Research On The Algorithm Of Generating Mould NC Program By Point Cloud Directly

Study on the algorithm of generating mould NC program by point cloud directly is areverse engineering method of generating mould NC program by scattered point cloud data onthe part surface without any topological relationship directly. The surface reconstruction basedon point cloud data has been done in the process of the traditional reverse engineering firstly,surface fitting, triangulation to construct the surface model, and then the tool path in NCmachining based on the curved surface model was generatied, and then the NC machining Gcode of parts was generatied. But the traditional processing method of reverse engineering is arelatively cumbersome and time-consuming process, it is very easy to cause the surfacemodeling error and it is difficult to ensure the accuracy. In order to improve the precision andefficiency of the reverse engineering, more and more researchers begin to study on thealgorithm of generating mould NC program by point cloud directly.The two kinds of main data acquisition method of point cloud was introduced firstly inthis paper. The pretreatment process of point cloud data was introduced briefly.Accordingto the existing pretreatmented point cloud data of parts, the principal component analysis,covariance matrix to calculate the local surface of point cloud was used, the minimumeigenvalue of feature vectors should be the normal vector of the local surface. The globalsurface normal vector of mould was producted by the method of vector’s reverse and bias ofsurface.The algorithm of directly generating constant scallop-height tool path for point clouds isproposed. The method of the coordinate transformation from the work piece coordinate systemto the machine tool coordinate system were introduced and the workpiece coordinatesystem of cutter location data—the tool center and tool axis orientation were transformed tothe machine coordinate system, and then the NC machining G code of mould was generatedultimately.