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Research Papers

An Investigation of Magnetic-Field-Assisted Material Removal in Micro-EDM for Nonmagnetic Materials

[+] Author and Article Information
Ken Heinz, Shiv G. Kapoor, Richard E. DeVor

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

Vijay Surla

Department of Nuclear, Plasma, and Radiological Engineering, Center for Plasma-Material Interactions, University of Illinois at Urbana-Champaign, Urbana, IL 61801

J. Manuf. Sci. Eng 133(2), 021002 (Mar 08, 2011) (9 pages) doi:10.1115/1.4003488 History: Received May 03, 2010; Revised November 13, 2010; Published March 08, 2011; Online March 08, 2011

Previous magnetic-field-assisted microelectrical discharge machining (μ-EDM) techniques have been limited to use with magnetic materials. Therefore, a novel process has been developed and tested to improve material removal rate in magnetic-field-assisted μ-EDM for nonmagnetic materials. The workpiece electrodes were oriented to promote directionality in the current flowing through the workpiece, while an external magnetic field was applied in such a way as to produce a Lorentz force in the melt pool. Single-discharge events were carried out on nonmagnetic Grade 5 titanium workpieces to investigate the mechanical effects of the Lorentz force on material removal. Erosion efficiency, melt pool volume analysis, plasma temperature, electron density, and debris field characterization were used as the response metrics to quantify and explain the change in material removal with the applied Lorentz force. By orienting the Lorentz force to act in a direction pointing into the workpiece surface, volume of material removed was shown to increase by up to nearly 50%. Furthermore, erosion efficiency is observed to increase by over 54%. Plasma temperature is unaffected and electron density shows a slight decrease with the addition of the Lorentz force. The distribution of debris around the crater is shifted to greater distances from the discharge center with the Lorentz force. Taken together, these facts strongly suggest that the Lorentz force process developed produces a mechanical effect on the melt pool to aid in increasing material removal. The application of the Lorentz force is not found to negatively impact tool wear.

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Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic of parallel magnetic field with directional current

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Figure 2

Single-shot spark current pulse (1 μm spark gap, 100 V open gap voltage, and 100 W discharge power)

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Figure 4

FEM simulation results at maximum current

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Figure 5

Digitizing the discharge crater surface

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Figure 6

3D surface topography from laser scan

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Figure 7

Side view of 3D surface map

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Figure 9

Electron path of travel when E-field and B-field are perpendicular

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Figure 10

Debris field distribution

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Figure 11

SEM and laser scan images of Lorentz force into workpiece surface and no-field experiments

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Figure 12

Melting/splashing material removal mechanism

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