Analytical design of a special whirling cutter for a flawless cutting of the concave cycloid profile in whirling milling for various types of vacuum pump screw rotor

A vacuum pump mainly consists of intermeshing screw rotors, which apply a cycloid profile to enhance the operating performance. However, it yields a concave rotor profile, increases the machining difficulty, and requires precision accuracy in the manufacturing process. This study proposes an analytical design of a particular whirling cutter and the rotor cutting method considering double tilt angles and assembly offset setting. The cutting simulation is demonstrated in analytical methods and virtual machining for various vacuum pump screw rotors. The analytical cutting result indicates that the overall lengthwise rotor profile deviation is identical. Besides, the virtual machining result indicates that the tooth surface topology is smooth and uniform, and the maximum profile deviation is still much more undersized than the grinding allowance. Moreover, the proposed method is still reliable for various vacuum pump rotors of Kashiyama type, Quimby type, Hanbell Precise Machinery P series, and Hanbell Precise Machinery P series with clearance design, where their delta deviations consistently tinier than 0.1 mm. Finally, it verifies that the proposed analytical design of the whirling cutter design, utilization of double tilt angles, and assembly offset setting are reliable for various vacuum pump rotors applying whirling milling machining.