Electrical discharge machining

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Electrical erosion is the removal of material by electrical current .

Technological use (electrical discharge machining)

Electroerosion processes (eroding for short) are used for high-precision material processing. As a rule, the electrically conductive workpiece to be processed (often metals) is processed in a non-conductive liquid ( dielectric ), usually deionized water or special oil. For this purpose, an electrically conductive tool is brought close to the material, which has a negative electrical voltage (typically 40 to 150 V) compared to the workpiece. This leads to numerous small discharges between the tool and the workpiece. This leads to recurring sparks , which primarily remove material from the workpiece. However, the tool is also eroded, so it must be replaced.

Known electrical discharge processes are:

  • Wire EDM ; a thin metal wire is used as a tool. With the help of wire EDM, very fine cuts can also be made in thick or difficult to machine materials.
  • Sinker or drill eroding ; rods or negative forms are used here as tools.

Harmful electrical discharge

Disassembled, burned and fissured contactor contact of a forklift truck

Unwanted electrical discharges (switching sparks, voltage flashovers, electric arcs, switching arcs ) can lead to damage to electrical conductors, electrodes and contacts according to the same principle. Discharges on the electrical components lead to alternate material erosion (contact or electrode erosion). This can lead to a loss of function if, for example, a relay contact is so severely fissured or burned out that contact is no longer guaranteed when the contact is closed. This electrical erosion primarily removes the negative electrode, the positive electrode can even increase ( electromigration ).
Contact wear can be reduced by measures to extinguish switching sparks or arcs .

The electrolytic corrosion of metal parts due to stray currents in electrolytes (e.g. soil or seawater), on the other hand, is not referred to as electrical erosion, but rather as electrical corrosion .
Electrical corrosion is z. B. caused by incorrect or inappropriate grounding .

Web links

  • Spark erosion - detailed information, work and links on die sinking and wire erosion at erosion.de