Time- and spatially-resolved characterization of electrical discharge machining plasma

Abstract

Plasma created during electrical discharge machining (EDM) is investigated with fast imaging and with time-and spatially-resolved optical emission spectroscopy. After the breakdown, the plasma develops very fast (< 50ns) and then remains stable. The plasma excites a broad volume around the electrode gap. Typical spectra show a strong H α and continuum radiation, with many lines emitted by impurities coming from electrodes materials. The plasma contamination from the electrodes is mostly concentrated in their vicinity. The electron density reaches 2·10 18 cm -3 at the beginning of the discharge. This extreme density causes merging of lines, strong Stark broadening and shift of the H α line. The density decreases afterwards rapidly with time. The electron temperature remains roughly constant around 0.7eV. The low temperature, the high density measured and other spectroscopic evidences prove that the EDM plasma is non-ideal (Γ ≅ 0.45).

A Model of Micro Electro-Discharge Machining Plasma Discharge in Deionized Water

“…[25]. Furthermore, the values of electron temperature and density predicted by the model are found to be consistent with the range of electron temperature and density (5000-10,000 K, 10^^-10^^ m"^) reported in the literature [6,8,25,30]. (3) Application of higher field at a fixed gap increases the electron density, plasma temperature, plasma radius, plasma pressure and the heat flux to the workpiece, while increasing gap distance for a fixed electric field results in decrease of overall plasma density and increased heat flux.…”

“…pressure, and radius. Another drawback of these models is the assumption of a cylindrical plasma column compared to the spherical-shaped geometry of the discharge observed experimentally [6,7]. Therefore, a comprehensive model of /¿-EDM plasma is required with emphasis on the complex chemistry of H2O plasma that presents a clear understanding of the interaction between the high energy electrons and heavy ions/neutrals to eventually reach a common equilibrium temperature.…”

“…By modeling the plasma, one would be able to predict the plasma characteristics that influence the material removal process, viz., the size of the plasma (radius), the heat flux transferred to the electrodes, and the pressure force exerted on electrode surfaces. Deionized (DI) water is considered as an dielectric for the model as it is one of the most commonly used dielectric for the EDM process [6,8]. The global plasma model approach [9][10][11] is used to model the plasma, which assumes uniform spatial distributions of plasma characteristics and involves simple governing equations of conservation of mass and energy to estimate the time-transients.…”

Synthesis of carbon-incorporated titanium oxide nanocrystals by pulsed solution plasma: electrical, optical investigation and nanocrystals analysis

“…This phenomenon was attributed to short discharge on-time, which causes high plasma density and the merging of spectral lines. 27 Therefore, it is difficult to assign the spectra with a high resolution, but it can be possible to identify the existence of specic elements qualitatively with distinct heads of merging lines. The spectral lines and emission bands were identied using the reference data.…”

Ultra-high-precision industrial robots calibration

“…It is recommended for hard materials or for materials typically machined by grinding [6]. It is suited for applications characterized by extremely exacting tolerances (accuracy ∼1 μm).…”