To judge the level of a machine tool, it depends on its repeated positioning accuracy. If the repeated positioning accuracy of a machine tool can reach 0.005mm (ISO standard, statistical method), it is a high-precision machine tool. If it is 0.005mm (ISO standard), it is a high-precision machine tool. ., statistical method) The following are ultra-high-precision machine tools. High-precision machine tools must have the best bearings and screws.
When talking about the "accuracy" of CNC machine tools, it is important to clarify the definitions and calculation methods of standards and indicators.
When Japanese machine tool manufacturers specify "accuracy", they usually use JISB6201 or JISB6336 or JISB6338 standards. JISB6201 is generally used for general machine tools and ordinary CNC machine tools.
JISB6336 is generally used in machining centers, while JISB6338 is generally used in vertical machining centers. The above three standards are basically the same when defining position accuracy.
This article only uses JIS B6336 as an example, because on the one hand, this standard is relatively new, and on the other hand, it is slightly more precise than the other two standards.
European machine tool manufacturers, especially German manufacturers, generally adopt the VDI/DGQ3441 standard.
American machine tool manufacturers usually adopt the NMTBA (National Machine Tool Builder's Assn) standard (this standard originated from a study by the American Machine Tool Builders Association and was promulgated in 1968 and later revised).
The standards mentioned above are all related to ISO standards.
For example, the dimensional accuracy and shape accuracy of typical parts processed by machining centers are compared with domestic and foreign levels. In China, they are roughly 0.008~0.010mm.
The international advanced level is 0.002~0.003mm.
Although the development of my country's machine tool manufacturing industry has had ups and downs, it has always paid greater attention to CNC technology and CNC machine tools and has strong market competitiveness.
However, in terms of medium and high-end CNC machine tools, there is still a large gap between the development of some advanced foreign products and technology, and most of them are in the technology tracking stage.
Ultra-precision machining currently refers to dimensional and positional accuracy of 0.01~0.3μm, shape and contour accuracy of 0.003~0.1μm, and surface roughness of steel parts Ra≤0.05μm.
Copper parts Ra≤0.01μm. Domestically developed ultra-precision CNC lathes and CNC milling machines have been put into production. Currently, there is a need to develop ultra-precision grinding machines and ultra-precision composite processing machine tools in terms of varieties.
At the same time, it is necessary to further improve the performance of ultra-precision spindle units, ultra-precision guide rail sub-units, ultra-precision smooth drive systems, ultra-precision contour control technology and nanometer-level resolution CNC systems and accelerate their engineering.
Ultra-precision machine tools are mainly used to solve the ultra-precision processing of domestic high-tech and key national defense products. Although the demand is not large, it is a sensitive technology blocked by foreign technology.
On the other hand, in-depth research on ultra-precision machining technology and the extension of its results will contribute to the development and industrialization of high-precision machine tools that require large amounts of machining accuracy at the sub-micron level.
