Micro Electro Discharge Machining is a market growing processing technology due to the industrial interest and the increasing number of applications.

The process concept is not very different to conventional WEDM. This fact makes easier to understand the features that can be machined. In spite of this, the process similarities, the process and the applied systems present some important differences with respect to conventional WEDM.

The most important difference between microEDM and EDM (for both wire and die sinking EDM) is the dimension of the plasma channel radius that arises during the spark: in conventional EDM is much smaller than the electrode but the size is comparable for microEDM [17].

Such small electrodes (WEDG can produce electrodes as small as Ø5mm and thin wires can be <Ø20 mm) present a limited heat conduction and low mass to dissipate the spark heat. An excessive spark energy can produce the wire rupture (or electrode burn in die sinking EDM) , being the maximum applicable energy limited by this fact.

Together to the energy effects, the Flushing pressure acting on the electrode varies much with respect to the conventional process: the electrode pressure area is smaller but the electrode stiffness is lower, making it more “nervous”. The debris removal is more difficult because the gap is smaller, the dielectric viscosity is high and the pressure drop in microvolumes is higher.

As it happens in conventional EDM, the higher precision can be achieved only if electrode vibrations and wear are contained. This implies an important limitation for conventional EDM that turns out to be more restrictive in micro EDM.

For each discharge, the electrode wear in micro EDM is proportionally higher than conventional EDM. The electrode is softened, depending the section reduction on the spark energy.  For thin WEDM, the maximum traction force than can be applied to the wire will depend on the effective section and, therefore the traction control must be more accurate than that in conventional wires (0.20~0.33 mm) because the wire rupture can arise with fluctuations as small as 3~5 grams.

In micro EDM, the maximum Peak energy must be limited to control the unit removal rate per spark (UR, [18,19])  and use small electrodes and wires.

The balance between productivity, accuracy and spark energy reduction must be considered according to the application:

For high precision applications the energy must be reduced

For higher productivity, the energy per pulse must be increased, reducing the feeds (and the wire tension in WEDM)

Some key aspects to machine with small electrodes can be extracted from the presented ideas [18][19]:

-           Control the pulse energy

-           Control the wire traction force (for WEDM)

-           Increase the gap estability obtained by the control (avoid discharge fluctuations)

-           Increase the machine positioning accuracy (a finer control must be applied for smaller gaps)

For microEDM, all the machine, the electrodes, the programme, the control, the measuring instruments and the operators play an important role in the process [14].

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