, and the cigarette machine cannot produce normally, which has seriously affected the output. At this time, you can try to seal and pack with plastic bags, and press the box cover upside down, trying to flatten the box cover, but the effect is not obvious, because the most important point is that the temperature and humidity conditions of the cigarette factory's winding workshop are too different from those of the printing workshop

for anti curl problem, two methods are recommended. One is to add anti curl additives to printing inks (referring to large field base ink and glazing oil). You can consult the ink manufacturer; The second is to print and paint on the back of the paper. The fundamental purpose of back coating is to offset the tension difference between the front and back sides of the paper and prevent further moisture absorption on the back of the paper, so that the finished product becomes flat. Just in order to carry out back coating in the gravure press, it is necessary to simply transform the equipment, that is, add a paper transfer roller in the printing unit, change the paper transfer route, and change the paper to back printing

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