How to quickly solve the paper wrinkle problem dur

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How to quickly solve the paper folding fault during printing

the author checked the roller pressure and the tooth handover time when dealing with a paper folding fault, and found no abnormalities. Some models have better detection limits, and the paper is also very flat on the cardboard, without "Ruffle edge" and "tight edge" phenomenon. Replace the roller tooth pad, level it, adjust the tooth gripping force, try the machine for printing, and the fold fault still looms and appears from time to time. After many times of startup, shutdown and repeated debugging of the gripping force of the drum, it is found that most of the drum gripping teeth are in the state of full gripping, but some are in the state of virtual gripping, that is, unilateral gripping is not tight. It seems that the cause of the fault is here. Sure enough, there is a little gap between the worn dental shaft and the dental socket (you must try it out with force). Therefore, the copper sleeve of the tooth shaft and the bushing of the supporting foot were replaced, and the tooth was evenly mixed to try the machine again. The fault was completely eliminated. Inspired by this, our company has overhauled many equipment with this fault, effectively eliminating the wrinkle fault and ensuring normal production

the paper wrinkle fault is commonly known as wrinkle, paper rolling, paper squeezing, etc. when the paper teeth hold the paper and roll it between the rollers, there is air flow on the paper surface. If the air flow is rolled evenly at the moment of rolling, so that the paper is pressed smoothly, there will be no wrinkles; If the displacement or deformation of the paper increases instantly, wrinkles will occur. Causes include uneven paper. The drum pressure is inconsistent or too large, and its teeth are loose, etc

due to the influence of ambient temperature and humidity, the water content of paper changes, which is prone to "Ruffle edge", "tight edge" and other phenomena. If the paper is not printed in the horizontal direction, the wrinkle is characterized by the fineness on both sides of the trailing tip, and the general rule is that the pleats are similar. In order to avoid wrinkles, it is suggested that the paper should be cut and printed immediately, and the paper should be knocked before printing to increase the flatness of the paper, or covered with plastic cloth

fold failure caused by equipment is characterized by folds on both sides or in the middle of the paper from its mouth to the trailing tip, ranging from large to small, sometimes regular, sometimes irregular

for the wrinkle fault caused by equipment, the author summarizes its solutions into the following three aspects

1. check the drum pressure

the drum pressure should be adjusted according to the standard lining and standard pressure specified by the equipment. In order to ensure its accuracy, it should be measured many times, calculated many times and adjusted repeatedly. The "leveling" roller is a necessary condition for the normal operation of the equipment. It is necessary to prevent the phenomenon of excessive pressure and inconsistent pressure between rollers, so as to prevent excessive paper deformation and unilateral rolling. To ensure that the pressure between the impression cylinder and the rubber cylinder is less than the pressure between the plate cylinder and the rubber cylinder, the contact width is generally less than 2mm. Special attention should be paid to that the rubber pad is easy to swell due to oil and water, which affects the pressure. At this time, it needs to be treated to ensure the uniformity of the imprinting ink bar. Replace the blanket in time to prevent it from aging and losing elasticity, which will cause paper wrinkles

2. Check the teeth of the drum

the basic requirements for the teeth of the drum are that the teeth are flat, the teeth are aligned, and the force is uniform. The paper quantity shall be controlled within 4 ~ 6mm, preferably 5mm, and the same paper quantity shall be ensured on both sides. It is necessary to focus on checking whether the fit clearance between the roller tooth shaft and the tooth sleeve is excessive. If the gap is large, the paper is unstable, which is easy to cause the paper to shift and wrinkle. This is the most important and direct cause of fold failure. Therefore, the key to solve the wrinkle fault is to ensure that the paper does not creep and deform when it is held tightly by its teeth. Secondly, check whether there is fracture or elastic fatigue in the tooth holding spring to prevent wrinkles due to insufficient holding force. The gripping force should be greater than the sum of the drum pressure and the paper stripping force. Then check the delivery time of the paper to avoid picking teeth, pulling gauge, paper counting needle competing for paper, and letting the paper out of control. In addition, if the paper delivery mechanism of the upper swing frame is used, it should be carefully adjusted to ensure the smooth handover of the paper

3. Check other details

the printing area is often changed, which is easy to cause the drum to accumulate dirt on the main frame twice the maximum experimental force and affect its flatness. It is necessary to clean the dirt on the drum surface and roller pillow in time. Check whether the regular board is bent and whether the paper is flat and natural on the paperboard. When the printing speed is too high, unstable factors increase, which is easy to cause paper wrinkles, so the printing speed should be adjusted appropriately. The local field area of the printed matter is too large, or the ink is too thick and viscous, which will cause the local paper to bear too much force and wrinkle failure. You can appropriately dilute the ink or adjust the printing process. Pay attention to check whether the relevant screws or pins on the equipment are loose or broken

the accuracy of the equipment should also be known at any time. In the pressed state, the size of the drum gear meshing foundation is specified according to the shape and foundation drawing, whether the clearance of the drum shaft sleeve is within the use standard, and the wear condition of the drum surface are related to the paper fold fault, which needs to be adjusted and repaired in time

to quickly solve the problem of paper folding, we must first be familiar with the offset printing process principle and mechanical principle, not only comprehensively analyze, but also break the shackles of conventional experience and dare to innovate. For example, some offset printers use electric heating to blow paper while printing (using a small offset press); Some improve the mechanical structure to better stabilize the paper feeding and handover. Find out the direct or indirect causes of paper folding, adjust or repair in time, and effectively control the static → dynamic → static process of equipment and printing paper, so as to quickly solve the paper folding fault

source: Shandong Wenshang Xinhua Printing Co., Ltd. (huyongmin)

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