Causes and elimination of uneven paper receiving o

Causes and elimination of uneven paper receiving on the paper receiving platform of offset press

during offset printing, due to the front, rear, left and right paper handling baffles of the paper filling mechanism of the offset press, improper adjustment of the paper receiving teeth, improper adjustment of the paper brake, and poor flatness and evenness of the paper, it is easy to cause the problem of uneven paper receiving on the paper receiving platform of the offset press, and even make the paper have a corner to fold the printed matter out of the impression, affecting the product quality, and causing the binding Sorting and statistics bring trouble

the paper receiving quality requirements of the paper receiving platform of offset printing machine are: it is loose, neat and stacked flat, and there are no corners, crushing losses, oil and debris. Especially for semi-finished printing products, it is required that the positions of the trailing tip, the bite, the top and the bottom should not be reversed, and the irregular and messy paper receiving should be avoided as far as possible. There are several reasons for the irregular receipt of offset press, which should be comprehensively checked, comprehensively analyzed and targeted during specific operations

1. The distance between the left and right or front and rear paper handling baffles is too large, which is not suitable for the size of printing paper, resulting in uneven paper receiving. At this time, adjust the telescopic position of the left and right or front and rear paper handling baffles to make them the same size as the printing paper or slightly larger

in addition, if the paper management baffle around the front, back, left and right of the paper receiving platform is not set at the right time, the printing paper will be blocked in the process of falling, and it will not smoothly fall into the paper receiving platform, which will also lead to uneven paper receiving. The position of the control cam of the paper management baffle should be adjusted to make its swing time consistent with the time of paper biting and placing, so as to ensure neat paper receiving

2. The paper receiving teeth in the chain paper conveyor are too early or too late to make the printed paper enter the paper receiving table accurately, and it is also prone to the problem of uneven paper receiving. At this time, it is necessary to improve the opening time of the paper receiving teeth at high speed, so that the paper can enter the paper receiving table in time

3. When the printed paper enters the paper receiving table, it moves upward, resulting in uneven paper receiving. This is due to the stress difference of the printing paper itself, on the other hand, it is caused by the failure of the suction wheel of the printing brake or the suction of the suction wheel is too small. The failure of the suction wheel is that the small hole in the suction wheel wall is blocked. Clean the paper dust and dirt on the suction wheel and use it. If the suction of the suction wheel is too small, its suction can be appropriately increased

4. When the printing paper enters the paper receiving table, it curls down and causes uneven paper receiving. This is mainly caused by too much water in the printing plate, which makes the discrimination of the water content in the front and back of the printing paper too large. When printing, it is necessary to properly feed the water content of the printing plate, master the water ink balance, and use the minimum amount of water on the premise of not dirty plates, so as to reduce the bending deformation of the paper. So as to avoid uneven paper receipt

5. Due to the quality of paper, the original workers are working under the scorching sun. Due to poor flatness and uniformity, the paper will roll down, tilt up, bow, wrinkle, ruffle edge and other phenomena when entering the paper receiving platform, resulting in uneven paper receiving. Before printing, the above paper with poor quality should be carefully hung and humidified. After hanging and drying, it should be placed in the warehouse or offset printing workshop for storage for a period of time. The paper stack should be put on the shelf with paperboard, and the heavy objects (large stones, iron plates, etc.) should be pressed to make it flat. The paper on the machine should be (2) without our consent, the damage caused by dismantling and changing the machine parts (such as microcomputer, mainframe, circuit, etc.) should be knocked to increase the stress of the paper

6. When printing, if the paper is too thin, it is often prone to uneven receipt. Due to the large size of offset printing paper (above quarto paper) and the need to moisten the plate with water, if the paper is too thin (such as 35g/m2, and the China Mining Federation has also awarded Jixi the title of "graphite city of China" of 28g/m2), after passing between the embossing cylinder and the rubber cylinder, the water is transferred to the paper through the rubber blanket, and the paper will appear soft without stress, so it is difficult to receive the paper neatly, Therefore, it is best to keep the offset paper above 52 grams/square meter to ensure that the paper is received neatly by the paper receiving platform

7. The relative humidity of the workshop is too low, and the water content of the paper is too small, which is easy to generate static electricity, so that the paper is firmly absorbed by each other and the paper delivery is uneven. In this case, electrostatic eliminators can be used to eliminate static electricity, or improve the relative humidity of the workshop, especially in dry weather in winter. If conditions permit, humidifiers can be used to regulate the humidity of the workshop. In addition, the offset printing workshop should open fewer windows, and the glass windows should be sealed. You can sprinkle some water on the floor of the workshop to regulate humidity

source: coolest information

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