Study On Path Planning Of Multi-layer And Multi-pass Robotic Welding For Thick Plate

With the maximization of welded structures,the application of thick plates has increased greatly.At present,the commonly used manual welding production methods have problems such as low welding productivity and poor stability of quality.Intellectualization and automation are the development directions of the manufacturing industry.Therefore,intelligent robot welding is an effective method to solve this problem.And the key to the robotic multi-layer and multi-pass welding of thick plate is the planning of welding process parameters and welding paths.Thus this paper studied the planning of welding process parameters and welding paths in detail.The relationship between welding process parameters and weld bead geometry parameters such as weld cross-section area,melting width,and bead height is the basis for welding path planning.The single-pass deposition is used in this paper,and the welding process test plan was designed by quadratic general rotational regression method.The regression equation model between melting width,bead width,cross-section area of CO2 gas shielded welding bead and welding current,welding speed has been established,according to the test results.Then,the fitting,saliency,and significance of the regression coefficients of the regression equation were tested.This paper established a welding path planning model for V-groove and single-sided V-groove basis on the equal height strategy.The model includes parameters such as torch position,dip angle,swing and welding current.It achieves the goal of only two different cross-sectional area welding beads were used in per layer to complete the entire groove filling,avoiding frequent changes in welding process parameters.In order to solve the problem of the welding torch inclines to touch the side wall of the groove in thick plate welding,the model of welding torch wall impingement was established,which lays a foundation for the design of the thick plate groove and the adjustment of the dip angle of the welding torch when the welding torch touches the groove.In order to solve the problem of deformation and groove size change of thick plate during welding,this paper proposes a dynamic welding path planning which considering welding deformation.The general idea is to plan the weld bead location of the next layer according to the present welding deformation.In this paper,two methods for determining the welding deformation are given.One is based on the material mechanics theory.The bending angle of the workpeice is calculated according to the welding heat input and the current weld bead restraint intensity,and the welding path of next layer is planned with the current groove angle.The second way is to use laser vision detection system to capture the groove features image which formed by the line laser scanning.The distance between the two points at the top of the cross section of the groove is calculated through computer image processing.According to the distance and the total height of the present welding seam,the current groove angle is calculated,so as to realize the welding path planning of the next layer.This paper built the Python+PyQt5+Eric6 program development platform,and designed the planning software of welding process parameters and bead location by Python language.The user inputs the information such as the thickness of the plate,the shape and size of the groove,the the software calculates the planning results of the position of the arching point,dip angle of the welding torch,the swing amplitude,etc.Then the software will give the appropriate welding process parameters such as welding current and welding speed according to the according to the requirements of the weld forming.At the same time,the software imports Matplotlib and Numpy modules,display the planning results in a graphical form by the codes which makes the results more intuitive.The Python's own Openpyxl module outputs the planning results in Excel form which input into robot controller and form data of control commands.