Sheetfed offset printing bite paper edge bite broken fault analysis
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After the sheetfed offset printing machine has been running for a period of time, since the various parts have different degrees of wear, especially the open cams, bumps, pads and sockets, the paper transfer cannot be performed normally during printing, and it is easy to bite. The edge of the paper was bitten, causing inaccurate overprinting. The bite of the paper edge was not allowed in the previous position, and the quality of the printed product was affected.
1. In the process of receiving the paper, the fault of the bite paper being bitten is comprehensively analyzed, and the difference is treated. Carefully check that the position of the paper receiving teeth is too close to the position of the roller teeth, and make the paper in the process of printing paper transfer. The edge of the bite is bitten and broken, and the solution is to cross it properly.
2. Under normal circumstances, the size of the impression cylinder and the paper-feeding teeth are about 12mm, so the distance between the roller and the paper-feeding paper can not be too large, so that the biting distance of the delivery paper is too large. If the continuity of the paper edge is bitten, and the position remains the same. If you find such a fault, you should find the cause on the transfer paper and the big tooth of the roller. Slowly open the offset press and carefully check whether the process of transferring the paper and the large tooth of the roller is in place. The time of the tooth is too slow or the angle of the tooth is opened. Larger, it is easy to cause the paper edge to bite and break, check the paper cam wear of the transfer paper teeth, if the cam wear is serious, you can repair the repair or replace the new parts. When the paper is required to transfer the paper to the large cylinder of the impression cylinder, the paper and the large teeth of the roller simultaneously control the paper.
3. The bite paper edge of the bite row of the offset paper-receiving part is bitten by the improper adjustment of the teeth, mainly because the height of the teeth of each bite is inconsistent, or the pad is not straight, so that the individual teeth are not enough, or Closed. Therefore, the papermaking paper is broken at the edge of the paper. Solution: Re-adjust each tooth pad of the delivery pad to make it straight, high and low, and then carefully adjust its bite force. Adjust the bite force of each bite. Use a piece of 80g/m2 kraft paper, put it into the teeth, and pull it out by hand to test the size of the bite force.
4. The position adjustment of the front gauge is not good, so that the distance between the drum biting teeth and the paper is too much, so that the biting distance of the paper receiving teeth is too much, so the paper bite edge is broken during the handover process. Solution: Adjust the distance of the front gauge to properly control the bite distance of 3-5mm.
5. The offset bite is bitten by the edge of the paper, the paper is not broken regularly, and the break is wide for a while, and then narrows. This phenomenon is generally caused by the inconsistency of the tape on the offset printer. In addition, when the paper is turned on, the pressure roller of the paper feeding belt can be flexibly rotated. Open the offset printing machine and see if the paper arrives at the front gauge. The general requirement is that when the current gauge reaches the paper receiving position, the distance between the paper edge and the front gauge is 8-10mm. If it is not suitable, it needs to be carried out. Adjustment.
6. The most important point is that the biting paper edge is bitten. The intersection position of the paper receiving teeth and the roller teeth is not on the public normal line, or the parallel connection time of the paper receiving teeth and the roller teeth is too long. Solution: First, adjust their transfer position. When adjusting, use both hands to move the machine and check it carefully to correct it. Second, the parallel time of the delivery of the paper-crushing teeth and the roller-cuttering teeth can be appropriately shortened.
7. The paper edge is broken due to paper reasons. In the papermaking process, only the fibers interwoven with each other form paper, which will result in uneven density. There are many sand holes and voids in the tissue, and the paper surface is not flat. Therefore, a certain amount of filler, rubber, color, etc. should be added to improve the surface of the paper. Smoothness, reduce paper transparency, reduce paper absorbency, increase paper whiteness, weight, water resistance, toughness, etc. If the paper is too dry, poor fiber toughness, brittleness, loose paper, poor flatness, etc., it will easily cause paper to break in the process of paper feeding, short gauge, and embossing.
In short, there are three forms of failure in the offset printing process when the bite paper is bitten.
1 The paper bite is continuously bitten and the damage position is unchanged. The reason for this is that the transfer of the transfer paper and the roller teeth is not correct or the transfer of the paper and the large teeth of the drum is improperly adjusted.
2 The edge of the paper is not bitten by each bite, but is partially separated by a few sheets that are not bitten, and has regularity, mainly due to the delivery of the delivery system. Pay attention to adjusting the bite force of the delivery tray.
3 When the bite of the paper breaks, it is big and small, it will be good for a while, it will be bad for a while, and it will not have regularity. This phenomenon is generally caused by improper adjustment of the offset paper feeder, or the adjustment of the front gauge height is not appropriate, the two parts should be adjusted separately. In daily work, the offset printing should be adjusted from the paper feeding, the rules, the embossing, and the delivery of the paper. The edge of the paper at the bite is bitten and related to each component. The worn open cam requires welding and replacement. Accessories, do not blindly move after the occurrence of problems, avoid adjustment disorder, bring a series of process failures, according to the data required in the manual relationship table of the offset printing machine manual to make reasonable adjustments, transfer paper teeth, roller teeth, paper delivery teeth The height of the three large bite paper transfer parts must be adjusted consistently. The closing time and the closing size of the three parts of the transfer paper, the roller big teeth and the delivery paper pad must be the same, and the handover is accurate in place, all of which are excluded from the bite paper. Several problems should be paid attention to during the adjustment process when the fault is broken.