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Precision machining

Overview of ultraprecision machining technology

At present, the ultra-precision machining is to achieve the high-precision machining that can not be achieved by the conventional common precision machining means, and in terms of quantity, it is required to process the shapes and sizes of sub-micron and even nanometer- Nano-surface roughness, but exactly how much precision can be considered ultra-precision machining section depends on the size of the part, the complexity and whether it is easy to deformation and other factors.

Ultra-precision machining includes ultra-precision cutting (car, milling) ultra-precision grinding, ultra-precision grinding (mechanical grinding, mechanochemical grinding, grinding and polishing, non-contact floating grinding, flexible launch processing, etc.) and ultra-precision special processing Beam, ion beam and laser beam machining, etc.). The above methods can be processed out of ordinary precision machining up to the dimensional accuracy, shape accuracy and surface quality. Each ultra-precision machining method is based on the requirements of different parts of the choice.

1. Ultra-precision machining

Ultra-precision machining is characterized by the use of diamond cutting tools. Diamond cutter and non-ferrous metal affinity, hardness, wear resistance and thermal conductivity are very good, and can be sharpened very sharp (edge ​​arc radius can be less than ρ0.01μm, the actual application of ρ0, 05μm) can be machined Better than Ra0.01μm surface roughness. In addition, the ultra-precision machining also uses high-precision basic components (such as air bearings, air guide rails, etc.), high-precision positioning detection components (such as grating, laser detection system, etc.) and high-resolution micro-feed mechanism . The machine itself to take constant temperature, vibration and vibration isolation and other measures, but also to prevent contamination of the workpiece device. The machine must be installed in a clean room. Parts for ultra-precision machining must be of uniform texture with no defects. In this case, processing oxygen-free copper, the surface roughness can reach Ba0.005μm, processing φ800mm aspherical lens, the shape accuracy of up to 0.2 / μm. Ultra-precision machining technology in the aerospace, optics and civil applications such as a very wide range (see Table 1) and to a higher precision direction.

2 ultra-precision grinding

Ultra-precision grinding technology is based on the general precision grinding developed. Ultra-precision grinding not only to provide a mirror-level surface roughness, but also to ensure accurate geometry and size. To this end, in addition to considering a variety of process factors, but also must have high precision, high stiffness and high damping characteristics of the benchmark components to eliminate the impact of a variety of dynamic errors and to take high-precision detection and compensation tools.

At present, the object of ultra-precision grinding is mainly hard and brittle materials such as glass and ceramic. The goal of grinding is to form a smooth surface with a smoothness of 3-5 nm, that is, the required surface roughness can be achieved without grinding by grinding degree. As a nanoscale grinding process, the machine is required to have high precision and high rigidity, and brittle materials can be ductilely grinded. Nano-grinding technology is an important and effective processing technique for gas turbine engines, particularly for processes requiring high fatigue strength materials such as ceramic materials for jet engine turbines for aircraft.

In addition, the grinding wheel dressing technology is also very crucial. Although grinding is more effective than grinding removal

Material, but it is difficult to obtain the mirror when grinding glass or ceramic, mainly because the grinding wheel surface is too small, the surface of the grinding wheel is easily blocked by the chip. Electrolytic online dressing (ELID) cast iron fiber binder (CIFB) grinding wheel technology invented by the Japanese physico-chemical Institute scholar Omori Dr. Omori can be a good solution to this problem.

Current ultraprecision grinding technology can produce cylindrical parts with 0.0 1μm roundness, 0.1μm dimensional accuracy and Ra0.005μm roughness. Planar ultra-precision grinding can produce a surface of 0.03μm / 100mm.

3 ultra-precision grinding

Ultra-precision grinding including mechanical grinding, chemical mechanical polishing, floating grinding, elastic launch processing and magnetic grinding and other processing methods. Ultra-precision grinding of the spherical sphericity up to 0.025ttm, surface roughness of RaO.003μm. The use of elastic launch processing can be processed without deterioration of the mirror, the roughness up to 5A. The highest precision ultra-precision grinding can be machined flatness of λ / 200 parts. The key conditions for ultra-precision grinding are virtually vibration-free grinding movements, precise temperature control, a clean environment and fine, uniform abrasives. In addition, high-precision detection methods are also indispensable.