Research On Method Of Laser Cladding With Equal Overlapping For Free-Form Surface

Curved parts are widely used in industry because of good hydrodynamic and dynamic characteristics.However,it is difficult to manufacture these parts and the production cost is high due to the irregularity and complexity of the free-form parts' surface.Besides,it is hard to repair free-form parts when the surface is damaged or broken.Laser cladding technology is a new type of strengthening and repairing technology,which has the characteristics of high energy utilization rate,small thermal impact on the substrate,and good bonding between the cladding layer and the substrate.The scanning path is very important in surface strengthening and repairing by laser technology.With the development of reverse engineering technology,it has become a research hotspot that planning the laser cladding path accord to the collected point cloud data.Combining laser cladding and reverse engineering,a laser cladding path planning method for spatially complex curved surfaces is proposed in this article.This method can generate cladding paths at equal intervals,thereby ensuring the ratio of cladding layers are equal and the cladding quality is high.This article builds a free-form surface laser cladding system which is made up of laser cladding forming equipment,point cloud data acquisition and processing equipment,and independently developed path planning software.Firstly,the internal parameters of the depth camera Kinect V2 were calibrated and the point cloud data of the part was collected using the camera.The RANSAC algorithm was used to segment the point cloud data containing the surface to be processed.Then the point cloud data of the surface to be processed is projected,and the contour of the horizontal point set is used as the boundary conditions.According to the equal overlap rate laser cladding path planning algorithm proposed in this paper,a point cloud beam is fitted as the initial cladding path.A series of path points are determined on the initial cladding path.On each local contour that passes through the path points and is perpendicular to the cladding direction,a point on the next path is searched for based on the width of cladding layer and overlap rate.The searched point set is fitted as the latter cladding path,and repeat the above steps until the cladding path traverses the surface.In order to solve the problem that the fitting function cannot directly represent the cladding path,a series of points in the cladding path are selected,and VTK is used to visualize the 3D point set to visually display the cladding path.In addition,a robot model in Robotics Toolbox is established according to the D-H parameters of the robot.The joints'displacements and angular velocities are simulated in the situation of robot gripping the nozzle and keeping the axis perpendicular to the processing surface to confirm whether the robot will be limited during movement.Finally,the laser cladding experiment was carried out according to the planned cladding path and nozzle attitude,and the morphology,microstructure,hardness,thickness,and spacing of the cladding layer were analyzed.It was found that the surface of the cladding layer was bright,and there were no obvious bumps or depressions between the channels.The microstructure was fine columnar dendrites and equiaxed dendrites.The hardness of the cladding layer was greatly improved compared to the substrate.The spacing of cladding layer is equal and the overlap rate is same.