Over the years, in the field of sewing machine head processing, the level of production automation is still at a low level. In the whole process, the sewing machine head is usually loaded and unloaded manually. With the rising cost of personnel, the profit margin of processed products is lower and lower. Using manual loading and unloading, the problems of high risk, low efficiency and high rate of defective products have been puzzling manufacturers. In order to improve the product performance and reduce the adverse factors in the production process, some manufacturers began to use robots to load and unload the machine head. As intelligent equipment, robots have the characteristics of high precision, good stability and high flexibility. Through the use of robots, not only can reduce the cost of personnel, improve the utilization rate of equipment, but also can effectively control the quality of products. In this paper, the er50-c20 industrial robot developed by Anhui EFTE Intelligent Equipment Co., Ltd. is taken as the application object. Through the simulation software, the robot's working path is planned to realize the process of carrying the sewing machine head blank for machining. The results show that the robot not only improves the quality of products, but also reduces the labor intensity of employees, and reduces the requirements of production skills.
1. Robot structure and parameters
The robot is mainly composed of mechanical body, driving part, computer control system, sensor system, input / output system interface. In this project, the er50-c20 robot independently developed by Everett company is used, which is a 6-DOF serial robot. The main parameters are as follows:
2. Project process description and analysis
2.1 station Description:
The process is as follows:
There are 18 machine tools for 6 processes in total.
In this project, the robot is equipped with flexible compensator grab at the end, with air circuit unit, master station PLC, etc.
According to the sewing machine processing technology and machine size, the project is divided into seven stations. The station is a manual loading station, mainly for destacking and conveying. The second station has one robot for four machine tools, the third and fourth stations have two machine tools for each robot, and the fifth and Sixth stations have four machine tools for each robot. The seventh station: one robot serves two machine tools and stacks the processed products. (transfer materials between stations through the material transfer table. The station is the feeding table to transport the blank.) The whole line adopts PLC control and PROFIBUS communication, with an average loading and unloading time of 25s. The detailed layout is shown in Figure 2-1:
Station equipment includes: conveying material track, er50-c20 robot, flexible grab for robot, button box, PLC control system, safety protection.
2.2 end actuator - flexible gripper
According to the process requirements of the project, the flexible gripper is needed in the project, that is, the gripper is connected with the robot through a flexible compensator. When the robot places the workpiece on the machine tool for processing, the positioning accuracy of the workpiece is required to be 0.03mm and higher, while the repeated positioning accuracy of the robot is / - 0.15mm. If only the robot is used for positioning, the positioning requirements cannot be met. For this reason, a flexible compensation mechanism is introduced into the project. If there is a position deviation between the workpiece and the machine tool tooling, the flexible compensator will actively compensate the robot from different angles to reduce the hard contact force of the working positioning pin on the robot. By using the flexible compensator, not only the robot overload caused by the hard contact between the robot and the machine tool can be avoided, but also the wear of the locating pin on the machine tool can be reduced, so as to realize the loading and unloading of high-precision products. In this project, the accuracy of the positioning pin between the sewing machine head and the machine tool is required to be high. In order to avoid hard contact between the robot gripper and the machine tool, a flexible compensator is installed on the gripper for compensation. The gripper is designed according to the product digital model or actual sample provided by the manufacturer, and the sample drawing is shown in Figure 2-2
3. Control system working principle and simulation.
3.1 system control logic diagram is shown in Figure 3-1:
The whole project adopts PLC as the main control unit, through the operation on the human-computer interface and monitoring the status of the robot, in the automatic state, the start and stop of the production line can be realized only by operating the button station. PLC coordinates operation by controlling independent robot system and machine tool system.
First, power on the electric control system, start PLC, PLC control robot and machine tool for self inspection, machine tool for self inspection, if there is a fault machine tool will stop. At this time, the robot detects whether it is waiting for the working position, if not, it will stop. If the robot and the machine tool are in the designated position, the robot, the material path and the machine tool will carry out coordinated operation. After finishing one operation, it will automatically enter the next month's cycle.
3.4 station simulation layout:
By using the off-line simulation software of DELMIA, the three-dimensional layout of the field robot is carried out. Then verify whether there is interference between the robot and the robot. At the same time, according to the simulation results, calculate the working beat of the robot, confirm the height of the robot base, the position of each machine tool, verify the reach range of the robot, and ensure the large effective service distance between the robot and the machine tool. The detailed simulation diagram is shown in Figure 3-2. :
3.5 robot teaching
The cooperation between the robot and the robot is completed by recording the robot track, modifying the position and pose, setting the IO signal. After the initial debugging, optimize the robot's motion track, delete some redundant motion track points, shorten the robot's signal communication time, improve the robot's working efficiency, and prevent the potential collision between machines and between robots and machine tools, and improve the stability of the production line by setting the robot interference area. When two robots have potential collision danger, the starting robot enters the interference area signal to prevent other robots from entering the potential collision area.
Conclusion: by using robot to load and unload the sewing machine head, not only the labor intensity of employees can be reduced, but also the output can be increased, and the potential risk of products in the production process can be reduced. The sewing machine head produced by robot can not only guarantee the machining accuracy, but also reduce the scrap rate greatly. The product consistency and quality are far better than the products produced by man.