Modern ultra-precision machining technology

Mechanical manufacturing technology has grown rapidly both in terms of improving accuracy and productivity. In terms of improving productivity, improving the degree of automation is the direction that countries are committed to developing. In recent years, the development from CNC to CIMS has been rapid and has been applied within a certain range. From the aspect of improving precision, from the development of Precision Machining to ultra-precision machining, this is also the direction that the major developed countries in the world are committed to. Its accuracy ranges from micron to sub-micron, and even nanometer, and its application range is becoming more and more widespread. It is widely used in high-tech fields, military industries, and civil industries. Such as laser fusion systems, ultra-large-scale integrated circuits, high-density disks, precision radar, missile fire control systems, inertial gyro, precision machine tools, precision instruments, video recorder heads, copier drums, gas rotary valves, etc. Ultra-precision machining technology.
It is closely related to the development of some major contemporary science and technology and is an important part of the development of contemporary science. The development of ultra-precision machining technology has promoted the development of machinery, hydraulics, electronics, semiconductors, optics, sensors and measurement technologies, and materials science. .

1 Overview of Ultra-precision Machining Technology

Ultra-precision machining currently requires a high-precision machining that cannot be achieved with existing ordinary precision machining methods. In terms of quantity, it is necessary to process submicron and nanometer-sized shapes and sizes and obtain them. Nano-scale surface roughness, but how much accuracy value can be regarded as ultra-precision machining depends on the size of a part, complexity and whether it is easy to deformation and other factors.
Ultra-precision machining includes ultra-precision cutting (cars, milling), ultra-precision grinding, ultra-precision grinding
(Mechanical polishing, mechanical chemical polishing, polishing, non-contact floating polishing, elastic emission processing, etc.) and ultra-precision special processing (electron beam, ion beam, laser beam processing, etc.). All of the above methods can process dimensional accuracy, shape accuracy, and surface quality that ordinary precision machining cannot achieve. Each ultra-precision machining method is selected for the requirements of different parts.

1.1 Ultra-precision cutting

Ultra-precision cutting is characterized by the use of diamond tools. Diamond tools and non-ferrous metals have low affinity, hardness, wear resistance and thermal conductivity are very superior, and can sharpen very sharply (edge ​​radius can be less than ρ0.01 μm, practical application generally ρ0,05 μm) Machinable surface roughness of better than Ra 0.01 μm. In addition, ultra-precision cutting also uses high-precision basic components (such as air bearings, air-float guides, etc.), high-precision positioning detection elements (such as gratings, laser detection systems, etc.) and high-resolution micro-feed mechanism . The machine tool itself adopts measures such as constant temperature, anti-vibration and vibration isolation, and it also has means for preventing contamination of the workpiece. The machine must be installed in a clean room. The material for the ultra-precision cutting must be uniform in texture and free of defects. In this case, oxygen-free copper processing, surface roughness up to Ba0.005μm, processing φ800mm aspheric lens, shape accuracy up to 0.2/μm. Ultra-precision machining technology has been widely used in aerospace, optics, and civil applications (see Table 1) and has evolved toward higher precision (see Table 2).

1.2 Ultra-precision grinding

Ultra-precision grinding technology is developed on the basis of general precision grinding. Ultra-precision grinding not only provides mirror-grade surface roughness, but also guarantees precise geometry and dimensions. Therefore, in addition to considering various process factors, reference components with high precision, high stiffness, and high damping characteristics must also be provided to eliminate the influence of various dynamic errors and adopt high-precision detection means and compensation means.
At present, the ultra-precision grinding is mainly performed on hard and brittle materials such as glass and ceramics. The target of grinding is a smooth surface of 5-10 nm, which means that the required rough surface can be achieved without grinding. degree. As a nano-scale grinding machine, the machine tool is required to have high precision and high rigidity, and the brittle material can be subjected to ductile grinding (Ductile Grinding). Nano-grinding technology is an important and effective machining technology for gas turbine engines, especially for materials that require high fatigue strength materials, such as jet engine turbines for airplanes.
In addition, the grinding wheel dressing technology is also quite critical. Although grinding is more effective than grinding to remove matter, it is difficult to obtain a mirror surface when grinding glass or ceramics, mainly because the grinding wheel surface is easily blocked by chips when the grain size of the grinding wheel is too small. The Electrolytic On-Line Finishing (ELID) cast iron fiber binder (CIFB) grinding wheel technology invented by scholar Ohmori Ohmori of the Japan Institute of Physical Chemistry can solve this problem.
The current ultra-precision grinding technology can process roundness of 0.0 1μm, O. With 1μm dimensional accuracy and Ra 0.005μm roughness cylindrical parts, plane ultra-precision grinding can produce 0.03μm/100mm plane.

