Maybe once a conceptual clarification. "Dry EDM" is actually incorrect, because we would then have to call the EDM with liquid dielectrics "Wet EDM". But since we are talking about EDM in liquid dielectrics, would be the "dry" an EDM in gaseous dielectrics. The term "near" actually means that the discharges take place in gas fields in the liquid medium. This can happen if the flushing is not ideal or is caused by a high material removal rates and gas development in the working gap. But it can also be an intended EDM in gaseous media, because the workpiece must not come into contact with the known liquid media (biologically pure, medical application). Under these circumstances, the air humidity can be an influence on the "(near) dry EDM" occur.

Best regards

Hans-Peter

Near Dry EDM is EDM performed using mixture of liquid and gaseous dielectric. Tiny mists are to be formed of liquid dielectric by using high pressure air or gases and that mist or fog is spread on the sparking gap. It is basically developed to minimise the used of liquid dielectric and harness some advantages of deposition of decomposition products of liquid dielecttrics. 

there are some good researches available on web, you may refer that.

Near-dry wire electrical discharge machining is a process variant of wire EDM, which utilizes two phase dielectric medium (mist) instead of a conventional deionized water.

find a latest article on near-dry EDM process

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