History of CNC machine tools

Development history of CNC machine tools

abstract

"Science and technology are the primary productive forces" has become the highest truth of today's social development. Whoever can master the most cutting-edge and advanced science and technology will be able to grasp the initiative of development and make major breakthroughs and achievements.

Advanced manufacturing technology with numerical control technology as the core is one of the important symbols of a country's comprehensive national strength.

This paper mainly introduces the definition, development stage and history of CNC machine tools, the development of machine tools in the world and China, and briefly describes the future development direction of CNC machine tools, indicating the importance of CNC machine tools in today's social development.

By searching relevant information, I have deepened my understanding of mechanical specialty, especially CNC machine tools, and made clear the development trend of mechatronics in today's society and the direction of further study in the future.

Keywords development history, development trend of machine tool power

I. Description of terms

Numerical control, namely numerical control (NC).

Numerical control technology, that is, NC technology, refers to the technology of issuing instructions with digital information (digital quantities and digital characters) to realize automatic control.

It is an automatic control technology developed in modern times.

At present, numerical control technology has become the basic support of modern manufacturing technology, and numerical control technology and equipment are the important foundation of manufacturing modernization.

Whether this foundation is solid or not directly affects a country's economic development and comprehensive national strength, and is related to a country's strategic position.

Therefore, every industrialized country in the world has taken great measures to develop its own numerical control technology and industry.

Numerical control machine tool refers to a machine tool which adopts digital control technology to automatically control the machining process of the machine tool.

The Fifth Technical Committee of the International Information Processing Union defines a CNC machine tool as: "A CNC machine tool is a machine tool equipped with a program control system, which can logically process programs specified by codes or other coded instructions." It integrates modern mechanical manufacturing technology, automatic control technology and computer information technology, and uses numerical control devices or computers to partially or completely replace manual control of various actions (such as starting, machining sequence, changing cutting parameters, spindle speed change, selecting tools, starting and stopping coolant, etc.). ) ordinary machine tool processing parts. It is a high-efficiency, high-precision, high-flexibility, high-automation optical-mechanical-electrical integrated numerical control device.

Second, the development stage of numerical control system

The world's first electronic computer was born in 1946, which shows that human beings have created tools that can enhance and partially replace mental work.

Compared with those tools created by human beings in agriculture and industrial society that only enhance physical labor, it has made a qualitative leap and laid the foundation for human beings to enter the information society.

Six years later 1952, computer technology was applied to machine tools, and the first CNC machine tool was born in the United States.

Since then, the traditional machine tool has undergone a qualitative change.

In the past half century, CNC system has experienced two stages and six generations of development.

1, numerical control stage (1952 ~ 1970)

The early computer operation speed was low, which had little influence on the scientific calculation and data processing at that time, but it could not meet the requirements of real-time control of machine tools.

People have to use digital logic circuits to "build" a computer dedicated to machine tools as a numerical control system, which is called HARD-WIRED NC.

With the development of components, this stage has experienced three generations, namely the first generation 1952- electron tube; Second generation 1959- transistor; Third Generation 1965- Small Scale Integrated Circuit.

2, computer numerical control (CNC) stage (1970 ~ now)

By 1970, general minicomputers had appeared and been mass-produced.

So it was transplanted as the core component of the numerical control system and entered the stage of computer numerical control (CNC) (omitting the word "universal" in front of the computer).

By 197 1 year, Intel Corporation of the United States used large-scale integrated circuit technology to integrate two core components of a computer-arithmetic unit and controller on one chip for the first time in the world, called microprocessor, also called central processing unit (CPU).

Through 1974, the microprocessor is applied to the numerical control system.

This is because the small computer is too powerful and has rich ability to control a machine tool (so it was used to control multiple machine tools at that time, called group control), so it is more economical and reasonable to use a microprocessor.

Moreover, the reliability of minicomputers at that time was not ideal.

Although the speed and function of early microprocessors are not high enough, they can be solved by multi-processor structure.

Because microprocessor is the core component of general computer, it is still called computer numerical control.

By 1990, the performance of PC (personal computer, commonly known as microcomputer in China) has developed to a very high stage, which can meet the requirements as the core component of CNC system.

Since then, the numerical control system has entered the stage based on PC.

In short, the computer numerical control stage has also experienced three generations.

The fourth generation 1970- minicomputer; The fifth generation 1974- microprocessor and the sixth generation 1990- PC-based.

