Research on the real meshing clearance distribution of conical dry screw vacuum pumps

The reliability of dry screw vacuum pumps constitutes a critical factor governing the performance of vacuum systems, particularly within the semiconductor industry. Rational clearance design hinges on a comprehensive understanding of the actual clearance distribution between rotors under the combined effects of machining and assembly errors, rotor thermal deformation, and axis motion. This paper first establishes sensitivity analysis models for these influencing factors on meshing clearance, tailored to screw rotors with Quimby-Tooth and Double-Cycloid profile structures, respectively. Subsequently, the influence mechanisms of the aforementioned factors on rotor clearance and leakage area are systematically elucidated. The quantitative results reveal that the axial assembly error (Z-axis) exhibits the highest sensitivity, with a sensitivity coefficient of approximately 1.0, especially in small-pitch regions. Under the combined influence of machining and assembly errors, the minimum meshing clearance of the Double-Cycloid profile is found to decrease from the initial 0.150 mm to 0.082 mm, representing a 45.3% reduction and posing a significant scuffing risk. Furthermore, compared to the ideal design state, the total leakage area increases by 22.3% for the Quimby-Tooth profile and 25.1% for the Double-Cycloid profile. These findings provide a theoretical basis for the high-precision compensation and tolerance optimization of conical screw rotors.