Cutting of ultra precision parts
The machining of ultra precision parts mainly includes ultra precision turning, mirror grinding and grinding. Micro turning is carried out on ultra precision lathe with a single crystal diamond turning tool which has been finely ground. The cutting thickness is only about 1 μ m. It is commonly used to process high-precision and smooth surface parts such as spherical, aspheric and plane mirrors of non-ferrous materials. For example, the aspherical mirror with a diameter of 800 mm used for processing nuclear fusion device has a maximum accuracy of 0.1 μ m and a surface roughness of rz0.05 μ M.
Special machining of ultra precision parts
When the machining precision of ultra precision parts is nanometer, or even the atomic unit (atomic lattice distance is 0.1-0.2nm), the cutting method of ultra precision parts can not adapt. It needs to use the special precision parts processing method, that is, chemical energy, electrochemical energy, thermal energy or electric energy, to make these energy exceed the combined energy between atoms, so as to remove the surface of the workpiece In order to achieve the purpose of ultra precision machining, some atoms are attached, combined or lattice deformed. These processes include mechanical chemical polishing, ion sputtering and ion implantation, electron beam exposure, laser beam processing, metal evaporation and molecular beam epitaxy.
The feature of these ultra precision parts machining methods is that the amount of material removed or added to the surface layer can be controlled very slightly. However, to obtain the machining accuracy of ultra precision parts, it still depends on the precise machining equipment and precise control system, and the ultra precision mask is used as the intermediary. For example, in VLSI plate making, electron beam is used to expose photoresist (see photolithography) on the mask to make the atoms of photoresist polymerize (or decompose) directly under electron impact, and then developer is used to dissolve the polymerized or unpolymerized parts to make the mask. It is necessary to use the ultra precision machining equipment with the positioning accuracy of ± 0.01 μ M.