Research On Laser Cladding Path Optimization Method Of Complex Surface Based On Streamline Field

Remanufacturing is one of the best ways to recycle the resources of electromechanical products.China has initially formed a remanufacturing development model with the main technical features of "size recovery and performance improvement".Laser cladding is one of the most important processes in laser remanufacturing,for example,the aero-engine blade has realized large-scale laser cladding remanufacturing,and the path planning is a very important technology in the laser cladding remanufacturing on complex surfaces.However,the existing size recovery method often appears problem which conclude oversizing or surface accuracy cannot meet the requirements of cooperation.Starting from the control of dimensional accuracy and material saving(enhancing efficiency),it is of great significance to make reasonable planning of the cladding path on complex surfaces.Considering that the streamline field concept can be used to find the local optimal solution which combines geometric information(part surface)and mechanical information(laser nozzle feeding direction),the surface can be divided into different regions by using the intrinsic topological relationship of the streamline field.When the roughness accuracy requirement is satisfied,the cladding path is generated in each area,which will partially improve laser cladding efficiency.In this thesis,the path planning on the complex surface is the optimization goal.Based on the derivation of the waviness method and the relationship between the surface quality and the overlapping ratio,the method of path generation based on streamline field theory method has been studied.Besides,some related theoretical calculations and experimental verification has been conducted.So the main content of the thesis is summarized as follows:(1)For the problem that there is no clear index parameter in laser remanufacturing,the concept of surface waviness of molten layer is studied to quantify the cladding surface quality.Starting from the single-track cross-section profile,the recursive method is used to derive the profile equation of the multitrack laser cladding;the theoretical value of the roughness(surface waviness)is calculated by determining the least squares centerline of the clad profile,which is verified by experiment.(2)An ISO-resudual depth method for generating laser cladding path is proposed.By determining the relationship between the residual depth of the clad and the parameters of the single channel profile and the curvature of the surface,an appropriate path interval is calculated so that it can eventually form a uniform waviness(roughness).Facing the 3+2 axis laser cladding platform,the fuzzy surface clustering method is used to divide the surface into different plane-like regions,and the residual depth cladding paths are generated in each region.The spherical coordinate system is applied to visualize the normal vector at the center of the cluster,and this is used as the orientation of the displacement table so that the laser cladding processing path planning for the complex curved surface under discrete five axis platform can be realized.(3)In order to further optimize the cladding path on the complex surface,based on the previous research,combined with the concept of streamline field,a path planning model of additive manufacturing method on complex surface is established,and generate the optimal laser cladding feed direction on the complex surface.Then the least square method is applied to fit the streamlines of the directional field as the basis of the path re-planning.First,the topological structure of the flow field can be obtained;then the rest of the cladding path can be generated by the offsetting of chosen streamline.Finally,the effect of the path planning is verified through the simulation of visualizing waviness on the surface.The complete laser cladding path should include the position and posture information.In the end,the paper try to explore the influence of the laser nozzle pose on the clad profile.The relationship between the laser nozzle and the substrate(the laser beam axis and the substrate normal vector does not coincide)is divided into three cases,and the corresponding mathematical model is proposed to derive the relationship of tilt angle with cladding width,height and the highest point shifting.Finally,the reliability of the parameters prediction of the formula are verified by experiments,which provides a research basis for the post-laser cladding path optimization in posture.