CNC machining accuracy and tolerance standards
Precision And Tolerance Standard:
CNC machining is associated with ISO standards. It needs to look at the level of a machining center. It depends on its repeat positioning accuracy. If a machine tool's repeat positioning accuracy can reach 0.005mm (ISO standard, statistical method), it is a High-precision machine tools, in the 0.005mm (ISO standard, statistical methods) below, is ultra-high-precision machine tools, high-precision machine tools, have the best bearings, screw.
When it comes to the "accuracy" of CNC machine tools, it is important to understand the definition of standards, indicators, and calculation methods. When the Japanese machine tool production mark is set to “accuracy”, JISB6201 or JISB6336 or JISB6338 standards are generally used.
JISB6201 is generally used for general-purpose machine tools and general CNC machine tools, JISB6336 is generally used for machining centers, and JISB6338 is generally used for vertical machining centers.
The above three standards are basically the same when defining the positional accuracy. Herein, only JIS B6336 is taken as an example because on the one hand the standard is relatively new, on the other hand it is slightly more accurate than the other two standards.
European machine tool manufacturers, especially German manufacturers, generally use the VDI/DGQ3441 standard.
U.S. machine tool manufacturers usually use the National Machine Tool Builder's Assn (NMTBA) standard (this standard originates from a study of the American Machine Tool Manufacturing Association, which was promulgated in 1968 and later modified).
The dimensional accuracy and shape accuracy of the typical machining parts in the machining center are compared with those in other countries. The value in the country is generally about 0.008 to 0.010 mm, It is roughly 0.008 to 0.010mm in China, and the international advanced level is 0.002 to 0.003mm.
KFS ultra-precision machining currently refers to the size and position accuracy of 0.01 ~ 0.3μm, shape and contour accuracy of 0.003 ~ 0.1μm, surface roughness of steel Ra≤0.05μm, copper Ra≤0.01μm.
Domestically developed ultra-precision CNC lathes and CNC milling machines have been put into production.
At present, ultra-precision grinding machines and ultra-precision compound processing machines need to be developed on the varieties, and at the same time, super-precision spindle units, ultra-precision rail sub units, ultra-precise and smooth drive systems, ultra-precise contour control technologies, and nano-resolution numerical control systems must be further improved. Performance and speed up its engineering.
