Gravure printing common tension problems and solutions

【Chinese Packaging Network News】 Gravure press tension control system through the swing roller to achieve tension detection, the pendulum roll end installed tension detection potentiometer, when the tension changes, the tension detection potentiometer detection value will follow When the change occurs, the tension controller will obtain the deviation amount, and adjust the speed of the corresponding motor through the PID controller to keep the tension of the material coil stable. In the gravure production, factors such as changes in the running speed of the controlled coil, changes in the coil diameter, changes in the rotational inertia of the mechanical transmission system, and changes in the mechanical loss all disturb the stability of the tension. The operation condition of the tension control system is directly related to the quality of the gravure printing product. Once the tension is abnormal, it will affect the yield and cause a certain material waste. In this article, the author summarizes several common tension problems in gravure printing and their solutions. He is willing to share and communicate with people in the industry.

Question one: How to establish a stable initial tension more easily?

1. phenomenon

In the actual gravure production, the diameter and width of the roll of different printing substrates will be different. When the unwinding unit installs a roll with a smaller diameter, the gravure press can smoothly establish the initial tension of the whole machine, but If a larger diameter roll is used, the pendulum roll of the gravure press will vibrate frequently and will not stabilize for a long time. In severe cases, the roll will deform and the roll may even break.

This situation will not only result in serious waste of materials, but also increase the workload of the operators, causing many unnecessary troubles for the printing companies.

2. analysis

Changes in the diameter of the roll will cause changes in its inertia, but before the initial tension of the complete machine is established by the gravure press, the position of the roll does not change, that is, the tension deviation amount collected by the tension controller does not change, accordingly, The output of the tension controller also does not change. However, for different diameter rolls, the motor has the same angular velocity, so the larger the diameter of the roll, the faster the surface line speed, and the faster the speed, the less controllable the motor will be for different diameters. The roll, gravure printing machine to establish a different degree of difficulty in the stability of the initial tension.

3. solution

For different diameter rolls, by setting different proportional units and integral units for the PID controller, the surface speeds of the rolls with different diameters are not much different when the initial tension is established. Specifically, a larger proportional unit and integral unit are set for a smaller diameter roll, which does not affect the running speed of the motor when the initial tension is established, but also establishes a stable initial tension; for larger diameters The smaller volume unit and integral unit are set in the material coil, so that the running speed of the motor becomes slower, so that a smooth initial tension can be established.

Question two: How to achieve a smooth transition of tension when automatic roll change cutting?

Automatic roll change cutting, that is, under the action of the tension controller, the duplex position axis can realize the automatic switching of old and new material rolls. The specific process is as follows: First, pressing the button for ready picking, the rotary frame of the gravure press will rotate counterclockwise, and the new material roll will be stopped at a predetermined position through the detection device, and at the same time, the potentiometer will detect the possibility of a new material roll. Diameter, and drive the new material roll to rotate at a certain surface line speed, so that it is basically equal to the surface line speed of the old material roll; Secondly, press the catch button, the cutting device completes the pasting of the old and new material rolls by corresponding actions. Automatic cutting; Finally, the old roll is reduced from the current speed to zero speed and the cutting is completed.

Automatic roll change cutting not only improves work efficiency, but also reduces the operator's workload and work intensity.

1. phenomenon

The automatic roll change cutting process is performed during the high speed operation of the gravure printing machine. Therefore, there are many influencing factors in the process of automatically replacing the old and new material rolls. This can easily lead to abnormal vibration of the swing roll, old material rolls and new material rolls. It is impossible to achieve a smooth transition of tension. Once this problem arises, it will take a long time for adjustment to return to normal, resulting in a double waste of materials and time.

2. analysis

In the automatic roll change and cutting process, the new roll can only achieve the smooth transition of the tension at the same surface line speed as the old roll. This requires the potentiometer to accurately detect the diameter of the new roll to ensure the new roll. The surface line speed is the same as that of the old material roll, providing the prerequisite for automatic cutting.

Of course, it is only an ideal situation that the surface line speeds of new and old materials are completely identical. In fact, there is a certain speed difference between the two. In general, when the automatic roll change is completed, the new material roll tension will still be slight. Change, but it will not affect the quality of the final product.

3. solution

In order to ensure accurate detection of the diameter of the new roll, the potentiometer can be replaced with a more accurate encoder. After the roll change is completed, due to a certain change in the state of the roll, it will cause some interference in its diameter detection, so the roll should be allowed to stabilize before testing. The proportioning unit and the integrator unit of the roll are more detailed, and when the roll diameter changes, the tension controller adjustment amount also changes accordingly, so that the tension fluctuation is smaller.

Constant tension control is the guarantee of product quality. When tension control problems occur, as long as careful observation and careful analysis, we can certainly find a solution.