Design And Experiment Of Welding Robot With Welding Seam Tracking Function For Roller

The pressing roller is one of the core components of the seeder,and its demand is very large.Its stable performance is the key to ensure efficient pressing operation during sowing.The press roller is mainly composed of a press roller and a shaft.At present,in Xinjiang agricultural machinery manufacturing enterprises,the press roller mainly adopts manual welding.This operation method has low welding efficiency and high labor intensity,which makes it difficult to meet the market demand.Today’s semi-automatic welding equipment,due to the lack of weld tracking function,will lead to the deviation of the trajectory of the welding torch in the Y-axis direction from the actual weld to be welded,and the deviation of the welding wire of the welding torch from the height of the roller,resulting in the stability of the field operation of the roller cannot be guaranteed.In order to solve the problems of low efficiency,low intelligence and unstable welding quality caused by manual welding and semi-automatic equipment welding,this paper designs a set of roller welding robot with weld tracking function.The following are the main research contents and results of this paper:（1）Two weld seam recognition and tracking schemes are designed for comparison,which are based on machine vision and laser displacement sensor.According to the comprehensive performance comparison of production cost and recognition accuracy,the weld recognition and tracking scheme based on laser displacement sensor is determined.Simufact welding software was used to compare and analyze the influence of triangular welding path,circular welding path and sawtooth welding path on the weld pool morphology and temperature field distribution under two different welding speed process parameters.It is concluded that the welding simulation effect is the best when the process parameters are triangular welding path and welding speed of 15mm/s respectively.According to the t_8/5at the welding speed of 15mm/s and30mm/s,and combined with the welding CCT diagram of Q235 steel,it can be seen that at the welding speed of 15mm/s,the hardness of the press roller is 195 HV,and the microstructure is a mixture of ferrite,pearlite and bainite.The welding simulation results provide technical support for the control of process measures in the manufacturing process of the welding robot.（2）The whole structure of the welding robot is designed,including the frame,three-axis displacement compensation mechanism,welding torch and laser displacement sensor fixture.The dynamic theory analysis of X,Y and Z three-axis displacement compensation mechanism is carried out,and the polygon effect analysis is carried out.Through the calculation of the linear transmission movement error of X,Y and Z three axes,it is concluded that the linear motion error in X axis direction is 35.4μm,the linear motion error in Y axis direction is 19.2μm,and the linear motion error in Z axis direction is 27.7μm.（3）The model parameters of key components such as PLC,communication module,laser displacement sensor and actuator are determined by analysis.According to the requirements of weld tracking,the scheme of real-time weld tracking is designed.Based on the software LJ-Navigator of laser displacement sensor,the corresponding conditions are configured,and the design of control program is completed,including the design of control main program,communication program,manual operation program,automatic control program and HMI man-machine interface.（4）According to the design scheme,the prototype is developed,and the weld tracking test and welding performance test are carried out.According to the seam tracking test,it is concluded that the end of the welding torch of the welding robot always moves along the S-shaped seam trajectory.During the whole seam tracking process,the welding robot runs stably under the guidance of the laser displacement sensor without jitter.The system can complete the seam tracking task stably and efficiently.According to the national standard DL/T 868-2004 welding procedure qualification procedure,the appearance of the weld after welding of the press roller is analyzed,and the working performance is compared with manual welding and semi-automatic welding equipment.It is concluded that the welding efficiency of the press roller welding robot with weld tracking function can reach 2-3 times that of manual welding,and 25-30press rollers can be welded per hour.The weld is well formed and can meet the needs of practical engineering.