Dual NURBS Path Smoothing for 5-Axis Linear Path of Flank Milling

Linear path is still widely used to describe the five-axis machining trajectory. Five-axis tool path consists of two parts, one trajectory describes the tool tip position, and the other one represents the second point on tool axis to define the tool orientation. The natural disadvantages of G01 path are tangential and curvature discontinuities at freeform surface, which will lead to feedrate fluctuation and accuracy decrease due to the drive constraints of machine tool. In this study, a path smoothing method is proposed to smooth and optimize the linear path by using dual NURBS curves. Firstly, according to the accuracy requirements, the tool tip spline can be fitted. Secondly, the tool orientation spline can also be obtained by a coordinate system mapping method. Then, the synchronization equation of the two spline parameters is established to achieve interpolation synchronization of cutter location points. Finally, the smoothing dual NURBS tool path can be obtained with continuous curvature to improve the surface quality, motion stability and machining efficiency. Simulations and experiments validate its practicability and reliability. This method is no need to upgrade the CAM, and also could be integrated into CAM system to perform the 5-axis path smoothing.