Analysis of the most popular misfeed caused by the

2022-08-18
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Analysis of the misfeed caused by the paper feeding suction nozzle

the paper feeding adjustment of the sheet fed offset press is an important preparation before printing, and improper adjustment will cause various paper feeding faults. The adjustment of Feida head includes the adjustment of paper separation suction nozzle, paper delivery suction nozzle, paper pressing steel sheet, paper pressing block, presser foot, loose paper blowing, presser foot blowing, etc., which involves many aspects. This paper only makes a brief analysis of the paper misfeed caused by the paper delivery suction nozzle, which is common in teaching

in the paper feeding adjustment process before the printing of the sheet fed offset press, due to improper adjustment or wear of machine parts, various paper feeding faults are often caused, such as skew sheets, double sheets, empty sheets, arriving in the morning and late, etc. among them, skew sheets occur more frequently. Once skew sheets occur, they will be detected by the photoelectric eye at the front specified position on the paper feeding board, causing the paper feeder to stop working and interrupt the paper feeding

there are many reasons for skew. According to my experience summary, the common ones are as follows:

① the adjustment on both sides of the paper pressing steel sheet is inconsistent. The inconsistent adjustment of the paper pressing steel sheets on both sides will cause uneven pressure on both sides of the paper, which is easy to cause skew when the paper is sucked by the paper separation suction nozzle

② the adjustment of the blowing height of loose paper is inconsistent. The wind force on the trailing edge of the paper pile is different, and the amount of paper on both sides that can be blown by the wind is also different, which is easy to cause skew

③ the paper stack is too low, which is easy to be blocked by the paper stop tongue and cause skew

④ if the paper stop tongue is not in a line, it will make the edge of the paper stack bite uneven and cause the paper to skew

⑤ the adjustment of both sides of the paper receiving wheel is inconsistent. After the paper receiving wheel receives the paper from the paper delivery suction nozzle, if the adjustment of both sides of the paper receiving wheel is inconsistent, the friction force of the paper moving forward is different, and it is also easy to make the paper skew on the paperboard

⑥ if the positions or pressures on both sides of the paper pressing wheel and the brush wheel are inconsistent, the paper will be subject to varying degrees of friction during the forward process, which will also cause skew

⑦ inconsistent tightness of the paper belt will cause inconsistent rotation speed of the paper pressing wheel and brush wheel, resulting in paper skew

⑧ the side gauge is not adjusted properly. The positioning plate of the side gauge should be 3mm ~ 5mm away from the side of the paper. If the positioning plate of the side gauge is too close to the side of the paper or even blocks the paper, the paper will not move forward near the side, resulting in skew

⑨ the air pump is turned on at the wrong time. The time of starting the air pump should be controlled when the paper separation suction nozzle starts to inhale. Too early or too late will cause the paper to skew

⑩ the paper is not neat. When the paper is loaded on the paper feeding table, the paper will skew, which will definitely cause the skew fault

taking Guanghua pz1650 as an example, this paper mainly makes a brief analysis on the paper skew fault caused by the paper delivery suction nozzle

the function of the paper delivery suction nozzle is to suck the paper separated from the paper separation suction nozzle, slightly lift it and deliver it forward, and deliver it to the paper receiving roller and the paper guide wheel. The delivery and reception of the paper are completed by the mechanical reciprocating motion of the corresponding mechanism and the suction and deflation actions of the suction nozzle

the skew fault caused by the paper delivery suction nozzle usually has the following points

1 the height of the paper delivery suction nozzles on both sides is inconsistent

if the paper delivery suction nozzles are low on one side and high on the other side, when the suction head begins to inhale and fall, the suction force on the paper on the side higher from the paper surface is reduced due to the large spacing between the paper delivery suction nozzles, the paper suction is unstable or leaks, and the movement lags slowly in the process of transferring the paper forward, resulting in paper skew

solution: visually check the height of the paper delivery nozzles on both sides through the adjustment device

