Bilateral irregular longitudinal overprint refers to the overprinter produced at the same time on the operating surface or transmission surface. There is no rule to follow for the distance between the cross line and the standard line on the same sheet. According to the previous printing work experience, the causes and treatment methods are summarized as follows: 1. The two front gauges are not on the same line, and there are differences on both sides of the paper biting amplitude, which is caused by improper operation. In the actual production, the front gauge controls the biting range of paper teeth, and it is better to keep a bite distance of about 5mm on both sides. When adjusting the printing plate, the correct method is to use the plate drawing to achieve the standard size of image and text positioning. If the front gauge is not adjusted without pulling the plate, the width of biting paper on both sides is different, so that when the paper contacts the front gauge, it is not in a "line" shape, but in a "point" shape. The impact force of the paper is concentrated on two points. On these two points, the edge of the paper can not bear the effect of the forward impact and produce a difference At the same time, due to the different thickness of the paper, the front impact force is large or small, resulting in inconsistent front impact force on two points of the front gauge, resulting in irregular vertical overprinter, which is more common in monochrome machines. The general treatment method is to readjust the front gauge to make the bite reach the 5mm standard, keep the balance consistent and form a line, and then pull the plate again to solve the problem. 2. The static time of swinging paper teeth is too short. When swinging the paper biting teeth, it should be carried out in a static state to ensure the accuracy of paper biting. The static time is controlled by the adjusting screw on the "backing". When the swing gripper swing rod block contacts with the "backing", the roller on the connecting rod handle should be at the minimum surface of the cam, with a clearance of 0.03-0.05 mm. If it is less than 0.03 mm or there is no gap at all, it means that the static time is too long Short or no static time, will be in an unstable state, more likely to cause bilateral irregular overprint inaccuracy. The general treatment method is to readjust the adjusting screw on the "back" so that the clearance between the roller and the cam is 0.03-0.05mm. During the adjustment, the two "back" screws should be calibrated at the same time. First, loosen the locking nut, then turn the adjusting screw clockwise, and insert the 0.05mm thickness gauge between the cam and the roller until it is tight enough to insert. At the same time, in order to prevent the weight difference between the two "backing" screws, the machine should be started for a retest. Kraft paper with the same thickness is placed on the "backing" screw at both ends, so that the machine can rotate slowly. When both ends leave the kraft paper strip at the same time, it is considered that the adjustment is good.3. The distance between swing bite and imprint roller bite is too short. According to the design of printing machinery, the period when the high-speed press swings the gripper roller to contact the cam is very short. For beiren high-speed machine, according to the factory standard, the bite teeth of the imprint drum are 0 ° when they are engaged, 359 ° when they are opened when they are swinging, and only need to rotate 1 ° according to the circumference length of the roller, which is about 2.62mm. Such a short distance can complete the biting at high speed The paper transfer is obviously very short-lived. Of course, the hand over time can be adjusted to extend it, but it should be based on the principle of not tearing the paper. If the hand over distance is further reduced, it may appear that the swing bite teeth start to loosen, while the paper teeth of the imprint roller have not started to bite the paper. There are also some cases that the slow handover is good, but the irregular overprinting is not accurate due to vibration and other factors during high-speed operation The situation. Therefore, on the basis of the paper bite teeth of the imprint roller, the opening time of the swing bite teeth should be extended as far as possible, and the opening cam of the swinging bite teeth should be adjusted a little bit, so that after the two sides are engaged, the imprint roller can rotate 3-5mm to ensure the accuracy and stability of the handover. However, the premise should be that the paper is not torn and the overprint is accurate after the printing. 