After the sheet-fed offset printing machine has been in operation for a period of time, due to the various degrees of wear of the machine parts, especially the opening cam, projections, tooth pads and tooth seats, the paper transfer cannot be carried out normally during printing, and it is often easy to bite The edge of the paper is bitten, resulting in inaccurate overprinting. The bite of the edge of the paper is not correct in the previous position, and the quality of the printed product is affected. 1. In the process of receiving the paper, the fault of the bite edge of the offset printing machine should be comprehensively analyzed and treated differently. Carefully check that the position of the teeth of the receiving paper is too close to the teeth of the roller. During the process of handing over the printing paper, make the paper The edge of the bite is broken, the solution is to cross it properly. 2. Under normal circumstances, the size of the platen of the printing machine and the bite of the delivery tooth is about 12mm. The distance between the roller and the bite of the delivery tooth cannot be too large, so that the bite distance of the delivery tooth is too large. If the continuity of the paper edge is bitten, and the position remains unchanged. If you find such a fault, you need to find the reason on the delivery tooth and the roller tooth. Turn off the offset press slowly and carefully check whether the process of handing over the paper and the roller tooth is accurate. The time for the tooth extension is too slow or the angle of the tooth extension Larger, and it is easy to cause the paper edge to bite and break. Check the wear of the paper tooth cam of the paper delivery tooth. If the cam wear is serious, repair welding or new parts may be required. When the delivery tooth is required to pass the paper to the impression cylinder big teeth, the delivery teeth and the drum big teeth control the paper at the same time. 3. The bite edge of the bite bite caused by improper adjustment of the bite row of the offset collection part is mainly broken, mainly due to the inconsistency of the height of the tooth pads of each bite, or the tooth pads are not straight, so that the individual teeth are not stretched enough, or not Zhang closed. Therefore, the bite of the papermaking paper is broken. The solution: readjust the pads of the paper-grip row to make it straight and uniform in height, and then carefully adjust the bite force. To adjust the bite force of each bite, a piece of 80g /? Kraft paper can be used to reach into the bite and pull it out by hand to test the bite force. 4. The position of the front gauge is not adjusted well, so that the roller bites the paper too much, and the receiving teeth bite too much, so the paper bite edge is broken during the handover process. Solution: Properly adjust the bite distance of the front gauge to control the bite distance of 3-5mm. 5. The edge of the offset printing paper is bitten, the paper is broken irregularly, and the tear is wide for a while and narrows for a while. This phenomenon is generally due to the inconsistency of the tightness of the tape on the feeder of the offset printing machine. In addition, turn on the paper to see whether the pressure roller of the paper conveying line can rotate flexibly. Drive the offset press slowly to see if the time when the paper arrives at the front gauge is appropriate. In general, the requirement is that when the current gauge reaches the paper receiving position, there is a distance of 8-10mm from the front edge of the paper edge. Adjustment. 6. The most important thing is that the edge of the bite paper is bitten. The transfer position of the collection teeth and the roller teeth is not on the public normal line, or the transfer time between the collection teeth and the roller teeth is too long. Solution: First, adjust their handover position, move the machine with both hands during the adjustment, and carefully check and correct it; Second, shorten the handover parallel time of the paper collection and roller teeth. 7. The paper edge is broken due to paper reasons. In the papermaking process, only interwoven fibers are used to form paper, which will cause uneven density. There are many trachoma and voids in the structure, and the paper surface is uneven. Therefore, a certain amount of fillers, glues, and colorants should be added to improve the paper surface. Smoothness, reduce paper transparency, reduce paper ink absorption, increase paper whiteness, weight, water resistance, toughness, etc. If the paper is too dry, the fiber has poor toughness, is brittle, the paper is loose, and the flatness is poor, it will also easily cause the paper edge to break during the paper feeding, short regulation, and embossing. In short, there are three forms of faults that bite the paper edge during the offset printing process: â‘ The paper bite is continuously broken, and the damaged position remains unchanged. The reason for this is that the delivery teeth and the roller teeth are not properly transferred or the delivery teeth and the roller teeth are not adjusted properly. â‘¡ Not every bit of the paper edge is bitten, but a few pieces of unstuck printed sheets spaced at a certain interval, and with regularity, mainly because of the arrangement of the delivery teeth of the delivery system. Pay attention to adjust the bite force of the delivery row. â‘¢ The bite edge of the paper is large and small when it is broken, and it is good for a while, and bad for a while, and it does not have regularity. This phenomenon is generally due to the improper adjustment of the offset press feeder or the improper adjustment of the height of the front gauge. These two parts should be adjusted separately. In daily work, the offset printing should be adjusted properly from paper feeding, regulation, imprinting, and paper receiving. The paper edge at the bite is broken and related to each part. The worn open tooth cam requires welding and replacement. For accessories, do not move blindly after problems occur to avoid adjustment disorder and bring a series of process failures. Reasonable adjustments should be made according to the data required in the motor relationship table in the instruction manual of the offset printing machine. Paper delivery teeth, roller teeth, and paper receiving teeth The height of the three parts of the pad biting paper transmission must be adjusted uniformly. The opening and closing time and the size of the three parts of the delivery tooth, the roller tooth, and the receiving tooth pad must be consistent. The handover is accurate and in place. Several problems should be paid special attention to during the adjustment process when the fault is broken.
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