Identification of patterns of repeated parts in solid objects

The feature-based modeling approach for designing a mechanical component has been widely adopted by most CAD modelers to maintain the design intent on models. A set of higher level information is requested to enrich the usual geometrical and topological data, in terms of feature information. A well known example of semantically significant data of this type is represented by the knowledge of the existence of symmetrical arrangements of repeated subparts in CAD models. Because of the information transferring, repeated modifications of the models and different tolerances used by the various CAD systems, these specific data can be lost. In this report, after having provided the necessary mathematical background and the state of art of the existing symmetry detection methods, we propose an approach for retrieving symmetries involving a set of user-selected sub-parts in a given BRep part model. The approach is based on a preliminary analysis of the position of points (centroids), each of them representing one repeated feature; a further examination on the faces of the sub-parts is performed to confirm the existence of symmetric arrangements. We have provided the description for the detection of linear translational, reflectional, and circular translational patterns of repeated sub-parts.