As a paper feeding device in printing production, the zero-speed automatic paper feeder must adjust and control the movement tension of the web to meet normal printing requirements. An important device for this task in the paper machine is the tension control system. In the production process, the tension control system is frequently used and has a high work intensity, so the frequency of failures is also very high. Therefore, for a printing company using a zero-speed automatic paper machine, maintenance and use of the tension control system can ensure the normal operation and operation of the paper machine and even the printing host. This article will combine the working principle of the tension control system of the Z4050-35 zero-speed automatic paper machine and the extensive practical experience of maintenance and troubleshooting during machine operation.
In the printing production, the tension control system usually has the following three kinds of fault conditions: 1 During the printing process, the tension floating roller frequently swings up and down, and the amplitude is large, which causes the tension of the paper strip to be unstable, which affects the overprint; 2 during the printing process, the paper The tension of the belt is too small, the paper or the rotation speed of the web is unstable, so that the paper can not be printed normally after entering the main machine; 3 during the paper-taking process, the electromagnetic brake cannot reliably brake the running web, resulting in the connection At the moment of paper, the two webs are not at zero speed, causing the paper to fail.
1. Analysis and solution to the failure of tension control system in printing
In the printing process, the failure phenomenon of the tension control system is: the tension floating roller frequently swings up and down, and the amplitude is large; the tension control system can not properly monitor and adjust the tension of the paper tape.
There are three reasons for this type of fault: one is that the air pressure of the tension cylinder is unstable; the other is that the tension angle shift potentiometer and the electric control box are not accurate and the control is abnormal; the third is the mechanical failure of the electromagnetic brake. .
The air circuit failure of the tension cylinder is eliminated by monitoring the air pressure and taking measures to stabilize it. The mechanical failure of the electromagnetic brake needs to be handled separately for the phenomenon. This section mainly addresses the failure of the tension angle displacement potentiometer and the tension control adjustment of the electric control box.
The tension angular displacement potentiometer is responsible for sampling the tape tension. If the relative position of the tension axis is not accurately positioned, the signal parameters transmitted to the electric control box will change, resulting in the electric control box not outputting the correct control voltage to the electromagnetic brake. In this way, the electromagnetic brake will not work properly and the tension of the paper tape cannot be controlled.
When the above-mentioned abnormal condition occurs in the tension floating roller, the tension control adjustment is required. The specific adjustment steps are as follows.
(1) Adjust the tension regulating valve on the operation panel of the paper machine so that the air pressure value of the tension cylinder reaches the normal value of 0.15~0.3Mpa. At this time, the tension floating roller is raised and is at the intermediate height position.
(2) Loosen the locking screw on the tension angle displacement potentiometer and the tension shaft coupling; slowly rotate the potentiometer shaft (there is a turning screw on the shaft), and observe the debugging voltage meter in the electric control box. When the pointer on the watch points roughly to 0V, tighten the locking screw.
(3) Loosen the three platen screws on the potentiometer and slowly turn the potentiometer so that the pointer of the debugging voltmeter is accurately pointed at 0V and lock all the platen screws.
(4) Close the tension regulating valve to make the tension floating roller fall to the end; then rotate the tension regulating valve to raise the tension floating roller to the highest position. In this process, the W1 potentiometer on the tension control box in the electric control box is synchronously adjusted; when the tension floating roller is at the highest point and the lowest point, the voltage values ​​on the debugging voltmeter are respectively displayed as +0.5V, -0.5V. Also observe whether the voltage on the voltmeter changes linearly. If the voltage value does not match the specified value, you need to re-commission from the first step to the third step until the value is correct.
(5) Adjust the tension regulating valve to raise the tension floating roller to the highest position. Turn the W2 potentiometer on the tension control box so that the pointer of the output voltmeter points to 10V.
After the tension control voltage is adjusted, the tension angular displacement potentiometer can accurately sample, so that the electric control box can normally output the control voltage to the electromagnetic brake (up to 10V, that is, the braking voltage), to ensure the stability of the tension during the printing process.
During the printing process, when the tension of the paper tape is too small, it is first judged whether the sampling of the tension angle displacement potentiometer is correct, and whether the output of the electromagnetic brake control voltage of the electric control box is normal. If the above components are not working properly, the tension control can be debugged. If it works normally, it can be judged that the electromagnetic brake is faulty, and the electromagnetic brake part needs to be inspected.
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