Enhancing formability via reciprocating counter-roller spinning: Dynamic coordination of complex flexible return path

Abstract

To address the inherent trade-off between high performance and insufficient precision in the conventional counter-roller spinning (CRS) process, a novel reciprocating counter-roller spinning (RCRS) methodology is proposed, featuring coordinated control between the working path and a complex flexible return path. Crucially, the return stroke is transformed from an idle movement into a "dynamic compensation path" with active error-correction capability, fully leveraging the trajectory flexibility inherent in CRS to achieve path-level dynamic correction of forming errors. To realize this, a flexible return path optimization model based on ideal shape discrepancy compensation is established. A multi-objective optimization framework correlating the compensation coefficient k with geometric accuracy is developed. The optimal path design is achieved using the non-dominated sorting genetic algorithm (NSGA-II) on a Kriging surrogate model. Furthermore, an adaptive return path interpolation program is developed by integrating MATLAB and Mastercam, ultimately enabling the high-quality integrated forming of geometric precision and mechanical properties in cylindrical workpieces. Simulation and experimental results demonstrate significant improvements: The average straightness L and maximum outer generatrix contour deviation ΔD_R of formed parts are remarkably enhanced from the 10⁻¹ to the 10⁻² level, representing improvement rates of 71.38 % and 77.37 %, respectively. This effectively resolves the "precision bottleneck" of CRS. Although localized stress state changes occurred in the "inner concave" correction zone due to intensified material flow, the overall forming performance showed a clear enhancement over the original blank. Microstructural analysis further revealed a uniform {001}< 100 > texture and η-fiber structure. The primary strengthening mechanism is identified as dislocation multiplication and entanglement induced by geometrically necessary dislocation density ρ_GND. These results provide verifiable theoretical mechanisms and a key technical pathway for promoting the application of highly flexible CRS in high-precision manufacturing.