It should also be pointed out that although it has long been renamed as Computer Numerical Control (CNC) abroad, it is still used to be called Numerical Control (NC) in China.

So the "numerical control" we talk about every day actually refers to "computer numerical control".

Third, the development history of CNC machine tools

In the mid-20th century, with the development of electronic technology, the emergence of automatic information processing, data processing and electronic computers brought new concepts to automation technology. Using digital signals to control the movement and machining process of machine tools has promoted the development of machine tool automation.

In the early 1940s, ParsonsCorporation, a small aircraft industrial contractor in northern Michigan, USA, first realized the application of digital technology in machining.

When they were manufacturing the frame of an airplane and the rotary wing of a helicopter, they used a full digital computer to process the data of the machining trajectory of the wing, and considered the influence of the tool diameter on the machining trajectory, so that the machining accuracy reached 0.0381mm (0.001.5 in), which reached the highest level at that time.

1952, MIT installed a set of experimental numerical control system on a vertical milling machine, which successfully realized the simultaneous control of three-axis motion.

This CNC machine tool is called the first CNC machine tool in the world.

This machine tool is an experimental machine tool. By June 1954 1 1, on the basis of Paterson's patent, Bendix-Cooperation Company of the United States officially produced the first industrial CNC machine tool.

After that, from 1960, Germany, Japan and other industrial countries developed, produced and used CNC machine tools one after another.

CNC milling machine was first used in CNC machine tools, because CNC machine tools can solve the curve or surface parts that are difficult to be done by ordinary machine tools and need contour machining.

However, because the numerical control system at that time used electron tubes, which were huge in size and high in power consumption, it was not widely used in other industries except military departments.

After 1960, CNC machine tools with point control developed rapidly.

Because the numerical control system of point control is much simpler than contour control.

Therefore, CNC milling machines, punching machines and coordinate boring machines have developed in large numbers. According to statistics, 85% of about 6,000 CNC machine tools actually used in 1966 are point-controlled machine tools.

In the development of CNC machine tools, it is worth mentioning the machining center.

This is a CNC machine tool with automatic tool changing device, which can realize multi-process machining by loading the workpiece at one time.

This product was originally produced by Carnegie &；; It was produced in March 1959. terek & amp； TreckerCorp)。

This machine tool is equipped with taps, drills, reamers, milling cutters and other tools in the tool magazine. According to the instructions of the punching belt, the cutter is automatically selected, and the cutter is installed on the spindle through the manipulator to process the workpiece.

It can shorten the loading and unloading time of parts on the machine tool and the time of replacing tools.

Machining center has now become a very important variety of CNC machine tools, including not only vertical and horizontal boring and milling centers for machining box parts, but also turning centers and grinding centers for machining rotary integral parts.

1967, for the first time in Britain, several CNC machine tools were connected into a flexible machining system, which is called flexible manufacturing system &: After mdash——FMS), the United States, Europe, Japan and so on have also developed applications.

After 1974, with the rapid development of microelectronics technology, microprocessors were directly used in CNC machine tools, which strengthened the functions of CNC software and developed into computer CNC machine tools (CNC machine tools for short), further promoting the popularization and development of CNC machine tools.

In 1980s, 1 ~ 4 flexible manufacturing unit (FMC) with machining center or turning center as the main body and equipped with automatic loading and unloading, monitoring and detection devices for workpieces appeared.

This kind of unit has the advantages of less investment and quick effect, which can be operated independently for a long time with fewer people, and can also be integrated into FMS or more advanced integrated manufacturing system.

At present, FMS is also developing from sheet metal cutting to cold working, welding and assembly, and from small and medium batch processing to large batch processing.

Therefore, machine tool numerical control technology is considered as the basic technology of modern mechanical automation.

Four, the world power and the development of CNC machine tools in China.

The United States, Germany and Japan are the countries with the most advanced technology and experience in the research, design, manufacture and use of CNC machine tools.

Because of their different social conditions, each has its own characteristics.

USA: The development of machine tools pays attention to basic scientific research.

The characteristic of America is that * * * attaches great importance to the machine tool industry. Because of its military needs, the U.S. Department of Defense and other departments constantly put forward the development direction and scientific research tasks of machine tools, and provided sufficient funds to recruit talents, paying special attention to efficiency and innovation and basic scientific research.

