Research On Key Techniques Of Open CNC System Based On STEP-NC

With the rapid development of numerical control technology, openness, intelligent, standardization, network, high speed and high precision has become a main trend in the development of numerical control system. But current NC system still use IS 06983 (G, M code) as the NC programming data interface, the programming interface does not include any other information other than the tool motion information, has become the bottleneck of blocking manufacturing system information integration, and seriously restricts the development of numerical control system and manufacturing. To this end, a new NC programming interface standard STEP-NC have been proposed, which is an extension of the STEP standard to NC machining field, its core idea is to implement the standardization of product information description and integrity. With the appearance of STEP-NC, it is not only laid a solid foundation for the realization of the intelligent and flexible and open CNC system, but also for the exchange and sharing of information between CNC system and other systems.With the continuous development and perfection of STEP-NC, how to apply STEP-NC standard in the development of numerical control system, and how to implement STEP-NC technology, overcome the shortcoming of ISO6983, meet the demand of the development of advanced numerical control system, is still a problem to be resolved at present numerical control field. First, the open architecture of intelligent CNC system was researched Based on STEP-NC data model, the related key technologies for STEP-NC NC system were studied, and through the simulation, experiment and comprehensive analysis to verify the proposed method and technology. It provides a theoretical basis for the construction of STEP-NC CNC system, and the realization of the STEP-NC technology. The main research contents are as follows:(1) Discusses the background of the thesis and STEP-NC NC system key technology development present situation at home and abroad, by analyzing the problems existing in the current numerical control system, and STEP-NC influence on numerical control technology and manufacturing, pointed out the necessity and frontier of the new type of open CNC system based on STEP-NC and its key technology.(2) In view of the openness of STEP-NC NC system, respectively from the hardware system, software system, the data model to solve. Using the "PC + PMAC" embedded dual CPU hardware architecture to solve the problem of the openness of the hardware system; Based on the layered architecture of scheduling software, is used to solve the problem of the openness of the software system, and simplify the development of the numerical control system. The STEP-NC data model to construct the numerical control system, from the aspect of data model to solve the problem of the open the numerical control system.(3) In view of feed speed fluctuation of the NURBS curve direct interpolation, using adaptive correction interpolation algorithm to control the calculation precision of interpolation points, the simulation experiment results show that the proposed algorithm can reduce the interpolation feed rate volatility and improve the interpolation precision. For NURBS direct interpolation feed speed planning, the calculation is complex, in order to solve this problem, use the feed speed planning method based on the feed speed pretreatment curve, reduce the amount of computing tasks in real-time interpolation cycle, so as to improve the real time interpolation, to obtain more smooth feed speed curve.(4) For the problems of the large amount of calculation, low machining efficiency and the inconsistent machining accuracy in the five-axis machining tool path planning of complex parametric surface, use the tool path planning method based on iso-phote line, reduced the amount of calculation, at the same time improve the efficiency and accuracy. Use the five-axis machining tool interference detection method based on coordinate transformation, to solve the problem of the traditional distance test method, which is the large amount of calculation, low efficiency. And greatly reduced the amount of calculation in the process of detection, improve the processing efficiency.(5) For NURBS curve’s evaluation and derivative calculation is complex, NURBS fast recursion method based on B-spline basis function matrix was proposed, reduced calculation of the NURBS curve interpolation algorithm and tool path planning algorithm and improve the performance of the interpolation.(6) Established the machinability evaluation system of STEP-NC NC machining program, to determine whether a target machine tool meet the processing requirements. On this basis, the cooperative particle swarm optimization algorithm with adaptive parameter to multi-objective optimization of machining parameters was proposed, which exert the maximum performance of machine tool, at the same time improve the machining efficiency and machining accuracy.