I. Overview
The main motion characteristics of printing machinery: The processing objects are various flexible printing substrates. During processing, it is necessary to ensure the substrate moves according to specified requirements while simultaneously completing the printing of various colors or processing of the substrate. This results in two motion chains in the printing machinery: the paper-carrying motion and the printing motion, which are coordinated with each other. Taking offset printing presses as an example, to ensure variable speed operation and printing needs, many current machines still use DC speed control to drive the two motion chains of the entire machine. To complete the printing, several other motions need to be performed, such as ensuring the requirements of jogging operations (plate loading, cleaning cylinders, paper feeding). Coaxial with the DC motor is an AC motor and a cycloidal pinwheel reducer to achieve low-speed, jogging operation. In addition, during the printing process, the water and ink supply is directly related to the printing speed; therefore, the water and ink output rollers are driven by two separate DC servo motors. Several other fixed-speed motors are responsible for operations such as adjusting the plate cylinder alignment, paper loading, and adjusting the left and right position of the paper roll. To ensure printing quality, the printing substrate needs to use a magnetic powder brake to control the paper feeding force, a speed measuring motor to guide the ink supply, and a deviation adjustment device to control the paper's path. Different types of motors are also involved in these mechanisms.
II. Process Requirements for Dyeing Machines
Intermittent offset printing presses primarily print trademarks and labels. When controlling tension, the requirements for tension control are very high, mainly reflected in the following aspects:
1. The tension should be stable, with a fluctuation of less than 3%.
2. Quick start and quick stop cause no impact on printing materials.
3. The tension response speed should be fast.
Why do intermittent offset printing presses have such requirements for frequency converters? Mainly because their winding process is intermittent. There is a material storage space between the printing traction roller and the winding traction roller. When the lower limit photoelectric sensor detects material, it sends a start signal to the traction frequency converter, and simultaneously the winding motor winds the printing material. When the printing material senses the upper limit photoelectric sensor, the traction motor stops, while the winding motor maintains a constant tension on the printing material. The entire process takes approximately 3 seconds. Therefore, this type of application requires a very fast tension response speed.
III. Weichuang Solutions
Features of AC200T series frequency converters:
1. Unique automatic roll diameter calculation function
As the diameter of the take-up roller continues to increase, the output frequency of the inverter for the take-up motor needs to be continuously reduced. The AC200T series inverter has a dedicated roll diameter calculation function that dynamically, in real time, and automatically calculates the current roll diameter of the take-up roller to achieve the best constant tension take-up effect.
2. Constant tension control
With its superior tension control function, the AC20OT can adjust the torque output in real time according to the tension changes on the material, thereby ensuring a constant tension on the material.
IV. Conclusion
The dyeing machine system implemented with Weichuang frequency converters operates smoothly and reliably throughout the entire process, bringing significant economic benefits to the company. Through actual production testing, the client is highly satisfied with Weichuang's overall solution. Its advantages are mainly reflected in the following aspects:
1) The winding tension adjustment is simple, and the tension and synchronization control are both completed in the frequency converter, which greatly improves the reliability and stability;
2) Vector control is adopted, which has fast dynamic response and high control accuracy. The tension is constant during acceleration and deceleration, avoiding misalignment of colors.
3) The tension inverter has a long service life, and the system is very easy to use and maintain;
4) No tension sensor or encoder is required, which can save costs for equipment manufacturers.
