Development of 1 CNC system at home and abroad
With the rapid development of computer technology, the traditional manufacturing industry has begun a fundamental change. Developed countries have invested heavily in the research and development of modern manufacturing technology and put forward a brand-new manufacturing model. In modern manufacturing system, numerical control technology is the key technology, which integrates microelectronics, computer, information processing, automatic detection, automatic control and other high and new technologies. It has the characteristics of high precision, high efficiency and flexible automation, and plays a decisive role in realizing flexible automation, integration and intelligence in manufacturing industry. At present, the numerical control technology is undergoing fundamental changes, from the dedicated closed-loop control mode to the universal open real-time dynamic full closed-loop control mode. On the basis of integration, the numerical control system has realized ultra-thin and ultra-miniaturization; On the basis of intelligence, it integrates computer, multimedia, fuzzy control, neural network and other multidisciplinary technologies. The numerical control system realizes high-speed, high-precision and high-efficiency control, and can automatically correct, adjust and compensate various parameters in the machining process, thus realizing online diagnosis and intelligent fault handling. On the basis of networking, CAD/CAM is integrated with CNC system, and machine tools are networked to realize centralized control of group control machining.
For a long time, China's numerical control system is a traditional closed architecture, and the numerical control system can only be used as the motion controller of non-intelligent machine tools. The variables of machining process are preset in the form of fixed parameters according to experience, and the machining program is compiled manually or through CAD/CAM and automatic programming system before actual machining. There is no feedback control link between CAD/CAM and CNC, and CNC is only a closed open-loop actuator in the whole manufacturing process. In complex environment and changeable conditions, machining parameters such as tool combination, workpiece material, spindle speed, feed speed, tool path, cutting depth, step length and machining allowance can not be dynamically adjusted in real time according to external interference and random factors in the field environment, and the set values in CAD/CAM can not be randomly corrected through feedback control, thus affecting the working efficiency of CNC machine tools and the machining quality of products. It can be seen that the fixed program control mode and closed architecture of the traditional numerical control system have restricted the development of numerical control to multivariable intelligent control, and have not adapted to the increasingly complex manufacturing process. Therefore, it is imperative to reform the numerical control technology.
2 CNC technology development trend
2. 1 performance development direction
(1) High speed, high precision and high efficiency are the key performance indexes of mechanical manufacturing technology. Due to the adoption of high-speed CPU chip, RISC chip, multi-CPU control system and AC digital servo system with high-resolution absolute detection elements, and effective measures to improve the dynamic and static characteristics of machine tools, the high speed, high precision and high efficiency of machine tools have been greatly improved.
(2) Flexibility includes two aspects: flexibility of numerical control system itself, modular design of numerical control system, large functional coverage and strong tailoring, which can easily meet the needs of different users; The flexibility of the group control system, the same group control system can automatically and dynamically adjust the logistics and information flow according to the requirements of different production processes, thus maximizing the efficiency of the group control system.
(3) The complexity of working procedures and multi-axis compound machining with the main purpose of reducing working procedures and auxiliary time are developing to multi-axis and multi-series control functions. The process compounding of NC machine tool refers to the compound machining of multi-process and multi-surface by automatic tool changing, rotating spindle head or turntable after the workpiece is clamped on the machine tool once. Siemens 880 system can control 24 shafts.
(4) Real-time Intelligentization The early real-time system is usually aimed at a relatively simple ideal environment, and its role is how to schedule tasks and ensure that tasks are completed within the specified time limit. Artificial intelligence, on the other hand, tries to use computational models to realize various intelligent behaviors of human beings. With the development of science and technology, real-time system and artificial intelligence are combined with each other, artificial intelligence is developing towards a more realistic field with real-time response, and real-time system is also developing towards a more complex application with intelligent behavior, thus creating a new field of real-time intelligent control. In the field of numerical control technology, the research and application of real-time intelligent control are developing along several main branches: adaptive control, fuzzy control, neural network control, expert control, learning control, feedforward control and so on. For example, the numerical control system is equipped with self-adaptive adjustment systems such as programming expert system, fault diagnosis expert system, automatic parameter setting, automatic tool management and compensation, etc., and functions such as advance prediction and budget, dynamic feedforward are introduced into the comprehensive motion control during high-speed machining, and fuzzy control is adopted in the pressure, temperature, position and speed control, so that the control performance of the numerical control system is greatly improved, thus achieving the purpose of optimal control.
2.2 Functional development direction
(1) User Interface Graphical user interface is a dialogue interface between CNC system and users. Because different users have different requirements for interface, the workload of developing user interface is huge, and user interface has become one of the most difficult parts in computer software development. At present, the Internet, virtual reality, scientific computing visualization and multimedia technology also put forward higher requirements for user interface. Graphical user interface greatly facilitates the use of non-professional users, and people can operate through windows and menus, which is convenient for blueprint programming and rapid programming, three-dimensional color three-dimensional dynamic graphic display and graphic simulation.
(2) Visualization of scientific computing Visualization of scientific computing can be used to process and interpret data efficiently, so that information exchange is no longer limited to words and languages, but can directly use visualization information such as graphics, images and animations. The combination of visualization technology and virtual environment technology further broadens the application fields such as drawing-free design and virtual prototype technology, which is of great significance for shortening product design cycle, improving product quality and reducing product cost. In the field of numerical control technology, visualization technology can be used in CAD/CAM, such as automatic programming design, automatic parameter setting, dynamic processing and display of tool compensation and tool management data, visual simulation demonstration of machining process, etc.