Numerical control technology refers to the use of digital instructions composed of numbers, characters and symbols to realize the action control of one or more mechanical equipment. Usually control mechanical quantities such as position, angle and speed, as well as switching quantities related to the flow direction of mechanical energy. The appearance of numerical control depends on the appearance of data carrier and binary data operation. 1908, perforated metal foil interchangeable data carrier came out; At the end of 19, a control system with auxiliary functions was invented with paper as the data carrier. During the period of 1938, Shannon carried out rapid data calculation and transmission at MIT, which laid the foundation for modern computers, including computer numerical control systems. Numerical control technology is closely combined with machine tool control and developed. 1952, the first CNC machine tool came out, which became an epoch-making event in the history of the world machinery industry and promoted the development of automation.
Now, numerical control technology is also called computer numerical control technology. At present, it is a technology to realize digital program control by computer. This technology uses a computer to execute the control function of the equipment according to the pre-stored control program. Because the numerical control device composed of hardware logic circuit is replaced by computer, the realization of various control functions such as storage, processing, operation and logical judgment of input data can be completed by computer software.
Numerical control machine tool is a kind of mechatronics processing equipment with high technical density and high automation. It is a comprehensive application of computer, automatic control, automatic detection and precision ... with high processing accuracy, easy quality assurance and very broad development prospects. Therefore, it is particularly important to master the machining programming technology of CNC lathe.
Development trend of CNC machine tools
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On April 19, I learned from the 7th China International Machine Tool Exhibition that with the continuous development of science and technology, the development of CNC machine tools is getting faster and faster, and CNC machine tools are also developing in the direction of high performance, high precision, high speed, high flexibility and modularization. High performance: With the improvement of the integration of CNC system, CNC machine tools have realized centralized control and even remote control. High precision: the precision of CNC machine tools and machined parts is getting higher and higher, and the precision retention is better. High speed: the speed of each axis of CNC machine tools will be greatly accelerated. High flexibility: the flexibility of CNC machine tools will develop towards a higher degree of automation, and management, logistics and corresponding auxiliary machines will be integrated into the flexible manufacturing system. Modularization: In order to shorten the cycle and reduce the cost, CNC machine tools must develop in the direction of modularization, which is beneficial to both manufacturers and customers. Although China's CNC machine tools have developed rapidly in recent years, there is still a certain gap with the international advanced level, mainly in poor reliability, poor appearance quality, long product development cycle and poor adaptability. In order to narrow the gap with the world's advanced level, relevant experts suggest that machine tool enterprises should focus on the following six aspects: 1. Strengthen the implementation of quality engineering to improve the trouble-free rate of CNC machine tools. 2. Keep up with the international level and make CNC machine tools develop in the direction of high efficiency and high precision. 3. Improve the development capability of complete sets of design and make breakthroughs. 4. Give full play to service advantages and expand market share. 5. Multi-variety manufacturing to meet different levels of users. 6. Modular design, shortening the development cycle and responding to the market quickly. The use of CNC machine tools is more and more extensive, and the market capacity at home and abroad is increasing, but the competition will also intensify. Only by keeping up with the general direction of advanced technological progress and constantly innovating can we catch up with the advanced level in the world. china metallurgical news
Development trend and countermeasures of numerical control technology and equipment
1 development trend of numerical control technology
The application of numerical control technology has not only brought revolutionary changes to the traditional manufacturing industry, making the manufacturing industry a symbol of industrialization, but also played an increasingly important role in the development of some important industries (it, automobile, light industry, medical care, etc.). ) With the continuous development of numerical control technology and the continuous expansion of application fields, the digitalization of equipment required by these industries has become a major trend of modern development. According to the development trend of numerical control technology and its equipment in the world, its main research hotspots are [1 ~ 4].
1. 1 New trend of high-speed and high-precision machining technology and equipment
Efficiency and quality are the main components of advanced manufacturing technology. High-speed and high-precision machining technology can greatly improve efficiency, improve product quality and grade, shorten production cycle and improve market competitiveness. Therefore, Japan Advanced Technology Research Association listed it as one of the five major technologies of modern manufacturing, and cirp identified it as one of the central research directions in 2 1 century.
In the field of automobile industry, the production cycle of 300,000 cars per year is 40 seconds, and multi-variety processing is one of the key problems that automobile equipment must solve. In the aerospace field, most of the machined parts are thin-walled ribs with poor stiffness, and the materials are aluminum or aluminum alloy. Only under the condition of high cutting speed and small cutting force can these ribs and walls be machined. Recently, large-scale components such as wings and fuselage are manufactured by hollowing out large-scale integral aluminum alloy blanks, instead of assembling multiple components through numerous rivets and screws, so that the strength, stiffness and reliability of the components are improved. All these require high speed, high precision and high flexibility for processing equipment.
