Dry Electric Discharge Machining Process

By: Sourabks
Electrical Discharge Machining (EDM) is a process widely used to machine electrically conductive materials through the process of controlled spark generation. Thermal energy generated due to the electrical sparks melts and vaporizes material from the surface of the work piece and produces a replica of the tool electrode on the work piece surface. Tool and work piece electrodes are separated by a very small gap (of the order of 0.5 mm or even less). The electrodes are immersed in a dielectric fluid which helps in flushing away the debris from the spark gap and in cooling of the work piece and the tool.

Typically mineral oil is used as the dielectric medium. This poses a threat to the environment and in the immediate surrounding of the machine due to the toxic fumes produced during the process.

Dry EDM is a 'green' environment friendly EDM technique in which instead of mineral oil based liquid dielectric, gas at high pressure is used as the dielectric medium. Some added advantages are lower tool wear, lower residual thermal stresses and higher precision. However, the major roadblocks in its commercialization have been the low material removal rate (MRR) and poor process stability.

Reasons prompting dry EDM Research:

Dry EDM is a completely 'green' machining process (in terms of health, safety & environmental reasons)

Factors favoring dry EDM:
i.No fire hazard
ii.No toxic fumes generated
iii.No need for special treatment for disposal of sludge, dielectric waste, filter cartridges, etc.

Other advantages:
i.Very low tool wear
ii.Thinner white layer and lower residual stresses
iii.Higher Precision
iv.Smaller Heat Affected Zone (HAZ)
v.Narrower discharge gap length
vi.No electrolytic corrosion of w/p (as compared to water based dielectrics)
vii.Arbitrary machining directions possible, irrespective of gravity because of absence of dielectric tank.

Major disadvantages:
i.Low material removal rate (MRR)
ii.Poor process stability

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