Tire tread length cutting is one of the key processes in radial tire production. After the rubber compound is fed into the extruder, it is pressed out and then subjected to traction stretching, cooling, and length cutting to obtain the tire blank. The control process for tread length cutting detection is a process of first cutting to a fixed length and then weighing each piece individually. Developing a tread cutting device with high cutting accuracy (including the inclination and smoothness of the processing end face and the accuracy of the length cutting) and the ability to adapt to high cutting speeds is extremely important for improving output, reducing scrap rate, and improving raw material utilization. This article mainly describes a control system that uses fieldbus and servo control technology to achieve high length cutting accuracy. The system's operating indicators are as follows: High operating speed not less than 30m/min; When the set length is greater than 1m, the length cutting error is less than 2‰; The inclination and smoothness of the cutting end face meet the requirements of the next process. I. Equipment Composition and Functional Introduction of the Cutting System 1. Mechanical Composition The cutting system consists of several parts as shown in Figure 1. Their composition and functions are described below. The cutting device consists of a fixed-length conveyor, a cutting blade device, a glue-pressing device, and a blade holder rotation device. The fixed-length conveyor has a low-platform structure, and the conveyor belt is driven by an AC servo motor, meeting the requirements for high-precision fixed-length cutting. The speed can be infinitely adjusted within a certain range. The cutting blade device consists of a cutting blade holder and a blade holder transmission device. The cutting blade, a miniature cylinder, and a motor are mounted on the cutting blade holder. The cutting blade rotates at high speed driven by the motor and is raised and lowered by the miniature cylinder. It is lowered during cutting and raised during the return stroke. The cutting blade holder moves back and forth on a Rexroth high-precision linear motion guide rail driven by a servo motor to cut the tire tread. The glue-pressing device consists of a sponge roller and a pressure brush driven by a cylinder that can be raised and lowered to press down on the tire tread during the cutting process to prevent slippage. The entire cutting blade transmission device can rotate around a vertical axis to adjust the cutting angle. After cooling, the tire tread enters the fixed-length cutting conveyor belt via a storage tank. An ultrasonic sensor is installed above the storage tank to detect the degree of tire tread storage, causing the conveyor belt to run at different speeds. The conveyor belt servo motor starts running, and at the same time, the rotary encoder directly mounted on the shaft starts pulse counting. The motor drives the conveyor belt forward. When the tire tread length reaches the preset value, the conveyor belt decelerates and stops running. At this time, the pressing brush of the pressing device is driven by the cylinder to press the tire tread downward. The cutter servo motor drives the cutter to move quickly from the initial end along the linear guide to the other end and cut the tire tread. During the tire tread cutting process, the water spray solenoid valve is activated and sprays water onto the cutter. After cutting, the tire pressing device rises, the cutter is raised, the cutting cutter on the linear guide returns to the initial position and stops running, the water spray solenoid valve stops spraying water, and the cutter is lowered, returning everything to the initial state for restarting. 2. Electrical Control Components This control system adopts the single-master linear network topology structure with the highest transmission efficiency of Profibus fieldbus. The network topology is shown in Figure 2. Based on the requirements of the entire production line, a Siemens S7-315-2DP was selected as the main control PLC, serving as the DP master station. Two Rexroth DKC servo controllers driving the motors and two absolute displacement encoders are connected to a Rexroth CLM1.4-LAP position controller. The position controller itself has a DP interface, allowing direct connection to the PROFIBUS bus as a slave station of the fieldbus control system. Remote parameter configuration can also be performed through the master station. The control panel has numerous operation and display requirements. Setting and displaying the cutting length, controlling the left and right movement of the cutter head, manual control signals, and modifying certain system parameters are all handled through the TP270, a powerful Windows-based operating terminal from Siemens. The cutting system's detection devices include various non-contact limit switches, ultrasonic sensors, and absolute displacement encoders to measure mechanical displacement and operating speed, ensuring the orderly, safe, and reliable operation of the cutting servo control system. The status detection signals are connected to the digital input ports (E1-E16 in terminals X3) of the Rexroth position controller CLM, including the lifting and lowering signals of the cutter and pressure brush, the left and right limit signals of the tool holder, and the tool holder positioning origin. The actions of the cutter, pressure brush, and steam valve are controlled by the digital output ports (A1-A16 in terminals X4). Ultrasonic sensors are installed in the storage tanks at the front end of the fixed-length conveyor belt and the rear end of the preceding tire tread conveyor belt. The high and low signals (0-10V) of the tire tread position detected by the sensors are input to the PLC through the analog input ports. Two displacement encoders that detect the positions of the conveyor belt and the tool holder are connected to the position controller CLM (terminals X1 and X2). II. Software Design and Analysis The software design of this system mainly includes three parts: the design of the PLC control program and the communication program between the PLC and the position controller CLM, including the system Profibus-DP network configuration, system hardware configuration, and control program design; the Rexroth position controller cut-off servo control program; and the design of the monitoring program, mainly including the design of the human-machine interface such as the monitoring main interface, cut-off control interface, report generation, and data query interface required for system operation. 