Since China listed "equipment manufacturing" as a national development strategy, China's equipment manufacturing industry has made rapid progress. The manufacturing capabilities of many large-scale equipment have reached the world's advanced level, or even the world's top level. However, China's overall manufacturing industry is still lagging behind, and its backwardness lies in the backwardness of precision manufacturing.
Ultra-precision machining technology is a crucial supporting technology for modern high-tech warfare, a foundation for the development of modern high-tech industries and science and technology, and a direction for the development of modern manufacturing science.
The development of modern science and technology is based on experimentation, and almost all experimental instruments and equipment require the support of ultra-precision machining technology. The shift from macroscopic to microscopic manufacturing is one of the future trends in manufacturing. Currently, ultra-precision machining has entered the nanoscale, and nano-manufacturing is a cutting-edge topic in ultra-precision machining. Developed countries around the world attach great importance to it.
Development stages of ultra-precision machining
Current ultra-precision machining aims to achieve the ultimate shape accuracy, dimensional accuracy, surface roughness, and surface integrity (no or minimal surface damage, including defects such as microcracks, residual stress, and structural changes) without altering the physical properties of the workpiece material.
The research content of ultra-precision machining, namely the various factors affecting the accuracy of ultra-precision machining, includes: ultra-precision machining mechanism, workpiece material, ultra-precision machining equipment, ultra-precision machining tools, ultra-precision machining fixtures, ultra-precision machining inspection and error compensation, ultra-precision machining environment (including constant temperature, vibration isolation, cleanroom control, etc.), and ultra-precision machining process. Scholars both domestically and internationally have been conducting systematic research on these topics. The development of ultra-precision machining has gone through the following three stages.
1) From the 1950s to the 1980s, the United States took the lead in developing ultra-precision machining technology represented by single-point diamond cutting, which was used for machining large parts such as laser nuclear fusion mirrors, spherical and aspherical parts in aerospace, defense, astronomy and other fields.
2) The 1980s and 1990s saw the initial application of ultra-precision machining equipment in civilian industries. With government support, companies such as Moore & Co. and Pritec in the United States, Toshiba and Hitachi in Japan, and Cranfield in Europe commercialized ultra-precision machining equipment for use in the manufacture of civilian precision optical lenses. However, individual ultra-precision machining equipment remained scarce and expensive, primarily ordered as custom-made special-purpose machines. During this period, ultra-precision diamond grinding technology and grinding machines capable of machining hard metals and brittle materials also emerged, but their processing efficiency could not compare to that of diamond lathes.
3) Since the 1990s, civilian ultra-precision machining technology has gradually matured. Driven by industries such as automobiles, energy, medical equipment, information, optoelectronics, and communications, ultra-precision machining technology has been widely applied to the processing of parts such as aspherical optical lenses, ultra-precision molds, disk drive heads, disk substrates, and semiconductor substrates. With the gradual maturation of related technologies for ultra-precision machining equipment, such as precision spindle components, rolling guides, hydrostatic guides, micro-feed drive devices, precision CNC systems, and laser precision detection systems, ultra-precision machining equipment has become common production equipment in industry. Furthermore, the accuracy of the equipment has gradually approached the nanometer level, and the range of workpiece sizes that can be processed has become larger, leading to increasingly widespread applications. With the development of CNC technology, ultra-precision five-axis milling and flying cutting technologies have also emerged, enabling the processing of complex parts such as non-axisymmetric aspherical surfaces.
Development of ultra-precision machining abroad
The United States, the United Kingdom, and Japan are among the world's leading countries in ultra-precision machining technology. These countries possess not only high overall levels of complete systems of ultra-precision machining technology, but also a very high degree of commercialization.
In the late 1950s, the United States developed ultra-precision cutting technology for diamond tools, known as "SPDT technology" (Single Point Diamond Turning) or "micro-inch technology" (1 micro-inch = 0.025 μm). It also developed corresponding ultra-precision machine tools with air bearing spindles for machining large spherical and aspherical parts for laser nuclear fusion mirrors, tactical missiles, and manned spacecraft.
In the field of large-scale ultra-precision machine tools, the LLL National Laboratory in the United States successfully developed two large-scale ultra-precision diamond lathes in 1986: one is the horizontal DTM-3 diamond lathe with a diameter of 2.1m , and the other is the LODTM vertical large-scale optical diamond lathe with a diameter of 1.65m . The LODTM vertical large-scale optical diamond lathe is widely recognized as the world's most precise ultra-precision machine tool. The United States later developed a large 6-axis CNC precision grinding machine for the precision grinding of large optical mirrors.
