Direct toolpath generation from pointcloud input

Abstract

An efficient method of direct machining has been developed. The method takes advantages that generate the toolpath directly without the construction of the surface patch. In traditional reverse engineering approach, the product will be scanned into a set of the scattered data. Based on these information, the surface fitting process are implemented. The process is a time-consuming work. The cutter path can be generated through the resultant profile. Obviously the surface fitting process plays an important role in the overall reverse engineering process. Therefore the goal of the research is the direct cutter path generation that free of the surface re-construction. In this research, the algorithms of direct 3-axis and 5-axis machining have been studied. The essential criterion for both algorithms is the definition of the cutter location (CL). In the area of 3-axis machining, based on the massive scanned data, the cutter location can be found by the intersection among two spheres and the cutter-moving plane. Two spheres are generated from two data points that located at both side from the cutter location plane. The radius of two spheres is identical to the cutter radius. In the application of direct 5-axis machining, the definition of the cutter location is similar to 3-axis machining. It uses three points to define the sphere (cutter) position. However, regarding to the properties of the 5-axis machining, the tool axis direction should align with the surface normal at any instantaneous position. Thus, the triangular apparent facet is engaged to approximate the normal direction. Then the apparent normal can be approximated by the vector that connected from the intersection point among spheres, to the facet in perpendicular direction. After the CL points are fixed, the circular arc spline can be employed to fit the data points as machining toolpath. The arc splines can direct input to the NC machine. It can save the time in pre-processing.