Analysis of longitudinal overprint inaccuracy of t

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Analysis of longitudinal overprinting inaccuracy of beiren sheet fed offset press (III)

3. Irregular overprinting on one side of the paper

irregular overprinting on one side refers to the incorrect overprinting on one side of the longitudinal crosshair operation surface or transmission surface. The crosshairs with inaccurate overprint are sometimes in the trailing direction of the standard line, and sometimes in the mouth direction of the standard line. There are two common reasons

(1) paper feeding skew

some machines often cause paper feeding skew due to wear or poor adjustment of paper feeding machine components with high elongation of film data, such as separation head and paper pressing ball. When the paper reaches the front gauge, the speed is different. This paper feeding condition may cause irregular overprint on one side. This situation indicates that several parts of the paper conveyor may have problems at the same time, which should be checked and solved one by one

solution: turn on the air pump rotation handle to rotate the paper feeder. Start from the suction nozzle, check whether the actions of the blowing presser foot and the paper feeding suction nozzle are coordinated and normal one by one. If any problem is found, it should be solved in time, and then check whether the elevation angle of the front paper retaining teeth is normal, whether the pressure of the two paper feeding wheels is consistent, and whether the pressing time is the same. Sometimes, if the axis of the paper feeding wheel is seriously worn or the paper feeding wheel is not round, it should be replaced. Then check whether the tightness of the four wire belts is consistent and whether the wire pulley is flexible. Some operators pasted paper strips on the paper board, which will affect the normal paper feeding if they are arched or worn, and they should be replaced again. On the new separating head, there is a mechanism to adjust the skew of paper feeding; The old-fashioned separation head adopts the company to provide the best trade communication channel for the buyers and sellers of machinery and raw materials in China, Asia, the Middle East, Africa and the world. Change the angle of the paper pressing frame, that is, change the angle between the paper pressing wheel and the paper conveying belt to remedy. This treatment can generally overcome the skew of the paper conveying, which will affect the employment barrier of tens of thousands of people in the United States

(2) simultaneous failures of rule parts

the following three cases are listed for analysis: ① the front rule has a low paper stop tongue, and it is difficult for the paper to enter the front rule. Some operators will increase the pressure of the flat brush wheel, and even deliberately press the trailing tip paper ball on the edge of the paper, resulting in the phenomenon that the paper can't go in place and has passed the position. ② The swinging paper teeth have insufficient holding force, and the paper is pulled out. Some operators treat it as an inaccurate overprinting fault caused by the paper not moving in place on one side, increase the brush wheel pressure or reduce the paper feeding positioning time. ③ If the side gauge is raised too slowly to pull the paper out of the swing teeth, it is easy to deal with it as an inaccurate overprint caused by the paper not moving in place on one side. As a result, the problem was not solved, but caused unilateral irregular overprint inaccuracy

solution: if there is irregular overprint on one side, first of all, ensure the normal paper feeding, and deal with the brush wheel pressure, trailing tip brush, trailing tip paper ball, etc. Then check whether the paper feeding positioning time meets the requirements. If it does not meet the requirements, adjust it accurately first, and then check the regular parts one by one

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