In the first half of the twentieth century, scientists proposed the processing of metal using a spark charge. This method is called EDM. The processing principle is simple and consists in the following: in a liquid dielectric medium, two electrodes are energized together under voltage (anode and cathode). Moreover, the role of the cathode is performed by the workpiece. An electric discharge occurs between the anode and cathode . During the interaction, energy is released that can heat and remove metal particles from the surface of the electrode. In other words, the destruction of metal layers occurs under the influence of electric discharges (metal erosion).
Due to the supply of voltage to the electrodes in the form of short pulses, the energy does not act deep into the metal. This ensures that the part during processing does not lose its physical properties.
Electroerosive processing. Principle of operation
In practice, EDM is as follows:
- The workpiece (cathode) is installed on the table.
- Preparation of a processing tool (wire, part made of copper, graphite, brass, aluminum) with a pre-treated surface. The surface should be in the form of the plane that should be obtained on the workpiece.
- Fastening the tool in the moving part of the machine. An impulse voltage is applied to the instrument. Next, the tool approaches the workpiece.
- The occurrence of "breakdown" of the dielectric in the form of a spark between the surface of the workpiece and the tool.
- In the zone of contact of the spark with the surface of the workpiece, metal microparticles are knocked out. A small funnel forms. Its depth is equal to the voltage between the part and the tool.
It should be noted that the spark slips between very close to each other parts of the surface of the tool and the workpiece. Grain after grain, millions of small sparks remove spoiled metal from the work surface. Sparks bring this surface closer in shape to the surface of the instrument in an inverted form. In the process, you can achieve maximum purity and uniformity of processing due to a change in the voltage on the tool and the variation of the spark gap. If you use wire as a tool, then the workpiece is cut with greater accuracy. In addition, you can achieve contours of increased complexity. With other processing methods, complex contours cannot be obtained.
Electroerosive processing of metals has several advantages:
- achievement of high quality of the processed surface (uniformity, accuracy). At the same time, there is no need for further finishing;
- the possibility of obtaining different surface textures;
- the possibility of processing very hard surfaces (above 60 units);
- elimination of deformation of thin parts due to the absence of mechanical load;
- minimum wear of the anode;
- obtaining surfaces of various geometric shapes;
- lack of noise during processing.
Electrospark treatment. Using method
The electrospark processing method has found its application in the following:
- flashing holes in workpieces of various hardness;
- the formation of recesses;
- cutting of parts of various hardness;
- removal of worn areas of hardened parts;
- grinding surfaces of any hardness;
- cleaning parts after cooking alloys.
Electroerosive processing has also found its application in the repair of construction machines. It is used to cut worn parts, remove broken fastener parts, and build up slightly worn parts.
In conclusion, you should know that the strength and wear resistance of machine parts hardened by the spark method depends to a large extent on the processing conditions and the hardening material.