According to emo200 1, the feed speed of high-speed machining center can reach 80m/min or even higher, and the idling speed can reach about 100m/min. At present, many automobile factories in the world, including Shanghai General Motors Corporation in China, have partially replaced modular machine tools with production lines composed of high-speed machining centers. The hypermach machine tool of Cincinnati, USA has a maximum feed speed of 60m/min, a fast speed of 100m/min, an acceleration of 2g, and a spindle speed of 60 000r/min. It only takes 30 minutes to process a thin-walled aircraft part, while it takes 3 hours to process the same part on a common high-speed milling machine and 8 hours on a common milling machine. The spindle speed and acceleration of the double-spindle lathe produced by German dmg company reach 12* respectively! 000 rpm and 1 g.
In terms of machining accuracy, in recent 10 years, the machining accuracy of ordinary CNC machine tools has increased from 10μm to 5μm, and the precision machining center has increased from 3 ~ 5μ m to 1 ~ 1.5μ m, and the ultra-precision machining accuracy has begun to enter the nanometer level (0.0 1μm).
In terms of reliability, the mtbf value of foreign numerical control devices has reached more than 6 000h, and the mtbf value of servo system has reached more than 30000h, showing very high reliability.
In order to realize high-speed and high-precision machining, motorized spindle, linear motor and other supporting functional components have developed rapidly and their application fields have been further expanded.
1.2 Five-axis linkage machining and compound machining machine tools have developed rapidly.
Using five-axis linkage to process three-dimensional curved parts, the tool can cut the best geometric shape, which not only has high smoothness, but also greatly improves efficiency. Generally speaking, the efficiency of 1 five-axis machine tool can be equivalent to that of two three-axis machine tools, especially when cubic boron nitride, a superhard material milling cutter, is used for high-speed milling hardened steel parts, five-axis machining can bring more benefits than three-axis machining. However, in the past, due to the complex structure of five-axis CNC system and host computer, the programming technology was difficult, and its price was several times higher than that of three-axis CNC machine tools, which restricted the development of five-axis CNC machine tools.
At present, due to the appearance of motorized spindle, the structure of compound spindle head used for 5-axis linkage machining is greatly simplified, its manufacturing difficulty and cost are greatly reduced, and the price gap of CNC system is narrowed. Thus, the development of compound spindle head five-axis linkage machine tool and compound machining machine tool (including five-sided machining machine tool) is promoted.
At emo200 1 exhibition, NIKO's 5-face machining machine tool adopted the compound spindle head, which can realize the machining of 4 vertical faces and arbitrary angles, so that 5-face machining and 5-axis machining can be realized on the same machine tool, and the machining of inclined planes and inverted cone holes can also be realized. Dmuvoution series machining centers exhibited by German dmg company can carry out 5-face machining and 5-axis linkage machining under one clamping, and can be directly or indirectly controlled by cnc system or cad/cam.
1.3 intelligence, openness and networking have become the main trends in the development of contemporary CNC systems.
The numerical control equipment in 2 1 century will be an intelligent system, which includes all aspects of the numerical control system: in order to pursue the intelligence of machining efficiency and machining quality, such as adaptive control of machining process and automatic generation of process parameters; 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-correction. Simplify programming and simplify the intelligence of operation, such as intelligent automatic programming and intelligent man-machine interface; There are also intelligent diagnosis, intelligent monitoring, convenient system diagnosis and maintenance.
In order to solve the problems existing in closed traditional numerical control system and industrial production numerical control application software. At present, many countries are studying open CNC systems, such as NGC (Next Generation Workstation/Machine Tool Control) in the United States, OSACA (Open System Structure of Control in Automation System) in Europe, Osec (Open System Environment of Controller) in Japan, onc (Open CNC System) in China, etc. The openness of CNC system has become the future of CNC system. The so-called open CNC system means that the development of CNC system can be oriented to machine tool manufacturers and end users on a unified operating platform. By changing, adding or reducing structural objects (CNC functions), serialization can be formed, and users' special applications and technical know-how can be easily integrated into the control system, so as to quickly realize open CNC systems of different varieties and grades and form brand-name products with distinctive personality. At present, the architecture specification, communication specification, configuration specification, running platform, CNC system function library and CNC system function software development tools of open CNC system are the core of current research.