1.3 Ultra-precision grinding

Ultra-precision grinding includes mechanical grinding, chemical mechanical grinding, floating grinding, elastic emission processing, and magnetic grinding. Ultra-precision grinding produces a spherical surface with a non-spherical degree of 0.025 ttm and a surface roughness of RaO. 003μm. Elasto-emissive processing can be used to process mirrors with non-deteriorating layers, with a roughness of up to 5A. Ultra-precision grinding with the highest precision produces parts with a flatness of λ/200. The key conditions for ultra-precision grinding are almost vibration-free grinding motion, precise temperature control, a clean environment, and small, uniform abrasives. In addition, high-precision detection methods are also indispensable.

1.4 Ultra-precision Special Processing 1.4.1 Electron Beam Processing

Ion beam processing refers to the acceleration of negative electrons continuously emitted from the cathode (electron gun) to the positive electrode in a vacuum and focusing on a very fine beam with a very high energy density. High-speed moving electrons hit the surface of the workpiece and the kinetic energy is converted into Potential energy that melts, vaporizes, and is pumped away in a vacuum. The control of electron beam strength and deflection direction, with the XY direction of the worktable CNC displacement, can achieve drilling, forming, cutting, etching, lithography exposure and other processes. Electron beam lithography with a much shorter wavelength than visible light is widely used in the manufacture of integrated circuits, so that line pattern resolution strings up to O.25 μm can be achieved.

1.4.2 Ion Beam Processing

The ions produced by the ion source are accelerated and focused in a vacuum to impact the surface of the workpiece. Because the ions are positively charged and their mass is ten million times larger than that of electrons, the accelerated kinetic energy can be obtained later. It is processed by the micro mechanical impact energy instead of kinetic energy and can be used for surface etching. Ultra clean cleaning, achieving atomic and molecular cutting.

1.4.3 Laser Beam Processing

The high energy density laser is further focused by the laser generator. When it hits the surface of the workpiece, light energy is absorbed instantaneously and converted into heat energy. According to the level of energy density, punching, precision cutting, processing fine anti-counterfeit signs, etc. can be achieved.

1.4.4 Micro EDM

EDM refers to the melting and vaporization of metal in an insulating working fluid by transient local high temperatures generated by pulse spark discharge between the tool electrode and the workpiece. There is no macroscopic cutting force between the tool and the workpiece during the processing. As long as the single pulse discharge energy is precisely controlled and precise micro-feeding is performed, very fine metal materials can be removed, and micro shafts, holes, narrow slits, flat surfaces, etc. can be processed. Surfaces, etc.

1.4.5 Micro Electrolytic Processing

The water in the conductive working solution dissociates into hydrogen ions and hydroxide ions, and the workpiece acts as an anode. The metal atoms on the surface become metallic cations that dissolve into the electrolyte and are electrolyzed layer by layer, followed by hydrogen and oxygen in the electrolyte. Root ions react to form metal hydroxide precipitates, and the workpiece cathode is not depleted. There is no macroscopic cutting force between the tool and the workpiece during machining. As long as the current density and electrolysis site are carefully controlled, nanometer accuracy can be achieved. Electrolysis processing, and the surface will not process stress. Commonly used in mirror polishing, precision thinning, and some applications where stress-free machining is required.

1.4.6 Compound processing

Composite machining refers to the use of several different energy forms, several different methods of processing, mutual complement each other, composite processing technology, such as electrolytic grinding, ultrasonic electrolytic machining, ultrasonic electrolytic grinding, ultrasonic EDM, ultrasonic cutting processing, etc. The processing method is more effective and the scope of application is wider.

