Effect of Machining on Workpiece Surface Characteristics in Electric Discharge Drilling (EDD)

Abstract

In electric discharge drilling (EDD), rapid local heating and cooling of the workpiece surface by means of electric discharges results in surface layers (recast, heat affected and base material). In this study, the main workpiece surface texture measures, namely the recast layer thickness (RLT) and average surface roughness (R a) characteristics were investigated for varying machining parameters (discharge current and pulse on time). The conducted experiments revealed the strong dependence of surface characteristics on machining parameters.

Thermo-fluid multi-physics modeling and experimental verification of volumetric workpiece material removal by a discharge pulse in electric discharge machining process

“…The formation of the re-solidified layer (RSL) was also taken into account when calculating the volume removed for a single discharge (V v ) by using the results of the numerical model. The calculated V v values according to the model were found to be lower than those found in the experimental results of the authors' prior work [59] for AISI4140 and Ti6Al4V workpieces (43.3% and 42.6%, respectively). Similar difference was also found in another study of the authors [60] for Ti6Al4V and Inconel 718 workpieces (38.3% and 46.9%, respectively).…”

“…Table 1 displays the machining parameters utilized in the machining operations and numerical analyses. The E1 and E2 experiments have been conducted using the experimental setup shown in figure 1, which was also used by the author's previous study [59]. In E3 and E4 experiments of Yılmaz et al study [60], a copper electrode with a through hole water dielectric flushing was used for drilling Ti6Al4V and Inconel 718 workpieces.…”

“…-Since an electrical discharge occurs between the two nearest points of the electrode and the workpiece, the electrode and workpiece surface profiles were formed by protrusions in modeling [61]. The protrusion geometry was selected as a triangle as a result of examining the surface geometries of EDMed specimens in the literature [6,32] (figure 3).…”

“…-The dielectric medium in the model has been assumed to be pure water [59,61]. The change in the density and contamination of the dielectric due to material removal (chips) from the workpiece and the electrode and because of dielectric decomposition and gas formation after the first discharge cycle (i.e.…”

“…The T p , J, T w distributions, dielectric temperature (T d ) distributions, radiation characteristics, electrical characteristics (electrical field, etc) and channel energy distribution (to electrode, dielectric, workpiece) values were obtained by the model analyses. From T w distributions, regions exceeding T mw were determined by FEA and used to calculate the WRR and V v for comparison with the experimental findings of AISI4140, Ti6Al4V alloy and Inconel 718 workpieces with results of other works [60,61].…”