Introduction In sheet and strip production enterprises using roll production lines, such as steel rolling, aluminum foil, and roll paper, many companies still rely on closed-loop control systems composed of DC or AC frequency converters for their cutting systems. While these systems meet basic cutting accuracy requirements, they are often not very high. With societal development, manufacturers are increasingly striving for excellence, which is crucial for enhancing their brand image and meeting ever-higher customer demands. Kangda Printing Equipment Co., Ltd. (hereinafter referred to as Kangda) is a manufacturer of printing sheet materials. In recent years, it has successively upgraded the cutting systems of its three production lines, replacing the original AC frequency converter control system with an AC servo control system. This has significantly improved accuracy, reducing the error per sheet from 1mm (the national standard is 1.5mm) to 0.5mm. The improvement is substantial, and the system only requires the purchase of one PLC and one servo motor (with driver). The program is developed and the system is installed independently, resulting in lower costs. System Principle The system composition of Kangda is shown in Figure 1. [align=center]Figure 1: Konda Company's AC Servo Fixed Shearing System[/align] Assuming the length to be cut is S, the circumference of the drive roller is L, and the number of revolutions (or angles) of the main roller is N, then S=LN, which is a linear equation, meaning S and N are directly proportional. Assuming the gear ratio of the belt reducer is K, then S and the number of revolutions of the motor X can be calculated: S=L*X/K. This formula shows that S and X are still a linear equation. Therefore, to obtain the required length S, it is only necessary to control the number of revolutions of the motor. In the original system, a frequency converter, PLC, encoder, and high-speed counting module were used to form a control system. The PLC setpoint (the pulse quantity corresponding to the length) was sent to the frequency converter to drive the motor. The motor operation, in turn, drove the encoder to rotate and generate pulses, which were fed back to the high-speed counter and sent to the PLC for comparison with the original setpoint. The motor stopped when they were equal. In actual use, although this system reduced the motor's inertia by adjusting the frequency converter and introducing the first and second acceleration and deceleration times, allowing the motor to stop when crawling at extremely slow speeds. However, the accuracy of this system is still not very high. Its disadvantages are: (1) the encoder and motor are not coaxial and are not integrated; (2) the motor needs to be stopped by a brake, and the speed and force of the brake will affect the accuracy. However, by using an AC servo system, these two disadvantages are overcome, thus achieving higher accuracy. Process equipment ■ Operating table - the master control electrical control the automatic and manual cutting of the length system, and the required cutting size is provided by the 8421 coded DIP switch. ■ PLC - adopts FX1N-40MT, which has low cost and has the required high-speed pulse output. One PLC unit can output 2 points of 100KHz pulses at the same time. The PLC is equipped with 7 special instructions, including zero return, absolute position reading, absolute or relative drive and special pulse output control. It also has strong anti-interference ability, is easy to program, widely used and easy to purchase. ■ Servo Motor and Driver—The servo motor uses a Panasonic MDMA202A1G servo motor, which is equipped with a high-precision coaxial rotary encoder. This encoder is incremental at 2500p/r with a resolution of 10000. The driver uses a Panasonic MDDA203A1A. The system composed of the servo motor and driver has excellent control performance. This system has good stability, requires no manual intervention after parameter settings, has high reliability, and requires virtually no maintenance, thus eliminating maintenance costs. Control System Hardware Diagram See Figure 2. [align=center] Figure 2: Control System Hardware Diagram[/align] Control System Software Because a Mitsubishi FX1N-40MT is used, ladder logic programming is performed using its accompanying FXGP/WIN software. This is very intuitive and easy to understand. The entire program is concise, and communication with the driver is convenient, requiring only simple wiring. [align=center]Figure 3: Flowchart Figure 4: Program Diagram[/align] Advantages of using AC servo : ■ Smooth operation, no vibration even at low speeds; ■ High control precision, the control precision of the AC servo is guaranteed by the rotary encoder at the rear end of the motor shaft; ■ Fast response speed, acceleration and deceleration can be completed in a very short time; ■ Constant torque output, unaffected by speed; ■ Strong overload capacity; ■ The AC servo drive system itself forms a closed loop, making control more reliable. Conclusion After adopting this system, stability and precision were greatly improved, losses were reduced, higher customer requirements were met, and economic benefits were significant. It also accumulated experience for future promotion. In the following years, our company successively modified other production lines, achieving excellent results at a lower cost. Later, it was recognized and promoted by peers, and all subsequent lines adopted similar systems, abandoning the original frequency converter clamping method.