2 Nanotechnology 2.1 Overview

With the continuous development of biology, environmental control, medicine, aviation, aerospace, precision guided-missile drugs, smart weapons, advanced intelligence sensors, and data communications, new and higher requirements have been constantly raised in the miniaturization of structural devices. At present, the development of nanotechnology is very rapid. It has enabled humans to enter a new level in transforming nature. It will develop the potential information and structural capabilities of the material, enabling a qualitative leap in the ability to store and process information per unit volume, which will have a profound impact on the national economy and military capabilities.
Nanotechnology refers to nanoscale (<10 nanometers) materials, design, manufacturing, measurement, and control technologies. With the development of nanotechnology. We have created new high-tech clusters such as nanoelectronics, nanomaterials, nanobiology, nanomechanics, nanofabrication, nanomicroscopy and nanometer measurement. Nanotechnology is an important technology for the 21st century and has a broad military-civilian dual-use perspective. Countries such as the United States, Japan, and Western Europe have invested a lot of manpower and material resources for development, and have been applied in aviation, aerospace, medical, and civilian products.

2.1.1 Microelectron-mechanical systems (MEMS)

10 years ago, people realized that using semiconductor bulk manufacturing technology can produce micro-scale prototypes of many macro-mechanical systems, and then started new research in the field of small-scale machinery manufacturing, which led to the emergence of micro-electromechanical systems (MEMS), such as Micrometer-sized sensors and various valves.
The main civilian areas of MEMS are: medicine, electricity, industry, aviation, and aerospace. Such as the use of electrostatic-driven micro-motor control computer and communication system. In environmental and medical applications, miniature sensors measure the flow, pressure, and concentration of various chemicals. In the military, there are mainly the following: hazardous chemical warfare agents alarm sensors, enemy identification, smart skin, distributed battlefield sensor networks, micro-robots electronic disability systems, insect platforms and other applications.

2.1.2 application specific integrated micro-instrument (ASIM)

Microengineering includes the design, material synthesis, micromachining, assembly, assembly, and packaging of sensors and actuators with millimeter, micron, and nanoscale structures. With this technology, sensors, actuators, and data processing acquisition devices can be integrated on a common substrate. The integrated integration of microelectromechanical systems and microelectronics technology has led to the emergence of specialized integrated micro-devices (ASIMs).
Submicron-based ASIMs will enable sub-millimeter devices to reduce development and test costs, reduce size, and reduce weight. At the same time, they will reduce power and temperature control requirements, reduce vibration sensitivity, and increase reliability through redundancy. ASIM will be in spacecraft and spaceflight. The system technology has caused a revolution in the emergence of ultra-small satellite systems, and eventually the realization of "nano-satellites."

2.1.3 Material Engineering and Functional Fabrics

In material engineering, it has been possible to design and control the microstructure of a material to obtain the required macroscopic properties. Therefore, it is an indispensable technique for today's materials engineering to test the molecular, atomic, and physical-chemical properties of materials at the molecular scale.
Utilizing the catalytic properties of nanoparticles, great chemical activity, great surface area, excellent electromagnetic properties, optical properties, etc. can produce products with strange functions, such as anti-ultraviolet, anti-visible light, anti-infrared, anti-electromagnetic and other functional fabrics .
In addition, nanotechnology also has broad application prospects in microelectronics engineering, biogenetic engineering, micromechanical optics and so on.

2.2 nanometer processing technology

Just as the manufacturing technology plays an important role in all fields today, nanofabrication technology also plays a key role in various fields of nanotechnology. Nano-processing technologies include many methods such as machining, chemical etching, energy beam processing, and STM processing. There is currently no unified definition of nanofabrication technology. The processing and use of nanoscale (<10nm) materials is called nanofabrication. The surface roughness of the machined nanometer is also referred to as nanofabrication. The author believes that the so-called nano-machining technology means that the dimensional accuracy, shape accuracy, and surface roughness of the parts are all nanometer (<10 nm). Nano-scale processing can be achieved by the following processing techniques.

