Research And Realization Of Information Extraction System Based On STEP-NC

Numerical controlled program based on conventional standard ISO 6983 increasingly expose a good many disadvantage, and no information can be feed back to the CAD/CAM/CAPP. The most important reason is that no high level information (such as 3D geometry, process technology, and so on) has been included in the conventional NC program . Therefore, International Standard Committee introduce a new standard STEP-NC(STEP-Compliant Data Interface for Numeric Controls), which is used as new data interface standard of numerical controlled system. STEP-NC (ISO 14649) extends the current STEP standard into the application area of manufacturing. It helps CNC system to use data models of products in three dimensions according with STEP directly in order to output NC programs the control machines directly. STEP-NC-based NC program will include the process technology and machining information, which will overcome lots of disadvantage of the conventional ISO 6983-based NC program. STEP-NC makes information bidirectional between CNC and other CAX systems, and eliminates choke points of the information stream between CAX.Based on the newest international standard-STEP-NC, the author studies the information extraction system of STEP-NC-based NC program, the main contents are described as follows:1. After analyzing the conventional NC standard ISO 6983, the develop background and course at home and abroad has been summed up concisely. It was pointed out the research results and advantages of STEP-NC.2. The produce,develop and application of STEP was introduced, and the relationship between STEP and STEP-NC was pointed out. The STEP-NC data model and the structure of STEP-NC program was analyzed. The system composed of Standard Data Access Interface (SDAI) was expounded, and the principle of language binding was studied.3. The functioning structure and main feature of the information extraction system based on STEP-NC was introduced, and the general plan of system was finished. The object-oriented programming thought was adopted in the system, which has the extensibility and reuse.4. According to the structure feature of STEP-NC program, the interpreting course to STEP-NC program was designed, which can translate the date describing in EXPRESS language to the date that can be identified by computer. And design the date structure to store the data after being interpreted.5. The mode of data dictionary which was used to save and mange the entity information defined in STEP standard was designed, and the corresponding interfacing function was pointed out. Data matching between entity data from data dictionary and instance data from STEP-NC program was realized.6. The function of STEP-NC program information's classification and feature identity was initially realized and showed on the man machine interface. At the same time, the three-dimensional graphics display of workpiece was initially realized in OpenGL technology, and tested the ?feasibility of system.