1. PLC Control Program Design: The system uses a Siemens S7-315-2DP as the Profibus fieldbus master station to provide direct and convenient high-speed cyclic communication services with the Rexroth position controller CLM. It features high communication speed, good control real-time performance, strong anti-interference capability, and simple programming. Import the position controller CLM device database file (IN2_04eb.gsd) into the STEP7 PLC programming software to complete the hardware network configuration. Assign a network address to the position controller; this address must be the same as the one set in the controller parameters. In the organization block OB, select the SFC14 "DPRD_DAT" and SFC15 "DPWR_DAT" system function blocks to receive/send process data to the position controller. In position controller parameter B007, set the bus communication rate with the master station; in parameter B008, set the slave station network address and select the parameter process data object (PPO) type. This allows the system's field devices and the PLC to read and write data and transmit control data, such as control words, status words, setpoints, and actual values, via the Profibus-DP bus. In addition to process data, Profibus-DP also transmits drive system parameter settings and diagnostic signals. The PLC coordinates the control of the belt and cutter head based on the operating speed of the transmission line, operating commands, and the status of the cutting device. The amount of tread stored between the two conveyor belts causes the sensor to generate a corresponding analog output signal. This signal, combined with the speed of the preceding conveyor belt, is used to determine the running speed of the cutting belt according to a certain algorithm. The PLC then adjusts the speed accordingly to ensure smooth and coordinated operation of the conveyor belts. Users set parameters such as the tread cutting length according to product production needs, and data transmission between the PLC and the position controller is completed via a bus. 2. Servo Program Design of the Position Controller CLM The Rexroth Position Controller CLM is a compact, modular two/four-axis CNC system that directly drives Rexroth DKC servo drives to achieve precise positioning of the AC servo motors. In this system, two sets of Rexroth DKC servo drives respectively control the fixed-length conveyor belt transport and the lateral movement of the cutting blade holder. The position controller has a rich instruction set, and control programs can be written on its operation panel or on a computer equipped with programming software (MotionManager). The cutting servo control program flowchart is shown in Figure 3. The program mainly consists of three parts: bus communication, conveyor belt control, and cutting blade holder control. The transmission of control and status information between the controller and the PLC is accomplished by a bus communication program. The controller receives control information such as speed values, length values, and operation commands from the PLC, and simultaneously transmits operating status information to the PLC for analysis and display. The conveyor belt control program controls the speed and position of the conveyor belt servo motor, ensuring precise length determination and smooth, rapid operation for tread cutting. The cutting blade holder control program controls the lateral movement of the cutting blade holder and its auxiliary devices, ensuring the normal execution of the cutting blade's actions and achieving a good cut end face. 3. Monitoring System Design The system uses a PLC as the primary master station and an industrial PC as the secondary master station. The industrial PC acts as the host computer, providing a good human-machine interface environment to realize production management and monitoring of the entire production line and connect to the workshop-level INTRANET network. The primary master station (main control PLC) is the core of the entire tread production line control system, realizing the acquisition and processing of production process data, as well as the transmission of control signals and communication with the industrial PC, facilitating operators to monitor the equipment on-site. The entire system's operation, working status, and measurement analysis results are graphically displayed and monitored on an industrial PC. Relevant data is uploaded to the PLC via a fieldbus, system alarms are processed, historical data is stored, various reports are generated, and graphical displays and human-machine interfaces are provided. Control commands are sent to the PLC, thus achieving information management between the monitoring computer and field devices. The human-machine interface for control uses a TP270 touchscreen, connected to the PLC host via a Profibus bus. Touchscreen programming is performed using Siemens' ProTool/ProCS configuration software. ProTool/ProCS's complete graphical user interface, along with its built-in project configuration wizard, allows users to easily create various object-oriented and symbol-based projects. In ProTool/ProCS, communication between the operating units and actuators on the interface is achieved through variables stored on the PLC, which can be directly read or written by the HMI. The software design philosophy is to create a software system that allows operators to learn operating procedures independently, based on the completion of basic human-machine interaction functions. Through the human-machine interface, operators can set basic parameters such as fixed length value, error adjustment, and cutting count, monitor system alarm status, learn system operation procedures, and set passwords. During automatic operation, parameters such as speed and position can be easily adjusted and modified on the touchscreen when the equipment operates according to its designed workflow. In case of abnormal stop, the servo motor should immediately stop operating and generate an error code displayed on the touchscreen, allowing maintenance personnel to promptly understand the problem. III. Conclusion This control system fully utilizes advanced technologies such as PLC, Profibus fieldbus technology, and servo control. The system adopts a distributed open structure, offering fast response, flexible configuration, comprehensive control functions, and simple and standardized operation. After completion, the fixed-length cutting system has been put into use in several all-steel radial tire production lines, achieving a control accuracy of ±1mm. Practice has proven that this Profibus-DP fieldbus-based control system is safe, reliable, and has a low failure rate. The product fully meets the high standards of the next process, possesses a high level of production and management automation, improves production efficiency, and creates significant economic benefits.