On a web offset press, paper is unrolled from the feeder in the form of tape and fed continuously to the printing device. In order to improve productivity and reduce waste products, most paper feeding machines have automatic tension control system, automatic roll change (automatic paper) device. At present, most of the advanced web offset printing machines imported from abroad are produced by MEGTEC company. The following takes the MEG DLP machine which is used most as an example.
Automatic tension control system
When simple roll paper is printing, the tape must have a certain tension in order to control the movement of the tape. In order to make the printing process stable, the tension of the tape must be kept constant and constant, and the size is appropriate. Too little tension will lead to the paper tape slack wrinkles, overprinting is not allowed to such ills, too much tension will increase the load of the machine and increase the stress of the paper tape, if the stress exceeds its strength limit will break. The tension is not stable paper tape will pulsate, so that there will be inaccurate overprint, double image and other problems. Therefore, in the process of printing production, in order to maintain the quality of printing lady and production efficiency, maintain a constant tension is very necessary.
For the feeder, the pull that moves the tape forward is generally produced by the printing drum. Because the paper roll is not round, the automatic change of the paper roll or some other accidental factors, the paper roll brake can not adjust the braking force quickly and timely, so that the tension fluctuation of the paper tape into the printing device is too large. In order to accurately control the tension of the paper tape into the printing device, most of the imported rotary presses are driven by a special motor to feed the paper stick to generate tension. Also called secondary tension system. The paper feed wheel is installed on the paper road between the printing device and the paper feed machine. Because the paper feed roller forces the paper tape to run, the fluctuation of the tension of the paper tape when the paper roll is opened does not directly affect the tension of the paper tape after the paper feed stick. The paper tape entering the printing device has a stable tension after two tension controls. The braking principle of the secondary tension system relies on the difference between the speed of the paper belt and the linear speed of the paper conveyor to generate braking force through friction. The linear speed of the paper conveyor is smaller than that of the paper conveyor. By remotely adjusting the rotational speed ratio between the paper conveyor and the printing roller from the main console of the printer, the paper conveyor entering the printing device can obtain the appropriate tension. To achieve the purpose of controlling the tension of paper tape entering the printing device. Therefore, the paper-feeding kun plays a more precise role in controlling the tension of the paper tape entering the printing device.
