The operation status of the tension control system is directly related to the quality of gravure printing products. Once the tension is abnormal, it will affect the yield and cause a certain amount of material waste. This article summarizes several common tension problems and their solutions in gravure printing production. We are willing to share and exchange with industry insiders.
Question 1: How to more easily establish a stable initial tension?
1. Phenomena
In actual gravure printing production, the diameter and width of the rolls of different printing substrates may vary. When a smaller diameter roll is installed in the unwinding unit, the gravure printing machine can smoothly establish the initial tension of the entire machine. However, if a larger diameter roll is replaced, the swing roller of the gravure printing machine will vibrate frequently and cannot stabilize for a long time. In severe cases, the roll may deform or even break the roll.
This situation not only causes serious waste of materials, but also increases the workload of operators, bringing many unnecessary troubles to printing enterprises.
2. Analysis
The change in roll diameter can cause a change in its inertia, but before the gravure press establishes the initial tension of the entire machine, the position of the swing roller does not change, that is, the tension deviation collected by the tension controller does not change, and accordingly, the output of the tension controller does not change.
However, for coils with different diameters, the motor has the same angular velocity. Therefore, the larger the diameter of the coil, the faster its surface linear velocity. The faster the speed, the harder it is to control the motor. Therefore, there will be different difficulties in establishing stable initial tension for coils with different diameters in the gravure printing machine.
3. Solution
By setting different proportional and integral units for the PID controller for coils with different diameters, the surface linear velocity of coils with different diameters does not differ significantly when establishing initial tension.
Specifically, for coils with smaller diameters, larger proportional and integral units are set, which not only does not affect the operating speed of the motor when establishing initial tension, but also establishes a stable initial tension; For larger diameter coils, set smaller proportional and integral units to slow down the motor's operating speed, thus establishing a stable initial tension.
Question 2: How to achieve a smooth transition of tension during automatic roll changing and cutting?
Automatic roll changing and cutting, that is, under the action of a tension controller, the duplex position axis can achieve automatic switching between new and old material rolls.
The specific process is as follows: first, press the preparation receiving button, the rotary rack of the gravure printing machine will rotate counterclockwise, control the new roll to park at the predetermined position through the detection device, at the same time, the Potentiometer detects the approximate diameter of the new roll, and drives the new roll to rotate at a certain surface linear speed, so that it is basically equivalent to the surface linear speed of the old roll; Secondly, by pressing the material receiving button, the cutting device completes the pasting and automatic cutting of new and old material rolls through corresponding actions; Finally, the old material roll is reduced from its current speed to zero speed to complete cutting.
Automatic roll changing and cutting can not only improve work efficiency, but also reduce the workload and work intensity of operators.
1. Phenomena
The automatic roll changing and cutting process is carried out during the high-speed operation of the gravure printing machine. Therefore, there are many factors that affect the automatic transfer of new and old material rolls, which can easily lead to abnormal vibration of the swing roller and the inability to achieve a smooth transition of tension between the old and new material rolls. Once this problem occurs, it takes a long time to adjust to restore normal, resulting in a dual waste of materials and time.
2. Analysis
In the process of automatic roll changing and cutting, the new roll and the old roll can achieve a smooth transition of tension only at the same surface linear speed, which requires the Potentiometer to accurately detect the diameter of the new roll, so as to ensure that the surface linear speed of the new roll and the old roll is as same as possible, providing a prerequisite for automatic cutting.
Of course, it is only an ideal situation for the surface linear speed of the new and old coils to be completely consistent. In fact, there is still a certain speed difference between the two. Usually, after the automatic roll changing and cutting is completed, the tension of the new coil will still change slightly, but it will not affect the final product quality.
3. Solution
To ensure accurate detection of the diameter of the new roll, the Potentiometer can be replaced with an encoder with higher accuracy. After completing the roll change, due to certain changes in the state of the roll, it may cause some interference in its diameter detection. Therefore, the roll should be stabilized before testing. The proportion unit and integral unit of the material coil should be further refined. When the diameter of the material coil changes, the adjustment amount of the tension controller also changes accordingly, resulting in smaller tension fluctuations.
Constant tension control is the guarantee of product quality. When there is a problem with tension control, as long as you carefully observe and analyze, you can definitely find the corresponding solution.