2.2.1 Ultra-precision machining technology

Ultra-precision machining methods include single-point diamond and CBN ultra-precision cutting, diamond and CBN ultra-precision grinding and other multi-point abrasive processing, as well as grinding, polishing, elastic emission processing and other free abrasive processing or mechanical and chemical composite processing.
At present, the single-point diamond ultra-precision cutting process has obtained 3 nanometer chips in the laboratory, and also uses the ductile grinding technology to achieve nano-level grinding, while the elastic emission processing and other processes can achieve sub-nanometer-level removal. Get Angstrom grade surface roughness.

2.2.2 Energy Beam Processing Technology

Energy beam processing can be used to remove, add, and surface treat processes on processed objects, including ion beam processing, electron beam processing, and beam processing, in addition to electrolytic jet machining, EDM, electrochemical machining, molecular beam epitaxy, and physics. Chemical vapor deposition and the like are also energy beam processing.
Ion beam processing Sputter removal, deposition and surface treatment, ion beam assisted etching is also used for research and development of nano-scale processing. Compared with solid tool cutting, the position and processing rate of ion beam machining are difficult to determine. In order to achieve nano-scale machining accuracy, a sub-nanometer-level detection system and a closed-loop adjustment system for processing positions are needed. Electron beam processing removes atoms that penetrate the surface of the layer in the form of thermal energy and can be etched, photolithographically exposed, soldered, micro- and nano-scale drilling and milling.

2.2.3 LIGA Technology (Lithographie, Galvanoformung, Abformung)

The LIGA process is an integrated technology composed of deep synchrotron radiation X-ray lithography, electroforming, and plastic molding. Its most basic and most essential process is deep synchrotron radiation lithography, and electroforming and plastic molding. The process is the practical application of LIGA products. Compared with traditional semiconductor technology, LIGA technology has many unique advantages, mainly including:
(1) Wide range of materials, including metals and their alloys, ceramics, polymers, glass, etc.
(2) A three-dimensional microstructure having a height of several hundred micrometers to one thousand micrometers and a height ratio of more than 200 can be fabricated.
(3) The lateral dimension can be as small as O. 5μm, processing accuracy up to 0.1μm
(4) It can realize large-scale copying and production with low cost.
With LIGA technology, various micro devices and micro devices can be produced. LIGA products that have been successfully developed or are being developed include microsensors, micro motors, micro-machined parts, integrated optics and micro-optical components, microwave components, vacuum electronic components, and micro medical devices. , nanotechnology components and systems. The applications of LIGA products cover a wide range of applications such as processing technology, measurement technology, automation technology, automotive and transportation technology, power and energy technology, aerospace technology, textile technology, precision engineering and optics, microelectronics, biomedicine, environmental science. And chemical engineering.

2.2.4 Scanning Tunneling Microscopy (STM) Technology

C. Binning and H. Scanner tunnel microscopy, invented by Robrer, not only allows one to observe the surface structure of an object with a single atomic resolution, but also provides an ideal way for nanoscale processing in single atom units. The application of scanning tunneling microscopy technology can perform the original level of operation, assembly and modification. The STM places a very sharp metal needle close to the surface of the test piece to about 1 nm. The tunnel current is generated when the voltage is applied, and the tunneling current changes by 0.1 order of magnitude every 0.1 nm. The surface structure can be resolved by keeping the current scanning the surface of the specimen. The general tunnel current passes through one atom of the tip of the probe and thus its lateral resolution is at the original level.
Scanning tunneling micromachining technology can not only perform single original removal, addition and movement, but also perform new STM processing technologies such as STM lithography, probe tip electron beam induction deposition and corrosion.

2.3 nanometer measurement and control technology

Nano-scale processing can not be separated from nano-scale measurement technology, and both of them can not be separated from the control technology, ultra-high-precision positioning technology is the key to achieving nano-level control.