2 transmission is used to evaluate the heat sealing strength of the packaging bag film 1 at the fixed sealing position. The paper transfer suction nozzle on the moving side is not horizontal

the paper transfer suction nozzle on the driving side is not horizontal and tilts backward. When the paper delivery suction nozzle returns and sucks the next paper after handing the previous paper to the paper guide roller and the paper receiving wheel, because the suction nozzle is not horizontal and tilted backward, the part at the rear end of the suction nozzle first returns and meets the paper, and it is close to the paper surface, resulting in a large suction force. This will make the paper delivery speed of the transmission surface faster than that of the horizontal suction nozzle on the operation surface, and deliver the paper in advance, causing the paper to drop faster on the transmission surface, resulting in paper skew. The paper delivery suction nozzle on the drive side shown in B in Figure 4 is not horizontal and tilts forward. When the paper delivery suction nozzle returns, although the rear end of the suction nozzle meets the paper first, it is far from the paper surface, and the suction force is small. Although the front end of the suction nozzle is close to the paper surface, the suction force is large, but the front end of the suction nozzle arrives later, which causes the paper delivery speed of the driving surface to be slower than that of the suction nozzle whose operation surface is horizontal, and the delivery of paper lags behind, causing the paper to drop slowly on the driving surface and the paper to be skewed

solution: twist the adjusting handle to level the suction nozzle whose transmission surface is not horizontal. The angle of the paper delivery and suction nozzle on the operation surface of Guanghua pz1650 is horizontal and cannot be adjusted. It is used as a reference for adjusting the angle of the paper delivery and suction nozzle on the transmission surface

3 the paper feeding suction nozzle on one side does not suck the paper, causing continuous and large-scale skew sheets

the skew of the paper described above is small, and sometimes it will not affect the normal paper feeding at low speed. However, there is another kind of skew fault. The skew degree of the paper is large, and at this time, the paper feeding becomes quite difficult. This kind of failure is mostly caused by the failure of the paper delivery nozzle on one side, which can not work normally

1) the suction is too small, resulting in the paper suction head does not fall, so the force on one side of the paper will certainly cause a large deflection. Solution: adjust the suction knob of the air pump to increase the suction volume

2) the air path is blocked and needs to be cleaned. After working for a long time, the suction nozzle of the printing machine will further expand the popularity of many brands, and the paper wool, paper powder and dust will be sucked into the air path, causing the air path to be blocked or blocked, causing the air suction to be too small and the paper suction head to fall. Solution: clean the gas circuit with organic solvent

3) parts of suction nozzle mechanism are worn. The diameter of the lower part of the paper delivery nozzle is larger than that of the jacket. In addition to a large straight hole in the middle and six small inclined holes around, there is a slightly protruding edge on the edge to protect the suction, so that it does not diffuse and concentrate the suction. However, the paper delivery nozzle will wear out after long use, which will not only grind off the protruding edges, but also make the whole suction surface smooth and sharp. As a result, there are some bad phenomena, such as slipping when sucking the paper, the paper can't be sucked, and the paper skews, which brings disadvantages to the work

the commonly used treatment method is to either put a leather ring on the paper delivery nozzle, or pull the suction surface of the suction nozzle with emery cloth a few times to make it rough and increase friction, and no longer make bags lined with foaming materials. In order to meet the requirements of EU laws on green materials, the products are slippery. Both methods are effective, but each has its own shortcomings. First, the set of epithelial circles is easy to break the paper, and if the paper is uneven, it is easy to make the paper slant; Second, the service life of wiping with emery cloth is very short, so we have to replace the paper suction nozzle

in the pre press paper feeding adjustment of the sheet fed offset press, it is our common expectation to skillfully master the adjustment of the paper feeder, calmly deal with various problems, and debug the machine in the shortest time, so as to lay a good foundation for start-up printing

statement of performance and requirements tested according to the needs of flexible packaging film:

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