Servo rectification machine is used in printing and packaging machinery, textile machinery, rubber machinery, battery machinery and other related manufacturing industries.
In the production process of biaxially stretched plastic film, the deviation correction control system greatly reduces the probability of horizontal pull-off, folding, film breakage, ripple jitter and other problems, and realizes the high-speed and efficient production of film. Based on the application of rectification control system at home and abroad, the rectification system is briefly introduced from several aspects such as working principle and control mode.
Application example of rectification system in biaxial stretching equipment;
EPC device is installed at the TDO entrance of the film production line to accurately track the position of the film edge. Its working principle can be simplified as a closed-loop control loop: the starting point of automatic deviation correction is to horizontally pull the current position of the film at the entrance, and the current position of the film is scanned by one or more sensors and transmitted to the controller; The controller compares the measured actual position with the set position, and if there is a deviation between them, the controller will send a correction signal to the driver; The driver drives the track at the entrance of TDO quickly, so as to track the film edge in time. In this way, the EPC system continuously drives the crawler to reciprocate, and the pinch-off phenomenon will not occur.
Structure and classification
According to the different power devices of EPC system, it can be generally divided into four categories: electromechanical, electro-hydraulic, gas-liquid and electromagnetic.
The structure principle of electromechanical EPC system is shown in the following figure, which is mainly composed of three parts: sensor, controller and electromechanical driver.
The structure principle of electro-hydraulic EPC system is shown in the following figure, which is mainly composed of five parts: sensor, controller, electro-hydraulic servo valve, electro-hydraulic power device and hydraulic driver.
The structure principle of gas-liquid EPC system is shown in the following figure, which is mainly composed of four parts: sensor, gas-liquid servo valve, gas-liquid power device and hydraulic driver.
The magnetic lost foam casting system is still in the experimental stage, which is mainly applied by German brukner Company, and there is still a lack of relevant information in China. At present, the above three kinds are mainly used in the production line of biaxially stretched plastic film at home and abroad.
These three control systems are similar in structure and all contain sensors, which can be divided into infrared sensors, reflective infrared sensors, ultrasonic sensors, digital sensors, pneumatic sensors, laser sensors and camera sensors. Among them, infrared sensors and ultrasonic sensors are mainly used in electromechanical and electro-hydraulic types. Electromechanical and electro-hydraulic EPC systems also have controllers, which are simple to operate and powerful. High-speed film production has extremely high dynamic response level and detection accuracy, which can not only monitor in real time, but also realize remote control.
The electromechanical EPC drive mainly depends on the electric push rod, with simple equipment, small recoil and maintenance-free; It is directly driven by the controller, so it has the most sensitive dynamic response performance, and the typical precision error is less than 0.002s s. However, this kind of push rod is mainly driven by belt, screw or gear, and its service life is not as good as that of gas-liquid EPC system and electro-hydraulic EPC system under the conditions of assembly error and long-term wear. The gas-liquid EPC system is mainly driven by the gas-liquid servo valve control cylinder, and its biggest feature is its smooth operation. Different from the electromechanical EPC drive, it tracks the position of the side film through pneumatic sensors. The detected air pressure signal is directly fed back to the gas-liquid servo valve. Because the diaphragm is far away from the air source, the dynamic response accuracy is not as good as that of electromechanical control. Moreover, the hydraulic oil used in it will block the oil circuit under the condition of impurity pollution, so the maintenance frequency is high. Electro-hydraulic EPC system combines the advantages of these two control methods, adopts infrared or ultrasonic sensors to realize accurate detection, and feeds back signals to electro-hydraulic servo valve through the controller to realize accurate control of the controller. It not only avoids the shortcoming that the dynamic response level of pneumatic sensor is not high enough, but also retains the advantages of gas-liquid operation, but also has the problem of oil impurities.