3D Information Extraction And Welding Path Trajectory Planning Of Multi-layer Multi-pass Welds

With the rapid development of our country’s aerospace,shipbuilding,construction,railway and other industries,the application of medium and heavy plates in these fields is becoming more and more extensive.At present,manual welding generally has the shortcomings of low labor efficiency and unstable product quality.Although the use of robots can carry out multi-layer and multi-pass welding of medium and heavy plates,its"teaching-reproducing"method still requires a large amount of time and labor costs.If the point cloud technology is applied to the welding process,the production efficiency and product quality can be greatly improved.Therefore,applying 3D point cloud information to multi-layer multi-pass welding path trajectory planning can effectively solve the above problems,and the scheme has practical significance for the research of multi-layer multi-pass automatic welding.In this paper,the test scheme is designed by using the quadratic regression orthogonal combination,and the regression equation of the weld bead width,excess height,cross-sectional area,welding speed and welding current of CO₂ gas shielded welding is established.The significance and fit of the equation were tested.A groove point cloud information collection system was built,and the RANSAC algorithm was used to fit the point cloud data of the V-shaped groove with bottom welding.The normal vector calculated by the principal component analysis method completes the point cloud segmentation and obtains the three-dimensional information of the weld.According to the formula of the cross-sectional area of the weld bead,the process parameters of the backing welding are designed,and a groove filling scheme is designed independently.On the premise of the position of the first weld bead,the plate thickness is used to correct the number of layers of the weld bead;it is preset that the two adjacent weld beads are arranged according to a certain coverage ratio,and the scale factor is adjusted by the groove width of this layer to complete the groove.The two limit angles of the center line of the welding torch are determined,and the collision between the welding torch and the side wall of the groove is avoided by means of a uniform transition between the two angles.The robot simulation model is established by using the Matlab robot toolbox,and the changes of the robot joint angle and the motion trajectory of the end effector are analyzed.The feasibility of the multi-layer multi-pass welding path planning scheme is verified.This paper uses Python language to develop and design a multi-layer multi-pass welding path planning program on the PyQt platform.First,import the regression equation of welding seam forming size and process parameters,and three-dimensional information of welding seam point cloud.Then input data such as groove size and welding process parameters actually required in production.Planning results such as number,limit angle of the center of the welding torch,coordinates of the start and end points of the weld bead,etc.In this paper,a multi-layer and multi-pass welding test is carried out for the established path planning model.The results show that the actual number of layers and the number of passes are the same as the planning scheme.Under the influence of welding deformation,except for the coordinates of the last bead of each layer,all have small errors,thus verifying the reliability of the path planning scheme.