Precision machining is the process of changing the size or performance of a workpiece with a processing machine. According to the temperature state of the workpiece being processed, it is divided into cold working and hot working. Generally processed at room temperature, and does not cause chemical or physical phase changes of the workpiece, called cold processing. Generally, processing at a temperature higher or lower than the normal temperature causes a chemical or physical phase change of the workpiece, which is called thermal processing. Cold machining can be divided into machining and pressure machining according to the difference in processing methods. Thermal processing is commonly used for heat treatment, forging, casting and welding.
There are mainly ultra-precision turning, mirror grinding and grinding. It is micro-turned on a super-precision lathe with a finely ground single crystal diamond turning tool. The cutting thickness is only about 1 micron. It is often used for the processing of spherical, aspherical and planar mirrors of non-ferrous materials with high precision and high surface roughness. Components. For example, an aspherical mirror with a diameter of 800 mm for processing a nuclear fusion device has a maximum precision of 0.1 μm and a surface roughness of Rz 0.05 μm.
Ultra-precision special processing
When the processing precision is nanometer, or even the atomic unit (atomic lattice distance is 0.1-0.2 nm), the cutting method can not be adapted. It requires special processing methods, that is, applying chemical energy, electrochemical energy, thermal energy or Electrical energy, etc., allows these energies to exceed the binding energy between atoms, thereby removing adhesion, bonding or lattice deformation between some atoms on the surface of the workpiece to achieve ultra-precision processing. Among these processes are mechanical chemical polishing, ion sputtering and ion implantation, electron beam exposure, laser beam processing, metal evaporation, and molecular beam epitaxy. These methods are characterized by very fine control of the amount of surface layer material removed or added. However, in order to obtain ultra-precision machining accuracy, it still relies on sophisticated processing equipment and precise control system, and uses an ultra-precision mask as an intermediary. For example, the plate making of VLSI is to expose the photoresist (see photolithography) on the mask by electron beam, so that the atoms of the photoresist are directly polymerized (or decomposed) under the impact of electrons, and then The polymerized or unpolymerized portion is dissolved with a developer to form a mask. Electron beam exposure plate making requires ultra-precision processing equipment with a table positioning accuracy of ±0.01 μm.