Abstract: When blowing film production, if the tension can not be controlled well, the film surface will be stretched and deformed, the film roll is not smooth, and the quality problems such as easy adhesion when the next process is released. This paper introduces the characteristics, composition and principle of the tension control system, and describes in detail how to install and debug the tension sensor, tension controller, frequency converter and other devices. Only by correctly adjusting the tension control system can we truly control the tension and produce a film with stable quality.
When the film blowing machine produces plastic film, if the surface tension of the film is not properly controlled, it will affect the quality of the film, resulting in the film surface being stretched and deformed, the film roll is uneven, and the quality problems such as easy bonding when the next process is rolled. Film blowing machines without tension control often need to manually adjust the motor speed, so that the film is not too loose or too tight, especially in the process of speed up and down, the adjustment is more frequent. Using tension control can better solve the above problems and improve the production quality of film coil.
First, tension control structure characteristics
Generally, there are three tension control points installed on the film production line, which are respectively located at traction 2, winding 1, winding 2 (surface double-station winding machine). The installation positions of the three tension control point sensors are shown in Figure 1. The tension control device is used to detect the tension of each section of film, and set the tension of each section of film according to the width, thickness and process requirements during operation. By controlling the speed of the motor at the traction roll, winding 1 and winding 2, the film tension is adjusted to keep the film tension constant.
second, composition and tension control principle
Each tension control system is composed of tension sensor, tension controller, frequency converter, etc. The tension sensor is installed on the guide roller, the detected film tension signal is transmitted to the tension controller, and the output analog signal (0~10V or 4~20MA) is amplified and adjusted after operation and adjustment, so as to control the tension.
Third, installation
1.tension sensor installation
Generally speaking, the tension sensor has two mounting methods, one is the force direction is fixed, the other is the force direction is adjustable.
A: Installation mode with fixed force direction
As shown in Figure 2, one end of the guide roller is installed on the left plate with a spherical bearing, and the other end is installed on the sensor bearing. 60% of the sensor is embedded in the right plate, and the sensor is pressed on the right plate with four holes of Φ6 using M6 bolts. The red point of the sensor should point to the force direction during installation.
B: Installation mode with adjustable force direction
A rotating disc and a clamping end cover are added between the sensor and the right plate, as shown in Figure 3. The sensor is installed on the rotating disc, and then fixed on the right plate through the clamping end cover. The direction of the stress point can be adjusted by rotating the rotating disc.
This installation mode is recommended.
After installation, the center of the roller should be on the same line with the center of the bearing at both ends, and the operation should be easy and natural, without jamming and friction with the outer wall of the bearing. During installation, hard objects such as iron filings shall not fall into the gap between the cover plate and the bearing, and the sensor bearing shall not flow into this gap when lubricating oil is added, otherwise the performance will be affected.
2.tension controller, inverter installation
The electrical connection is shown in Figure 4. The start and stop control end of the inverter, the input end of the potentiometer and the output end of the analog quantity are determined according to different brands. The synchronous linear speed signal of the controller T1 is taken from the traction 1 frequency converter, and the synchronous linear speed signal of the winding controller T2 and T3 is taken from the traction 2 frequency converter. K12, K22 and K32 are used for testing, and are not usually connected externally.
Fourth. Debugging
1.tension sensor adjustment
A: Tension detector zero adjustment
When the tension detection shaft is not stressed (empty shaft), adjust the ZERO potentiometer and use the voltmeter to detect the output voltage (VO, COM) so that its output is zero, the output increases in the clockwise direction and decreases in the counterclockwise direction.
After adjustment, turn the roller, measure the voltage at both ends of VO and COM, and the change should be less than 0.05V.
B: Tension detector output adjustment
Hang the standard weight (5KG) on the tension detection shaft according to the direction of material movement, the weight must be hung in the middle of the roller, adjust the SPAN potentiometer, use the voltmeter to detect the output voltage (VO, COM), and make its output to the corresponding value.
Example: The tension detector size is 50KG, using 5KG weights
Output voltage U = 5*(10/50)=1V
Output current I = 5*(20/50)=2mA
At this point, adjust the SPAN so that the V0 and COM outputs are 1V or the IO and COM outputs are 2mA
The output increases in clockwise direction and decreases in counterclockwise direction.
