A high-efficient numerical control (NC) turning method for double-enveloping worms using spindle forward- and reverse-rotating strategy

Double-enveloping worms are widely used in aerospace, wind power generation, and machine tools due to their heavy carrying capacity, efficiency, and precision. However, when machining double-enveloping worms on general computerized numerical control (CNC) lathes, challenges such as low efficiency and accuracy persist. To address this issue, this paper proposes a novel process route for machining these worms using general CNC lathes. In the rough machining process, the worm surface profile at any given time is first calculated, and the cross-section of the rotating worm relative to a defined plane is determined using numerical methods. Subsequently, a constant number of cutter location (CL) points are designed within the worm groove in the cross-section. By connecting these CL points, a rough tool path is generated. Additionally, a rhomboidal cutter is innovatively employed to enhance machining efficiency. In the semi-finish and finish process, the tool paths are constructed based on the machining allowances left from the previous process. Forward and reverse spindle rotations are used to machine the working and non-working surfaces of the worm, respectively, preventing the reduction of the working relief angle during turning. Through simulations and experimental machining, this study verifies the effectiveness of the proposed method for machining double-enveloping worms on general CNC lathes.