Research On United Planning Of Welding Trajectory And Parameters Of Welding Robot For Intersecting Pipes

At present,tubular intersecting structures are widely used in offshore oil platforms,shipbuilding,steam pipelines and pressure vessels for thermal power generation.The weld formed by tubular intersecting structure is a space curve weld.The shape of weld groove is irregular and varied which puts forward special technological requirements for multi-pass welding of robot.So,it is of great value for engineering application to develop and research the robotic welding method of complex curve weld.This paper realizes the united planning of welding trajectory and parameters of welding robot for intersecting pipes.It can solve the problem of overfilling or deficiency of weld caused by the uneven change of groove shape in multi-layer and multi-pass welding.It can reduce or avoid the repair welding and secondary machining of this complicated weld effectively.In this paper,aiming at the intersecting structure of pipes with weld inclination ? less than 30 °,the weld model and groove model were established.The attitude of welding torch and trajectory were planned,and the feasibility of welding trajectory was verified by virtual simulation.A novel planning method in which the weld was divided into several segments according to the change rate of cross-sectional area was put forward in this paper.It is guaranteed that the change rate of cross-sectional area of each section relative to the whole weld is equal and the maximum change rate of cross-sectional area of each section of weld is within the range of 15%.It was effective to avoid repair welding and secondary processing for such complex joints.By controlling the welding parameters in each segment,the amount of filler metal varies with the cross-sectional area of weld groove,thus the number of weld passes kept unchanged in each layer and the appearance of the weld remained flat.For each segment,the appropriate welding parameters were identified according to the target value of the size of welding seam through the second order regression prediction model which is related to the width and height of weld seam,respectively.In addition,the uphill and downhill welding tests were carried out on workpieces with different dip angles by single factor test method.The influence of workpiece dip angle on weld pool width,length,area,rear drag angle and weld forming was analyzed by high-speed camera.It is proved that when the inclination of weld is less than 30°,the influence of weld inclination on weld formation can be neglected and the change rate of cross-section area of groove is the main factor affecting weld formation.Finally,the feasibility of the welding trajectory was verified by virtual simulation.Welding experiment was carried out and the actual welding seam was basically consistent with the planning results.The error between the planned value and the test value of the cross-section area of weld seam is less than 15%.It was proved that the planning method for sectional welding of the welding seam according to the variation of cross-sectional area is feasible and can be applied to practical welding engineering.