Generation principle of consistent toolpath for precision smoothing curved blades

Abstract

Achieving high-precision and uniform material removal in robotic grinding of blades remains a critical challenge in aerospace manufacturing. A major contributing factor is that existing toolpath planning methods fail to consider the flexible contact characteristics and tangential discontinuities in belt grinding, leading to uneven material removal. To address these challenges, a consistent toolpath generation method with corner smoothing is introduced for robotic belt grinding. First, cutter-contact points are discretized using an optimized constant chord height strategy and adjusted according to contact constraints. Then, the row spacing direction is determined through an iterative search algorithm to ensure uniform overlap between adjacent toolpaths. To further eliminate residual height errors, a dual-constraint interval contraction algorithm is introduced to accurately locate and suppress peak residual height regions on the blade surface. In addition, a Pythagorean-Hodograph (PH) spline-based corner smoothing algorithm is developed to effectively utilize error constraints, thereby improving the robotic feed rate at blade corners. Finally, robotic grinding experiments on turbine blades were conducted to validate the effectiveness of the proposed method. The results showed that consistent toolpath generation (CPG) method outperforms Iso-parametric toolpath generation (IPG) method with improvements of up to 41.67 % in root mean square error (RMSE) and 26.07 % in normalized root mean square error (NRMSE) across blade surfaces. Furthermore, quadratic row spacing planning led to 26.83 % and 30.77 % reductions in blade RMSE and peak-to-valley (PV) across four sections compared to without planning. Additionally, corner smoothing led to reductions of 55.95 % in root mean square (RMS) and 54.99 % in PV waviness errors compared to the unsmoothed surface.