Kinematic analysis of cylindrical coordinate CNC machine in integral impeller machining

The purpose of this study is to research a new impeller machining method that can improve a machine tool's rigidity and reduce its machining cost. This paper presents and analyzes the structure model and kinematic configuration of a novel machine tool from the viewpoint of mechanism. The machine tool, which is called a cylindrical coordinate CNC machine, consists of two linear motion axes, one rotational axis and two auxiliary axes used to adjust the spindle's posture, which are fixed during machining. By traversing every sampling point selected from an impeller's blade, the corresponding feasible region of the spindle's posture can be found in each sampling point. The common feasible region is obtained based on all these feasible regions. Then the spindle's posture can be confirmed in this common feasible region. The motion of the CNC machine is calculated by using the proposed algorithm to machine impellers. And the simulation of an impeller's machining is completed in software VERICUT to verify the cylindrical coordinate CNC machine and the relevant algorithm. For this impeller, the feasible value of the machine tool's B' is between -5° and 9°, the relevant value of C' is between -3° and 3°. The torus is used to calculate the cutter path which is simulated in VERICUT. The simulation result shows that, 95% of the machining region's undercut is less than 0.02 mm, which means this method is useful in impeller machining. It is believed that this methodology of using the novel cylindrical coordinate CNC machine for impeller manufacturing is workable and valuable in the manufacturing industry.