2.3.1 Nanometer Measurement Technology

In order to measure the surface appearance, the main development directions of nanometer measurement technology include optical interferometry and scanning microscopy.
Optical heterodyne interferometers: The use of interferometric fringe measurement methods for nanoscale measurements has its limitations, and heterodyne interferometry can be used to obtain O. 1nm spatial resolution, measuring range up to 50mm.
· X-ray interferometer: The distance between interference fringes of visible light and ultraviolet light is several hundred nanometers, and it is not easy to measure the nano-scale small displacement. However, ultra-short wavelength interferometry technology using X-ray can realize O. Olnm resolution displacement measurement. Measuring range up to 200μm.
Frequency Tracking F-P etalon: The measurement technology based on F-P etalon has extremely high sensitivity and accuracy, its precision can reach 10 - 3nm, but the measurement range is only O. 1 μm, which is limited by the frequency range of the laser.
· Laser frequency split length measurement: The value of the laser frequency split is related to the displacement of the splitting element. By measuring the frequency displacement, the precision has reached 1 nm, and the further laser frequency stabilization can reach 0. Olnm, measuring range 150 μm.
Scanning tunneling microscopy can directly observe atomic scale structures with vertical resolution up to O. 1nm, on the basis of STM in recent years has derived a series of scanning probe microscopy technology, such as photon scanning tunneling microscope, atomic force microscope (AFM), magnetic display micromirror (MFM) scanning near-field optical microscope (SNOM) Lateral force microscope (LFM), ballistic electron emission microscope (BEEM), light scanning tunneling microscope (PSTM), scanning ion-conductance microscope (SICM), etc.

2.3.2 Nanopositioning Control Technology

In the nano-scale measurement and processing, nano-scale three-dimensional positioning and control are required. At present, it is difficult to use a single actuator to achieve a wide range of nanometer positioning. Therefore, the actual positioning mechanism is often implemented by a combination of a large displacement actuator and a nanopositioning actuator. To achieve three-dimensional positioning and control, piezoelectric ceramic actuators are commonly used at present, and it can achieve approximately three-dimensional driving through a control system in a micrometer range. In addition, the use of electro-active materials, electrostatic or magnetic bearing type structures, as well as electrostatically actuated high-precision positioning control technology also develops to the nano-level precision, and frictional drive devices and screw positioning elements can also be adopted. Positioning.

3 Aspheric Surface Ultra-precision Machining Technology 3.1 Overview

Aspherical optical components are a very important optical component. The most common ones are parabolic mirrors, hyperbolic mirrors, and ellipsoidal mirrors. Aspherical optics have excellent imaging qualities unmatched by spherical optics. The application in the optical system can well correct a variety of aberrations, improve the image quality of the apparatus, improve the instrument discrimination ability, and increase the action distance. It can replace more spherical parts with one or several small aspherical parts. This simplifies the structure of the instrument, reduces the cost, and effectively reduces the weight of the instrument. In the fields of aviation and aerospace, due to the application of aspherical radar antennas, aspherical lenses, and mirrors in recent years, the performance of the product has been greatly improved. Advanced optical telephoto systems, high-resolution serial television video systems, and high-sensitivity infrared sensor systems in satellites all rely on aspheric lenses in their optical systems. The use of aspherical mirrors in laser gyros, a key component of inertial navigation devices, not only greatly reduces the volume, but also significantly improves the control accuracy and control stability. Infrared parabolic reflectors are the key components in infrared detection systems. Their processing accuracy has a great influence on the consistency of missile detonation distance. In civil use, laser fusion can provide long-term, clean, economical energy and produce cheap nuclear fuel. One of the key components of the laser fusion mirror is an aspherical mirror. The use of aspherical mirrors instead of group lenses reduces the number of reflections and reduces power loss. The large aspherical mirror with a diameter of 2.4 ln and a weight of 卯OK8 in the space exploration Hubble Space Telescope has been ground and polished to have an accuracy of O. 01LLm.
The application of aspherical optical components in civilian optoelectronic products has become even more widespread. Its scope has been related to camera lenses and viewfinders, television camera tubes, zoom lenses, movie projection lenses, satellite infrared telescopes, video camera lenses, video recordings, and audio recordings. Optical disc read heads, bar code read heads, optical brazed solder joints, medical instruments, and the like.
From the above discussion, we can see that in terms of airborne equipment, satellites, inertial guidance and inertial navigation systems, laser guidance systems, infrared detection systems, laser fusion and other aspects are inseparable from the aspheric parts, so as soon as possible to improve China's non- Ultra-precision machining technology of spherical surfaces has become an urgent matter, which is conducive to improving China's aviation, aerospace, weapons systems and other defense industries.
Since the 1980s, many new modern aspherical processing technologies have emerged. They are mainly:
(1) Computer Numerical Control Single Point Diamond Turning Technology:
(2) Computer numerical control box grinding and polishing technology;
(3) Computer Numerical Control ion beam forming technology:
(4) Computer numerical control ultra-precision polishing technology:
(5) CNC grinding technology:
(6) Optical Glass Aspheric Lens Molding Technology:
(7) Plastic lens molding technology;
(8) Epoxy replication aspheric technology:
These processing methods basically solved the processing problems of various aspherical mirrors. The first five methods all use numerical control technology. The precision of the processed parts is high, the processing efficiency is high, and mass production is possible. Aspherical surfaces use different processing methods depending on the material. For soft materials such as copper and aluminum, ultra-precision machining can now be performed using single-point diamond cutting (SPDT). For glass or plastics, the current processing method is to first ultra-precision processing of its mold, and then use the molding method to produce aspherical surfaces. For some other high-hardness brittle materials, it is currently processed mainly by ultra-precision grinding and super-precision grinding and polishing. In addition, there are special processing technologies for aspherical parts such as ion beam polishing.

