Breakthroughs in the processing and application technology of basic components of ultra-precision machine tools can provide strong technical support for the survival and development of the manufacturing industry. However, my country's ultra-precision machine tools and key basic components previously relied mainly on imports.
The cylindrical roundness processing of shaft parts at home and abroad is basically achieved by ultra-precision cylindrical grinding machines. Taking the grinding of a shaft core with a diameter of 100 mm and a length of 300 mm as an example, our country's cylindrical grinder can probably grind to a level of 1 to 2 microns, while foreign countries can achieve a level of 0.3 to 0.5 microns.
In order to solve the technical problems of machine tools and key components, Dai Yifan, a professor at the National University of Defense Technology, and his team spent 5 years proposing a deterministic modification processing technology for the outer roundness of shaft parts, which improved the roundness accuracy of the shaft core to 0.1 micron, and successfully developed it. Introducing ultra-precision air static pressure spindle. Recently, after testing by the China Institute of Metrology, the relevant parameters of the hydrostatic spindle have reached the international advanced level, which will effectively improve my country's ultra-precision machining accuracy. Relevant research results have been published in "Materials" and "Micro Machinery".
picture
Mandrel multi-sensor in-situ measurement. Photo courtesy of National University of Defense Technology
Grind ultra-precision parts like a shovel
The reason why my country's ultra-precision machine tools and key basic components have mainly relied on imports before is that the biggest technical problem lies in the lack of "work machines" for processing core parts, that is, machines that manufacture machines and machinery, also known as machine tools, including lathes, grinders, planers, Drilling machines, etc., are the tools for tool making and the basis for industrial self-reliance.
General machining is a process of "copying" the precision of machine tools to parts. In other words, without high-precision machine tools, high-precision parts cannot be processed. Without high-precision parts, high-precision components and machine tools cannot be assembled. The absence of a working machine for manufacturing high-precision parts limits the development of the entire ultra-precision machine tool industry.
Dai Yifan's team has been engaged in the research and development of modern optical manufacturing technology for a long time. They found that the final manufacturing accuracy of optical parts far exceeds the accuracy of the processing equipment used, and the basic principle of optical manufacturing is to gradually remove high error points in precision evolutionary processing. The team tried to apply this processing method based on the "precision evolution" principle to high-precision processing of mechanical parts. Finally, through the innovation of processing principles, they proposed a deterministic modification process for the outer roundness of shaft parts, breaking through the high-precision "work machine" limit.
How does the deterministic shaping process work? "It's like using a shovel to level a piece of land, that is, shoveling an appropriate amount of soil from the ridged and uneven areas, and repeating this until a very flat ground is obtained." Dai Yifan said that this process relies on a set of digital equipment, including obtaining High-precision roundness meters for cylindrical shapes, time-controlled grinding machine tools that realize digital and precise control of material removal, special computer programs that obtain the residence time of grinding tools at specific spatial positions, etc.
Machinery replaces experienced workers
With the help of new technology, Dai Yifan's team broke through the time-controlled grinding processing technology based on the principle of precision evolution, formed an integrated process method for on-site processing and testing of cylindrical parts, and successfully developed an ultra-precision aerostatic spindle.
Test results from the China Institute of Metrology show that the radial runout of the air static pressure spindle is less than 15 nanometers, and the end face runout is less than 15 nanometers. If it were a main axis as big as the earth, the amplitude caused by the rotational motion would not exceed 1 meter.
The test results show that the radial static stiffness of the aerostatic spindle is greater than 200 N per micron, and the axial static stiffness is greater than 200 N per micron. In layman's terms, it means that the spindle can remain motionless under a gravity load of 20 kilograms, and the deformation will not exceed 1 micron. Comparing the product manual of Precitech, which represents the highest level in the field of ultra-precision in the United States, the above technical indicators are equivalent to or even higher.
At present, the outer roundness of shaft parts can be processed and ground to a level of a few tenths of a micron at home and abroad. If you want to improve it, you can only rely on manual grinding and trimming. "Our new technology can get rid of the dependence on extremely experienced worker masters, and can easily organize production according to the modern industrialization model, promoting the mass and high-efficiency production and application of ultra-precision basic components." Dai Yifan said, ultra-precision Breakthroughs in the processing and application technology of basic machine tool components will provide strong technical support for the survival and development of the manufacturing industry, improve the supporting industry chain of high-end machine tools, greatly enhance the competitiveness of high-performance functional components, and promote the localization of high-end precision and ultra-precision machine tools.
Dai Yifan added that these breakthroughs will also effectively solve the ultra-precision equipment and core process problems faced by ultra-precision processing of key detection and guidance components, further facilitate the mass production of ultra-precision processing of high-end core components, and achieve the rapid transformation of scientific research results.
