From 1952, MIT developed the first experimental numerical control system, and it has been 46 years since then. Numerical control system from the initial electron tube, has experienced the following development stages:
Discrete transistor type-small scale integrated circuit type-large scale integrated circuit type-small computer type-very large scale integrated circuit type-microcomputer numerical control system. In the 1980s, the overall development trend was: the numerical control device developed from NC to CNC, and 32-bit CPU was widely used to form a multi-microprocessor system; Improve the integration of the system, reduce the volume, and adopt a modular structure, which is convenient for cutting, expanding and upgrading functions to meet the needs of different types of CNC machine tools; The driving device is developing in the direction of AC and digitalization; Numerical control devices are developing towards artificial intelligence; Adopt a new automatic programming system; Enhance communication function; The reliability of numerical control system is constantly improving. In a word, the technology of CNC machine tools is constantly developing, with more and more perfect functions, more and more convenient use, higher reliability and higher cost performance. By 1990, professional manufacturers of numerical control systems around the world will produce about130,000 sets of numerical control systems every year. The overall development trend of foreign numerical control system technology development is:
1, the new generation CNC system adopts open architecture.
Since 1990s, due to the rapid development of computer technology, the technology of CNC machine tools has been updated faster. Many CNC system manufacturers in the world use PC's rich software and hardware resources to develop a new generation of CNC systems with open architecture. The open architecture makes the numerical control system more universal, flexible, adaptable and extensible, and develops in the direction of intelligence and networking. In recent years, many countries are researching and developing this kind of system, such as NGC, "Next Generation Workstation/Machine Tool Controller Architecture" led by NCMS in the United States, "Open Architecture in Automation System" in Europe, and OSEC plan in Japan. The research results have been applied. For example, Cincinnati-Mielack Dragon Company has adopted the open architecture A2 100 system in its manufacturing centers, CNC milling machines, CNC lathes and other products since 1995. The open architecture can adopt the advanced technology of a large number of general microcomputers, such as multimedia technology, to realize automatic programming of voice control and graphic scanning. The numerical control system is developing in the direction of high integration, and more transistors can be integrated on each chip, making the system smaller, smaller and miniaturized. The reliability is greatly improved. Using the advantages of multi-CPU to realize automatic troubleshooting; Enhance communication function, improve incoming line and networking ability. The hardware, software and bus specifications of the new generation CNC system with open architecture are all open to the outside world. Due to the availability of sufficient software and hardware resources, it not only strongly supports the system integration of CNC system manufacturers and users, but also brings great convenience to the secondary development of users, and promotes the development and wide application of multi-grade and multi-variety CNC systems. It can not only form various grades of CNC systems through upshifting or cutting, but also form CNC systems of different types of CNC machine tools through expansion. This numerical control system can be upgraded with the upgrade of CPU without changing the structure.
2. The control performance of the new generation CNC system is greatly improved.
Numerical control system is developing towards intelligent control performance. With the penetration and development of artificial intelligence in the computer field, the control mechanism of adaptive control, fuzzy system and neural network is introduced into the numerical control system, which not only has the functions of automatic programming, feedforward control, fuzzy control, learning control, adaptive control, automatic generation of process parameters, three-dimensional tool compensation, dynamic compensation of motion parameters and so on. It also has a friendly man-machine interface and fault diagnosis expert system, which improves the functions of self-diagnosis and fault monitoring. The intelligent spindle AC drive and intelligent feed servo device of the servo system can automatically identify the load and automatically optimize and adjust the parameters. The linear motor drive system has been put into practical use.
In a word, the technical level of the new generation of CNC system has been greatly improved, which has promoted the development of CNC machine tools in the direction of high precision, high speed and high flexibility, and continuously improved the technical level of flexible automatic processing.
Second, the development trend of CNC machine tools
In order to meet the needs of the market and the development of science and technology, and meet the higher requirements of modern manufacturing technology for numerical control technology, at present, the development trend of numerical control technology and its equipment in the world is mainly reflected in the following aspects:
1, high speed, high efficiency, high precision and high reliability.
To improve the machining efficiency, firstly, the cutting and feeding speed should be increased, and at the same time, the machining time should be shortened. In order to ensure the machining quality, it is necessary to improve the accuracy of the motion trajectory of machine tool components, and reliability is the basic guarantee to achieve the above objectives. Therefore, high-performance numerical control equipment is needed as a guarantee.
(1) high speed and high efficiency
The development of high-speed machine tools can give full play to the performance of modern tool materials, which can not only greatly improve the machining efficiency and reduce the machining cost, but also improve the surface machining quality and accuracy of parts. Ultra-high speed machining technology is widely used in manufacturing industry to achieve high efficiency, high quality and low cost production.
A new generation of CNC machine tools (including machining centers) can further improve productivity only by greatly shortening cutting time at high speed. Ultra-high-speed machining, especially ultra-high-speed milling, is closely related to the development and application of a new generation of high-speed CNC machine tools, especially high-speed machining centers. Since the 1990s, Europe, the United States and Japan have been scrambling to develop and apply a new generation of high-speed CNC machine tools to speed up the development of high-speed machine tools. High-speed spindle unit (motorized spindle, rotating speed15000-100000 r/min), high-speed and high-acceleration/deceleration feed moving parts (fast moving speed 60~ 120m/min, cutting feed speed up to 60m/min), high-performance numerical control and servo system, numerical control tool system, etc. With the solution of a series of key technologies in the technical field, such as ultra-high-speed cutting mechanism, ultra-hard and wear-resistant long-life tool materials and abrasives, high-power and high-speed motorized spindle, high-speed acceleration and deceleration linear motor driving feed parts, high-performance control system (including monitoring system) and protection device, we should seize the opportunity to develop and apply a new generation of high-speed CNC machine tools.
