Automated retrieval and comparison of sheet metal parts

With the number of 3D CAD models increasing rapidly, retrieving models of similar parts has become an important activity as existing designs may contain vital information regarding design and manufacturing. This paper is targeted at retrieving and comparing sheet metal parts. In the method proposed herein, the general shape of a sheet metal part is represented by a simplified hierarchical tree wherein the nodes represent the planar walls of the part and feature-related information is attached to these nodes as textual attributes. A shape index is derived from this simplified tree and subsequently used to retrieve similar parts from the database. The retrieved parts are assessed for their similarity with the enquiry part using five criteria: the general shape of the part, bends and their direction, feature types, feature location and feature size. In addition to determining the degree of similarity, the main advantage of the proposed method is that the assessment provides useful feedback to design and manufacturing engineers based on these five criteria. A prototype system developed in C++ has been tested on a database containing a few hundred parts and the effectiveness of the proposed method in retrieving and comparing the parts is discussed.