Since China's "equipment manufacturing industry" as a national development strategy, China's equipment manufacturing industry has made rapid progress in the development of many large-scale equipment manufacturing capacity has jumped to the world's advanced level, and even become the world's top level, but China's manufacturing industry is still lagging behind, the backwardness of the The backwardness lies in the backwardness of precision manufacturing.

Ultra-precision machining technology is an important support technology of modern high-tech war, is the basis for the development of modern high-tech industries and science and technology, is the direction of development of modern manufacturing science.

The development of modern science and technology based on the test, the required test instruments and equipment almost invariably need the support of ultra-precision processing technology. By the macro-manufacturing into the micro-manufacturing is one of the future development trend of manufacturing industry, the current ultra-precision machining has entered the nanometer scale, nanometer manufacturing is the ultra-precision machining of cutting-edge topics. The world's developed countries have attached great importance to it.

01 The development stage of ultra-precision machining

The current ultra-precision machining, without changing the physical properties of the workpiece material as a prerequisite, in order to obtain the limit of shape accuracy, dimensional accuracy, surface roughness, surface integrity (no or very little surface damage, including defects such as micro-cracks, residual stress, tissue changes) as the goal.

Ultra-precision machining research content, that is, the impact of ultra-precision machining accuracy of various factors including: ultra-precision machining mechanism, machined materials, ultra-precision machining equipment, ultra-precision machining tools, ultra-precision machining fixtures, ultra-precision machining detection and error compensation, ultra-precision machining environment (including constant temperature, vibration isolation, cleanliness control, etc.) and ultra-precision machining process. Since then, scholars at home and abroad have carried out systematic research around these contents. The development of ultra-precision machining has experienced the following three stages.

(1) From the 1950s to the 1980s, the United States took the lead in developing the ultra-precision machining technology represented by single-point diamond cutting, which was used in aerospace, national defence, astronomy and other fields of laser fusion mirrors, spherical and aspherical large parts processing.

(2) From the 1980s to the 1990s, it entered the early stage of application in the private industry. The United States Moore, Pritec, Japan's Toshiba and Hitachi, as well as Europe's Cranfield and other companies in the government's support of the commercialisation of ultra-precision machining equipment, began to be used in the manufacture of civilian precision optical lenses. Single ultra-precision machining equipment is still rare and expensive, mainly in the form of special machines ordered. In this period also appeared in the processing of hard metals and hard and brittle materials can be ultra-precision diamond grinding technology and grinding machine, but its processing efficiency can not be compared with the diamond lathe.

(3) After the 1990s, civil ultra-precision machining technology gradually matured. Driven by the automotive, energy, medical equipment, information, optoelectronics and communications industries, ultra-precision machining technology is widely used in the processing of aspherical optical lenses, ultra-precision moulds, disk drive heads, disk substrates, semiconductor substrates and other parts. With the gradual maturation of technologies related to ultra-precision machining equipment, such as precision spindle components, rolling guides, hydrostatic guides, micro-feed drives, precision numerical control systems, and laser precision inspection systems, ultra-precision machining equipment has become a common production facility in industry. In addition, the precision of the equipment is gradually approaching the nanometer level, the size range of the workpiece can be processed has become larger, and more and more widely used. With the development of CNC technology, there is also the emergence of ultra-precision five-axis milling and fly-cutting technology. Can already process non-axisymmetric non-spherical and other complex parts.

02 The development of foreign ultra-precision machining

Ultra-precision machining technology in the international leading countries are the United States, Britain and Japan. Ultra-precision machining technology in these countries is not only the overall complete set of high level, and the degree of commercialisation is also very high.

The United States in the late 1950s developed a diamond tool ultra-precision cutting technology, known as "SPDT technology" (Single Point Dia-mond Turning) or "micro-inch technology" (1 micro-inch = 0.025μm), and the development of the corresponding ultra-precision machining technology. (1 micro-inch = 0.025μm), and the development of the corresponding air bearing spindle of the ultra-precision machine tools for processing laser fusion mirrors, tactical missiles and manned spacecraft with spherical, aspheric large parts.

In large-scale ultra-precision machine tools, the United States of America's LLL National Laboratory in 1986 developed two large-scale ultra-precision diamond lathe: one for the processing of the diameter of 2.1m horizontal DTM-3 diamond lathe, the other for the processing of the diameter of 1.65m LODTM vertical large optical diamond lathe. Among them, LODTM vertical large optical diamond lathe is recognised as the world's highest precision ultra-precision machine tool. The United States later developed a large 6-axis CNC precision grinding machine for precision grinding of large optical mirrors.

The Cranfield Institute of Technology of the Cranfield Institute of Precision Engineering (CUPE for short) is a unique representative of the level of ultra-precision machining technology in the United Kingdom. Such as CUPE production Nanocentre (nanometer machining centre) can be both ultra-precision turning, but also with a grinding head, can also be ultra-precision grinding, the shape of the processed workpiece accuracy of up to 0.1 μm, the surface roughness Ra Cranfield Precision Machining Centre in 1991, the development of a successful OAGM-2500 multi-functional three-coordinate linkage CNC grinding machine (table area) 2500mm × 2500mm), can be processed (grinding, turning) and measurement of precision free-form surfaces. The machine tool adopts the method of assembling machined parts, and it can also process large mirrors with a diameter of 7.5m in astronomical telescopes.

