Application prospect of the hottest micro machinin

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The application prospect of micro machining

the miniaturization of structures and parts is one of the development trends in the technical field. The development of economically feasible micro machining technology is of great significance for the development of micro technology. At present, the industrialized micro manufacturing technology is mainly used in the semiconductor industry, which is only economical for mass production; The micro manufacturing technology used in the printing plate making industry has great limitations on the geometry and materials that can be processed. Compared with these two manufacturing technologies, micro machining can make up for the above shortcomings. Therefore, the development of micro machining technology is a new field of micro manufacturing technology

the first devices for micro machining were developed in the United States in the late 1960s, mainly for machining the surface of optical parts, from which came the ultra precision machining technology. At present, the precision of micron and submicron and the surface roughness of dozens of nanometers have been achieved in the processing of optical, electronic and mechanical parts. In the late 1980s, the karrouth research center in Germany used micro cutting to process micro textures on the surface of micro components to manufacture micro heat exchangers: they grooved the copper foil or aluminum foil on a cylinder with the tip made of single crystal diamond, and finally made a micro and highly efficient heat exchanger

until the 1990s, micro cutting mainly used diamond tools to process non-ferrous metal parts. With the continuous expansion of the application field of micro technology, it is required to process more diverse materials, especially the micro cutting of steel and ceramics, which has become the development direction of micro cutting technology

diamond -- an ideal cutting material

in the field of ultra precision machining, single crystal diamond tools are almost the only practical tools. Diamond has low friction coefficient and high thermal conductivity, which is very beneficial to the cutting process; It also has high hardness and can be processed into sharp edges close to the atomic size. Making sharp edges is a key technology that must be solved in the field of micro cutting. A sub micron sharp edge can produce a surface roughness of several nanometers. Sharp cutting edge and low friction coefficient can greatly reduce the cutting force, which is conducive to the accuracy of micro cutting, but also reduce the requirements for the rigidity of ultra precision machining machine tools

diamond tools are suitable for processing aluminum, pure copper, brass and copper nickel alloys. Copper nickel alloy has high hardness and excellent surface quality can be obtained during processing. Diamond is not suitable for processing ferrous metals. In order to enable diamond to process steel, some devices are being developed, and one device has a good effect. It superimposes an ultrasonic vibration on the motion of the tool, which greatly reduces the contact time of the tool during cutting, thus reducing the cutting temperature and inhibiting the conversion of diamond to graphite

micro cutting comes from ordinary cutting

the knowledge of micro cutting is actually obtained from ordinary cutting, including turning, milling, drilling, grinding, and in some cases, micro machining is also used for sawing or planing

at present, the most studied and mature is ultra precision turning. For example, making non-ferrous metal molds for pressing Fresnel lenses or making sample blocks of surface roughness

by superimposing a high-frequency vibration driven by piezoelectric crystal into the feeding mechanism, when properly synchronized with the rotation frequency and vibration of the spindle, it can produce a non rotationally symmetrical machined surface to achieve a polished mirror. At present, the technical level of ultra precision turning has been able to process extremely fine shaft diameters

in micro machining, milling is also considered to be the most flexible machining method. Compared with the above-mentioned groove on the film, the groove with various angles can be machined with a single tooth diamond disc milling cutter. It can be used to manufacture molds for pressing optical grid structures, such as 100 lines per millimeter. The minimum width of the commercialized disc milling cutter is about 100 μ m。

a shank milling cutter made of diamond, with a diameter of about 300 μ m. It has also been commercialized. The structure of this milling cutter is a general straight groove single tooth milling cutter, which can also be made into an engraving cutter with an end edge. It is particularly suitable for processing diaphragms only a few microns thick. The disadvantage of this groove milling cutter is that the minimum groove width depends on the diameter of the cutter and the accuracy of clamping

steel is the object of micro cutting technology in the future.