During the use of the tension amplifier, if the sensor is used improperly or the pressure exceeds the rated value for a long time, the structure of the mechanical equipment changes, which will cause detection errors, should be re-adjusted, the adjustment diagram is shown in Figure 5:
2.line speed synchronous adjustment
A: Traction 1, 2 synchronous adjustment
Short-circuit the synchronous control end C2 and OV of controller T1, disconnect the manual control end C3 and OV, start the inverter traction 1 and 2, adjust the speed of traction 1 to 25HZ, measure the linear speed of traction 1 roller with a wire speedometer, and adjust the linear speed R of controller T1 to ensure that the linear speed of traction 2 roller is consistent with the linear speed of traction 1 roller. At the same time, record the speed of traction 2 VT2 (used in tension adjustment) at this time, after the adjustment is completed, C2 and OV are disconnected, and pay attention to the maximum designed linear speed of traction 1 ≤ the maximum linear speed of traction 2.
B: Traction 2 is adjusted synchronously with winding 1
Short-circuit the synchronous control end C2 and OV of controller T2, disconnect the manual control end C3 and OV, start the inverter of traction 2 and winding 1, set the speed of traction 2 to 25HZ, measure the linear speed of traction 2 roller with a wire speedometer, and adjust the linear speed R of controller T2 to make the linear speed of winding 1 roller consistent with the linear speed of traction 2 roller. After adjustment, C2 and OV are disconnected.
C: Traction 2 and winding 2 are adjusted synchronously
The adjustment method of controller T3 is the same as that of controller T2.
3.manual adjustment
Short-circuit C3 and OV of the controller T1, T2 and T3 respectively, disconnect C2 and OV, adjust the line speed of the respective potentiometer from the minimum to the maximum, and the corresponding output frequency of the inverter changes from 0 to 50HZ.
4. synchronous control adjustment
The C2 and OV of the controller T1, T2 and T3 are short-circuited respectively, and the C3 and OV are disconnected. The potentiometers set respectively are adjusted to the maximum, and four frequency converters are started to traction 1 speed up, traction 2, winding 1 and winding 2 frequency up the corresponding speed and the amplitude of the speed up are consistent.
5. tension control adjustment
Disconnect the C2 and OV of controller T1, T2 and T3 respectively, and disconnect C3 and OV, and the controller is in tension control mode.
A: Traction 1, 2 tension adjustment
Start the traction 1 and traction 2 frequency converter, set the speed of traction 1 to 25HZ, and the tension of traction 2 to 5KG. At this time, the actual detection value is 0KG, the actual tension is less than the set tension, and the speed of traction 2 will rise. And it is higher than the speed VT2 during synchronous adjustment, fine tune the line speed to make the speed of traction 2 to the synchronous speed VT2+3HZ during synchronous adjustment, and then hang 10KG weight on the roller, the actual test value is 10KG, greater than the set tension 5KG, traction 2 speed will slowly drop to about VT2-3Hz, the tension adjustment is normal.
B: Traction 2 and winding 1,2 are adjusted synchronously
The adjustment method of controller T2 and T3 is the same as above. Start all frequency converters and run with the film. During operation, first adjust the tension stability and then adjust the tension deviation. The stability is mainly manifested in the actual displayed tension fluctuation size, and the linear speed of the respective controller can be adjusted until the tension is stable.
Tension deviation is mainly manifested in the deviation between the actual tension and the displayed tension value, if the tension is stable and can not keep up for a long time, it should increase the line speed (clockwise adjustment) or check whether the pinch roll pressure is normal, if the tension is high for a long time, it must reduce the line speed (counterclockwise adjustment).
Fifth. Operation and use
1.automatic/manual switch, manual state, with the potentiometer linear speed directly adjust the speed of the inverter.
2. in the automatic state, set the tension according to the film requirements (adjust the potentiometer), the tension display meter shows the current film tension value, the automatic state to adjust the potentiometer only changes the tension size, after stability does not change the frequency converter speed.
3. During operation, traction 1, traction 2, winding 1 and winding 2 can be turned into automatic state at the same time, and the frequency converter can be started. During operation, when traction 1 speed up, traction 2, winding 1 and winding 2 speed up at the same time and keep the tension unchanged; when traction 2 speed up, winding 1 and winding 2 speed up and keep the tension unchanged.
Sixth. Adjust requirements
1.the highest line speed of traction 1 should be less than or equal to the highest line speed of traction 2, the highest line speed of traction 2 should be less than or equal to the highest line speed of winding 1, winding 2, line speed = roller speed (r/min) x roller circumference (m).
2.the weight of the roller force direction should be less than 30% of the sensor measurement range, generally 30KG sensor roller weight is less than 12KG.
3.all guide roller operation should be easy and natural, no jamming phenomenon, dynamic balance is good, so as not to affect the tension stability during operation, reduce the control accuracy.
4.the whole machine equipment, frequency converter, motor, etc., should be well grounded to avoid interference and affect the control accuracy.
5.the sensor has been strictly adjusted before the factory test, can not be disassembled at will, change the original installation state, especially can not change the position of the force point.