A generic approach to recognising isolated, nested and interacting features from 2D drawings

Many useful three-dimensional (3D)-feature recognition systems have been developed over the past few decades. However there is a shortage of feature recognition systems in the two-dimensional (2D) domain. This has an adverse effect on the realisation of CADCAM benefits in Small and Medium Enterprises. Here is an attempt to redress this deficit. This paper presents a hint-based feature recognition system which recognises machining features from 2D orthographic projections through a two-stage process of profile searching and feature completion. Three types of profiles: Type I, II or III are defined in this system. Together they are sufficient to describe most profiles, if not all, in any 2D drawing. Profile searching identifies these profiles while feature completion establishes the cavity emanating from these profiles using a multi-level top–down approach. This process enables the system to deal with the isolated, nested and interacting features using a common framework. The nested features are handled by applying the same reasoning used for isolated features recursively while interacting features are decomposed automatically by the process of profile searching into their constituent isolated features.