Therefore, machine tool technology is constantly innovating, such as 1952, the development of the world's first CNC machine tool, 1958 machining center, the development of FMS in the early 1970s, and 1987 open CNC system.

Because the United States first developed a large number of automated production lines to automate mass production in combination with the production requirements of automobiles and bearings, and its electronics and computer technology are world-leading, its CNC machine tool host design, manufacturing and CNC system are solid, and it has always attached importance to scientific research and innovation, so its high-performance CNC machine tool technology has always been in the leading position in the world.

Today, the United States not only produces high-performance CNC machine tools for aerospace, but also produces cheap and practical CNC machine tools for small and medium-sized enterprises.

Such as Haas and Fadal.

The lesson of developing CNC machine tools in the United States is that it pays more attention to basic scientific research and ignores applied technology. In the 1980s, * * * once relaxed its guidance, resulting in a slow growth in the output of CNC machine tools. 1982 was overtaken by backward Japan and imported in large quantities.

Since the 1990s, correcting the past bias, CNC machine tools have turned to practical technology, and the output has gradually increased.

Germany: machine tool development pays attention to practicality

Germany * * * has always attached importance to the important strategic position of the machine tool industry, paying special attention to practicality and effectiveness, insisting on people-oriented, mentoring and constantly improving the quality of personnel.

On the basis of the development of a large number of production automation, the first CNC machine tool was developed in 1956, and it has always adhered to the spirit of seeking truth from facts and made steady progress.

Germany pays special attention to scientific experiments, combines theory with practice, and pays equal attention to basic research and applied technology research.

Enterprises and scientific research departments in colleges and universities work closely together to conduct in-depth research on user products, processing technology, machine tool layout and structure, characteristics and characteristics of CNC machine tools, and strive for Excellence in quality.

German CNC machine tools have good quality and performance, advanced and practical, and genuine products are exported to all parts of the world, especially large, heavy and precision CNC machine tools.

Germany pays special attention to the advanced nature and practicability of CNC machine tools and accessories. The quality and performance of its machinery, electricity, liquid, gas, light, tools, measurement, numerical control system and various functional components are among the highest in the world.

For example, the numerical control system of Siemens and the precision grating of Heidenham are world-famous and adopted in the competition.

Japan: The development of machine tools should be imitated before being created.

Japan attaches great importance to the development of machine tool industry, and puts forward the development direction of Japanese CNC machine tool industry through planning and regulations (such as mechanical vibration law, electromechanical law, machine letter law, etc.). ), and provide sufficient research and development funds to encourage scientific research institutions and enterprises to vigorously develop CNC machine tools.

Japan has learned from Germany in attaching importance to talents and machine tool parts, and from the United States in quality management and CNC machine tool technology, perfecting and developing the achievements of the two countries, and achieved good results, even surpassing shine on you.

Similar to the United States and Germany, Japan has fully developed a large number of production automation, and then fully developed small and medium-sized CNC machine tools for flexible production automation.

Since 1958 developed the first CNC machine tool, the output of 1978 (7342 sets) has surpassed that of the United States (5688 sets), and its output and export volume have always ranked first in the world (46604 sets were produced and 27409 sets were exported in 200/kloc-0, accounting for 59%).

Strategically, mid-range CNC machine tools with large and wide output are exported in large quantities, occupying a vast global market.

In 1980s, we began to further strengthen scientific research and develop into high-performance CNC machine tools.

Strategically, first, by learning from the United States, total quality management has become a conscious activity of all employees to ensure product quality, thus accelerating the development of electronics and computer technology into the forefront of the world and paving the way for the development of mechatronics CNC machine tools.

In the process of developing CNC machine tools, Japan pays close attention to the key points and highlights the development of CNC system.

Japan FANUC Company has a correct strategy, combines imitation and creation, and develops all kinds of low, medium and high-grade numerical control systems needed by the market with leading technology and the highest output in the world.

The company has 3674 employees, more than 600 scientific researchers and a monthly production capacity of 7000 units. Its sales account for 50% of the world market and 70% of the China market, which has played a great role in accelerating the development of CNC machine tools in Japan and even in the world.

The present situation of China's development

The development of CNC technology in China began in 1950s, and the first CNC machine tool was developed in 1958. The development process can be roughly divided into two stages.

The first stage is from 1958 to 1979 and the second stage is from 1979.