Cranfield Precision Engineering Institute (CUPE), part of Cranfield Institute of Technology in the UK, is a unique representative of the UK's ultra-precision machining technology. For example, CUPE's Nanocentre can perform ultra-precision turning and grinding, and can also perform ultra-precision grinding with a grinding head . The shape accuracy of the machined workpiece can reach 0.1μm and the surface roughness Ra<10nm.
In 1991, Cranfield Precision Machining Center successfully developed the OAGM-2500 multi-functional three-axis linkage CNC grinding machine (2500mm×2500mm worktable area), which can process (grind, turn) and measure precision free-form surfaces. This machine tool uses a workpiece assembly method and can also process large reflecting mirrors with a diameter of 7.5m for astronomical telescopes.
Japan started its research on ultra-precision machining technology later than the United States and the United Kingdom, but it is currently the country with the fastest development of ultra-precision machining technology in the world.
Development of Ultra-Precision Machining in my country
For a considerable period in the past, my country's imports of ultra-precision machine tools were severely restricted due to embargoes imposed by Western countries. However, after my country successfully developed its own CNC ultra-precision machine tools in 1998, Western countries immediately lifted the ban, and my country has since imported several such machines.
In my country, institutions such as the Beijing Machine Tool Research Institute, the Aviation Precision Machinery Research Institute (Aeronautical 303), Harbin Institute of Technology, and the National University of Defense Technology are now capable of producing several types of ultra-precision CNC diamond machine tools.
The Beijing Machine Tool Research Institute is one of the leading institutions in China conducting research on ultra-precision machining technology. It has developed various types of ultra-precision machine tools, components, and related high-precision testing instruments, such as precision bearings with an accuracy of 0.025μm , the JCS-027 ultra-precision lathe, the JCS-031 ultra-precision milling machine, the JCS-035 ultra-precision lathe, ultra-precision lathe CNC systems, photocopier photosensitive drum processing machine tools, infrared high-power laser reflectors, and ultra-precision vibration-displacement micrometers, reaching the leading level in China and the advanced level in the world.
The NAM-800 nanometer CNC lathe is the latest generation of nanoscale machining tools developed by the Beijing Machine Tool Research Institute. It represents a perfect integration of current CNC technology, servo technology, and mechanical manufacturing technology. This machine tool provides excellent machining capabilities for my country's cutting-edge technological development.
The 303 Institute of the Ministry of Aerospace Industry has conducted in-depth research and product manufacturing in areas such as ultra-precision spindles and granite coordinate measuring machines.
Harbin Institute of Technology has conducted fruitful research in areas such as diamond ultra-precision cutting, diamond tool crystal orientation and grinding, and online electrolytic dressing technology for diamond micron powder grinding wheels.
Tsinghua University has conducted in-depth research on ultra-precision processing equipment for integrated circuits, disk processing and testing equipment, micro-displacement worktables, ultra-precision belt grinding and polishing, ultra-precision grinding with diamond micro powder wheels, and ultra-precision cutting of non-circular sections, and corresponding products have been launched.
In addition, the Changchun Institute of Optics, Fine Mechanics and Physics of the Chinese Academy of Sciences, Huazhong University of Science and Technology, Shenyang No.1 Machine Tool Plant, Chengdu Tool Research Institute, and National University of Defense Technology have all conducted research in this field and achieved remarkable results.
However, in general, my country still lags significantly behind foreign countries and meets actual production requirements in terms of the efficiency, precision, reliability, and especially the specifications (large dimensions) and technical compatibility of ultra-precision machine tools. Furthermore, the precision machining of complex curved surfaces has always been a barrier to the development of my country's manufacturing industry, which is crucial to the long-term economic development of the country and requires substantial further research.
Development trend of precision machining
1. High precision and high efficiency.
High precision and high efficiency are the eternal themes of ultra-precision machining. Generally speaking, fixed abrasive machining constantly pursues the machining accuracy of free abrasive particles, while free abrasive machining constantly pursues the efficiency of fixed abrasive machining. Current ultra-precision machining technologies such as CMP and EEM can achieve extremely high surface quality and integrity, but at the expense of machining efficiency. Ultra-precision cutting and grinding technologies, while highly efficient, cannot achieve the machining accuracy of CMP and EEM. Exploring machining methods that balance efficiency and precision has become the goal of researchers in the field of ultra-precision machining. The emergence of semi-fixed abrasive machining methods reflects this trend. This is also manifested in the birth of composite machining methods such as electrolytic magnetic abrasive grinding and magnetorheological abrasive flow machining.
