The Aero-engine Blade Surface Inspection Based On 3D Scanned Point-cloud Analysis

Aero blades are the key components in aero-engine. The performance of engine is mostly determined by the blades, geometric accuracy as well as surface quality. How to inspect and evaluate form error of blade surface accurately and effectively has become an urgent key issue in the field of aero-engine manufacturing. In this paper, the 3D scanned point-cloud analysis technology for aero-engine blade surface is studied. A inspection and evaluation software for forging blade surface is developed on the basis of these studies. The specific research including:First, the commonly used methods of data collection for blade surface measurement are introduced. The FARO ScanArm portable measuring system with the data collection process is investigated in detail. The collected point-cloud is handled by Geomagic Qualify software, as well as denoising and simplification. The principle of point-cloud matching is studied intensively. The coarse matching is completed by Principal Component Analysis(PCA) algorithm to provide the ideal initial point-cloud. To improve the matching accuracy, a modified Iterative Closest Point(ICP) algorithm is proposed, and the modified ICP algorithm is compared with the traditional ICP algorithm on match effect.After that, section of point-cloud is extracted, which is handled by string elevation difference method and curvature of sampling method. In order to provide the ideal initial point-cloud for parameter extraction, the longest chord of section point-cloud is extracted, and the section is adjusted by the longest chord. Algorithms to extract the characteristic parameters of blade surface( such as trailing edge, middle arc, maximum thickness, etc.) are proposed. Compare with the traditional method, these algorithms are verified excellent on the accuracy and efficiency.Then, the method to adjust forging die by inspection result of die forging blade surface is studied. The calculation method of allowance distribution is recommended, and for unqualified blade, the error of blade section(insufficient pressure, lateral displacement) is extracted. The insufficient pressure and lateral displacement of blade section is analyzed, and the parameters for forging die adjustment are calculated. The allowance distribution after forging die adjustment is compared with that before the adjustment. The results show that our method is effective.Finally, on the basis of research on matching method of point-cloud, characteristic parameters extracting of blade surface, and adjustment method of forging die, the die forging blade inspection and evaluation software is developed through Visual C++, QT platform. The software include function module such as data import, point cloud matching, error calculation, the cross section analysis and report output. The functional module, operation method and the output report of the software is presented by taking a forging blade measurement for example.