This paper introduces the concept of STEP AP203(STandard for Exchange of Product model data) an ISO standard as a neutral format for exchange of CAD model data between different CAD/CAM systems, and how STEP AP 203 data is stored and how the feature information can be extracted and recognized from STEP file. In this paper a hybrid (graph and rule) based approach is used to recognize the features of mechanical prismatic parts. The Attribute Adjacency Graph (AAG) and Attribute Adjacency Matrix (AAM) approaches are used to recognize the form features, and rule based approach is used to recognize assembly features.The proposed methodology in this paper has been completely implemented by designing an integrated system called STEP-based Assembly Sequence Planning (ST-ASP) system. The (ST-ASP) system is built by using Visual Basic 6.0 supported by Solid works 2011 package and implemented on (HP Pavilion dv6) PC. The (ST-ASP) system is directed to 3D prismatic parts. The form features explored in this system include both depression and protrusion features, and the assembly mating relations explored in this system include; against, fit, and insert which is used in recognize assembly features. Finally the system has been tested to carry out a case study to demonstrate the feasibility of the proposed methodology.
Keywords:STEP, feature recognition, form feature, assembly feature, mating relations, attribute adjacent graph (AAG).