Measurement of Axial Orientation of Film Cooling Holes Based on a Laser Sensor

The axial orientation of a film cooling hole of an aero-engine turbine blade is one of the main factors affecting the cooling effect. However, due to the characteristics of free-form surfaces, small diameters of cooling holes and the machining error of EDM, measurement of the axial orientation of a film cooling hole is quite difficult on a manufacturing site. Many turbine blade manufacturing companies still use visual judgement assisted by gauge rods manually. The manual inspection is problematic and is not fully capable of giving accurate and reliable results. Thus, this paper proposes a method for measuring axial orientations based on an improved Gaussian image algorithm. First, a point cloud is obtained through a laser scanning sensor. Then, to address the problem of low accuracy of normal vector in traditional Gaussian image algorithms, small number of measured point clouds, and poor planar fitting accuracy, a Gaussian image transformation algorithm based on normal vector characteristics is proposed, which takes cylindrical generatrices into consideration. Further, an augmented normal vector algorithm and a planar fitting algorithm are also included. Finally, based on Geomagic and actual detection experiments, the algorithm is verified for its feasibility, accuracy, and reliability. Experimental results show that the extraction accuracy of the algorithm in the axial orientation can reach 0.6304 °.