A Study on Applying Whirling Milling Method to Manufacture Screw Rotors for Vacuum Pumps(2/2)

Whirling milling is a kind of high-efficient machining method for the screw manufacture. In the past, the form milling with the finger- or disk-type cutter is commonly used in the screw rotor manufacture for vacuum pumps, however, it is low-productivity and difficult to machine the screw rotor with a variable lead and a variable radial depth. In view of this, in the 1st year research work, a mathematical model will be established based on the relative motion coordinate system between the whirling milling cutter and the screw rotor. The cutter body and the cutting profiles are designed using the forming method, and the motion equation for each machining axis will also be derived. At last, the validity of proposed method will be verified through the analysis of rotor profile error enveloped by the CNC cutting trajectory. In the 2nd year research, the computer-aided simulation and analysis for the CNC whirling milling of screw rotors will be practiced with extending the 1st year research basis. The normal deviation between the simulated and the target rotor surfaces will be estimated and employed in the machining error compensation through the cutting profile modification and the cutting motion adjustment in order to obtain the required meshing clearance and increase the manufacturing accuracy. Further, the tool life, cutting force and material removal ratio will be investigated to attain the most adequate machine settings. The achievements of this project will provide key technologies for developing the whirling milling machine, and a novel and high-efficient machining method to the screw rotor for vacuum pumps.