The development trend of CNC machining

Since the emergence of numerical control technology in the middle of the 20th century, numerical control machine tools have brought revolutionary changes to the machinery manufacturing industry. CNC machining has the following characteristics: good processing flexibility, high processing precision, high productivity, reduce the labor intensity of the operator, improve working conditions, is conducive to the modernization of production management and the improvement of economic benefits. It is suitable for processing multi-variety small batch child parts, parts with complex structure and high precision requirements, parts that need frequent modification, key parts that are expensive and do not allow scrapping, parts that require precision reproduction, parts that need to shorten the production cycle and parts that require 100% inspection. The characteristics of CNC machine tool and its application range make it an important equipment for the development of national economy and national defense construction.

Entering the 21st century, China's economy is fully integrated with the international community and has entered a new period of vigorous development. Machine tool manufacturing industry is facing the opportunity for the development of manufacturing equipment caused by the improvement of the demand level of machinery manufacturing industry, and also encountered the pressure of fierce international market competition after joining the World Trade Organization, accelerating the development of CNC machine tools is a key to solve the sustainable development of machine tool manufacturing industry. With the large demand for CNC machine tools in the manufacturing industry and the rapid progress of computer technology and modern design technology, the application range of CNC machine tools is still expanding, and it continues to develop to better meet the needs of production and processing. This paper briefly analyzes the development trend of CNC machine tools such as high speed, high precision, compound, intelligent, open, network, multi-axis and green, and puts forward some problems existing in the development of CNC machine tools in our country.

The development trend of CNC machine tools

1 High speed

With the rapid development of automotive, national defense, aviation, aerospace and other industries and the application of new materials such as aluminum alloy, the requirements for high-speed CNC machine tool processing are getting higher and higher.

(1) Spindle speed: the machine adopts electric spindle (built-in spindle motor), and the maximum spindle speed is 200000r/min;

(2) Feed rate: When the resolution is 0.01μm, the maximum feed rate reaches 240m/min and the complex surface can be accurately processed;

(3) Computing speed: The rapid development of microprocessors provides a guarantee for the development of CNC systems to high-speed and high-precision direction, and the development of CPU has been developed to 32-bit and 64-bit CNC systems, and the frequency has been increased to hundreds of megahertz and thousands of megahertz. Due to the greatly improved operation speed, the feed speed of up to 24-240m /min can be obtained when the resolution is 0.1μm and 0.01μm.

(4) Tool change speed: At present, the tool exchange time of foreign advanced machining centers has generally been about 1s, and the high has reached 0.5s. The German Chiron company designed the knife library as a basket style, with the spindle as the axis, the tool is arranged in the circle, and the knife to the knife change time is only 0.9s.

2 High precision

CNC machine tool accuracy requirements are now not limited to static geometric accuracy, machine tool motion accuracy, thermal deformation and vibration monitoring and compensation more and more attention.

(1) Improve the control accuracy of the CNC system: high-speed interpolation technology is used to achieve continuous feed with tiny program segments, so that the CNC control unit is refined, and high-resolution position detection device is used to improve the position detection accuracy (Japan has developed an AC servo motor equipped with 106 pulse/revolution built-in position detector, The position detection accuracy can reach 0.01μm/ pulse), and the position servo system adopts feedforward control and nonlinear control methods.

(2) The use of error compensation technology: the use of reverse clearance compensation, screw pitch error compensation and tool error compensation technology, the thermal deformation error and space error of the equipment comprehensive compensation. The results show that the application of comprehensive error compensation technology can reduce the I addition error by 60%~80%.

(3) The grid decoder is used to check and improve the motion track accuracy of the machining center, and the machining accuracy of the machine tool is predicted by simulation to ensure the positioning accuracy and repeated positioning accuracy of the machine tool, so that its performance is stable for a long time, and it can complete a variety of processing tasks under different operating conditions, and ensure the processing quality of the parts.