3.2 Development Status at Home and Abroad

The precision and ultra-precision machining of aspherical surfaces must begin with CNC ultra-precision machine tools. CNC ultra-precision machining technology has been greatly developed in the United States, the United Kingdom, the Netherlands, Japan and other countries, mainly based on applications in aviation, aerospace, military, energy, etc., developed by the Institute of Precision Engineering (CUPE) of Cranfield University, UK Large-scale ultra-precision diamond mirror cutting machines can process aspherical mirrors (large diameter up to 1400mm and maximum length 600mm conical mirrors) used in large-scale X-ray astronomical telescopes.
The Institute has also developed a diamond cutting machine that can process the inboard revolution paraboloid and the outer revolution hyperboloid of the X-ray telescope. The development of the OAGM2500 six-axis CNC ultra-precision grinding machine for the ultra-precision machining of large-scale aspheric mirrors on the Hubble telescope is also based on this laboratory. The machine is mainly used for the processing of hard and brittle materials such as optical glass, and its processing accuracy Can reach 0.1μm. Representing today's highest level of ultra-precision diamond lathe LODTM in 1984 in the United States Lawrence. Developed by LLNl laboratory, it can process workpieces up to 2100mm in diameter and weighing up to 4500kg. Its processing precision can reach 0.25μm and the surface roughness Rmax is 0.0076μm. The machine can process flat, spherical and non-spherical surfaces. Spherical, mainly used for laser nuclear fusion engineering parts, infrared device parts and the processing of large astronomical reflectors. The Dutch company PHILPHS developed the CNC ultra-precision diamond lathe COLATH in 1978. It is mainly used for the processing of aspherical plastic lenses with a processing accuracy of 0.5 μm or less and a surface roughness of Ra O. 02μm. In addition, ultra-precision grinding and polishing of ultra-precision grinding and polishing are also effective tools for the processing of aspherical shapes of hard and brittle materials. Japan has invested more money and personnel in this area and achieved certain results. The use of special processing techniques such as ion beam polishing, elastic emission processing, etc., can significantly improve the quality of the machined surface. The precision aspheric mirror used for argon ion beam polishing fire control system is used in Frankfurt Arsenal, USA, with an accuracy of O. 02λ.
At present, many foreign companies have integrated ultra-precision turning, grinding, grinding and polishing processing, and developed a composite ultra-precision machining machine. The NANOFORM600 produced by Rank Pneumo and the NANOCENTRE developed by CUPE have the above processing functions, which makes the processing of aspherical parts more flexible.
At present, a variety of foreign aspherical processing technology is in a relatively mature stage, from large to several meters in diameter to a few millimeters in diameter, from single pieces to large quantities, from high-precision to general accuracy of aspherical optical parts can be processed. In contrast, our country still mainly adopts the traditional processing technology, and it needs to rely on the experienced aspheric surface processing technology workers to use the knife edge instrument and the box dense polishing tool to polish the non-spherical surface point by point. The process requires several months, poor repeatability, high processing costs, and is only applicable to the production of single parts and very small batches. It can only meet the single trial production requirements of the institute and the school.
Domestically, research on ultra-precision machining technology started in the early 1980s, and it lags behind that of foreign countries for 20 years. Among the units that have conducted research work are the Beijing Miyun Machine Tool Research Institute, the China Aviation Precision Machinery Research Institute, the Harbin Institute of Technology, and the Changchun Institute of Applied Optics, the Chinese Academy of Sciences. In 1992, the National Commission for Science, Technology, and Technology for National Defense established China's first key laboratory for ultra-precision machining at the China Aviation Precision Machinery Research Institute. These units have made a certain contribution to the development of ultra-precision machining technology in China, but for aspherical machining, the current domestic is still a blank. In the past few years, Changchun Optical Engine introduced the MSP-325 CNC ultra-precision lathe from Rank Pneumo, which is mainly used to process some metal and optical parts. However, this equipment currently seems to have fallen behind the international level and cannot meet the needs of the defense industry. While continuing to introduce advanced equipment from abroad, it is subject to many restrictions. Second, it can only lag behind others forever and it is not conducive to the development of China's national defense industry. Therefore, the state must invest sufficient manpower and material resources to enable China's ultra-precision machining technology, especially aspheric ultra-precision machining technology, to quickly adapt to the needs of national defense modernization such as aviation, aerospace, and weapons in a relatively short period of time.

