Definition and recognition of rib features in aircraft structural part

摘要

In this research, a new type of manufacturing feature that is commonly observed in aircraft structural parts, known as ribs, is defined and implemented using the object-oriented software engineering approach. The rib feature type is defined as a set of constrained and adjacent faces of a part which are associated with a set of specific rib machining operations. Computerized numerical control (CNC) operation experience and the machining knowledge are leveraged by analysing typical geometry interactions when generating machining tool paths where such knowledge and experience are abstracted as rules of process planning. Then those abstracted machining process rules are implemented in a feature recognition algorithm on top of an existing and holistic attribute adjacency graph solution to extract seed faces, identify individual local rib elements and further cluster these newly identified local rib elements into groups for the ease of machining operations. Out of the potentially different combinations of local rib elements, those optimised cluster groups are merged into the top-level rib features. The enhanced recognition algorithm is presented in details. A pilot system has already been developed and applied for machining many advanced aircraft structural parts in a large aircraft manufacturer. Observations and conclusions are presented at the end.