Research On Direct Generation Of NC Tool Path From Point Cloud

Traditionally,the complex surface is modeled by Bezier triangular surface or B-spline or non-uniform rational B-spline(NURBS) first and then the planing of the tool-path is followed in reverse engineering.But this require operator's great experience. Because of this, the research on direct generation of NC tool path from point cloud has become the focuse of research in reverse engineering.What we get from the laser scanning machine are coordinates of point cloud.For lack of the topological relations among the points,this paper presents the Octree structure to create spatial data indexes to search any points in their neighborhood.Pretreatment of cloud data includes the removal of noise and the thinning of point cloud. The purpose of clouds thinning is to compress non-necessary points to reduce the later procession capacity. This paper presents string-height law to remove the noise and use the angular-height limit to reduce the points on the scanning line.The rough machining is to remove the redundant materials to get the gross profile.So the rough machining is quite different from finish machining.This paper present the layer scan method to form the rough shape from the blank.This paper presents the complete data model which includes all the datas such as the coordinates,normal vector and the local curvature radius.To get the finish machining tool path, the points are offset along the normal vector.This paper has also presented the method to interpolate the offset-points in double circular arc.The research on the direct generation of tool-path avoids the surface reconstruction,which have the advantage of simple operation,computation stability and high efficency.It follows the development trend of rapid manufacturing and has great theoretical and practical application value.