Ultra-precision machining technology has become an important symbol of a country's manufacturing technology, an important pillar of advanced manufacturing technology and the key to improving the level of manufacturing technology.
Ultra-precision CNC machine tools, which are the basis of ultra-precision machining technology, have also been widely used in the processing of defense industry, information industry and civil products. They have become the key processing equipment for priority development in various countries. All countries have kept the CNC technology as the core of machine tools confidential. To ensure its superior position in the manufacturing field.
Developed countries such as the United States, Britain, Germany and Japan have developed ultra-precision CNC machine tool processing technology as an important strategy for developing national manufacturing technology, and have made great achievements. Although China has carried out a lot of research on ultra-precision numerical control technology, several institutions have developed ultra-precision CNC machine tools, but they cannot meet the demand for ultra-precision processing equipment in aerospace industry and civil electronics industry. Precision CNC machine tools still rely mainly on imports, especially the large-scale ultra-precision CNC machining equipment that can process parts larger than 600mm. Therefore, it is urgent to develop extremely relevant technologies for such ultra-precision CNC machine tools to fill the gap and improve the technical level of large-scale ultra-precision parts processing in China.
2 The hardware structure of the CNC system and the processing information sent by the bookmark1 carrier, after calculation and processing, control the machine tool to perform the machining task. The numerical control device adopts FANUC-18I, which has the characteristics of fast response and high precision. Its CPU is 32-bit count. When the full stroke is 600mm, the minimum pulse equivalent can reach 1nm. Therefore, the resolution of the numerical control system mainly depends on The detection feedback system, the high-speed serial communication interface FSSB protocol is selected between the numerical control device (CNC) and the servo unit, which can reduce the influence of external interference and minimize the connection cable; the AI ​​(artificial intelligence) nano contour control module is selected. Nano-interpolation of lines and arcs is possible without any special hardware. NURBS curve interpolation modules are also used to obtain a smooth surface that is closer to the shape of the part design and improve interpolation accuracy. Reduce the pressure on high-speed transmission of large-capacity small blocks.
The servo motor of the X and Z axes and the friction wheel drive motor of the C1 axis of the table are all selected from the ai series motor. The servo drive is controlled by high-speed and high-precision HRV (HighResponseVector) and has high-precision current detection capability, enabling high-speed, high-precision, and stable feed.
The feed axes X and Z adopt the double feedback strategy. The speed feedback is realized by the photoelectric encoder mounted on the servo motor. The position feedback is realized by the precision grating of Heidenhain and the frequency conversion card is selected. The position resolution reaches 40nm or more, which makes the resolution of the whole CNC servo system better than 50nm. This system is designed to provide the supporting CNC system for the "large-scale aspherical optical parts ultra-precision machine tool" that meets the technical requirements. Double-column and double-beam vertical gantry structure for X-axis and Z-axis simultaneous machining. The maximum stroke of the X-axis is 600mm, and the maximum stroke of the Z-axis is 200. The rotary table is driven by a friction wheel. The maximum diameter of the machined workpiece is 01000mm, the machining accuracy is better than 2Um, and the resolution of the CNC system is required to be 50nm. To meet the requirements of industrialization and practical use of ultra-precision CNC machine tools, the numerical control system of the numerical control system uses FANUC-18I as the CNC device of the system. The hardware structure is as shown.
The numerical control system of this ultra-precision machine tool is mainly composed of industrial PC, numerical control device (CNC), X, Z axis servo feed system, position 'feedback system, worktable feed system and spindle feed system 6 .
The numerical control device is the core of the numerical control system, and its function is to accept the reserved machine: bed and automatic processing technology (600mm), high resolution (50mi) index requirements, and can be artificial artificial nanometer contour control and high precision NURBS Interpolation.
3 CNC system software structure and function The software control management technology of bookmark4 ultra-precision machine tool numerical control system is its key technology.
In order to realize the openness and real-time of the system, a set of relatively complete control software for CNC machine tools has been developed, which has functions such as document management, numerical control programming, parameter setting, numerical control machining, machining simulation and fault diagnosis. The software flow diagram of the entire system is shown.
Control processing - I processing simulation - Li Shengyi and so on. Ultra-precision machine tool and its new technology development "J1. National Defense Science and Technology" 2 Xie Xuhui et al. Research on computer numerical control system of ultra-precision diamond machine tool "J. China Mechanical Engineering, 1998 (2) "3 Wang Jianxin, etc. Ultra-precision lathe control system The development of "J. China Mechanical Engineering, "4 spelling. Computer-aided geometric design and non-uniform favorable B-spline (CAGDNURBS) "M. Beijing: Beijing University of Aeronautics and Astronautics Press, 1994 1973-), Hunan, Beijing Institute of Technology Ph.D. student at the School of Mechanical and Vehicle Engineering. (Editor Li Xiumin) Process diagram of the automatic programming system for ultra-precision CNC machine tools
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