Generic Classification and Representation of Shape Features in Sheet-Metal Parts

This chapter presents classification and representation of shape features in sheet-metal parts. Shape features in a sheet-metal part model can be associated with volume subtraction from base-sheet (e.g., piercing/blanking operation), deformation/modification of base-sheet or forming operation on base-sheet. The shape features in a sheet-metal part model are classified as (i) Volumetric features and (ii) Deformation features. These features can also be classified as ‘2-dimensional (2D) features’ (volumetric features) and ‘3-dimensional (3D) features’ (deformation features) as a result of modification and forming of base-sheet. The thickness is constant for a sheet-metal part. Hence, the shape features in a sheet-metal part are also referred as constant thickness features. The representation, classification, and extraction procedures of the sheet-metal features are based on topology and geometry. The novelty is that the proposed classification and representation of sheet-metal features is based purely on shape entities and therefore it is possible to automatically extract the features from any sheet-metal part model. This enables the use of the proposed classification and representation to be unambiguous and application independent and to handle equivalences between feature labels and their representations among applications. The definition presented for a feature can also be extended to include application specific information.