In the field of microsystem technology, product development needs the common development of a variety of micro technologies. For example, it requires the joint efforts of micro mechanical parts, micro optical parts and micro electronic components. Micro digital cameras need the cooperation of the above micro technologies. The increase of product demand in the field of micro technology also leads to the increase of demand for micro machinery products, which puts forward higher requirements for the production and processing of mechanical products. Therefore, the production technology of micro products, the production and manufacturing of micro structural parts and the research and development of micro components are new areas that need to be strengthened urgently.
Because of the limited machinability, high precision and small manufacturing tolerance, the machining of high hardness micro parts is a very difficult task. In the industrial mass production, the main production process of micro structural parts is rolling, micro die casting, hot stamping and so on. In addition to grinding and laser cutting, EDM is also a feasible processing technology for micro structure parts with high wear resistance. Due to the corrosion characteristics of the electrode in micro machining system, EDM is widely used in micro parts. These two processing methods have nothing to do with the properties of the workpiece material, are not affected by the workpiece material, and almost do not produce cutting force, so they can produce very small structural parts.
The concept of micro EDM corrosion machining (abbreviated as μ – EDM) refers to the production and processing of micro workpieces and micro structural parts by means of EDM. It is an application of EDM in the field of micro machining in mechanical machining. In micro EDM, the contour size of the workpiece is obviously less than 1 mm. The difference between micro EDM and traditional EDM is first of all very small electrode. In addition, it is the electrical parameters and production process parameters suitable for micro workpiece and micro structural parts. Due to the small volume and size of the micro workpiece, all processing parameters can not exceed the limit of the thermal load of the workpiece. This means: to reduce the discharge energy, reduce the current density.
In addition to the standard motor with adjustable current, the modern EDM equipment is equipped with a relaxation oscillator, which can be used for micro EDM and surface precision machining. According to the discharge capacitance and distributed capacitance of the electrical conduction distance, the capacitive micro oscillator can generate very small discharge energy. 1 μ J / each discharge process; the minimum operating current is 0.1A; the shortest discharge duration is 50ns; and the discharge frequency reaches 10MHz. The minimum distance of spark can reach 15 μ M. At present, the minimum structure size that can be achieved by micro EDM is about 20 μ M. Japanese researchers have successfully machined holes with a diameter of 5 μ m on a steel sheet with a thickness of 10 μ M. When machining this kind of hole, they fully control the discharge capacitance of electrical wire and fixture system in the process of electric spark corrosion, making it less than 10PF. In micro EDM corrosion machining, the machine tool is only allowed to have very small discharge capacitance, such as using ceramic clamps and shielded electrical wires to reduce the discharge capacitance of the machine tool system; capacitors and circuit boards should also be strictly separated from the processing electrode in space.
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