Postprocessor algorithm and feedrate optimization for nine-axis milling machine tool with twin cutters

Abstract

Twin-tool synchronous milling is a new method for blade machining which can improve the machining efficiency obviously. It can be realized on a nine-axis machine tool with two cutters. However, the kinematic analysis and the feedrate planning are more difficult, due to the more complex structure than the traditional five-axis machine tool. In this paper, an efficient postprocessor algorithm is developed and feedrate optimization method is proposed to realize twin-tool synchronous milling. Based on a brief structure and kinematic chain analysis, the generalized kinematic model is built. Considering the characteristics that the A-axis is shared by two cutters in the nine-axis machine tool, the mathematical formulas of the motion coordinates and rotary angles are derived, which can simultaneously transform the location and orientation vectors of the two cutters into numerically controlled (NC) codes. Meanwhile, the feedrate is planned to maintain the simultaneous cutting with the two cutters, even though the displacements between adjacent cutting contact points on the opposite blade surfaces are unequal. Then, the feedrate optimization strategy is proposed to guarantee the continuity of the cutting speed; the saturation limit for each servo motor is also considered. Furthermore, the NC codes for machining a typical turbine blade are generated with the developed postprocessor algorithm, then the velocity and acceleration of each axis at different cutter-contact-point are calculated. The validity is demonstrated with simulation and experiments on a self-developed nine-axis machine tool.