吹膜生产时，如果不能控制好张力，就会发生薄膜表面被拉伸变型、膜卷不平整、下道工序放卷时易粘联等质量问题。 Abstract: In the production of blown film, if the tension cannot be controlled, quality problems such as stretch deformation of the film surface, uneven film roll, and easy adhesion when unwinding in the next process will occur. This article introduces the characteristics, composition and principle of the tension control system, and details how to install and debug tension sensors, tension controllers, inverters and other devices. Only by properly adjusting the tension control system can the tension control be truly achieved and a film of stable quality produced.
When the film blowing machine produces plastic film, if the film surface tension is not properly controlled, it will affect the quality of the film, resulting in quality problems such as the film surface being stretched and deformed, the film roll uneven, and easy to stick when unwinding in the next process. 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 during the speed-up and down process, the adjustment is more frequent. The use of tension control can better solve the above problems and improve the production quality of film rolls.
I. Characteristics of tension control structure
Three tension control points are generally installed on the film production line, which are respectively located at traction 2, rewinding 1, and rewinding 2 (surface double station winder). 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 the film. At the same time, the tension of each section of the film is set according to the film width, thickness and process requirements during operation. By controlling the motor speed at the traction roller, winding 1 and outer winding 2, Adjust the film tension to keep the film tension constant.
Figure 1 Schematic diagram of tension detection points
Composition and Tension Control Principle
Each tension control system consists of a tension sensor, a tension controller, and a frequency converter. The tension sensor is installed on the guide roller and transmits the detected film tension signal to the tension controller. After amplification, calculation and adjustment, it outputs an analog signal ( 0 ~ 10V or 4 ~ 20MA) directly drive the inverter and adjust the motor speed to achieve the purpose of controlling tension.
、张力传感器安装 1.Tension sensor installation
Generally speaking, there are two ways to install the tension sensor, one is fixed in the direction of force, and the other is adjustable in the direction of force.
：受力方向固定的安装方式 A : Installation method with fixed force direction
As shown in Figure 2, one end of the guide roller is mounted on the left side plate with a spherical bearing and the other end is mounted on the sensor bearing. 60% of the sensor is embedded in the right side plate. On the side panel, the red dot of the sensor should point in the direction of the force during installation.
Figure 2 Installation method of fixed load point
：受力方向可调的安装方式 B : Installation method with adjustable force direction
Add a rotating disk and clamping end cover between the sensor and the right side plate. As shown in Figure 3, the sensor is installed on the rotating plate, and then fixed on the right side plate by clamping the end cover. Turning the rotating plate can adjust the direction of the force point .
It is recommended to use this installation method.
Figure 3 Installation method with adjustable stress point
After installation, the center of the roller must be on the same line as the center of the bearings at both ends. The operation should be easy and natural, without jamming and friction with the outer wall of the bearing. Do not drop hard objects such as iron filings into the cover and bearing during installation. In the gap, the sensor bearing can not flow into this gap when lubricating, otherwise it will affect the performance.
、张力控制器、变频器安装 2.Tension controller and inverter installation
The electrical connection is shown in Figure 4. The inverter start and stop control terminals, potentiometer input terminals, and analog output terminals depend on different brands. The synchronous linear speed signal of controller T1 is taken from the traction 1 inverter, and the synchronous linear speed signals of winding controller T2 and T3 are taken from the traction 2 inverter. K12, K22, and K32 are used for testing, and they can not be connected externally.
Figure 4 Electrical wiring diagram
、张力传感器调校 1.Tension sensor adjustment
：张力检测器零位调整 A : Zero adjustment of tension detector
When the tension detection shaft is not under force (empty shaft), adjust the ZERO potentiometer, and use a voltmeter to detect the output voltage (VO, COM) to make its output zero, the output in the clockwise direction increases, and the output in the counterclockwise direction decreases.
After adjustment, rotate the roller and measure the voltage across VO and COM. The change should be less than 0.05V.
：张力检测器输出调整 B : Adjustment of tension detector output
Hang a standard weight (5KG) on the tension detection shaft according to the material moving direction. The weight must be hung in the middle of the roller, adjust the SPAN potentiometer, and use a voltmeter to detect the output voltage (VO, COM) to make the output a corresponding value.
Example: The tension detector is 50KG and a 5KG weight is used.
Output voltage U = 5 * (10/50) = 1V
Output current I = 5 * (20/50) = 2mA
At this time, adjust SPAN to make V0 and COM output 1V or IO and COM output 2mA
The output in the clockwise direction increases and the output in the counterclockwise direction decreases.
During the use of the tension amplifier, if the sensor is used improperly or if the pressure exceeds the rated value for a long time, the structural changes of the mechanical equipment will cause detection errors. It should be readjusted. The schematic diagram of the adjustment is shown in Figure 5:
Figure 5 Schematic diagram of tension adjustment
、线速度同步调整 2.Line speed synchronous adjustment
牵引1、2同步调节 A: Traction 1, 2 synchronous adjustment
Short the synchronous control terminal C2 of controller T1 to OV, disconnect the manual control terminals C3 and OV, start the traction 1, traction 2 inverter, adjust the speed of traction 1 to 25HZ, and measure the linear speed of traction 1 roller with a linear speed meter Adjust the linear speed R of the controller T1 so that the linear speed of the traction 2 roller is consistent with the linear speed of the traction 1 roller. At the same time, note that the traction 2 speed VT2 (for tension adjustment) is adjusted and C2 and OV are disconnected. Note that the maximum linear speed of traction 1 is ≤ the maximum linear speed of traction 2.
