Dry EDM (Electrical discharge machining in gas) is an innovative electrical discharge machining (EDM) method. The machining performances of dry EDM vary from that of the liquid medium due to the different physical properties of gases and liquids. The generator, a key component in an EDM machine tool, supplies electrical energy to ionize the dielectric, therefore generator mode plays important roles in EDM performance. In this work, experiments were conducted to study the machining performances of dry EDM with two generator modes: the iso-frequencial mode and the iso-pulse mode. Experimental results show that the material removal rate (MRR) and surface roughness (SR) value using the iso-frequencial mode are higher than that of the iso-pulse mode in dry EDM and reasons for the experimental phenomena were analyzed. Under the iso-pulse mode, MRR and SR present an approximately linear increase with an increase in the pulse width increase. The iso-frequencial mode could be used in the rough machining gauge and the iso-pulse mode might be used in finish machining. It is concluded that a high frequency and narrow pulse generator with a high opening voltage might be suitable for dry EDM under a certain conditions.

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