[Abstract]: This paper introduces the design and PLC control of an automatic feeder for punch presses, and analyzes the working principle of the mechanism and the PLC programming method. [Keywords]: Punch press; Automatic feeding; PLC control I. Technical Status of Automatic Feeder for Punch Presses The automatic feeder for punch presses introduced in this paper is a feeding machine used for cold-extruded ring-shaped parts, and is an ideal auxiliary machine for the technical transformation of punch presses. This feeder overcomes the shortcomings of related punch press feeders both domestically and internationally. For example, the Japanese RF20SD-0R11 robotic feeding device is integrated with the punch press (feeding from the lateral side), has a complex structure, is difficult to assemble, manufacture, and maintain, is expensive, and is not suitable for the longitudinal feeding requirements of Chinese punch presses. The RF20SD-0R11's structure consists of a crankshaft output shaft on the punch press, which extends and retracts via a splined shaft. A ball joint component connects to the robot's gears. A series of transmission components, including bevel gears, cylindrical gears, racks, cams, shift forks, and lead screws, cause the robot's grippers to perform extension, retraction, lifting, clamping, and releasing actions synchronized with the punch press cycle to complete the feeding. A separate, independently driven movable conveyor transports the workpiece to a predetermined position via a material separator. This configuration is limited to Japanese equipment and cannot be applied to domestically produced punch presses. Some domestic feeding mechanisms use a punch press worktable driven by a connecting rod and spring to slide a slider horizontally along a slide rail. The material coming down the inclined rail is pushed to the center of the die by a material separator, and a trigger plate removes the punched material. This reciprocating motion mechanism is relatively simple, lacks a conveyor mechanism, has reliable linkage, and is easy to manufacture. However, the robotic arm cannot lift or clamp the material. The material slides down the inclined feeder under its own weight. If the specifications and weight change, the workpieces slide down at inconsistent speeds, easily causing material stacking. The pushing mechanism fails to clamp the material properly, resulting in misalignment, a high scrap rate, and unsafe operation. Considering the characteristics of domestically produced punch presses, an automatic feeder with significant application value and promotional significance was designed, using a robotic arm and conveying mechanism as the main components, coupled with automatic unloading safety protection. II. Structural Design This feeder is mainly equipped on 3150kN punch presses, but can also be equipped on 1600kN or 1250kN punch presses. It mainly consists of a frame (including support legs, electrical box, angle iron frame), a conveyor (including motor, gearbox, rollers, conveyor belt, material table, feeder, material separation mechanism, and material blocking mechanism), a robotic arm (including lifting cylinder, clamping cylinder, slide plate, bracket, connecting rod hinge, etc.), an oil supply device (including oil tank, hydraulic pump, etc.), an unloading mechanism, and safety protection devices, as shown in Figure 1. [align=center]Figure 1 Simplified structure of automatic punch press feeder 1. Frame 2. Conveyor belt 3. Robot 4. Material separator 5. Punch press worktable 6. Hopper 7. Baffle 8. Workpiece 9. Motor 10. Mold[/align] The frame mainly connects to the punch press, houses the robot and allows it to slide on a certain track, and houses the conveying mechanism and electrical components. The conveyor is driven by a motor, which transmits power to the drive shaft via a belt and reducer, causing the conveyor belt to transport the workpiece at a certain linear speed. The workpiece enters the material channel (manually) via the material table, and is then transported to the predetermined position by the material separator. III. PLC Control The robot needs to move the workpiece from A to B. A schematic diagram of the robot is shown in Figure 2. Its operation process is shown in Figure 3. Each working arm of the robot has upper and lower limit switches and left and right limit switches, but its gripping device does not have limit switches. Once gripping begins, the timer in the control PLC starts, the timing constraint is applied, and the gripping action is completed. After the robot arm reaches point B, the time it takes to release the workpiece is also controlled by a timer. When the timer ends, the workpiece is released. The allocation of input and output points in the PLC is shown in Figure 4. The robot arm's operation process is as follows: When the start button is pressed, the robot arm descends from the origin. When it reaches the bottom, it touches the lower limit switch X401 (which is activated), and the descent stops. Simultaneously, the timer is activated, and the robot arm begins to clamp the workpiece. When the timer ends, the clamping is complete. The robot arm rises. When it reaches the top, it touches the upper limit switch X402 (which is activated), and the rise stops. The robot arm moves to the right. When it touches the right limit switch X403 (which is activated), the rightward movement stops. The robot arm descends. When it reaches the bottom, it touches the lower limit switch X401 (which is activated), and the descent stops. Simultaneously, the timer is activated, and the robot arm releases the workpiece. When the timer ends, the workpiece is released. The robot arm rises. When it reaches the top, it touches the upper limit switch X402 (which is activated), and the rise stops. The robot arm moves to the left, stopping when it reaches the origin and touches the left limit switch X404 (which is activated). This completes one cycle of the robot arm's operation. The automatic operation flowchart of the robot arm is shown in Figure 5. The state transition diagram is shown in Figure 6. The ladder diagram is shown in Figure 7. [ALIGN=CENTER] [/ALIGN] IV. Conclusion The automatic feeder for punch presses is essentially a robot arm, capable of automatically loading and unloading materials, improving production efficiency, ensuring product quality, reducing labor intensity, and ensuring personal safety. It has significant application prospects in the cold extrusion processing industry. Using a PLC to control the mechanism and a microcomputer as the human-machine interface effectively meets the control and system requirements. Furthermore, it offers accurate testing, high-speed and reliable operation, and a long service life. It is a real-time monitoring system and provides valuable reference for the control and design of related systems. References: 1. Zhou Yanxun. Computer Automatic Measurement and Control System. Beijing: National Defense Industry Press, 1992. 2. Zhang Xinhua. Discussion on Automatic Monitoring System Composed of PC-PLC. Telemetry and Remote Control, 1998(6). 3. Lu Zhikang, Zhang Xinhua. Research on Long-Distance Automatic Monitoring System. Microcomputer Applications, 1999(4). 4. Zhang Xinhua et al. Principle and Design of Automatic Feeding for Punch Press. Forging Technology, 1993(5).