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2022.12.14
Electronic discharge machining (EDM) is a manufacturing process that removes material from a workpiece by applying a series of current discharges between two electrodes separated by a dielectric bath. What are advantages and disadvantages of EDM? And how does the EDM machining process work?
In EDM, the electrode and the workpiece are respectively connected to the two poles of the pulse power supply and immersed in the working fluid, or the fluid is filled into the discharge gap. Through the gap automatic control system, the electrode is controlled to feed the workpiece. When the gap between the two electrodes reaches a certain distance, the pulse voltage applied on the two electrodes will decompose the fluid and generate spark discharge. A large amount of heat energy is instantaneously concentrated in the small discharge channel. The temperature will rise, and the pressure also changes rapidly. Therefore, a small amount of metal materials on the working surface will immediately melt, vaporize and explode into the working fluid. It will quickly condense and form solid metal particles, which will be taken away by the working fluid. Then, a small dent is left on the surface of the workpiece, the discharge is temporarily stopped, and the fluid between the two electrodes recovers the insulation state. After that, the next pulse voltage immediately hits the other side close to the two electrodes, generating spark discharge and repeating the above process. Under the condition that the discharge gap between the tool electrode and the workpiece is kept constant, the electrode is continuously fed into the workpiece while the workpiece metal is corroded. Therefore, as long as the shape of the tool electrode and the relative movement between the tool electrode and the workpiece is changed, various complex contours can be created.
1) It can process any hard, soft, tough, and brittle conductive materials, and the electrode is easy to process.
Because EDM removes materials by the heat energy of pulse discharge, the machinability of materials mainly depends on the conductivity and thermal properties of materials, such as melting point, boiling point, thermal conductivity, etc., but is almost independent of their mechanical properties. EDM can be used to machine hard workpieces with soft tools, and even to machine superhard materials such as polycrystalline diamond and cubic boron nitride. At present, electrode materials are mostly pure copper, brass, and graphite.
2) EDM is suitable for machining special and complex shape parts.
Because the tool electrode does not directly contact the workpiece during machining, and there is no cutting force during machining, it is suitable for machining low-stiffness workpieces and micromachining. The shape of the tool electrode can be simply copied to the workpiece, especially suitable for machining workpieces with complex geometric shapes, such as complex cavity mold processing. The adoption of numerical control technology makes it possible to process complex shaped parts with simple electrodes.
3) A wide range of machining accuracy.
Pulse parameters can be adjusted in a large range, and rough, semi-finish, and finish machining can be carried out continuously on the same machine tool.
1) It is mainly used for processing conductive materials such as metals. Certain conditions are required for processing semiconductor and non-conductive materials.
2) Generally, the machining speed is slow, so the cutting is usually arranged to remove most of the machining allowance, and then the EDM is carried out to improve the machining efficiency. The productivity of EDM with special water-based noncombustible working fluid is close to that of cutting.
3) There is electrode loss. In EDM, the electrode and workpiece are relatively static and easy to wear, so multiple electrodes are usually used for machining. Low-loss machining with a relative loss of less than 1% can be realized in rough EDM. In wire cutting, new electrode wires constantly supplement and replace the electrode wires that have been lost in the electrochemical machining area due to the continuous movement of electrode wires, thus avoiding the impact of electrode loss on machining accuracy.
4) The minimum corner radius is limited. The minimum corner radius in EDM is the machining gap, and the minimum corner radius in wire cutting is the radius of the electrode wire plus the machining gap.
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