Research On STEP-NC Program Generator And Its Key Technology

STEP-NC standard is the popularization of STEP standard turning towardsmanufacturing area, which covers the whole process of a product from the roughcast tofinished production. It relies on the advantages that cover comprehensive informationand does not need post processor to become the latest research content, and how togenerate the STEP-NC program has become the first issue in the field. To solve theproblem, the method of generating STEP-NC program is studied in this thesis on thebasis of ISO14649standard.EXPRESS language, STEP Part21format and the mapping rule between theformer and the latter are introduced. Then the mapping rule between EXPRESSlanguage and C++is established. A detailed analysis and classification of the STEP-NCfile structure are described, the framework for the STEP-NC program generator is built,which is composed of feature recognition module, process planning module and outputmodule.The current commonly feature recognition tools are deeply studied, because thetwo CATIA secondary development technology provides a series of library functions,which is more simple and convenient compared with the use of the STEP files,ultimately the use of CAA for feature recognition is determined. Then the characteristicsof2.5D milling manufacturing feature are studied, feature recognition method based onthe traces is used to identify the basic features such as plane, hole, pocket, slot, and theattribute adjacent graph method is used to identify the generalized trough. Functionlibrary provided by CAA is used to calculate the length, width, position, radius anddepth of the feature. Then the process planning of using feature as unit is discussed. Thefeature of hole is cited to explain the whole process of process planning, according tothe hole diameter, roughness and degree of accuracy, the workingstep, machiningallowance and the tool are determined. Using the shortest processing time and thelowest manufacturing cost as objective functions, the cutting speed and feedrate usinghigh-speed steel cutter to drill the hole are optimizated based on the use of cutting fluidand processing materials for structural steel. Finally, the information of the featurerecognition module, the process planning module is intergated and the basic informationabout the workpiece and the relative coordinates are set to output the STEP-NC file.According to the above theory, the software is developed to realize the abovefunctions, the STEP-NC program based on ISO14649is generated. Then the experimentis done to verify the the correctness of the program and the availability of the software.