08-02-2012, 04:40 PM
Finite-Element Simulation of Electrical Discharge Machining (EDM) Process
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I. INTRODUCTION
Electric discharge machining (EDM), sometimes
colloquially also referred to as spark machining, spark
eroding, burning, die sinking or wire erosion, is a
manufacturing process whereby a desired shape is obtained
using electrical discharges (sparks). Material is removed
from the workpiece by a series of rapidly recurring current
discharges between two electrodes, separated by a dielectric
liquid and subject to an electric voltage. One of the
electrodes is called the tool-electrode, or simply the ‘tool’ or
‘electrode’, while the other is called the workpieceelectrode,
or ‘workpiece’.
II. GENERALITIES
Electrical discharge machining is a machining method
primarily used for hard metals or those that would be very
difficult to machine with traditional techniques. EDM
typically works with materials that are electrically
conductive, although methods for machining insulating
ceramics with EDM have also been proposed. EDM can cut
intricate contours or cavities in pre-hardened steel without
the need for heat treatment to soften and re-harden them.
This method can be used with any other metal or metal alloy
such as titanium, hastelloy, kovar, and income. Also,
applications of this process to shape polycrystalline diamond
tools have been reported.
EDM is often included in the ‘non-traditional’ or ‘nonconventional’
group of machining methods together with
processes such as electrochemical machining (ECM), water
jet cutting (WJ, AWJ), laser cutting and opposite to the
‘conventional’ group (turning, milling, grinding, drilling and
any other process whose material removal mechanism is
essentially based on mechanical forces).
DEFINITION OF THE TECHNOLOGICAL PARAMETERS
Difficulties have been encountered in the definition of
the technological parameters that drive the process.
Two broad categories of generators, also known as
power supplies, are in use on EDM machines commercially
available: the group based on RC circuits and the group
based on transistor controlled pulses.
In the first category, the main parameters to choose
from at setup time are the resistance(s) of the resistor(s) and
the capacitance(s) of the capacitor(s). In an ideal condition
these quantities would affect the maximum current delivered
in a discharge which is expected to be associated with the
charge accumulated on the capacitors at a certain moment in
time. Little control, however, is expected over the time
duration of the discharge, which is likely to depend on the
actual spark-gap conditions (size and pollution) at the
moment of the discharge.
CONCLUSIONS
The following conclusions can be derived based on the
obtained results:
1. Experimental values of MRR and EWR can
satisfactorily be predicted using the developed model
by performing minimum number of experiments.
2. Reproducibility analysis and R2 values prove that
consistent and reliable results can be achieved within
acceptable error ranges.
3. Mathematical modeling of EDM hole drilling process
using RSM technique can enable the prediction of MRR
and EWR values without performing unnecessary
experiments.
