PHOTOGRAMMETRY APPLIED FOR INSPECTION OF ADDITIVE MANUFACTURED COMPONENTS

Abstract

. Three-D scanning methods can be used to reconstruct a part for different industrial purposes, varying from reverse engineering to dimensional inspection of a gas turbine. A wide variety of scanners is available, classified as active or passive sensors. In active sensors, as in laser scanning, energy is transmitted to the scene and the reflected energy is recorded. In contrast, passive sensors do not transmit energy but use natural light available to acquire information. An example of a technique that uses this last type of sensor is photogrammetry. Photogrammetry is an optical measurement technique that is used to obtain the geometry, displacement, and deformation of a structure using photographs. This technique can be used in several fields, such as medicine, biological sciences, civil construction, archeology and general inspection. Additive manufactured components require a strict inspection process before going into service, which demands qualified professionals, incurring into extra expenses to attest their integrity. Since the first stage of the process is visual inspection, this study presents the application of photogrammetry technic to inspect Wire Arc Additive Manufactured (WAAM) components. A 3D model is generated using a commercial DSLR camera combined with an open-source software, and it is compared with another one generated with a commercial laser scanning system. The accuracy of the photogrammetry system was 0.144 mm, from which 0.104 mm was due to the average measurement deviation between the models and 0.040 mm from the inner accuracy of the laser scanning system, making it adequate to inspect a 115 mm diameter component. The photogrammetry model was the only one that had color representation and, since small discontinuities that do not present large geometrical variations can be identified through the surface colors, this is fundamental for visual inspection. This study should also serve as stimulus for other researchers and engineers to use remote visual inspection through 3D models and virtual reality (VR).