Dry laminating machine is an important equipment produced by the packaging and printing industry. According to its process characteristics, the tension control requirements for the equipment are relatively strict. When the film is running on the equipment, it must be controlled that the film surface cannot be damaged, wrinkled and damaged due to tension changes. Tensile deformation, etc. At the same time, it is also necessary to ensure that the finished product (rewinding) cannot cause film relaxation or curling of the core.
Tension control requires the control system to be able to permanently control the running tension of the plastic film. This control must be effective at any running speed of the machine, including acceleration, deceleration and uniform speed of the machine. It has the ability to ensure that the film is not broken, wrinkled, and stretched even during an emergency stop.
Yongxin has a Taiwan dry laminating machine introduced in the mid-1990s. Since the equipment has been running for a long time, it has not reached the above-mentioned tension requirements. In order to enable it to continue to operate, we plan to carry out technical transformation.
First, the relevant performance characteristics of Taiwan dry composite machine
1. The working principle is shown in Figure 1:
Figure 1 Composite working principle block diagram
In this system, the film of the first unwinding mechanism first enters the gluing traction roller, is heated in a compound oven, and then is compounded with another layer of material (controlled by the second unwinding mechanism) through the laminating roller, and finally by the winding mechanism Wind up.
2. The unwinding tension control block diagram is shown in Figure 2:
Figure 2 Unwinding tension control block diagram
The unwinding tension control system adopts NIRECOTC640 tension controller. The operator manually adjusts the output voltage of the tension controller to control the output torque of the magnetic powder brake according to the width, thickness, process requirements and operating experience of the raw material.
3. The winding tension control block diagram is shown in Figure 3:
Figure 3 Block diagram of winding tension control
The rewinding tension system uses NIRECOTC440 tension controller. The tension sensor directly measures the actual tension value of the film, and then converts the tension data into a tension signal to feed back the tension controller. This signal is compared with the tension value preset by the controller. Calculate the control signal to automatically control the DC motor control board unit, and the DC motor control board unit controls the DC motor voltage output to make the actual tension value equal to the preset tension value to achieve the purpose of stable tension.
4. Advantages and disadvantages of tension control system
Advantages: mature manufacturing process, low cost and simple control.
Disadvantages: unwinding tension control is rough, winding tension control accuracy is low, reflection speed is slow, can not absorb the peak of tension, mechanical acceleration and deceleration is difficult to handle, it is not easy to achieve high-speed switching of the roll. Therefore, when the tension control system in the equilibrium state is strongly disturbed, the system has no time to respond, and the amplitude of the tension change on the tape will be larger, which is not good for the tension control to re-enter the equilibrium state as soon as possible.
In addition, the magnetic powder brake of the discharging system and the DC motor system of the receiving system have been running for a long time, and the mechanical performance and electrical parameters have not reached the normal production status. The unit consumption and equipment failure rate have always been high. The tension system of the equipment has been Cannot meet current production requirements.
In order to solve the problems existing in the existing technology, after comprehensive consideration, the equipment is reasonably transformed in accordance with the principles of cost saving and practicality. On the basis of the original equipment, the floating control system (DancerArm) and the tension control method of the vector inverter are used to replace the original control system. The original tension controllers TC640 and TC440 and MB25 tension sensors continue to be used as user settings. And actual tension display and tension calculation unit, adding tension floating roller deviation detection system, electro-pneumatic converter, Yaskawa G7 vector inverter and feedback encoder, magnetic powder tensioner with one and two amplifiers, and rewinding DC The motor is replaced by an AC vector frequency conversion motor to achieve the purpose of automatic tension control, as shown in Figure 4:
Figure 4 Block diagram of composite working principle after transformation
The newly added floating roller misalignment detection system drives the precision potentiometer to output misalignment signals through a low-friction precision cylinder to provide Yaskawa inverter speed correction values to ensure tension stability. At the same time, using a characteristic of the floating roller tension detection device, it has a good absorption and buffering effect on a wide range of tension jumps, and can also reduce the eccentricity (ellipse) of the roll and the impact of speed changes on the tension.
Added Yaskawa vector inverter and AC vector motor, added feedback encoder and PG speed card to form speed closed-loop control, and replaced magnetic powder tensioner and DC motor with its excellent performance, thereby overcoming the easy heating of magnetic powder tensioner and troublesome maintenance of DC motor. Disadvantages and greatly improve the tension characteristics.
(1) NERICOTC640 / TC440 tension controller is used for operating tension value setting, actual tension display and running tension calculation, and provides voltage output of electro-pneumatic converter and torque control signal of Yaskawa inverter;
(2) MB25 tension sensor is used for tension detection. The micro-millivolt voltage signal of the leaf spring is input to the NERICOTC640 / TC440 tension controller for comparison with the set value.
(3) The electro-pneumatic converter, low-friction precision cylinder, and precision potentiometer form a floating roller position detection system, which converts the change in the position of the floating roller into a ± 10V voltage signal output by the precision potentiometer, and provides the Yaskawa G7 vector inverter position correction signal This signal is superimposed with the speed signal of the host (fitting wheel) to perform speed control on the Yaskawa G7 vector inverter;
(4) Yaskawa G7 vector inverter controls the speed change of AC vector motor according to the speed command of A1 terminal and the torque command of A3 terminal. The PG speed feedback card is used to receive the speed pulse signal detected by the encoder to form a vector closed-loop control to ensure the accuracy of the AC vector motor running speed. The speed feedback encoder is installed on the tail shaft of the AC vector motor.
