Dry and Near-Dry Electric Discharge Machining Processes

Abstract

The electric discharge machining (EDM) is an un-conventional machining process. It is extensively used to generate complex profiles on electrically conductive materials having high temperature resistance and high strength. Due to its wide applicability in manufacturing industries, EDM has become the most popular machining process after conventional machining processes such as turning, milling and drilling, etc. Despite several advantages, EDM process suffers from some limitations such as low material removal rate (MRR), high tool wear rate (TWR) and poor surface integrity in some cases. In past, several attempts have been made to overcome these limitations by augmenting EDM with techniques such as electrode rotation, ultrasonic vibrations and suspensions of powders into the dielectric fluid. Although these techniques are excellent from research perspective, but in practice, are applicable only for fewer applications. Another limitation in EDM process is its possible environmental pollution causing characteristic. During EDM process, material removal is a consequent of thermal energy produced by series of discrete electrical sparks occurring between tool and work electrodes which are immersed in a dielectric medium mostly hydrocarbon oils. These oils produce serious toxic fumes causing health hazard to the machine operator and environmental pollution. To overcome these limitations of EDM process, dry and near-dry variants of EDM were introduced. Dry EDM process utilizes a pressurized gaseous medium as a dielectric whereas, near-dry EDM process uses a combination of liquid and gas (two phase) as a dielectric medium and are environmentally friendly. This chapter provides an insight into both these environmentally friendly variants (i.e. dry and near-dry EDM) of EDM process along with the research progress in this area.