At present, the development of CNC machine tools is changing with each passing day. High speed, high precision, compound, intelligent, open, parallel driven, networked, extreme and green have become the trend and direction of CNC machine tools. As a large manufacturing country, China mainly relies on its comparative advantages in labor, price, resources and so on. However, there is still a big gap between China and its foreign counterparts in technological innovation and independent development of products. China's numerical control industry can't be content with the current situation. It should seize the opportunity to develop continuously, strive to develop its own advanced technology, increase the strength of technological innovation and talent training, improve the comprehensive service ability of enterprises, and strive to shorten the gap with developed countries. Strive to realize the transformation of CNC machine tool products from low-end to high-end, from primary product processing to high-end product manufacturing as soon as possible, and realize the transformation from made in China to created in China, from a manufacturing power to a manufacturing power.
1. High speed
With the rapid development of automobile, national defense, aviation, aerospace and other industries, as well as the application of aluminum alloy and other new materials, the requirements for high-speed CNC machining are increasingly high.
(1) Spindle speed: the machine adopts the electric spindle (built-in spindle motor), and the maximum speed of the spindle is up to 200000 R / min;
(2) Feed rate: when the resolution is 0.01 μ m, the maximum feed rate is 240 m / min and the precise machining of complex profile can be achieved;
(3) Operation speed: the rapid development of microprocessors provides guarantee for the development of CNC system in the direction of high speed and precision. The CPU has been developed into 32-bit and 64 bit CNC system, and the frequency has been increased to hundreds of megahertz and thousands of megahertz. Because of the great improvement of the operation speed, when the resolution is 0.1 μ m and 0.01 μ m, the feed speed of 24-240m / min can still be obtained;
(4) Tool change speed: at present, the tool exchange time of foreign advanced machining centers is generally about 1s, and the high speed is up to 0.5s. Chiron company of Germany designed the tool magazine as a basket style, with the spindle as the axis and the cutter arranged in the circle. The tool change time from cutter to cutter is only 0.9s.
2. High precision
The requirement of the accuracy of CNC machine tools is not limited to the static geometric accuracy. More and more attention has been paid to the kinematic accuracy, thermal deformation and vibration monitoring and compensation of the machine tools.
(1) Improve the control accuracy of CNC system: adopt high-speed interpolation technology, realize continuous feeding with micro program section, refine CNC control unit, and adopt high-resolution position detection device to improve the position detection accuracy (Japan has developed AC servo motor with 106 pulse / revolution built-in position detector, whose position detection accuracy can reach 0.01 μ M / pulse), position servo system Feedforward control and nonlinear control are adopted;
(2) The error compensation technology is adopted: the reverse clearance compensation, screw pitch error compensation and cutter error compensation are used to compensate the thermal deformation error and space error of the equipment. The results show that the machining error can be reduced by 60% ~ 80% by using the comprehensive error compensation technology;
(3) The grid 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, so as to ensure the positioning accuracy and repeated positioning accuracy of the machine tool, make its performance stable for a long time, complete a variety of machining tasks under different operating conditions, and ensure the machining quality of parts.
3. Function compounding
The meaning of compound machine tool is to realize or finish as many elements processing from blank to finished product as possible on a machine tool. According to its structural characteristics, it can be divided into two types: process composite type and process composite type. Process compound machine tools such as boring milling drilling compound machining center, turning milling compound turning center, milling boring drilling compound machining center, etc.; process compound machine tools such as multi-faceted multi axis combined machining compound machine tool and dual spindle turning center, etc. The compound machine tool is used to process, which reduces the auxiliary time of workpiece loading and unloading, replacing and adjusting the cutting tool and the error in the middle process, improves the machining accuracy of the parts, shortens the manufacturing cycle of the products, improves the production efficiency and the market reaction ability of the manufacturers, and has obvious advantages over the traditional production method with scattered working procedures.
The compounding of machining process also leads to the development of machine tool to modularization and multi axis. The latest Turning Center launched by index company of Germany is a modular structure, which can complete turning, milling, drilling, hobbing, grinding, laser heat treatment and other processes, and complete all the processing of complex parts. With the continuous improvement of modern machining requirements, a large number of multi axis CNC machine tools are more and more welcomed by major enterprises. In 2005 China International Machine Tool Exhibition (CIMT2005), manufacturers at home and abroad exhibited various multi axis machining machines (including double spindle, double tool rest, 9-axis control, etc.), five axis high-speed gate machining center and five axis high-speed milling center which can realize 4-5 axis linkage, etc.
4. Intelligent control
With the development of artificial intelligence technology, in order to meet the development needs of manufacturing industry production flexibility and manufacturing automation, the intelligent degree of CNC machine tools is constantly improving. Specifically reflected in the following aspects:
(1) Adaptive control technology of machining process: by monitoring the cutting force, power, current, voltage and other information of spindle and feed motor in the process of machining, traditional or modern algorithm is used to identify the stress, wear, damage state of cutter and the stability state of machining, and the machining parameters (spindle speed, feed) are adjusted in real time according to these states
(2) Intelligent optimization and selection of machining parameters: Based on the experience of process experts or technicians and the general and special laws of part machining, the "intelligent optimization and selector of machining parameters" based on expert system or model is constructed by using modern intelligent method, and the optimized machining parameters are obtained by using it, so as to improve programming efficiency and machining process level, and shorten production preparation time Purpose;
(3) Intelligent fault self diagnosis and self repair technology: according to the existing fault information, the application of modern intelligent methods to achieve rapid and accurate fault location;