A brief analysis of the solution to the curl of pr

A brief analysis of the solution to the curling of printing paper

paper curling 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. Due to the faster and faster running speed of modern packaging machinery, printing companies must have higher and higher requirements for products. 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

analyzing the causes of paper curling, printing companies mainly have two aspects: one is caused by the difference of tension between the front and back sides of thin paper, and the other is caused by the change of humidity on the surface of paper. No matter how thin the thin paper is, it also has a certain thickness. If one side (or both sides) of the paper is damped and the tension between the front and back sides is inconsistent, and the stiffness of the fiber direction of the printing paper is generally better than that of the horizontal direction, then under the joint action of the two, the paper will inevitably curl. Here is an example. 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 bending state, which is caused by the moisture absorption of the paper

the printed product is flat, but the printed product is placed in the cigarette factory packaging workshop for a period of time. Therefore, the stress corresponding to the specified cycle is called the conditional fatigue limit, and 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. Most printing products have been covered with ink and varnish on the front, so it is difficult for moisture to enter the paper from the front. Therefore, in this environment, there is only one option, that is, the back of the product is hygroscopic, causing 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 further improve the sealed packaging of plastic bags with the level of manufacturing technology and overall strength, and flatten the box skin upside down, trying to flatten the box skin, but the effect is not obvious, because the most important point is that the temperature and humidity conditions in the cigarette factory crimping workshop are too different from those in the printing workshop

for anti curl problem, two methods are recommended. One is to add an anti curl additive to the printing ink (referring to large field base ink and glazing oil) to instantly measure and record the characteristic curve of the material in the process of impact. You can consult the ink manufacturer. The second is to print and paint on the back of the paper model: WDL (1) 000 sheets. 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

at this time, you can try to seal and pack with plastic bags, and flatten the box skin upside down, trying to flatten the box skin, but the effect is not obvious, because the most important thing is that the temperature and humidity conditions in the cigarette factory's crimping workshop are too different from those in the printing workshop

source: China and India