Abstract : This paper addresses the drawback of asynchronous conveyor belt speed and printer speed in Roland Cromoset newspaper printers using open-loop control. A solution is proposed: pre-setting an initial speed before the conveyor belt accelerates to provide a driving force for the conveyor motor before speed increase; and then employing closed-loop control to ensure synchronization between the conveyor belt speed and the printer speed. This method has proven highly effective in field operation. Keywords : PLC; Variable frequency speed control; Synchronization coordination; Serial communication Introduction Currently, newspaper conveyor belts in newspaper printers typically utilize DC speed control devices to regulate the output speed of DC motors. This control method suffers from several drawbacks. Step-by-step speed regulation of the newspaper conveyor belt leads to a mismatch between newspaper transport and printer speed. When the printer speed remains constant, excessively fast conveyor belt speeds can cause gaps in newspaper transport; conversely, slow conveyor belt speeds can cause the lower newspaper feeder to become clogged (paper jammed) and stop, resulting in unnecessary waste. Furthermore, the limited speed range of the motor and the open-loop control system require manual intervention during operation, making it inconvenient to use. Programmable Logic Controllers (PLCs), as one of the mainstream modern industrial computer systems, have become the backbone of industrial automation and are widely used in modern industry. They are a new generation of industrial automation control devices based on microprocessors, integrating computer technology, automatic control technology, and communication technology. They receive status signals from field devices and solve user-programmed logic programs through the CPU, outputting control signals to directly control the application devices. They are characterized by strong control capabilities, convenient and flexible operation, and high reliability. Therefore, a closed-loop control system based on a PLC to synchronize the speed of the newspaper printer with the speed of the newspaper conveyor belt was developed, which is of great significance for improving equipment utilization and reducing consumption. 1 Speed ​​Analysis and Control Scheme in the Control System The Roland CROMOSET newspaper printer, manufactured in Germany, has a maximum speed of 45,000 rpm. The main motor is a DC motor with a power of 190 kW, and a DC speed control system is used. Since the newspaper printer uses cold printing and the printing speed is high, the water and ink balance is required during the printing process. At startup, the printing speed is relatively low, and the water and ink adjustments must be well matched to the printing speed. When printing speed is out of sync with water and ink, excessive waste will result if the printing speed is too high. Conversely, excessive waste will lead to ink waste if the printing speed is too slow, which is also undesirable. [b][align=center]For more details, please click: Application of PLC-controlled frequency converters in newspaper printers[/align][/b]