Poor stretch film tension control will "cause a lot of trouble"
Since the stretched film is susceptible to tension, the dimensional stability is not high and it is easy to change. If the tension is too small, the coil is likely to relax and cause lateral drift; if the tension is too high, the surface of the coil will wrinkle or even break. Therefore, in the process of rewinding or unwinding, it is important to maintain a constant tension to ensure the quality and efficiency of production. In practical applications, it is also affected by other factors, such as the wrap angle and static balance of the guide roll. The stretch film manufacturer Qianghui Technology will analyze it one by one for you.
In the production process, the tension of the film roll is constantly changing during the movement, mainly caused by the following factors:
1. In the process of winding and unwinding, the diameter of the roll changes, and the change in diameter will cause the tension of the coil to change.
2. The shape of the film roll is not a standard cylinder, and it has a certain degree of eccentricity and local deformation. The weight of the roll is not consistent.
3. The thickness of the stretched film is not uniform.
4. There is a pressure difference and a diameter difference between the plate rollers, and the tension between the printing units is inconsistent.
5. When the running state of the printing press is changed, such as increasing speed, decelerating, starting, braking, and changing rolls, it causes a large change in tension.
The tension adjusting device directly affects the product quality. The tension control system is one of the core elements of the printing machine. Its performance reflects the performance of the gravure printing machine. The tension control system plays the following roles:
1. According to the law of tension change, control the coil unwinding speed.
2. According to the direction of the overprint error, change the local tension in printing to achieve higher overprint accuracy.
3. Adjust the speed of the rewinding shaft to make the rewinding neat.
4. Eliminate the tension fluctuation caused by the stretched film itself.
5. Control and adjust the speed of the stretched film.
The tension control method is generally divided into manual control and automatic control, and automatic control can be divided into constant tension control box taper tension control:
The automatic control method includes an open-loop semi-automatic tension controller and a closed-loop full-automatic tension controller. Open-loop semi-automatic tension controller adjusts the coil tension by detecting the change of the coil diameter, which is the taper tension control.
The closed loop full-automatic tension controller directly detects the tension of the coil through a tension sensor or a tension detector, and feeds it back to the controller. The controller adjusts the output according to the detection signal to ensure that the coil tension is constant.
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