The principle of the modified tension control system is as follows:
(1) The user sets the required tension value by setting the NERICOTC640 / TC440 tension controller, and extracts the set voltage signal (0-10V) and outputs it to the electro-pneumatic converter to supply a low-friction precision cylinder with an air pressure value. . The precision cylinder drives the precision potentiometer to generate a position offset voltage signal (-10V— + 10V), which is output to the Yaskawa vector inverter and superimposed with the host speed signal to calculate the speed correction value to control the speed of the AC vector motor. Variety;
(2) The tension signal detected by the tension sensor is input to the tension controller, compared with the tension value preset by the controller, the tension change torque control signal is calculated, and output to the Yaskawa vector inverter to provide the torque control signal to achieve control The purpose of tension changes.
(3) The feedback encoder at the end of the AC vector motor provides the speed signal of the motor and outputs it to the PG speed measuring card of the Yaskawa inverter to form a speed closed-loop control to ensure the accuracy of the speed and achieve the purpose of controlling the tension stability.
The principle block diagram of the modified tension control is shown in Figure 5:
Figure 5 Block diagram of the tension control system after transformation
Third, the actual hardware selection required for the transformation
1.AC vector motor
The maximum production speed of this machine is 160m / min, the maximum settable tension F = 50kgf, and the synchronous belt transmission efficiency n = 0.9. The average power P to be provided is:
P1 = f × V = F × g × V
Among them, f is the tension, the unit is N; g is the acceleration of gravity, the unit is m / s, then:
P1 = F × g × V = (50 × 9.8 × 160) / 60 = 1306 (W) = 1.3 (kW)
Using a synchronous belt drive to reduce speed, the minimum power P output by the motor is:
P = P1 ／ n = 1.3 ／ 0.9 = 1.45 (kW)
Considering the requirements of rapid response for acceleration and deceleration, compared with the choice of the original DC motor, the AC motor power is selected here as 3.7kW
Select Yaskawa 400V3.7KWG7 inverter with PG card.
3.Electric air converter
4. Precision cylinder
Using plastic precision potentiometer 2K
Fourth, hardware transformation
1.Add floating roller system
Added floating roller systems to the first unwinding, second unwinding and rewinding units, adding precision cylinders and precision gears driven by synchronous gears, and adding electro-pneumatic converters and ± 10V DC power supplies to the distribution cabinet;
2, NERECOTC640 / TC440 circuit transformation
(1) Through circuit modification, we extract the TC640 and TC440 tension setting V1 (0-10VDC) voltage signal as the control voltage of the electro-pneumatic converter;
(2) TC440 output voltage signal is 0-10V, which can directly control Yaskawa vector inverter. However, TC640 originally controlled the magnetic powder tensioner directly, and the output voltage signal was 0-24V6A. It was not possible to directly control the Yaskawa vector inverter. Therefore, through circuit modification, the V2 voltage signal at the front of the TC640 current amplifier unit was extracted. It can be used to control Yaskawa vector inverter, see Figure 6 and Figure 7.
Figure 6TC640 internal unit block diagram
Figure 7TC440 internal unit block diagram
Replace the magnetic powder tensioner and DC motor of the original system with 3.7KW1750RpmABBQABP series variable frequency motor, and install Omron LMA-60B-S185Y encoder at the end of the motor;
4. Install the inverter
Add the first unwinding, second unwinding and rewinding unit Yaskawa G7 AC vector inverter to the power distribution cabinet, and install PG-B2PG speed feedback card in the inverter;
Wiring each part according to design requirements
Five, hardware debugging
1.Inverter important parameter settings
2. Motor self-learning
When the Yaskawa inverter and AC vector motor run for the first time, self-learning operation is required. The purpose is to make the Yaskawa inverter automatically calculate and set the motor parameters to achieve the best matching effect.
3.Floating roller precision potentiometer position adjustment
When the floating roller is at the center position, adjust the output value of the precision potentiometer to 0V;
When the floating roller is deflected to the end of the film, adjust the output value of the precision potentiometer to -10V;
When the floating roller deflects to the opposite direction of the film exit, adjust the output value of the precision potentiometer to + 10V;
The potentiometer uses a 360 ° rotating conductive potentiometer with an effective swing angle of 330 °. In normal use, the rotation angle should be less than 330 ° with a little margin to prevent the swing of the voltage from affecting the tension control when the swing amplitude is large.
4.Electric-air converter voltage / pressure adjustment
Adjust the electropneumatic converter so that when the input voltage changes from 0 to 10V, the output air pressure value changes from 0 to 5Kg.
5, NEROCOTC640 / TC440 tension controller Zero and Span adjustment
(1) Zero adjustment
Without any film on the tension sensor guide roller, adjust the Zero potentiometer inside TC640 / TC440 so that the tension of TC640 / TC440 is displayed as 0Kg;
(2) Span adjustment
Hang a weight of 20kg on the tension sensor guide roller, adjust the span potentiometer inside the TC640 / TC440 so that the tension of the TC640 / TC440 is displayed as 20Kg.
6. Transformation effect
After the transformation, the trial operation has achieved satisfactory results. We made a comparison of the unwinding tension before and after the transformation, and the actual production unit consumption, as shown in Figures 8, 9, and 10 below:
Figure 8 Tension value before transformation
Figure 9 Tension value after transformation
Figure 10 Comparison of unit consumption before and after transformation
Because the transformed tension system uses advanced vector inverter control, it not only has high control performance, but also has a wide speed range, low-speed and large-torque operation, precise torque control, rapid command response, and safety and reliability. Features such as protection functions, and rewinding and unwinding work in closed-loop vector control mode, through the real-time detection of the floating roller precision potentiometer, tension control is more stable during acceleration and deceleration, and PID parameters are set to compensate The frictional resistance and material inertia cause uneven speed during the startup or acceleration process to obtain a very smooth tension control effect.
In general, through technological transformation, the old equipment has been rejuvenated and its service life has been extended, and valuable practical experience and technical accumulation have been gained for similar equipment transformation in the future.