Methodology for comparison of laser digitizing versus contact systems in dimensional control

Abstract

The massive acquisition of points in a very short inspection time has converted the scanning with laser triangulation sensors an adequate technology for reverse engineering activities. However, industry is demanding complementary uses for this technology, such as applications in the scope of dimensional measurement control of mechanical parts. A drawback arises in the scope of metrological applications—validity of laser scanning has not been tested in terms of accuracy for geometric and dimensional tolerance control. This paper studies the accuracy that can be achieved with these systems in the field of dimensional control. The methodology includes the comparison of two scanning technologies, laser scanning and contact scanning, considering the latter one as the reference system. The scope of this study is the measurement of surfaces based on canonical features: planes, spheres, cylinders (both outer and inner holes) and conical surfaces (countersink and counterboring holes). For the research, several devices have been designed, which include diverse form features. Reconstruction of surfaces and subsequent comparison with nominal geometry has been carried out using different CAD systems in order to analyze the convergence of results among them. Additionally, this research analyzes several issues that arise when making the comparisons, such as the setting up of a common reference system for the alignment of surfaces or the scanning strategies.