Manufacturing needs in many industries, especially the aerospace and the automotive, involve CAD remodeling of manufactured free-form parts using NURBS. This is typically performed as part of 'first article inspection' or 'closing the design loop.' The reconstructed model must satisfy requirements such as accuracy, compatibility with the original CAD model and adherence to various constraints. The paper outlines a methodology for realizing this task. Efficiency and quality of the results are achieved by utilizing the nominal CAD model. It is argued that measurement and remodeling steps are equally important. We explain how the measurement was optimized in terms of accuracy, point distribution and measuring speed using a CMM. Remodeling steps include registration, data segmentation, parameterization and surface fitting. Enforcement of constraints such as continuity was performed as part of the surface fitting process. It was found necessary that the relevant algorithms are able to perform in the presence of measurement noise, while making no special assumptions about regularity of data distribution. In order to deal with real life situations, a number of supporting functions for geometric modeling were required and these are described. The presented methodology was applied using real aeroengine parts and the experimental results are presented.

Date Published: 21 March 2000
PDF: 12 pages
Proc. SPIE 3966, Machine Vision Applications in Industrial Inspection VIII, (21 March 2000); doi: 10.1117/12.380095

Published in SPIE Proceedings Vol. 3966:
Machine Vision Applications in Industrial Inspection VIII
Kenneth W. Tobin Jr.; John C. Stover, Editor(s)