Research Papers

Effect of Dielectric Conductivity on Micro-Electrical Discharge Machining Plasma Characteristics Using Optical Emission Spectroscopy

[+] Author and Article Information
Soham S. Mujumdar

Department of Mechanical
Science and Engineering,
University of Illinois at
Champaign, IL 61801

Davide Curreli

Department of Nuclear,
Plasma and Radiological Engineering,
University of Illinois at
Champaign, IL 61801

Shiv G. Kapoor

Department of Mechanical
Science and Engineering,
University of Illinois at
Champaign, IL 61801
e-mail: sgkapoor@illinois.edu

1Corresponding author.

Contributed by the Manufacturing Engineering Division of ASME for publication in the JOURNAL OF MICRO-AND NANO-MANUFACTURING. Manuscript received June 5, 2017; final manuscript received March 1, 2018; published online April 23, 2018. Assoc. Editor: Martin Jun.

J. Micro Nano-Manuf 6(3), 031001 (Apr 23, 2018) (6 pages) Paper No: JMNM-17-1025; doi: 10.1115/1.4039508 History: Received June 05, 2017; Revised March 01, 2018

Electrical conductivity of the dielectric liquid has been shown to play main role in discharge initiation and electrical breakdown as revealed by several modeling and experimental studies on electrical discharges in liquids. However, there has been lack of systematic efforts to evaluate how dielectric conductivity affects the micro-electrical discharge machining (micro-EDM) process, in particular. Experimental investigation has been carried out to understand the effect of dielectric conductivity on micro-EDM plasma characteristics using optical emission spectroscopy. Plasma temperature and electron density estimations have been obtained at five levels of electrical conductivity of water. It is found that while the plasma temperature shows a marginal decrease, electron density of the plasma increases with an increase in the conductivity. At increased electron density, a higher heat flux at anode can be expected resulting in increased material erosion.

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Fig. 1

(a) Micro-EDM experimental test-bed and (b) optical spectroscopy setup

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Fig. 2

(a) Raw image of a micro-EDM discharge spectrum obtained by the spectroscope and (b) plot of intensity versus wavelength for a typical micro-EDM discharge

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Fig. 3

Estimation of experimental plasma temperature by comparison with simulated spectra

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Fig. 4

Full-width half-maximum of Hα peak

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Fig. 5

Plasma temperature versus dielectric conductivity using line-pair method (experimental error bars at ±standard deviation, note suppressed zero at vertical axis)

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Fig. 6

Plasma temperature versus dielectric conductivity using comparison with simulated spectra (experimental error bars at ±standard deviation, note suppressed zero at vertical axis)

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Fig. 7

Electron density versus dielectric conductivity with experimental error bars at ±standard deviation (note suppressed zero at vertical axis)

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Fig. 8

Schematic of the micro-EDM plasma model formulation [15,16]

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Fig. 9

Plot of wt % of NaCl versus electrical conductivity of NaCl–water solution [5,23]

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Fig. 10

Model prediction of electron density versus dielectric conductivity (note suppressed zero at vertical axis)

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Fig. 11

Model prediction of plasma temperature versus dielectric conductivity (note suppressed zero at vertical axis)



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