Research On Direct Generation Of NC Machining Tool Path Based On Point Cloud

Traditional reverse engineering needs surface reconstruction or triangular patch model to generate tool path from the obtained point cloud data.Tool path planning is carried out on the reconstructed surface model.But the process of surface reconstruction is cumbersome and time-consuming.The accuracy of reconstructed surface can not be guaranteed.The tool path planning of point cloud directly skips the step of surface reconstruction and shortens the time of tool path planning,which has become the current research focus of reverse engineering.This paper studies the direct generation of tool path from point cloud data,including point cloud data acquisition,data preprocessing,rough machining tool path planning,finishing tool path planning and post-processing simulation verification.The main research results of this paper are as follows:(1)Taking the upper surface of the mouse as the research object,the profilometer measurement scheme is designed and measured.The obtained scanning line point cloud data are denoised by radius filtering and the four point judgment method proposed in this paper.It is concluded that the four point judgment method is more suitable for scanning line point cloud denoising.The KD tree structure is established to judge the threshold of disordered point cloud for noise reduction,and the octree structure of point cloud is established to downsample the point cloud data,which provides high-quality point cloud data for subsequent tool path planning.(2)A rough machining tool path planning method based on point cloud is proposed.The point cloud is layered.The point cloud of each layer is divided into two-dimensional grids.The point cloud cutter plane composed of grids is calculated by row cutting method.This method is simple and suitable for rough machining tool path generation of uncomplicated point cloud data.(3)A tool path planning method for residual finishing such as point cloud is proposed.For the scattered point cloud,the five axis tool path planning of ring milling cutter is carried out.Firstly,the local coordinate system is established at the tool contact of the current tool path line and the local coordinate system at the tool contact is calculated.Then,the theoretical residual height point is calculated according to the geometric shape and residual height of the tool during cutting.The residual height calculated from the points corresponding to the theoretical residual height in the local contour point set is the actual residual height.Finally,the adjacent tool contacts are calculated from the geometric relationship.Compared with the traditional method of sequential calculation using point cloud contour point set,this method greatly reduces the amount of calculation and improves the calculation efficiency.(4)In order to verify the correctness of the tool path planning method for rough and finish machining proposed in this paper,the post-processing and simulation verification of NC machine tool are studied.MATLAB is used for programming to convert the tool position file generated in the previous chapter into G code for NC machining.Finally,simulation experiments are carried out with VERICUT software to verify the effectiveness and rationality of the algorithm in this paper.