The miniaturization of structures and parts is one of the development trends in the field of technology. The development of economically viable micro-machining technology is of great significance for the development of micro-technology. At present, industrial micro-fabrication technology is mainly used in the semiconductor industry, they are only economical for mass production; the micro-fabrication technology used in the printing plate-making industry has very much the processing geometry and the materials that can be processed. Big limitations. 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-fabrication technology.
The first batch of micro-machining equipment was developed in the United States in the late 1960s and was mainly used to machine the surface of optical parts, which led to the development of super-finishing technology. At present, micron and submicron precision and surface roughness of tens of nanometers are achieved in the processing of optical, electronic and mechanical parts. In the late 1980s, the Carusle Research Center in Germany used micro-cutting to machine fine textures on the surface of micro-components to make micro-heat exchangers: they used single crystals on copper or Aluminum Foil on a cylinder. The tip of the diamond is grooved and eventually made into a miniature, highly efficient heat exchanger.
Until the 1990s, micro-cutting was mainly the processing of non-ferrous metal parts with diamond tools. With the continuous expansion of the application of microtechnology, it is required to process more diverse materials, especially the fine cutting of steel and ceramics, which has become the development direction of micro cutting technology.
In the field of super finishing, single crystal diamond tools are almost the only practical tools. The low friction coefficient and high thermal conductivity of the diamond are beneficial to the cutting process; it has a high hardness and a sharp edge that can be processed close to the atomic size, and the sharp edge is a must in the field of micromachining. Key technology. A sub-micron sharp edge can produce surface roughness on the order of a few nanometers. The sharp edge and low friction coefficient greatly reduce the cutting force, which is conducive to the precision of micro-machining and reduces the rigidity of super-finishing machine tools.
Rigid stone cutters are suitable for processing aluminum, pure copper, brass and copper alloys. Copper alloys have a high hardness and excellent surface quality 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 works well. It superimposes an ultrasonic vibration on the movement of the tool, which greatly reduces the contact time of the tool during cutting, thereby reducing the cutting temperature and inhibiting the conversion of diamond to graphite.
The knowledge of micro-cutting is actually obtained from ordinary cutting operations, including turning, milling, drilling, grinding, and in some cases, micro-machining is also sawing or planing.
At present, the most researched and most mature is super-fine turning. For example, a non-ferrous metal mold for pressing a Fresnel lens or a sample for surface roughness is produced.
By superimposing a high-frequency vibration driven by a piezoelectric crystal into the feed mechanism, when it is properly synchronized with the spindle rotation frequency and vibration, a non-rotationally symmetrical machining surface can be produced to achieve a polished mirror surface. At present, the technical level of ultra-precision turning has been able to machine extremely fine shaft diameters.
Milling is also considered to be the most flexible processing method in microfabrication. A single-toothed diamond disc milling slot can be used to machine grooves that intersect at various angles as compared to the previously described grooves on the film. It can be used to make molds for pressing optical grid structures, such as 100 lines per mm. The commercial disc cutter has a minimum width of about 100μm.
A shank milling cutter made of diamond, having a diameter of about 300 μm, has also been commercialized. The milling cutter is constructed as a universal straight-groove single-tooth milling cutter or as an end-blade engraving knives. It is particularly suitable for processing separators that are only a few microns thick. The disadvantage of such a slot milling cutter is that the minimum groove width depends on the diameter of the tool and the accuracy of the clamping.
Micro-cutting technology has so far been limited to the processing of silicon or non-metallic materials, and various synthetic materials have been processed by the forming process for steel processing. The research on fine cutting 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 mold is an important prerequisite for the economics of forming processing. Especially when the structure of the mold has a high depth-width ratio, the bending strength of the material is reliable for the forming process. Sex is decisive and sometimes even related to whether it can be shaped.
The fine cutting of steel cannot use diamond tools, mainly carbide milling cutters. Cemented carbide is a sintered body composed of many grains, and the size of the grains determines the microscopic sharpness of the blade. Therefore, the surface quality obtained by using a diamond cutter cannot be processed, but since it is low in price and can process steel, it is still the main tool for finely cutting steel.
In order to have a sharp blade, a tungsten-cobalt-based ultrafine-grained carbide is usually used. The ultrafine particle cemented carbide tool has a grain size of 0.5 to 1.0 μm and a radius of a cutting edge of a few micrometers.
In order to develop the micro-machining technology of steel, the Institute of Machine Tool and Manufacturing Technology of the University of Carusle in Germany first tested the carbide disc milling cutter with a tool width of 0.15 mm. The cutting was performed with a milling cutter. For the 52hrc quenched and tempered steel, processed high 1
Carbide shank milling cutters for fine cutting are widely used in the industry, coated and uncoated, with a minimum diameter of 0.1.
In order to avoid accidental breakage and premature wear of the tool, when processing hard materials such as steel, pay attention to the safety of the machining process and the smoothness of the machine tool, so the machine tool must have sufficient rigidity and dynamic performance, adopt high cutting speed and medium. Feed per tooth to ensure the cutting of the tool.
There are some difficulties in the manufacture of carbide micro-milling cutters. In addition to machining sharp edges on uneven tool materials, grinding cutters with a diameter of a few millimeters are required to be ground. The role of the cutting force, in order to solve this problem, you can choose a surface that does not produce cutting force, or you can machine parts made of tool steel below 100μm, such as direct milling on mold steel with a hardness of 55hrc. A micro-car is processed to be z=0.5μm, the surface of the forming surface is mirror-finished, and the parts after injection molding need not be processed further.
Grinding is specifically designed for the processing of hard and brittle materials, allowing micro-components to be made of glass, ceramic, silicon or hard alloy. Grinding wheels of a few tenths of a millimeter wide currently used for wafer cutting have been commercialized, usually using plated or chrome diamond abrasives as the material of the grinding wheel, and recently a cvd diamond coated cemented carbide forming wheel has been developed. Similar to the tool, the grinding wheel also has a disc-shaped grinding wheel for forming a grinding wheel and a versatile finger-shaped grinding wheel, which can process a fine arbitrary shape surface. The minimum diameter of the finger grinding wheel currently used in the research department is 50 μm.
In order to manufacture a micro hollow drill bit with a diameter of 0.9 mm and a diamond particle of d91 μm in a hard and brittle material, the Bravschweig Technical University in Germany has newly developed a cvd diamond drill bit of the same diameter with a diamond grain size of 4 μm to 8 μm. With a large cutting force, 55 blind holes were drilled on single crystal silicon with this new type of drill, and all the quality was qualified. This blind hole drill bit can drill a pilot hole in front of a closed cavity of a finger grinding machined part. The electroplated diamond core drill bit is more suitable for processing through holes on the plate. However, in the test, the chipping surface of the hole has a chipping of more than 100 μm along the crystal axis of the silicon, and there is also a hole on the edge of the hole. The chipping of 20 μm to 150 μm is a problem to be further studied.
Micro-machining is an important extension of the micro-machining process. Although the details of the parts that can be processed by micro-cutting are not as good as those of micro-machining, it can be used on various materials together with laser etching and other techniques. Process any spatial structure.
In addition, it requires less equipment than lithography-based microfabrication and eliminates the need for expensive motherboard manufacturing. In short, the micro-machining of parts has great advantages for economically producing medium-sized micro-components.
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