Networked numerical control equipment is a new bright spot in the internationally renowned machine tool Expo in recent two years. The networking of CNC equipment will greatly meet the information integration needs of production lines, manufacturing systems and manufacturing enterprises, and it is also the basic unit to realize new manufacturing modes such as agile manufacturing, virtual enterprise and global manufacturing. Some well-known CNC machine tools and CNC system manufacturing companies at home and abroad have introduced related new concepts and prototypes in recent two years, such as "cyberproduction center" (CPC) exhibited by mazak Yamazaki at emo200 1; Daisuke Machine Tool Company of Japan exhibited "it Plaza" (Information Technology Plaza, referred to as it Plaza); The open manufacturing environment (ome) displayed by Siemens in Germany reflects the trend of NC machine tool processing towards networking.
1.4 Pay attention to the establishment of new technical standards and specifications.
1.4. 1 code for design and development of numerical control system
As mentioned above, the open CNC system has better universality, flexibility, adaptability and expansibility. The United States, Europe and Japan have successively implemented strategic development plans and studied and formulated open architecture CNC system specifications (omac, osaca and osec). The three largest economies in the world have made almost the same scientific plans and specifications in a short time, which indicates the arrival of a new period of change in numerical control technology. In 2000, China also began to study and formulate the standard framework of onc CNC system in China.
1.4.2 About CNC standards
Numerical control standard is the development trend of manufacturing informatization. In the 50 years after the birth of numerical control technology, information exchange is based on iso6983 standard, that is, G and M codes are used to describe how to process, and its essential feature is to face the processing process. Obviously, it can no longer meet the needs of the rapid development of modern numerical control technology. Therefore, a new numerical control system standard ISO 14649 (Step-NC) is being studied and formulated internationally, aiming at providing a neutral mechanism that can describe the unified data model of the whole product life cycle without depending on a specific system, thus realizing the standardization of product information in the whole manufacturing process and even in various industrial fields.
The appearance of step-nc may be a revolution in the field of numerical control technology, which will have a far-reaching impact on the development of numerical control technology and even the whole manufacturing industry. First of all, step-nc put forward a brand-new manufacturing concept. In the traditional manufacturing concept, NC machining programs are concentrated on a single computer. Under the new standard, numerical control programs can be published on the Internet, which is the direction of open and networked development of numerical control technology. Secondly, step-nc system can greatly reduce the processing drawings (about 75%), programming time (about 35%) and processing time (about 50%).
At present, European and American countries attach great importance to the study of step-nc, and Europe initiated the ims plan of step-nc (1999.1.1~ 2001.12.31). Twenty cad/cam/capp/cnc users, manufacturers and academic institutions from Europe and Japan participated in this project. Step tools is an American company and a global developer of data exchange software. He developed a super model for information exchange of CNC machine tools, with the goal of describing all machining processes with unified specifications. At present, this new data exchange format has been verified on the prototype equipped with Siemens, fidia and European osaca-nc numerical control systems.
2. Basic estimation of numerical control technology and its industrial development in China.
China's numerical control technology started from 1958, and the development course of nearly 50 years can be roughly divided into three stages: the first stage is from 1958 to 1979, that is, the closed development stage. At present, the development of numerical control technology is relatively slow due to the technical blockade of foreign countries and the limitation of basic conditions in China. The second stage is in the Sixth Five-Year Plan, the Seventh Five-Year Plan and the early Eighth Five-Year Plan, that is, the stage of introducing technology, digesting and absorbing, and initially establishing a localization system. At this stage, due to the reform and opening up and the attention of the state, as well as the improvement of R&D environment and international environment, China's numerical control technology research and development and product localization have made great progress. The third stage is the late Eighth Five-Year Plan and the Ninth Five-Year Plan, that is, industrialization research and market competition. At present, the industrialization of domestic CNC equipment in China has made substantial progress. At the end of the Ninth Five-Year Plan, the domestic market share of domestic CNC machine tools reached 50%, and the domestic CNC system (popular type) also reached 10%.
Looking at the development of numerical control technology in China in the past 50 years, especially after four five-year plans, the following achievements have been made in general.
A laid the foundation for the development of numerical control technology and basically mastered modern numerical control technology. At present, China has basically mastered the basic technology of CNC system, servo drive, CNC mainframe, special plane and its accessories, most of which have the foundation of commercial development, and some technologies have been commercialized and industrialized.
B. the numerical control industrial base was initially formed. On the basis of tackling key problems and commercialization of some technologies, CNC system manufacturers with mass production capacity such as Huazhong CNC and Aerospace CNC have been established. Servo system and servo motor manufacturers such as Lanzhou Motor Factory and Huazhong CNC, as well as CNC host manufacturers such as Beijing No.1 Machine Tool Factory and Jinan No.1 Machine Tool Factory. These factories have basically formed the numerical control industrial base in China.