Relying on the fast and accurate digital quantity transfer technology, the executive parts of high-performance machine tools are processed in real time with high precision and high response speed. Due to the adoption of new tools, the turning and milling cutting speed has reached more than 5000 m ~8000 m/min. Spindle revolutions are above 30,000 rpm (some as high as 65,438+million rpm); Table moving speed: (feed speed), when the resolution is 1 micron, it is above 100 m/min (partially to 200 m/min), and when the resolution is 0. 1 micron, it is above 24 m/min; The automatic tool changing speed is within 1 s; The feed speed of small interpolation reaches 12m/min. According to the demand of high efficiency and mass production, the rapid development of electronic drive technology and the popularization and application of high-speed linear motors, a number of high-speed, high-efficiency and high-speed response CNC machine tools have been developed to meet the needs of automobile, agricultural machinery and other industries. In addition, due to the accelerated cycle of new product upgrading, the parts processed in the industries such as mold, aviation and military industry are not only complicated but also increased in variety.
(2) High accuracy
The development from precision machining to ultra-precision machining (ultra-high-precision machining) is the direction that all industrial powers in the world are committed to. Its accuracy ranges from micron level to sub-micron level, even nanometer level (at present, the requirements for high accuracy in mechanical processing are: the ordinary machining accuracy is doubled to 5 microns; The precision machining accuracy has been improved by two orders of magnitude, and the ultra-precision machining accuracy has entered the nanometer level (0.00 1 micron). The spindle rotation accuracy is required to reach 0.0 1~0.05 micron, the machining roundness is 0. 1 micron, and the machined surface roughness Ra=0.003 micron.
Precision is to meet the needs of high-tech development, but also to improve the performance, quality and reliability of ordinary electromechanical products, reduce the workload during assembly and improve assembly efficiency. With the development of high technology and the improvement of performance and quality requirements of electromechanical products, machine tool users have higher and higher requirements for machine tool machining accuracy. In order to meet the needs of users, in recent 10 years, the machining accuracy of ordinary CNC machine tools has been improved from 10μ m to 5μ m, and that of precision machining centers has been improved from 3 ~ 5μ m to1~1.5 μ m. ..
(3) High reliability
It means that the reliability of the numerical control system is more than one order of magnitude higher than that of the controlled equipment, but it is not that the higher the reliability, the better, but it is still moderately reliable, because it is a commodity and is restricted by cost performance. For an unmanned factory with two shifts a day, if it is required to work continuously and normally within 16 hours, the failure-free rate P (t) = 99% or more, and the average failure-free running time MTBF of CNC machine tools must be greater than 3000 hours. When the MTBF is more than 3000 hours, there will be great differences in unmanned chemical plants composed of different numbers of CNC machine tools. For only one CNC machine tool, if the failure rate ratio between the host and the CNC system is 10: 1 (the reliability of CNC is one order of magnitude higher than that of the host). At this time, the MTBF of CNC system will be greater than 33,333.3 hours, and the MTBF of CNC device, spindle and drive must be greater than 65,438+million hours.
At present, the MTBF value of foreign numerical control devices has reached more than 6000 hours, and the driving device has reached more than 30000 hours.
2. Modularity, intelligence, flexibility and integration
(1) Modularization, specialization and personalization
Modularization of machine tool structure, specialization of numerical control function, remarkable improvement of machine tool cost performance and accelerated optimization. In order to adapt to the characteristics of multi-variety and small batch of CNC machine tools, the machine tool structure is modular, the CNC function is specialized, the cost performance of the machine tool is significantly improved, and the optimization speed is accelerated. Personalization is a particularly obvious development trend in recent years.
(2) intelligence
Intelligent content includes all aspects of the numerical control system:
-In order to pursue the intelligence of machining efficiency and machining quality, such as adaptive control, process parameters are automatically generated;
-In order to improve the driving performance and intelligent connection, such as feedforward control, adaptive operation of motor parameters, automatic load identification, automatic selection and self-tuning;
-Simplify programming and simplify the intelligence of operation, such as intelligent automatic programming and intelligent man-machine interface;
Intelligent diagnosis, intelligent monitoring, convenient system diagnosis and maintenance, etc.
(3) Flexibility and integration
The development trend of CNC machine tools to flexible automation system is: from point (CNC single machine, machining center, CNC compound machining machine tool) and line (FMC, FMS, FTL, FML) to surface (workshop independent manufacturing island, FA) and body (CIMS, distributed network integrated manufacturing system), on the other hand, it pays attention to application and economy. Flexible automation technology is the main means for manufacturing industry to adapt to dynamic market demand and update products quickly. It is the mainstream trend of manufacturing development in various countries and the basic technology in advanced manufacturing field. Its key point is to improve the reliability and practicability of the system, aiming at easy networking and integration; Pay attention to the development and perfection of unit technology; CNC stand-alone machine develops in the direction of high precision, high speed and high flexibility; CNC machine tools and their flexible manufacturing systems can be easily connected with CAD, CAM, CAPP and MTS, and will develop towards information integration. Network system is developing towards openness, integration and intelligence.