3.3 Research content

The ultra-precision machining technology for aspherical surfaces involves a wide area and a large amount of investment. According to the current situation in China, the following studies should be conducted first:
(1) Research on super-precision hydrostatic spindle;
(2) Research on guide rails and drive devices;
(3) Research on the machine tool displacement measurement device;
(4) Research on high-precision numerical control system:
(5) Research on on-line measuring device for aspherical surface profile accuracy:
(6) Research on ductile grinding devices;
(7) Research on a constant temperature oil supply device;
(8) Conduct research on aspherical surface processing technology and related technologies, including research on diamond tool grinding technology, and also conduct research on environmental technology and other aspects.
The above technologies can be integrated into a composite processing device that combines CNC ultra-precision vehicles and grinding processing. The specific indicators that this CNC ultra-precision composite processing device should achieve are as follows:
Spindle accuracy: radial, axial 0.03-0.05μm:
Guide accuracy: 0.1-0.2μm/lOOmm
CNC system: Resolution string O. 0025-O. 010μm;
Temperature control technology achieves control accuracy of ±0. Ol°C
Machine displacement measuring device resolution: O. O05μm-O. 01μm
Profile accuracy online measurement device resolution: O. 002μm
The aspheric curved surface machined on the CNC ultra-precision composite machining device achieves:
Processing surface accuracy: 0.3 - O. 5μm;
Processing surface roughness: Ra0.005-0.020μm;

4 Precision Coupling Ultra-precision Machining Technology 4.1 Overview

The shape of a precision coupling can be divided into a cylindrical surface coupling, a planar coupling, a spherical coupling, and a cylindrical surface coupling. Precision components are widely used in aerospace, precision machinery, precision instruments, energy transportation and other sectors. In terms of its professional nature, the hydraulic industry is the most widely used. There are various processing methods depending on the material, accuracy, application, and lot size of the coupling. For flat parts, ultra-precision grinding, lapping, or ultra-precision turning are mainly used. For cylindrical surfaces and spherical surfaces, grinding, grinding, rolling, grinding, diamond and CBN reaming processes are mainly used.
The development of precision mating parts manufacturing technology is also the development process of precision machining and ultra-precision machining technologies. In the 1960s, the United States made the first unit with a feeding resolution of 0.025 μm and machining roundness to O. With the cylindrical grinding machine of 125μm, the processing of precision coupling parts has gradually entered the field of ultra-precision machining. Subsequently, the development of various precision and ultra-precision machining technologies has led to the continuous development of the manufacturing technology of precision coupling parts.
The use of ultra-precision machining technology to solve the processing of precision coupling parts has attracted foreign attention, especially in the military industry has invested a lot of manpower and material resources to solve the manufacturing problems of precision coupling parts. At present, the use of ultra-precision machining technology to solve the key issues in the manufacture of precision coupling parts is still in its infancy. Some domestic units mainly use high-precision grinding machines to perform coupling grinding, and also use ultra-precision technology to modify existing precision equipment to improve accuracy. There is no real super-precision grinding machine, ultra-precision grinding machine and other ultra-precision processing equipment in China. Currently, based on the needs of manufacturing technologies such as aviation, aerospace, warships, and weapons systems, the Sanzuo Institute of Research and Development has developed a series of ultra-precision machining equipment (including ultra-precision vehicles and , Cylindrical grinding, ultra-precision flat grinding, ultra-precision grinding machine, ultra-precision diamond grinding machine) and axial grinding device, and further process research.