Japan's research on ultra-precision machining technology started late compared to the United States and the United Kingdom, but today the world's ultra-precision machining technology is the fastest growing country.

03 China's ultra-precision machining development

In the past quite a long period of time, due to the embargo restrictions by Western countries, China's imports of foreign ultra-precision machine tools are severely restricted. But when China's own CNC ultra-precision machine tools in 1998 after the successful development of Western countries immediately open to China, China has now imported a number of ultra-precision machine tools.

China's Beijing Machine Tool Research Institute, Aviation Precision Machinery Research Institute (Aviation 303), Harbin Institute of Technology, National University of Defense Technology and other units are now able to produce a number of ultra-precision CNC diamond machine tools.

Beijing Machine Tool Research Institute is one of the main units in China to carry out research on ultra-precision machining technology, and has developed a variety of different types of ultra-precision machine tools, components and related high-precision test instruments, such as precision bearings with an accuracy of 0.025 μm, JCS-027 ultra-precision lathe, JCS-031 ultra-precision milling machine, JCS-035 Ultra-precision Lathe, Ultra-precision Lathe CNC System, Photoreceptor Drum Processing Machine Tool for Photocopiers, Infrared High-power Laser Reflector, Ultra-precision Vibration-Displacement Micrometer, etc., which are at the domestic leading and international advanced level.

NAM-800 nano CNC lathe is the latest generation of nano-scale processing machine tool of Beijing Machine Tool Research Institute. It is the perfect unification of today's CNC technology, servo technology and mechanical manufacturing technology. The machine tool provides a good processing means for the development of the most cutting-edge science and technology in China.

Aviation Precision Machinery Research Institute in the ultra-precision spindle, granite coordinate measuring machine and other aspects of in-depth research and product production. Harbin Institute of Technology has carried out fruitful researches in diamond ultra-precision cutting, diamond tool crystal orientation and sharpening, and diamond micropowder grinding wheel electrolytic on-line dressing technology.

Tsinghua University in integrated circuit ultra-precision machining equipment, disk processing and testing equipment, micro-displacement table, ultra-precision belt grinding and research and polishing, diamond grinding wheel ultra-precision grinding, non-circular cross-section ultra-precision cutting and other aspects of in-depth research, and there are corresponding products.

In addition, Changchun Institute of Optical Precision Machinery and Physics, Chinese Academy of Sciences, Huazhong University of Science and Technology, Shenyang First Machine Tool Factory, Chengdu Tool Research Institute, National University of Defense Technology, etc. have carried out research in this field, with remarkable achievements.

But in general, China's ultra-precision machining machine tool efficiency, accuracy, reliability, especially specifications (large size) and technical support compared with foreign countries, compared with the actual requirements of production, there is still a considerable gap. In addition, the precision machining of complex surfaces has also been a barrier to the development of China's manufacturing industry, and the development of the manufacturing industry is related to the long-term development of the country's economy, still need to invest in a lot of research.

04 The development trend of precision machining

(1) high precision, high efficiency high precision and high efficiency is the eternal theme of ultra-precision machining. In general, the solid grain processing constantly pursuing the free grain processing accuracy, while the free grain processing constantly pursuing the efficiency of the solid grain processing. The current ultra-precision plus technology such as CMP, EEM, etc. can obtain very high surface quality and surface integrity, but at the expense of processing efficiency as a guarantee. Ultra-precision cutting, grinding technology, although high processing efficiency, but can not obtain such as CMP, EEM processing accuracy. Exploring the processing method that can balance the efficiency and accuracy has become the goal of researchers in the field of ultra-precision machining. The emergence of semi-fixed abrasive processing methods reflects this trend. On the other hand, the birth of electrolytic magnetic grinding, magnetorheological abrasive flow processing and other composite processing methods.

(2) process integration of today's competition between companies tends to heat up, high productivity is becoming more and more dependent on the conditions of survival of enterprises. In this context, the emergence of "grinding instead of research" or even "grinding instead of throwing" call. On the other hand, the use of a device to complete a variety of processing (such as turning, drilling, milling, grinding, finishing) the trend is becoming more and more obvious.

(3) large-scale, miniaturised for the processing of aviation, aerospace, astronautics and other fields require large-scale optoelectronic devices (such as large celestial telescopes on the mirror), the need to establish large-scale ultra-precision machining equipment. For the processing of micro-electronic machinery, optoelectronic information and other fields need micro devices (such as micro sensors, micro drive components, etc.), the need for micro ultra-precision machining equipment (but this is not to say that the processing of small and medium-sized workpieces must be required for small and medium-sized machining equipment). Ultra-precision machining technology is ushering in an era of prosperity. Ultra-precision cutting, ultra-precision grinding, ultra-precision grinding and polishing technology has made great progress, after processing the surface accuracy of the workpiece can reach the nanometer or sub-nanometer, and the processing method is becoming increasingly diversified. In the production of flowmeter sensors, in order to achieve high-precision measurement of the product, precision machining technology to ensure the accuracy of the product processing.