牵引2与收卷1同步调节 B: Traction 2 and Rewind 1 are adjusted simultaneously
Short-circuit the synchronous control terminal C2 of the controller T2 to OV, disconnect the manual control terminals C3 and OV, start the traction 2, rewind 1 inverter, adjust the speed of traction 2 to 25HZ, and measure the line of traction 2 rollers with a linear speed meter Speed, adjust the linear speed R of the controller T2 so that the linear speed of the reel 1 and the linear speed of the traction 2 rollers are consistent. After the adjustment, C2 and OV are turned off.
牵引2与收卷2同步调节 C: Traction 2 and Winding 2 are adjusted simultaneously
The adjustment method of the controller T3 is the same as that of T2.
、手动调整 3 , manual adjustment
C3 and OV of the controllers T1, T2, and T3 are short-circuited, and C2 and OV are disconnected. Adjust the respective set potentiometer linear speed from minimum to maximum, and the corresponding inverter output frequency changes from 0 to 50HZ.
、同步控制调节 4 , synchronous control adjustment
Short-circuit C2 and OV of controllers T1, T2, and T3, and disconnect C3 and OV. Set the potentiometers to the maximum, start 4 inverters, increase traction 1 speed, traction 2, rewind 1 、 Rewinding 2 The corresponding frequency increase speed and the speed increase amplitude remain the same.
、张力控制调节 5 , tension control adjustment
C2 and OV of controllers T1, T2, and T3 are disconnected, C3 and OV are disconnected, and the controller is in tension control mode.
牵引1、2张力调节 A: Traction 1, 2 tension adjustment
Start the traction 1 and traction 2 inverters, 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 increase and be higher than the synchronization. Adjust the speed VT2, fine-tune the line speed so that the speed of traction 2 is the synchronous speed VT2 + 3HZ during synchronous adjustment, and then hang a 10KG weight on the roller. At this time, the actual detection value is 10KG, which is greater than the set tension 5KG, and the traction 2 speed Will slow down to about VT2-3HZ, tension adjustment is normal.
牵引2与收卷1,2同步调节 B: Traction 2 and rewinding 1, 2 synchronous adjustment
Controller T2, T3 adjustment method is the same as above. Start all inverters and run with film. During the operation, adjust the tension stability first, and then adjust the tension deviation. The stability is mainly reflected in the tension fluctuations actually displayed, and the linear speeds of the respective controllers can be adjusted until the tension is stable.
The tension deviation is mainly reflected 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, you should increase the linear speed (adjust clockwise) or check whether the pressure of the nip roller pressure roller is normal. If the time is too high, reduce the line speed (adjust counterclockwise).
Five, operation and use
、自动/手动切换开关，手动状态下，用电位器线速度直接调整变频器转速。 1. Automatic / manual switch. In the manual state, use the potentiometer line speed to directly adjust the inverter speed.
、在自动状态下，根据薄膜要求设定张力(调整电位器)，张力显示表显示当前薄膜张力值，自动状态下调整电位器只改变张力大小，稳定后不改变变频器转速。 2. In the automatic state, set the tension according to the requirements of the film (adjust the potentiometer). The tension display table displays the current film tension value. In the automatic state, adjusting the potentiometer only changes the tension and does not change the speed of the inverter after stabilization.
、操作时可将牵引1、牵引2、收卷1、收卷2同时转为自动状态，启动变频器，运行过程中当牵引1升速时，牵引2、收卷1、收卷2同时升速且保持张力不变，当牵引2升速时，收卷1、收卷2同时升速且保持张力不变。 3. During operation, traction 1, traction 2, rewinding 1, and rewinding 2 can be turned to the automatic state at the same time, and the inverter is started. When the traction 1 speeds up during the operation, traction 2, rewinding 1, and rewinding 2 are simultaneously Speed up and maintain the same tension. When Traction 2 speeds up, Winding 1 and Winding 2 both speed up and maintain the same tension.
Six, adjustment requirements
、牵引1最高线速度应小于或等于牵引2最高线速度，牵引2最高线速度应小于或等于收卷1、收卷2最高线速度，线速度=辊筒转速（r/min）×辊筒周长（m）。 1. The maximum linear speed of traction 1 should be less than or equal to the maximum linear speed of traction 2. The maximum linear speed of traction 2 should be less than or equal to the maximum linear speed of winding 1, winding 2; linear speed = roller speed (r / min) × roller Tube circumference (m).
、辊筒受力方向重量应小于传感器测量范围30％，一般30KG传感器辊筒重量小于12KG。 2. The weight of the roller in the direction of force should be less than 30% of the measurement range of the sensor. Generally, the weight of a 30KG sensor roller is less than 12KG.
、所有导辊运转应轻松自然，无卡住现象，动平衡良好，以免运行时影响张力稳定性，降低控制精度。 3. All guide rollers should run easily and naturally, without jamming and good dynamic balance, so as not to affect tension stability and reduce control accuracy during operation.
、整机设备、变频器、电机等应良好接地，以免干扰，影响控制精度。 4. The complete equipment, inverter, motor, etc. should be well grounded to avoid interference and affect control accuracy.
、传感器出厂前已进行了严格的调整测试，不能随意拆装、改变原安装状态特别是不能改变受力点位置。 5. The sensor has undergone strict adjustment testing before leaving the factory. It cannot be disassembled or changed at will, especially the position of the force point.