micro cutting technology is still limited to processing silicon or non-metallic materials, and various synthetic materials have been processed by forming technology (including hard and brittle and soft and tough). Therefore, the next step of steel processing is very necessary. The research on micro machining of steel began in Germany in the 1990s and is still in the research stage. Its main application field is in the tool and die industry. The wear resistance of the die is an important premise for the wide demand of forming processing economy in the high-end utilization field. Especially when the structure of the die has a high depth width ratio, the bending strength of its material is of decisive significance to the reliability of forming processing, and sometimes even related to whether it can be formed

diamond cutters cannot be used for micro cutting of steel, and carbide milling cutters are mainly used. Cemented carbide is a sintered body composed of many grains, whose grain size determines the micro sharpness of the blade. Therefore, the surface quality obtained with diamond tools cannot be processed, but due to the low price and the ability to process steel, it is still the main tool for micro cutting steel

in order to have a sharp blade, tungsten cobalt ultrafine particle cemented carbide is usually used. The grain size of ultrafine cemented carbide tools is 0.5 ~ 1.0 μ m. Its cutting continues to be the most unqualified waste type detected in environmental protection, and the cutting edge arc radius is a few microns

in order to develop the micro cutting technology of steel, the school of machine tools and manufacturing technology of the University of karrouth in Germany first carried out the test of cemented carbide disk milling cutter, with a tool width of 0.15mm. Cross cutting with milling cutter, quenching and tempering steel with workpiece hardness of 52hrc has been processed with a height of 1mm and a section of 0.2 × Rows of 0.2mm2 are prisms used as molds for synthetic materials or powder injection materials

carbide shank milling cutters suitable for micro cutting have been widely used in industry. Coated and uncoated, with a minimum diameter of 0.1mm, and individual tool manufacturers can produce diameters of 50 μ M milling cutter

in order to avoid accidental breaking and early wear of the tool, when processing hard materials such as steel, we should pay attention to the safety of the processing process and the stability of the machine tool, so the machine tool is required to have sufficient rigidity and dynamic performance, and adopt high cutting speed and medium feed per tooth to ensure the cutting of the tool

There are some difficulties in the manufacture of cemented carbide micro milling cutters, that is, in addition to machining sharp edges on heterogeneous tool materials, milling cutters with a diameter of a few tenths of a millimeter should also be ground to withstand the effect of grinding force. In order to solve this problem, a processing method that does not produce cutting force (such as laser processing) can be selected. The surface with complex shape can be machined by milling method, and the 100 made of tool steel can also be machined μ For parts below m, such as directly milling a wheel housing mold of a mini car (1:160) on a mold steel with a hardness of 55HRC, its surface roughness reaches rz=0.5 μ m. The formed surface has a mirror finish, and the parts after injection molding do not need to be processed later

grinding is specially used for processing hard and brittle materials, so that micro components can be made of glass, ceramics, silicon or cemented carbide. At present, the 0.0 mm wide grinding wheel used for silicon wafer cutting has been commercialized. Usually, nickel plated or chromium plated diamond abrasive is used as the material of the grinding wheel. Recently, a CVD coated diamond cemented carbide forming grinding wheel experimental machine has been developed to measure the mechanical properties, safety performance and comfort performance of materials and parts. Similar to cutting tools, grinding wheels can also be used as disk-shaped grinding wheels for forming grinding wheels and finger shaped grinding wheels with good versatility. The latter can process micro arbitrary shaped surfaces. The minimum diameter of finger shaped grinding wheels currently used in research departments is 50 μ m。

grinding hard and brittle materials

in order to process micropores on hard and brittle materials (such as monocrystalline silicon), except for diamond particles with a diameter of 0.9mm and d91, which are usually manufactured by electroplating μ In addition to the micro hollow bit of M, the Technical University of brauschweig in Germany has newly developed a CVD diamond bit with the same diameter, and its diamond grain size is 4 μ m~8 μ m。 Despite the large cutting force, 55 blind holes were drilled on monocrystalline silicon with this new drill, and the quality was all qualified. The blind hole drill can drill a guide hole before the closed cavity of a part processed by a finger shaped grinding wheel. Electroplated diamond hollow drill bits are more suitable for machining through holes on plates, but in the test, there are more than 100 holes along the crystal axis of silicon on the drilling side of the hole μ The broken edge of M is also 20 on the edge of the hole μ m~150 μ M, this problem needs further study

conclusion and outlook

micro cutting is an important extension of micro machining technology. Although the details of parts that can be processed by micro cutting are not as good as those achieved by micro EDM at present, together with laser etching and other technologies, it can process arbitrary spatial structures on a variety of materials

in addition, it requires less equipment than the micro technology based on lithography, and saves expensive motherboard manufacturing. In short, micro machining of parts has great advantages for economically manufacturing medium batch micro components. (end)

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