Spiral tool path generation based on symbolic computation for machining of non-axisymmetric curved surface

Abstract

Bent mandrel, which consists of non-axisymmetric curved surface (NACS), has been widely used as precise mold in automobile industry, shipping industry, and aviation industry. To improve the versatility and efficiency of turning method of the NACS with fixed rotational center, a machining method of non-axisymmetric curved surface using symbolic computation is proposed in this paper. A spiral tool path generation approach in non-axisymmetric turning process (NATP) is developed as well to deal with the error of part-to-part repeatability in existed machining model. The actual cutter-contact points are obtained from the approach of spiral sweep process using equal-arc-length segment principle in polar coordinate system. The tool offset, which is used to avoid the interference between tool and workpiece, is also considered in the machining model. In the NATP, the model of CNC lathe is established based on machine kinematics, and the inserted cutter is mathematically modeled considering both its geometrical model and the positioning of the insert. Depending on the spindle rotational angle, the synchronized control of X-axis, Z-axis, and C-axis is adopted to generate the tool path of the NATP. NC program has been generated using symbolic computation method according to the presented model, including calculation of cutter-location points and generation of 2D tool path of cutting process. With the approach of a bent mandrel taken as an example, the experiment results have verified that the machining method is appropriate for the NACS