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Electrical discharge machining (EDM) is extensively used for machining difficult-to-machine materials and complicated shapes. Its performance in terms of material removal rate and surface roughness is usually analyzed using the process parameters such as setting voltage, setting current, pulse on time, and duty factor. It is well known that interelectrode gap condition controls the EDM performance, and it is difficult to observe the gap phenomena directly. Literature reveals that the combined influence of pulse types and their individual contributions on material removal rate and surface roughness has been ignored. In the present work, rough and finish EDM conditions are identified from a large set of 125 experiments carried out on hardened D3 die steel. From the voltage and current pulse trains in each regime, pulse characteristics and five different pulse types are assessed by a unique thresholding approach. Based on the pulse details, two new parameters such as energy expended (E) at the electrode gap over a second and a performance factor (PF) giving ratio of energy associated with the sparks to total energy expended have been proposed. It is found that a higher PF of 0.757 at a relatively lower expended energy of 113.7 J leads to a favorable condition in rough machining. A relatively lower E of 29.7 J and a higher PF of 1.00 are favorable for finish machining. Cross-sectional images of the ED machined workpieces are also included as evidences. The proposed thresholding methodology has a potential for online monitoring, analysis, and control of EDM process. [ABSTRACT FROM AUTHOR]

In the electrical discharge machining (EDM) of deep holes, electrode wear may cause the dimensions of the finished holes to deviate from their design values. In practice, the extent of the electrode wear and the surface roughness of the machined holes depend not only on the EDM machining parameters (e.g., the pulse duration, the pulse current, and so on), but also on the electrode route motion. Accordingly, the present study performs an experimental investigation into the effects of three different electrode routes (straight dip, spiral attack hole, and awl free expand hole) on the electrode wear and surface roughness of the machined holes in the EDM machining of PDS5A and PDS-1 mold steel, respectively. Overall, the experimental results show that of the three electrode route motions, the awl free expand hole motion results in a more uniform wear of the electrode and a lower surface roughness of the machined hole. [ABSTRACT FROM AUTHOR]

Electrical discharge machining is a very accurate non-traditional manufacturing process for creating tiny apertures, complex shapes and geometries within mechanical parts and assemblies. Its performance is evaluated in terms of surface roughness, existence of cracks, voids, and recast layer on the surface of product. The high heat generated on the electrically discharged material during the electrical discharge machining (EDM) process unfortunately decreases the quality of product. In this paper, the high strength and unique electrical and thermal properties of multi-wall carbon nanotubes are used to improve the EDM performance when machining the AISI H13 tool steel, by means of copper electrodes. Material removal rate, electrode wear rate, surface roughness, and recast layer were measured in presence of carbon nanotubes in the dielectric, then compared to the outcome of traditional EDM. Experiments show that mixing multi-wall carbon nanotubes within the dielectric makes the EDM more efficient, particularly if machining parameters are set at low pulse of energy. [ABSTRACT FROM AUTHOR]

This paper deals with the effect of copper tool vibration with ultrasonic (US) frequency on the electrical discharge machining (EDM) characteristics of cemented tungsten carbide (WC-Co). It was found that ultrasonic vibration of the tool (USVT) was more effective in attaining a high material removal rate (MRR) when working under low discharge currents and low pulse times (finishing regimes). In general, the surface roughness and the tool wear ratio (TWR) were increased when ultrasonic vibration was employed. It was observed that application of ultrasonic vibration significantly reduced arcing and open circuit pulses, and the stability of the process had a remarkable improvement. This study showed that, there were optimum conditions for ultrasonic assisted machining of cemented tungsten carbide, although the conditions may vary by giving other input parameters for those which had been set constant in the present work. [ABSTRACT FROM AUTHOR]