Automatic generation of interference-free five-axis sweep scanning paths for inspection of impeller blades

The traditional blade inspection methods generally suffer from the drawback of low efficiency due to the inefficient measurement motion manner of point-by-point probing. Although the emerging five-axis scanning probing could tremendously boost the inspection efficiency by adopting the advanced probing apparatus, the existing five-axis scanning path generation methods either require an empirical segmentation of the measured surface or totally ignore the interference-free constraint. Thus, they could not be applied to the inspection of impeller blades. This paper proposes an algorithm to automatically generate the interference-free five-axis sweep scanning path for inspection of impeller blades with the considerations of both the interference-free constraint and the geometric characteristics of the blade surface. First, the blade surface is segmented into several simple patches according to the curvature analysis. Then, each surface patch can be re-parameterized by the rectangular conformal mapping and four middle parametric lines are extracted as the candidate guiding curves. The optimal guiding curve is selected from the candidates according to its length and the interference-free constraints. Finally, the sweeping path on each surface patch and the transition path between patches are generated according to the optimal guiding curve. The experiments carried out on a centrifugal impeller and an axial impeller validate the effectiveness of the proposed method. The advantage of the proposed method is also verified by comparing with a leading commercial software ApexBlade, which needs lots of trial-and-error to generate the correct inspection path.