Method for forming single screw compressor tooth surface mold line enveloped by poly-cylindrical mill with non-equal length

The invention discloses a method for forming a single screw compressor tooth surface mold line enveloped by poly-cylindrical mill with non-equal length. The same tooth surface bus of a screw rotor is cut repeatedly by using a poly-cylindrical milling cutter in different directions to realize poly-cylindrical envelopment of mole lines. In an engagement period of a star-wheel tooth surface and the screw rotor tooth surface, at least 2/3 of the areas on the star-wheel tooth surface mold line can contact the screw rotor tooth surface mold line, that is to say, one complete bus on the screw rotor tooth surface is a combined mold line formed by enveloping multiple points on the star-wheel tooth surface mold line. By adopting the milling of the cylindrical milling cutter, the screw rotor tooth surface with the mold line can be processed. The screw rotor enveloped by the polycylinder with non-equal length and the star-wheel mold line can ensure that the star-wheel tooth surface is in even slide engagement with the screw rotor tooth surface, particularly the star-wheel tooth forms a small leakage triangle at the engagement exit area so that the gas leakage is greatly reduced in the exhaust process of the single screw compressor.