In the first stage, there was a lack of understanding of the characteristics and development conditions of CNC machine tools. In the case of poor personnel quality, poor foundation and poor accessories, they rushed up and down, and finally stopped because of poor performance and could not be used for production.

The main problems are blindness and lack of scientific spirit of seeking truth from facts.

In the second stage, CNC system technology was introduced from Japan, Germany, the United States and Spain, and advanced CNC machine tools were introduced from Japan, the United States, Germany, Italy, Britain, France, Switzerland, Hungary, Austria, South Korea and Taiwan Province Province * *11countries (regions), which solved the reliability and joint venture production.

Through the introduction of numerical control technology during the Sixth Five-Year Plan period and the digestion and absorption of "scientific and technological research" during the Seventh Five-Year Plan period, China's numerical control technology and numerical control industry have made considerable achievements.

Especially in recent years, China's numerical control industry has developed rapidly. From 1998 to 2004, the average annual growth rate of output and consumption of CNC machine tools in China was 39.3% and 34.9% respectively.

Nevertheless, the development momentum of imported machine tools is still strong. Since 2002, China has been the world's largest machine tool consumer and the largest machine tool importer for three consecutive years. In 2004, the consumption of machine tools in China reached 9.46 billion dollars. The gap between domestic CNC machine tool manufacturers and foreign countries in the research and development of high-end CNC machine tools is more obvious. More than 70% of this kind of equipment and most of its functional parts are imported.

Visible, domestic CNC machine tools, especially high-grade CNC machine tools, still lack market competitiveness. The main reasons are that the research and development depth of domestic CNC machine tools is not enough, the manufacturing level is still backward, the service consciousness and ability are lacking, the production and application of CNC and systems have not been well promoted, and there is a lack of CNC talents.

We should see the situation clearly, fully understand the shortcomings of domestic CNC machine tools, strive to develop advanced technology, increase technical innovation and training services, and shorten the gap with developed countries.

In more than 20 years, the design and manufacturing technology of CNC machine tools has been greatly improved, mainly in three aspects: (1) training a group of talents for design, manufacture, use and maintenance; Through the cooperative production of advanced CNC machine tools, the level of design, manufacture and use has been greatly improved, and the gap with the world's advanced technology has been narrowed; Using foreign advanced components and numerical control systems, we can design and manufacture high-speed, high-performance five-axis or five-axis CNC machine tools to meet the needs of the domestic market, but it is poor in testing, digesting, mastering and innovating key technologies.

Up to now, many important functional parts, automatic tools and numerical control systems are supported by foreign technology, and cannot be independently developed. They are basically in the stage from imitation to independent development, which is far from the level of Japanese numerical control machine tools.

The main problems include: lack of guidance like Japanese electromechanical law and machine function law; There is a serious shortage of experts and skilled workers in various fields; Lack of in-depth and systematic scientific research work; Components are not compatible with CNC system; There is a lack of cooperation between enterprises and majors, and they are basically fighting alone. Although there are many people in the factory, they cannot form a joint force.

Since 2003, China has become the world's largest consumer of machine tools and the world's largest importer of CNC machine tools.

At present, the numerical control rate of processing equipment is improving. 1999 In China, the numerical control rate of machining equipment was 5-8%, and it is currently expected to be between 15-20%.

At present, the state has formulated some policies to encourage citizens to use domestic CNC machine tools, and manufacturers are also trying to catch up.

China buys the most machine tools from military enterprises. 80% of a procurement plan is imported, and domestic machine tools can't meet the demand.

This trend will not change in the next five years.

But as far as domestic demand is concerned, China's CNC machine tools can meet the orders of middle and low-grade products at present.

Five, the future development trend of numerical control

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.

Judging from the development trend of numerical control technology and its equipment in the world, its main research hotspots are as follows.

1, the 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 60000r/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.

2. The rapid development of linkage machining and compound machining machine tools.

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 any angle, so that 5-face machining and 5-axis machining can be realized on the same machine tool, as well as the machining of inclined planes and inverted cone holes.

DMUVoution series machining centers exhibited by German DMG company can carry out five-sided machining and five-axis linkage machining under one clamping, and can be directly or indirectly controlled by CNC system or CAD/CAM.

3. Intelligentization, 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

Open system research.

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.

4, pay attention to the establishment of new technical standards and norms.

(1) Code for Design and Development of CNC 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.

(2) About numerical control 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 code and M code are used to describe how to process, and its essential feature is process-oriented. 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.