Established a basic team of CNC research, development and management personnel.
Although great progress has been made in the R&D and industrialization of numerical control technology, we should also clearly realize that the R&D of high-end numerical control technology in China, especially the technical level of industrialization, is still far from the actual demand in China. Although the development speed of China is very fast in the vertical direction, the horizontal ratio (compared with foreign countries) has a gap not only in the technical level, but also in the development speed in some aspects, that is, the gap in the technical level of some high-tech CNC equipment tends to expand. The international estimate of China's numerical control technology level and industrialization level is roughly as follows.
A from the technical level, it is about 10 ~ 15 years behind the advanced foreign level, and it is even bigger from the high-tech point of view.
B industrialization level, low market share and small variety coverage, which has not yet formed large-scale production; The specialized production level and complete set capacity of functional parts are low; The appearance quality is poor; The reliability is not high and the degree of commercialization is insufficient; Domestic CNC system has not yet established its own brand effect, and the user's confidence is insufficient.
C. In terms of sustainable development ability, the research, development and engineering ability of NC technology before competition is weak; The application field of numerical control technology has not been greatly expanded; The research and formulation of relevant standards and norms is relatively lagging behind.
The main reasons for the above gap are as follows.
A. cognition. Insufficient understanding of the arduousness, complexity and long-term nature of the domestic CNC industry process; Insufficient estimation of market irregularities, foreign blockade and strangulation, and institutional difficulties; Insufficient analysis of the application level and ability of numerical control technology in China.
B. System aspect. Pay more attention to the problem of NC industrialization from the technical point of view, and pay less attention to the problem of NC industrialization from the perspective of system and industrial chain; There is no complete high-quality supporting system, perfect training and service network and other supporting systems
C. mechanism. Poor mechanism leads to brain drain, which restricts the innovation of technology, technical route and products and the effective implementation of planning, which is often ideal and difficult to implement.
D. technical aspects. The independent innovation ability of enterprises in technology is not strong, and the engineering ability of core technologies is not strong. The standard of machine tools is backward and low, and the research on the new standard of CNC system is not enough.
3 China numerical control technology and strategic thinking of industrialization development.
3. 1 Strategic considerations
China is a big manufacturing country, so we should try our best to accept the front-end transfer rather than the back-end transfer in the world industrial transfer, that is, master the advanced manufacturing core technology, otherwise our manufacturing industry will be further hollowed out in the new round of international industrial restructuring. At the cost of resources, environment and market, we may only get the international "processing center" and "assembly center" in the new economic structure of the world, rather than the manufacturing center position with core technologies, which will seriously affect the development process of China's modern manufacturing industry.
We should pay attention to numerical control technology and industrial problems from the perspective of national security strategy. First of all, from the perspective of social security, as the manufacturing industry has the largest employment population in China, developing the manufacturing industry can not only improve people's living standards, but also ease the employment pressure in China and ensure social stability. Secondly, from the perspective of national defense security, western developed countries list high-tech CNC products as national strategic materials and impose embargoes and restrictions on China. Toshiba Incident and Cox Report are the best examples.
3.2 Development strategy
Starting from China's basic national conditions, guided by the national strategic demand and the national economic market demand, and aiming at improving the comprehensive competitiveness and industrialization level of China's manufacturing equipment industry, the key technologies that can lead the development and upgrading of China's manufacturing equipment industry at the beginning of 2 1 century, as well as supporting technologies and supporting technologies that support the industrialization development, are selected as research and development contents to realize the leap-forward development of China's manufacturing equipment industry.
Emphasis on market demand-oriented, that is, focusing on CNC end products, the whole machine (such as CNC lathes, milling machines, high-speed and high-precision CNC machine tools, typical digital machinery, key equipment in key industries, etc.). ) has promoted the development of the numerical control industry. Focus on solving the reliability and production scale of CNC system and related functional components (digital servo system and motor, high-speed motorized spindle system and new equipment accessories, etc.). ). Without scale, there would be no products with high reliability; Without scale, there will be no competitive products at low prices; Of course, it is hard to have a bright future without the numerical control equipment of China scale.
In the research and development of high-tech equipment, we should emphasize the close combination of production, learning, research and end users, take "making, using and selling" as the goal, and carry out key research according to the will of the country to solve the urgent needs of the country.
In the aspect of pre-competition CNC technology, it emphasizes innovation and research and development of technologies and products with independent intellectual property rights, which lays the foundation for the sustainable development of CNC industry, equipment manufacturing industry and even the whole manufacturing industry in China.