submerged in a dielectric fluid, which is generally light lubricating oil. A servomechanism
maintains a space of about the thickness of a human hair between the electrode and the work,
preventing them from contacting each other.
In EDM ram or sinker machining, a relatively soft graphite or metallic electrode can be
used to cut hardened steel, or even carbide. The EDM process produces a cavity slightly larger
than the electrode because of the overcut.
Wire-Cut EDM
The wire-cut EDM is a discharge machine that uses CNC movement to produce the
desired contour or shape. It does not require a special shaped electrode, instead it uses a
continuous-traveling vertical wire under tension as the electrode. The electrode in wire-cut EDM
is about as thick as a small diameter needle whose path is controlled by the machine computer to
produce the shape required.
Dielectric Fluids - Conventional EDM
During the EDM process the workpiece and the electrode are submerged in the dielectric
oil, which is an electrical insulator that helps to control the arc discharge. The dielectric oil, that
provides a means of flushing, is pumped through the arc gap. This removes suspended particles
of workpiece material and electrode from the work cavity.
Flushing
One of the most important factors in a successful EDM operation is the removal of the
metal particles (chips) from the working gap. Flushing these particles out of the gap between the
workpiece to prevent them from forming bridges that cause short circuits.
Flushing Ram Type EDM
Flushing is the most important function in any electrical discharge machining operation.
Flushing is the process of introducing clean filtered dielectric fluid into the spark gap.
Flushing applied incorrectly can result in erratic cutting and poor machining conditions.
There are a number of flushing methods used to remove the metal particles efficiently
while assisting in the machining process. Too much fluid pressure will remove the chips before
they can assist in the cutting action, resulting in slower metal removal. Too little pressure will
not remove the chips quickly enough and may result in short-circuiting the erosion process
Wire EDM Dielectric Fluids
The dielectric fluid must be circulated under constant pressure to flush (wash) away the
metal particles and assist in the machining or erosion process. If red sparks occur during the