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Research Papers

Modeling of Melt-Pool Formation and Material Removal in Micro-Electrodischarge Machining

[+] Author and Article Information
Soham S. Mujumdar

Department of Mechanical Science
and Engineering,
University of Illinois at Urbana-Champaign,
Urbana, IL 61801
e-mail: mujumda2@illinois.edu

Davide Curreli

Assistant Professor
Department of Nuclear,
Plasma, and Radiological Engineering,
University of Illinois at Urbana-Champaign,
Urbana, IL 61801
e-mail: dcurreli@illinois.edu

Shiv G. Kapoor

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

David Ruzic

Professor
Center for Plasma-Material Interactions,
Department of Nuclear,
Plasma, and Radiological Engineering,
University of Illinois at Urbana-Champaign,
Urbana, IL 61801
e-mail: druzic@illinois.edu

1Corresponding author.

Contributed by the Manufacturing Engineering Division of ASME for publication in the JOURNAL OF MANUFACTURING SCIENCE AND ENGINEERING. Manuscript received August 8, 2014; final manuscript received December 18, 2014; published online February 23, 2015. Assoc. Editor: Y. B. Guo.

J. Manuf. Sci. Eng 137(3), 031007 (Jun 01, 2015) (9 pages) Paper No: MANU-14-1424; doi: 10.1115/1.4029446 History: Received August 08, 2014; Revised December 18, 2014; Online February 23, 2015

This paper presents a micro-electrodischarge machining (EDM) melt-pool model to predict workpiece (anode) material removal from a single discharge micro-EDM process. To model the melt-pool, heat transfer and fluid flow equations are solved in the domain containing dielectric and workpiece material. A level set method is used to identify solid and liquid fractions of the workpiece material when the material is molten by micro-EDM plasma heat flux. The plasma heat flux, plasma pressure and the radius of the plasma bubble have been estimated by a micro-EDM plasma model and serve as inputs to the melt-pool model to predict the volume of material removed from the surface of the workpiece. Experiments are carried out to study the effect of interelectrode voltage and gap distance on the crater size. For interelectrode voltage in the range of 200–300 V and gap distance of 1,2 μm, the model predicts crater diameter in the range of 78–96 μm and maximum crater depth of 8–9 μm for discharge duration of 2 μs. The crater diameter values for most of experimental craters show good agreement with the simulated crater shapes. However, the model over-predicts the crater depths compared to the experiments.

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References

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Figures

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Fig. 1

Schematic of a single discharge of micro-EDM process [9] along with voltage and current conditions showing three main stages: (a) dielectric breakdown stage, (b) discharge stage, and (c) postdischarge stage ((1) electrodes, (2) dielectric, (3) vapor bubble, (4) plasma discharge column, (5) melt-pool, (6) debris, (7) bubbles, and (8) crater)

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Fig. 2

Schematic of the micro-EDM melt-pool modeling domain, (a) tool electrode (cathode), (b) workpiece electrode (anode), (c) dielectric fluid, (d) plasma channel, and (e) melt-pool at the workpiece surface

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Fig. 3

Schematic of the micro-EDM plasma model algorithm [9]

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Fig. 4

Smoothed Heaviside step function

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Fig. 5

Modeling domain with boundary condition

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Fig. 6

Typical micro-EDM discharge waveform (V0 = 200 V, L = 2 μm)

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Fig. 7

Evolution of temperature and velocities of the melt-pool in a typical micro-EDM discharge with V0 = 200 V, L = 2 μm (shape of the melt-pool is traced by a white contour line). (a) Temperature (t = 0.5 μs), (b) melt-pool velocities (t = 0.5 μs), (c) temperature (t = 1 μs), (d) melt-pool velocities (t = 1 μs), (e) temperature (t = 105 μs), (f) melt-pool velocities (t = 1.5 μs), (g) temperature (t = 2 μs), and (h) melt-pool velocities (t = 2 μs).

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Fig. 8

Approach for melt-pool model validation

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Fig. 9

3D imaging of crater surface with laser scanning [1]: (a) digitizing crater surface with laser scanning and (b) crater surface showing positive and negative volumes

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Fig. 10

3D image and cross-sectional profile of a typical discharge crater obtained in experimental trials and its comparison with simulated crater shape (V0 = 200 V, L = 2 μm). (a) 3D Image of experimental crater and (b) comparison of predicted crater profile with experimental measurement.

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Fig. 11

Comparison of crater profiles between model and the experiments (filled: model predictions, unfilled: experimental mean with error bars at ± standard deviation). (a) Comparison of crater diameters and (b) comparison of crater depths.

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