During the offset printing process, due to the offset mechanism of the offset printing press, the front and rear sides of the paper baffle, the improper delivery of the teeth, the improper adjustment of the paper brakes, and the flatness and unevenness of the paper, etc., may easily cause the offset of the offset printing machine. The problem is that even the corners of the paper appear to fold the prints out of the prints, affecting the quality of the products, and causing troubles for binding, sorting, and statistics of printed sheets. In addition, if the turnaround time of the right and left sides of the delivery table is not correct, the printing paper will be hindered during the falling process, and it will not be able to fall into the delivery table smoothly. It will also lead to uneven paper delivery and should be adjusted properly. The board controls the position of the cam so that its pendulum time coincides with the time it takes for the delivery to catch the teeth to ensure that the paper is received neatly. 2. The delivery of the teeth in the chain type paper feeder is too early or too late to allow the printed paper to enter the delivery table accurately, and the problem of uneven delivery is also likely to occur. At this time, it is necessary to take care of the teething time of the teeth at a high speed so that the paper can enter the delivery table at a proper time. 3. The printed paper flicks up when it enters the delivery table, causing the delivery to be uneven. This is due to the poor stress of the printed paper itself, and on the other hand due to the failure of the suction wheel of the print brake or the suction of the suction wheel being too small. The failure of the suction wheel is the obstruction of the hole in the suction wheel wall. The paper dust and dirt on the suction wheel can be cleaned and used. If the suction wheel is too small, the suction force can be adjusted appropriately. 4. When the printed paper enters the delivery table, it curls downwards and causes the delivery to be uneven. This is mainly due to the fact that when the printing plate has too much moisture, the water content on the front and back sides of the printing paper is too large to cause excessive printing, and it is necessary to properly feed the plate layout. The amount of water, to master the ink balance, the use of the least amount of water in the premise of not dirty version, in order to reduce the paper's bending deformation. In order to avoid paper delivery. 5 due to paper quality reasons such as flatness, poor uniformity, live and lead to the paper into the delivery table when the next roll, upturned, bow, wrinkle, lotus leaf and other phenomena, resulting in uneven delivery. Before the printing, the above-mentioned poor-quality papers should be carefully treated with hanging and drying humidity, stored in a warehouse after being hanged, or stacked and stored in the offset printing shop for a certain period of time. The cardboard box should be put on cardboard and the heavy objects (large stones, iron) should be pressed. Plates, etc.) to make it flat, the paper on the machine to knock processing to increase the paper's stress. 6. If the paper is too thin during printing, it is often prone to paper misfeeds. Since the offset printing paper format is usually large (above four sheets of paper), it also requires dampening with water, the paper is too thin (eg 35 g/m2, 28 g/m2), between the impression cylinder and the blanket cylinder. After one pass, the water is transferred to the paper via the blanket, the paper will appear soft and no stress, it is difficult to close the paper, so it is best to keep the offset paper at 52 g/m2 or more to ensure that the delivery table is in order . 7. The relative humidity of the workshop is too low, and the moisture content of the paper is too small, which is prone to static electricity, which causes the papers to stick to each other and collect the paper. In this case, static electricity can be used to eliminate static electricity, or to increase the relative humidity of the workshop, especially when the weather is dry in winter. If conditions permit, humidifiers can be used to humidify the workshop. In addition, the offset printing shop should have fewer windows, and the glass windows should be sealed. Sprinkle some water on the floor of the workshop to control humidity.
The quality requirements for the delivery press of the offset printing press are: looseness, good balance, and flat stacking. There must be no corners, crushing loss and oil debris. In particular, the printing of semi-finished products requires that the tipping and biting, and the position above and below must not be reversed, so as to avoid irregularities and messy delivery. There are several reasons why offset presses do not neatly receive paper. When performing specific operations, they must be comprehensively inspected and comprehensively analyzed and targetedly addressed.
1. The distance between left and right or front and back paper guards is too large. It is not suitable for printing paper size, resulting in uneven delivery. In this case, adjust the left and right or front and rear wiper flaps so that they are the same or slightly larger than the print size.
Reasons and elimination of uneven delivery at offset press