4. The bite force of paper teeth is too light. There are many reasons that cause the bite force of paper teeth to be too light or several paper teeth to bite. The common reasons are (1) the support spring and tension spring break or metal fatigue (all bite force is too light). (2) (3) the fastening screws of the paper bite teeth are loose (a few of them have light bite force), (4) the "backing" screw touches the "backing" (all bite force is too light), (5) the rigid tooth pad is smooth (most of the bite force is too light), (6) the paper bite teeth are not corrected properly (some or most of the bite force is too light). Due to the above reasons, the paper teeth work abnormally, resulting in irregular vertical overprint. The treatment methods for the paper bite teeth that are too light in (1), (2), (4) above are all common sense operation standards. If the rigid tooth pad at (5) points is too smooth, it can be removed and polished as a whole, and then the diamond stripe can be made again or a pair of dental chips can be replaced. For point (6), when correcting the biting force of the paper bite teeth, two cases should be handled separately. For the overall correction, a piece of paper with a thickness of 0.3mm should be padded on the "backing" screw, and then it should be corrected from the middle to the two sides. The pressure of the last one must not exceed the previous one. For individual correction, check whether the gap of the "backing" meets the above standards. If it is, continue to move from the middle to both sides Correction, a pair of paper teeth in the middle if there are individual bite force is too heavy, you can first adjust loose and then correct. 5. Paper teeth collide with "backers". Before correcting the biting force of the paper teeth of the embossing drum, a 0.3mm thick strip of paper or a thickness gauge should be padded on the "backing". When the paper teeth are leveled and the pressure is adjusted evenly, the paper strips at the "backing" position are taken out. At this time, the screws at the "backing" and "backing" can not be touched. However, sometimes, due to the wear of the tooth pad, improper correction of the paper bite teeth, and illegal rotation during mechanical maintenance, the "backing" and "backing" screws collide with each other, which affects the bite force of the paper teeth and causes inaccurate overprint. To find out whether this situation belongs to the "backing screw" factor or the paper teeth factor, and then treat them separately. If it is not corrected when repairing the machine, the screw should be readjusted to solve the problem. When the paper tooth pad is less than 0.5mm, it should be raised or replaced with a new one. If it is illegal to correct the paper biting teeth, causing "paper teeth" to collide with "backers", the paper biting teeth should be corrected again. 6. The paper biting tooth shaft or shaft sleeve of the imprint drum is worn. The paper biting shaft of the imprint drum, swinging the paper biting roller or the shaft sleeve are worn, which makes the paper biting teeth in the paper biting process in an unstable state, resulting in irregular longitudinal overprint on both sides. This situation is relatively easy to occur on low-speed machines, because the impact force of the tipping bucket of the low-speed machine is large, and the rotation range of the paper biting teeth shaft is relatively large. The high-speed machine uses swing indirect paper delivery, and the opening range of the paper bite teeth is small. At the same time, due to the lubrication of the automatic circulation oil system, the paper biting tooth shaft and shaft sleeve are not easy to wear, but pay attention to the oil hole and oil way blockage, which leads to oil break and bite. The general treatment method is to remove the paper teeth shaft or shaft sleeve, re process the shaft sleeve and install and correct it.7. The paper teeth support spring of the imprint drum is broken. The spring of paper biting tooth shaft requires good toughness and sufficient supporting force, but it is easy to fracture due to steel quality and quenching. The supporting spring is sheathed on a thin iron rod, even if it is broken, it will not fall down, so it is not easy to be detected and often ignored. It is found that the overprinter is more and more inaccuracy. Sometimes, because the spring has been used for a long time, or the paper is often changed to reprint, the spring will lose its supporting force or the supporting force can not be restored for a while, which will also cause irregular vertical overprint on both sides. Therefore, once such a situation is found, it is necessary to check the supporting spring first, and then replace it with a new one. Eight The pin on the swing bar of swing bite and embossing roller gripper shaft is loose or broken. There is a tooth opening swing rod installed at the end of the swing bite shaft and the paper bite shaft of the imprint drum. The swing rod and the shaft are fixed with pins. The pin bears a relatively large force, so it is easy to loose or fracture, resulting in inaccurate overprint. When checking this situation, clean it first, and then use a small pry Pry the swing bar to check the pin condition. At the same time, observe whether the paper teeth follow the movement. If the swing bar is not moved, the pin can be determined to be broken and a new one should be replaced.
Dongguan Beite packaging materials Co., Ltd. - located in Dongguan City, the world's manufacturing city, is a subsidiary of Beite packaging (China) Co., Ltd., with a plant area of 6000 square meters. It is a flexible packaging enterprise integrating R & D, production and sales. It has a complete set of domestic advanced production equipment, a scientific and humanized management system and a group of experienced technical personnel For backing, to provide customers with quality products and first-class service.
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