Analysis of Reasons for Empty Sheet Feeding in Offset Press

1. The improper adjustment of the distance between the paper stack and the paper-absorbing purple will cause failures. If the distance is too large, it will produce empty sheets. The distance between the paper suction nozzle and the paper stack is the suction paper distance, generally it should be between 2-7cm. When printing thick paper, it can be smaller. When printing thin paper, it is also necessary to prevent double sheets when preventing the empty paper. The creation of multiple sheets can slightly adjust the distance. The former is about 2-4cm and the latter is about 5-7cm. The general method is to loosen the screw that controls the height of the air blower and raise the air pressure foot appropriately. The reduced distance is the ideal distance between the paper stack and the paper suction nozzle.

2, block paper brush is too low or too far into the distance. The function of the paper blocking brush is to assist the loose paper blowing nozzle so that the blown paper maintains a certain height and no longer conforms to the underlying paper, which is conducive to the smooth feeding of the paper feeding system. Its function is to blow the paper loosely. The mouth closely cooperates. When the air volume of the air blown mouth is normal, it can lift the paper edge and lift it by about 5mm. This is the distance that the paper brush should leave the paper stack; when the paper suction nozzle pulls down the paper, Just touching the surface of the paper that has been blown by the wind, if the paper bristle brush is pressed too low and the paper cannot be blown, it cannot be lifted. It means that the distance from the paper nozzle to the paper surface is increased. Zhang. Sometimes the baffle brush protrudes too far into the tray. Although the paper suction nozzle can absorb the paper, it can be ejected by the bristles and cause empty sheets. The solution is to readjust the brush, adjust it to about 5mm from the stack of paper, and adjust the distance to about 8mm.

3, paper drag slightly curled. There are two reasons for this phenomenon. The first reason is that the airflow blown by the paper blowing nozzle is not easy to enter the gap of the paper. When the airflow reaches the edge of the paper, the paper cannot be separated. The other reason is that the paper is sucked down to suck the paper. At this time, due to the unevenness of the paper surface, air leakage will occur and the paper will not blow up. This will result in a vacant sheet. The usual method is to remove the paper and knock it out.

4, lack of suction. Sometimes the ink on the nozzle and rubber band is accumulated for a long period of time without being cleaned, or the rubber band is worn out and cracked. When the paper is sucked, there is not enough air or suction. This can also cause empty sheets. The treatment method is to strengthen the inspection and maintenance work, especially when the former color is the full version of the field and the printing of the next color should be paid special attention.

5, air blockage. The majority of this situation is due to plugging of the suction system (both from paper and dust) and most of them are clogged in the suction nozzle duct and control piston section. When there is oil in the piston, the paper dust and dust are adsorbed to this place, most of them are stuck by the oil, and they accumulate more and more. Finally, the suction air path is blocked, resulting in insufficient suction and creating empty sheets. In this case, it is necessary to regularly clean air lines and pistons, print paperboard and other relatively rough paper, to adhere to weekly cleaning. The oil in the piston should be replaced with a 1:1 mixture of train oil and engine oil.