AC310 Frequency AC Drive VFD used on Coating Machine in Bangladesh
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The coating machine needs to stick glue or ink evenly to the aluminum foil, plastic film or cloth textile surfaces, which has high requirements about the coating process: it not only requires the uniform height of coating process, but also requires to achieve high-speed and non-stop roller change to improve the production efficiency.
Generally speaking, there are several steps in coating process: constant tension unwinding, multi-steps synchronous control and constant tension winding. It requiresa constant material tension, constant line speed and smooth start / stopin the production process. Therefore, the key to control the mechanical and electrical performance of coating machine is to control the tension of coating system. The tension value directly affects the quality and quantity of products: if it is too large, the physical properties, service life and quality of coated paper will be destroyed ; if it is too small, the winding will be too loose, and the paper is not smooth, which will affect the product quality in subsequent process. During the whole process, no matter in starting acceleration or stop deceleration, the constant speed operation at any line speed requires the coating roller, compound roller and traction roller to keep an synchronous running line speed. Otherwise, there will be paper break, roll shift, aluminum foil fold or printing broken and other abnormalities. In addition, the compound coating motor is required to respond quickly with accurate speed control and small fluctuation of tension in the whole process.
Solution of VEICHI Products
The tension control of transmission is to control the tension stability by controlling the constant speed ofsystem.At present, most industries use high-end PLC for constant speed control, to which the feedback signal of reeling traction and reeling device is sent, and the inverter is only an actuator in the whole control system. This requires PLC to operate fast and requires more extensive A/D and D/A modules. Moreover, the dynamic response of system is slow because of the influence of PLC operation speed and signal transmission. Therefore, we can only use the most high-end vector inverter brand, with high resolution analog input, fast dynamic response and high accuracy speed, to compensate the delay caused by the shortages of solution.
1. During the unwinding process, VEICHI AC310 series AC drive VFD is adopted to perform the automatic PID closed loop control, aiming to keep a constant tension of material. The unwinding speed changes with the traction speed: when the line is loose,the winding speed varies with the unwinding speed;when the line is broken, it requires the unwinding plate to be stopped immediately. Considering that there are braking devices in the unwinding plate, it must be set free stop for inverters. The unwinding process operates separately.
2. It needs several open loop VC inverters in the coating and baking process, which adopts the proportional linkage control, and the main signal and the fine adjustment signal are operated by superposition in the coating process.Method for realizing synchronization of linear speed:Taking multi-stage synchronization control in multi coating process as an example, in order to keep the line speed synchronous, it adopts the superposition of main frequency + auxiliary frequency.In the synchronous control, the main frequency of the first inverter is transmitted to the second unit through RS485 communication, and so on, until to the last one. The frequency transmission by communication method could avoid the attenuation of analog signals in the transmission process. Realized by up / down function of inverter, the auxiliary frequency is used as fine tuning frequency, of which the accuracy could up to 0.01Hz.
3. AC310 tension controller is used for finished product winding, mainly aiming at the constant tension of finished products. Using open-loop control, automatic taper calculation and diameter calculation are performed without additional tension devices, to carry out the tracking operation on the finishing stage of coating machine.
The coating system realized with VEICHI inverter is stable and reliable in the whole operation process, and has gained good economic benefits for the enterprises. Through the actual production test, the customer is satisfied with the overall plan of VEICHI. Its advantages are as the following points:
(1) The constant tension control and synchronous control are both completed by inverter with no additional controller, and PLC control is adopted in electric control system with simple structure;
(2) Constant tension control. During the production process, tension is kepta constant value with high accuracy, and the base material will not be damaged.The coating effect is even, ensuring good product quality, and the site is clean and free of oil spills;
(3) Winding taper compensation to ensure the constant tension of finished products, which completely avoids the situation of inner tight and outer loosening;
(4) Mature technology, convenient for debugging, operation and maintenance.