| Over the last 60 years, there have been a great development in CNC technology. However, the traditional NC program is still based on G&M code(ISO 6893) that was established in the early time. This process-oriented programming method has become the bottleneck of the CNC technology. To overcome this bottleneck, the new CNC programming Interface, known as STEP-NC, is being developed to provide a feature-oriented programming method. STEP-NC program was based on STEP(ISO 10303), contains the product information from design to manufacturing, provides a great opportunity to develop CAX integration and intelligent CNC system.The research in this paper is aim at STEP-NC program generation method, the main contents are as follows.The paper first introduces the EXPRESS language, Application Protocol and file structure of STEP and STEP-NC. Analysis the STEP AP203 file structure, Complete the file checker and 3D Part display function. According to object-oriented characteristic of EXPRESS language, establish C++ classes corresponding with STEP geometry entity, extract and stored geometric and topology information according certain algorithm.Combine the attribute adjacent graph (AAG) with STEP-NC manufacturing, details describe the file structure of STEP AP203, design the concave/convex algorithm based on STEP file. Extend and transform the traditional attribute adjacent matrix (AAM) to solve the defects on ambiguous expression. Then several typical STEP-NC manufacturing feature AAG and AAM was predefined, decomposition Parts’s AAM through a certain method, design certain algorithm to recognition manufacturing feature.Analysis processing data that was necessary in STEP-NC program, design feature-based process planning to finish manufacturing features process planning, establish the process repository to save the added process information; Analyzes STEP-NC program generation process, combined with the geometric information, feature information and process information obtained by the above sections to generate STEP-NC program.Finally, using VC++ to development a prototype based on above theoretical research, gives a examples of the system implementation.Then, verification was done by NIST STEP-NC program parser. |