2. Process integration.
Competition among enterprises is becoming increasingly fierce, and high productivity is becoming a crucial condition for their survival. Against this backdrop, there are calls to replace grinding with grinding and even polishing. On the other hand, the trend of using a single machine to perform multiple processing operations (such as turning, drilling, milling, grinding, and finishing) is becoming increasingly apparent.
3. Large-scale and miniaturized.
To manufacture large optoelectronic devices needed in fields such as aviation, aerospace, and astronautics (such as mirrors on large astronomical telescopes), large-scale ultra-precision machining equipment is required. To manufacture micro-devices needed in fields such as micro-electromechanical systems and optoelectronic information (such as micro-sensors and micro-drive components), micro-ultra-precision machining equipment is required (but this does not mean that machining micro-small workpieces necessarily requires micro-small machining equipment).
Ultra-precision machining technology is entering a prosperous era. Significant progress has been made in ultra-precision cutting, ultra-precision grinding, and ultra-precision lapping and polishing technologies, achieving surface finishes at the nanometer or sub-nanometer level, and the processing methods are becoming increasingly diversified. In the manufacturing of flow meter sensors, precision machining technology ensures the product's machining accuracy in order to achieve high-precision measurement.
The U-How® volumetric rotary piston flow meter, developed and manufactured by Shanghai Kanghui, is a precision-machined metering device. It has been tested and certified by the Beijing Institute of Metrology and Testing, achieving an accuracy of 1.0 class. To ensure the flow meter rotor can reach over 500,000 revolutions per minute and the stability of the cavity volume, the cavity and rotor, along with other major components, are all precision-machined, guaranteeing dimensional accuracy of at least 1μm.
U-How® Fuel Flow Meter
U-How® Kanghui Flow Meter is a high-precision flow sensor independently developed and manufactured by Shanghai Kanghui Industrial Development Co., Ltd. based on the rotary piston working principle. It features low flow velocity measurement, wide measuring range, high accuracy, simple structure, and safe and reliable operation.
Working principle
A rotary piston flow meter is a type of volumetric flow meter. It operates based on the principle of maintaining a tangential seal between the piston and the metering chamber. It features a fixed eccentric metering element, the piston. Under pressure differential, a torque is generated on the piston, causing it to rotate eccentrically. The number of piston rotations is proportional to the fluid flow rate. By recording the number of piston rotations through a counting mechanism, the total fluid flow rate can be measured.
The inlet and outlet of the rotary piston flow meter are separated by a baffle. When the fluid to be measured enters the measuring chamber from the inlet, a pressure difference is created between the inlet and outlet, forcing the piston to rotate counterclockwise as shown in Figure a. As the fluid flows in continuously, the piston rotates as shown in Figure b, forming two crescent-shaped cavities. Under the action of the pressure difference, the piston is forced to rotate as shown in Figure c. Fluid V2 is discharged from the outlet, causing the piston to rotate as shown in Figure d. Under the action of the pressure difference, the fluid ejected per revolution of the piston is equal to the sum of V1 and V2.
Working principle diagram
Exploded view of flow meter
Product Parameters
1. Mechanical components:
2. Electronic components:
Measuring medium:
It can measure light and medium-quality oils, such as gasoline, diesel, kerosene, naphtha, and lubricating oil.
Product Qualification
1. Invention Patent: ZL201020504169 . 8 Flow Sensor
2. Vehicle inspection report from the National Automotive Quality Supervision and Inspection Center
3. Precision testing report commissioned by the Ministry of Transport from the Beijing Institute of Metrology
Fuel consumption monitoring solution
Application objects
1. Engine:
It measures the fuel consumption of various power machines in trains, automobiles, engineering vehicles, tractors, generator sets, and ships navigating inland waterways or coastal waters, as well as the loading and unloading of various heavier liquids and the measurement of liquid flow through pipelines.
2. Burner:
Fuel consumption measurement for equipment such as vehicle-mounted boilers and mobile boilers.
Data collection methods
By collecting flow meter pulse data, the system integration of the equipment unit is achieved via RS485/RS232 interface.
Solution
Implementation Cases
A large oil group:
Pipe laying machine, mobile power station, multi-functional vehicle, pipe bending machine, air compressor, etc.
A large oilfield:
Boiler trucks, wax removal trucks, superconducting trucks, cement trucks, cranes, etc.;
port:
Gantry cranes, forklifts, reach stackers, loaders, etc.
other:
Tire pressure and fuel consumption testing; driver skills competition; engine performance calibration
air compressor
