Paper feeders are an indispensable part of modern sheetfed offset presses. Its performance is related to the machine's running speed and the overprint accuracy of the product to some extent. The paper feeder shall ensure that the paper is separated smoothly and accurately, conveyed to the positioning mechanism, and then input into the printing device. Due to the blind pursuit of output by some printing manufacturers, the equipment (paper feeder) is not well-maintained, and with the long time of use of the machine, paper feeders often have problems with paper feed instability. The following analysis of some of the problems encountered by the author at work is as follows for your reference. One, universal shaft failure Because some presses have a cardan shaft fork barely exposed, fine powder such as paper powder is easily trapped between the cardan shaft fork and the connecting ball. Over time, the two forks are worn and the clearance is increased. Vibration is generated and reflected on the paper, causing jitter and causing paper feeds to be unstable. Solution: Replace the worn cardan shaft yoke and connecting ball. When replacing the cardan shaft fork, pay attention to make the fork at both ends into a plane, otherwise it will generate a new vibration source. Second, the poor maintenance of the gas distribution valve As paper powder and sand particles are often sucked into the suction valve by the suction nozzle, over time, the wear of the valve body and the valve housing is exacerbated, and some operators improperly operate the valve, thereby damaging the air duct of the valve body and causing the paper feeding nozzle to work. In the extreme position, when the take-up roller is pressed down, the suction nozzle still has suction force, and the paper feeding process generates a pause. This phenomenon has a great influence on the accuracy of overprinting of products, which seriously plagues operators. Solution: Remove the valve, observe the valve body of the wind groove, if the wear is serious, you can wash the wind tank, use the electrode to fill the tail of the wind tank about 2-4mm (according to the pause time and length) . Third, gear wear and pin break A pair of bevel gears on the edge of the paper feeding clutch, because the whole gear is exposed, the working environment is rather harsh. If the maintenance is not properly done, it is easy to make the tooth surface wear heavier, and the matching relationship between the bevel gear and the inside key becomes a clearance fit, resulting in walking Paper jitter and a series of unsteady phenomena. Sometimes due to long-term lack of oil rust rust or other parts of the valve caused by the failure of excessive force caused by a pin break, causing the host and the feeder with the wrong time, causing trouble printing. Solution: If the gear or square key is worn out, replace it. If the pin is broken, you should find out the reason of the break and carefully check whether the pin has any heat or iron powder. It should be eliminated according to the actual situation. . Of course, in addition to the above-mentioned factors that cause the paper to move unevenly, brake spring pressure springs are too loose, the bearing of the paper feed roller is shaken, and the bolts of the heads of the separation heads are worn out. Again one by one.