Answer Posted / sudheendra
Process.—During the EDM process, energy from the sparks created between
the electrode and the workpiece is dissipated by the melting and vaporizing of the workpiece
material preferentially, only small amounts of material being lost from the electrode.
When current starts to flow between the electrode and the work, the dielectric fluid in the
small area in which the gap is smallest, and in which the spark will occur, is transformed
into a plasma of hydrogen, carbon, and various oxides. This plasma forms a conducting
passageway, consisting of ionized or electrically charged particles, through which the
spark can form between the electrode and the workpiece. After current starts to flow, to
heat and vaporize a tiny area, the striking voltage is reached, the voltage drops, and the
field of ionized particles loses its energy, so that the spark can no longer be sustained. As
the voltage then begins to rise again with the increase in resistance, the electrical supply is
cut off by the control, causing the plasma to implode and creating a low-pressure pulse that
draws in dielectric fluid to flush away metallic debris and cool the impinged area. Such a
cycle typically lasts a few microseconds (millionths of a second, or μs), and is repeated
continuously in various places on the workpiece as the electrode is moved into the work by
the control system.
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