4.2 Research Contents 4.2.1 Ultra-precision Turning, Boring, and Grinding Technology of Inner and Outer Cylindrical Couplings and Planar Couplings

This technology can be directly used in factory production, such as the production of gyroscope parts, oil pump rotors, oil pans, plane mirrors, etc., to solve the processing of non-ferrous metal cylindrical couplings and planar coupling parts. The technical indicators that should be achieved are as follows:
Cylindricity: 0.1 - O.3μm
Roundness: O. 05-O. 1μm
Dimensional accuracy: O.1 - O. 5μm
Roughness: Ra0.005-O.02μm
Flatness: λ/5 (φlOOmm)

4.2.2 External Grinding Technology of Cylindrical Couplings

Research on the device for ultra-precision external cause grinding, and research on grinding wheel dressing, dynamic balance, size control, temperature control and ultra-precision grinding process in ultra-precision grinding. The above technology can be directly used in factory production, such as the servo servo valve plunger, inertial parts, vibration tube and other production, can be used for the processing of cylindrical metal parts of ferrous metals and other high hardness materials. The technical indicators that should be achieved are as follows:
Cylindricity: O. 1 - O. 3μm
Radial fitting accuracy: O. 3—0.8μm
Roughness: Ra0. O05——0.02μm

4.2.3 Ultra-precision Grinding Technology for Large Numbers of External Causes, Columns, Balls, and Planar Mate Parts

The research of ultra-precision grinding devices for grinding cylinders, balls, and planes that can be used for mass production and their corresponding processing technologies can be used for plunger pumps, inertial precision super-precision bearings, plane mirrors and other components. Processing can be used directly for production. The technical indicators that should be achieved are as follows:
Cylindricity: 0.3 - O. 5μm
Degree of sphericity: O. 05-O. 1μm
Flatness: 0.05 - O. 1μm
Dimensional accuracy: 0.1 - O. 5μm
Roughness: 0.01 - O. 02μm

4.2.4 Research on Ultra-precision Grinding and Boring Technology of Diamond and CBN Superhard Abrasives with Inner Hole

The research on the ultra-precision external cause grinding process and the ELID dressing process has enabled the accuracy of the mortar tool to reach an ultra-precise level, which has enabled the processed component to reach a higher level to solve the technical difficulties in the machining of the internal bore hole. Developed a set of ultra-precision grinding and boring tools and processing methods, providing ultra-precision grinding, boring tools and fixtures that can be used directly for production. The technical indicators that should be achieved are as follows:
Cylindricity: O. 1 - O. 5μm
Dimensional accuracy: 0.3-0.8μm
Roughness: RaO. 01—0.04μm

4.2.5 Research on Measurement Technology of Inner and Outer Diameter High Accuracy Dimensions

A method and instrument for measuring inner and outer diameter dimensions are studied. Its technical indicators are as follows:
Resolution: O. Ol-O. 02μm
Stability: 0.02 μm/2 hours Measurement instability: Soil 0.05 μm

5 Conclusion

Ultra-precision machining technology has been developing for more than 40 years since it was developed in the 1950s. With the development of modern science and technology, new requirements have been continuously put forward for ultra-precision processing technology. The appearance of new materials and parts, the demand for higher precision requirements, etc., require the development of ultra-precision machining technologies on the basis of the original ones, such as improving the precision of traditional ultra-precision machining, and proposing new ultra-precision machining processes to improve modern ultra-precision Processing technology to adapt to the development of modern technology.