Analysis of Feeding Sheet Failure Caused by Feeding Nozzle

The paper feeding adjustment of a sheet-fed offset press is an important preparatory work before printing. Improper adjustment can cause various paper feed failures. Feida's head adjustments include the following: paper nozzles, paper feed nozzles, paper presses, paper presses, pressers, loose paper blowers, presser foot blowers, and more. This article only briefly analyzes the failure of sheet feeding caused by feeding nozzles in teaching.

In the adjustment process of sheet feeding before the sheet-fed offset printing press, due to improper adjustment or the wear of machine parts, etc., various paper-feeding failures are often caused, such as squaring, double-sheeting, empty-sheeting, and sooner or later. There are more frequent occurrences. Once the arrogance occurs, it will be detected by the photoelectric eye at the predetermined position on the paper transport board, so that the paper feeder will stop working and the paper feed will be interrupted.

There are many reasons for arrogance. Based on my experience, summarizing the following points are common:

1 Inconsistent adjustment on both sides of the pressure steel sheet. The inconsistent adjustment of the two sides of the pressure paper can cause uneven pressure on both sides of the paper. When the paper is sucked by the suction nozzle, it can easily cause a splay.
2 The loose paper height adjustment is inconsistent. The wind power of the piles of the paper piles is different. The amount of paper that can be blown by the air blower is also different, and it is easy to cause arrogance.
3 The paper stack is too low and is easily blocked by the paper stopper.
4 The paper stopper is not in a line, which can cause the paper stack to be misaligned and cause the paper to be skewed.
5 Inconsistent adjustment of both sides of the feeder roller. After the take-up roller has received the paper from the delivery nozzle, if the adjustment on both sides of the take-up roller is inconsistent and the friction of the paper advances is different, it is also easy to skew the paper on the paper feeder.
6 Inconsistent position or pressure on both sides of the platen roller and brush roller causes the paper to be subjected to variability due to friction forces of different sizes during advancement.
7 Inconsistent transfer belt tension causes the rollers and brush rollers to rotate at different speeds, causing skewed paper.
8 Improper adjustment of the side gauge. The positioning plate of the side gauge should be 3 mm to 5 mm from the side of the paper. If the positioning plate of the side gauge is too close to the edge of the paper or even blocks the paper, it will make the paper unable to advance by the side and cause arrogance.
9 open air pump time is wrong. The opening of the air pump should be controlled when the paper suction nozzle starts to inhale. Too soon or too late can cause the paper to become skewed.
10 paper is not aligned. The paper is skewed when it is fed onto the feeder, which will definitely cause a severance failure.

This article uses the Guanghua PZ1650 as an example to briefly analyze the paper pick-up failure caused by the paper-feeding nozzle.

The function of the paper feeding nozzle is to suck the paper separated from the paper suction nozzle, slightly lift it and deliver it forward, hand it over to the take-up roller and the paper guide wheel, and the paper is delivered and received mechanically reciprocated by the corresponding mechanism. The suction and deflation motions of the movement and the suction nozzle are coordinated.

The failure of a squat caused by a delivery nozzle usually has the following points.

1 The feeding nozzles on both sides are inconsistent

If the delivery nozzle is low on one side, when the suction head starts to inhale and fall, the paper suction nozzle on the side higher than the paper side will cause the suction force of the paper to decrease due to the large spacing, and the paper suction will be unstable or leak. Slow movement of the paper while it is being conveyed forward causes the paper to be skewed.

Solution: Through the adjustment device, visually measure the height of both sides of the paper nozzle.

2 Drive side delivery nozzle is not horizontal

The feed side suction nozzle is not horizontal and tilts backward. When the paper feed nozzle forwards the previous sheet of paper to the paper guide roller and the pick-up roller to suck back the next piece of paper, because the suction nozzle is not inclined horizontally to the back side, the part of the rear end of the suction nozzle first returns to meet the paper, and The closer the paper is to the surface, the greater the generated suction force. This will cause the conveying surface of the transfer surface to be faster than the suction nozzle of the operation surface. The delivery of the paper is advanced, which causes the paper under the drive surface to be fast, causing the paper to be skewed. The drive side delivery nozzle shown in Figure 4 b is not horizontal and is tilted forward. When the delivery nozzle is retracted, the rear end of the suction nozzle first meets the paper, but is far from the paper surface, and the suction force is small. However, although the front end of the suction nozzle is closer to the paper surface, the suction force is larger, but the suction nozzle front end As a result, the transfer surface of the transfer surface is slower than the transfer nozzle, and the delivery of the paper is delayed. This causes the transfer surface to run slowly and the paper to be skewed.

Solution: Twist the adjustment handle so that the suction surface of the transmission surface is not horizontal. Guanghua PZ1650 operation surface delivery paper nozzle angle is horizontal, can not be adjusted, as the adjustment of transmission surface delivery paper nozzle angle reference.

3 One side feeding paper nozzles do not absorb paper and cause continuous large stretch of sheets

As mentioned earlier, the degree of skew of the paper is small, and it does not affect the normal feed at a low speed. However, there is also an arrogance failure. The degree of skewness of the paper is large, and it is very difficult to feed paper at this time. This type of failure is mostly caused by the failure of one side of the paper feed nozzle to malfunction.

1) The suction is too small, causing the suction head not to fall, so that the force on the paper side will certainly cause a large amount of distortion. Solution: Adjust the air pump suction knob to increase the inspiratory volume.

2) The air path is poor and needs to be cleaned. After a long period of time, the printer sucks a lot of paper, paper powder, and dust into the air path, causing obstruction of the air path or blockage of the air path, causing the suction to be too small and the suction head not to fall. Solution: Clean the air circuit with organic solvents.

3) The nozzle mechanism components wear. The lower diameter of the delivery nozzle is larger than the outer jacket, except for a large straight hole in the middle and six small inclined holes around it. There is also a slightly convex edge on the side to protect the inhalation and prevent it from spreading and concentrate the suction. However, the delivery nozzle wears for a long time, not only rubbing off the protruding edges, but also making the entire suction surface smooth and sharp. As a result, a slippery phenomenon occurs when the paper is sucked up, and the paper is not able to absorb the skewed paper so as to adversely affect the work.

The commonly used method of treatment is to either put a leather ring on the delivery nozzle or suck the surface of the suction nozzle with sand and make it rough, increase the friction, and no longer slip. Although both methods can be effective, but have their own shortcomings, one is easy to pull the paper on the apron, if the paper is not easy to make the paper go oblique; Second, the use of sand buffing is very short, but unfortunately had to replace the new Handing paper nozzle.

In the pre-press sheet feeding adjustment of the sheet-fed offset press, mastering the adjustment of the feeder, able to cope with all kinds of problems, and debugging the machine in the shortest time, laying a good foundation for the boot printing, It is what we expect together.

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