| dc.description.abstract | The screw vacuum pump utilizes a pair of interlocking screw rotors within a closed chamber to evacuate air and achieve the desired level of vacuum. It is widely used in industries such as manufacturing, the semiconductor industry, chemical processing, and biotechnology. In vacuum pumps, the screw rotors can be categorized into fixed-pitch and variable-pitch types. Compared to fixed-pitch screw rotors, variable-pitch screw rotors exhibit superior compression performance and greater design flexibility. However, due to the variation in pitch, the profile of variable-pitch screw rotors is influenced by changes in pitch, causing the instantaneous contact line to also change with the variation in pitch. This renders the use of form grinding impractical for variable-pitch rotors, thereby increasing the difficulty in the machining of variable-pitch screw rotors.
In the past, precision machining of variable pitch screw rotors typically involved the use of CNC (Computer Numerical Control) and conventional turning tools, processing the variable pitch screw rotor through several times point contacts. In contrast to the traditional method, this study proposes a machining technique utilizing a line contact approach for the tooth profile of variable pitch screw rotors. Compared to traditional machining methods, this approach completes the entire tooth profile with a single axial feed, achieving a more precise and efficient machining process.
Firstly, a general machining coordinate system for variable-pitch screw rotors is established. Based on the principle that the tooth profile of variable-pitch screw rotors remains unchanged at any rotational angle, the tooth profile of the rotor is used as the cutting edge geometry. Subsequently, numerical calculations are performed using software to solve for the variable-pitch screw rotor, and the results are compared with a standard rotor to validate the model′s accuracy. Additionally, finite element software and uniform design methods are employed to investigate the influence of tool chip grooves on the chips produced during cutting. | en_US |