Unfolding sheet metal parts: a graph-based approach

Abstract

In sheet metal fabrication, bending is used in order to obtain rigidity and to obtain a part of desired shape and function. In analysing a sheet metal part, an important consideration is how to unfold the part after a bending operation or series of bending operations. The unfolding process is the first major step in process planning for generating NC paths for a sheet metal blank. This paper addresses the problem of determining whether or not a part can be unfolded. A graph-based approach using the face-edge of the sheet metal part is at the heart of the algorithm presented here. Using this algorithm one can determine which faces are unfoldable and which cannot be unfolded. This algorithm can be used to help facilitate the process of NC path generation. It also sheds some light on the kind of design practices that make a part easily unfoldable or otherwise.