EDM is essentially a thermal process whereby an electrode (wire) is
brought into contact with the workpiece, and by discharge of electricity
(spark) the metal is eroded away. Wire EDM uses a power supply, a
thin wire electrode, and a workpiece holding table controlled by CNC to
feed the workpiece into the wire. It utilizes either flush cooling or total
immersion in deionized water to wash away the eroded metal. Wire size can
vary from .012" to .002" dia. Wire is usually either pure brass or
brass tungsten alloys. The wire is constantly fed from a spool, through
diamond or ruby guides and flush heads so that fresh wire is always doing
the cutting. The work is clamped to a holder that is mounted on a XY stage
whose motion is controlled by ball screws driven by stepper motors which
are driven by a computer program which defines its path. Wire EDM is a
highly controlled process so that with carefully set parameters of spark
cycle, voltage, current, feed rates, etc. a very accurate path can be cut
through a variety of conducting materials, including hardened steels, carbon,
and carbide. It is capable of cutting through materials over 4" thick.
A good machine, under optimal conditions, can cut contours within less
than .0001" accuracy with surface finishes of better than 4 microns.
A WEDM machine with all its attendent peripherals such as filters, power
supply, chiller, can fill up a 200 sq.ft. room in a hurry. They're usually
operated in an air conditioned environment ...