Study on 3D tool compensation algorithm for NC milling

Modern CNC machining centre are often equipped with powered tool magazine to enable radial or axial drilling, tapping or milling operations. If the machine tool is equipped with a rotatable and controllable C axis (spindle), milling for complex curved surface can be implemented. In this kind of NC machining, 3D tool compensation is an important way to get an exact surface. This is usually realized by programmer using appropriate G code to specify the coordinates of the point to be machined and giving the normal vector on the surface at that point. In this paper an algorithm for 3D compensation vectors is presented. For the purposes, the three points on 3D space are projected to the vertical plane along the normal vector of the intermediate point, and 2D tool compensation vectors are found by means of tool path offset. Then the last 3D tool compensation vectors are achieved by carrying out an inversion calculation. The post processing system of 3D tool compensation for NC milling is introduced as well, and the algorithm is verified to be correct by simulation software.