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Technical Briefs

Development, Modeling, and Experimental Investigation of Low Frequency Workpiece Vibration-Assisted Micro-EDM of Tungsten Carbide

[+] Author and Article Information
M. P. Jahan, T. Saleh, Y. S. Wong

Department of Mechanical Engineering, National University of Singapore, 10 Kent Ridge Crescent, Singapore 119260, Singapore

M. Rahman1

Department of Mechanical Engineering, National University of Singapore, 10 Kent Ridge Crescent, Singapore 119260, Singaporempemusta@nus.edu.sg

1

Corresponding author.

J. Manuf. Sci. Eng 132(5), 054503 (Sep 20, 2010) (8 pages) doi:10.1115/1.4002457 History: Received October 21, 2009; Revised August 10, 2010; Published September 20, 2010; Online September 20, 2010

This present study intends to investigate the feasibility of drilling deep microholes in difficult-to-cut tungsten carbide by means of low frequency workpiece vibration-assisted micro–electro-discharge machining (micro-EDM). A vibration device has been designed and developed in which the workpiece is subjected to vibration of up to a frequency of 1 kHz and an amplitude of 2.5μm. An analytical approach is presented to explain the mechanism of workpiece vibration-assisted micro-EDM and how workpiece vibration improves the performance of micro-EDM drilling. The reasons for improving the overall flushing conditions are explained in terms of the behavior of debris in a vibrating workpiece, change in gap distance, and dielectric fluid pressure in the gap during vibration-assisted micro-EDM. In addition, the effects of vibration frequency, amplitude, and electrical parameters on the machining performance, as well as surface quality and accuracy of the microholes have been investigated. It has been found that the overall machining performance improves considerably with significant reduction of machining time, increase in MRR, and decrease in EWR. The improved flushing conditions, increased discharge ratio, and reduced percentage of ineffective pulses are found to be the contributing factors for improved performance of the vibration-assisted micro-EDM of tungsten carbide.

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Copyright © 2010 by American Society of Mechanical Engineers
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References

Figures

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Figure 3

Schematic diagram representing the pressures exerted in a microfluid cell during the reduction of gap distance.

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Figure 4

Schematic diagram of the developed vibration unit

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Figure 5

Effect of (a) frequency, (b) amplitude, (c) gap voltage, and (d) capacitance on the percentage of short-circuit pulses

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Figure 6

Various pulse types in micro-EDM drilling of microholes without and with the assistance of vibration at V=100 V and C=10 nF for (a) a.r. 5 and (b) a.r. 7.5

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Figure 7

Effect of frequency and amplitude on MRR ((a) and (b)) and EWR ((c) and (d))

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Figure 8

Comparison of effective discharge ratio between without vibration and with vibration at f=750 Hz and a=1.5 μm

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Figure 9

Quality of the inner surface of the microholes (a.r. 7.5) obtained at 80 V and 2200 pF: (a) without vibration and (b) with vibration of f=750 Hz and a=1.5 μm

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Figure 10

Comparison of crater sizes and surface topography at the inner surface of the microhole (a.r. 10) obtained at 100 V and 10 nF for (a) without vibration and (b) with vibration of f=750 Hz and a=1.5 μm

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Figure 11

Variation of spark gap ((a) and (b) and taper angle ((c) and (d)) with vibration parameters during workpiece vibration-assisted micro-EDM of WC

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Figure 12

(a) Microelectrode of ∅50 μm, L 3 mm (a.r. 60) fabricated by block-μEDM process, (b) microhole with ∅60 μm in 0.5 mm WC without vibration, and (c) microhole with ∅60 μm in 1 mm WC (a.r. 16.7) using vibration-assisted micro-EDM.

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Figure 1

Displacement-time relationship for the workpiece vibration at different position of vibrating plate

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Figure 2

(a) Workpiece vibration-assisted micro-EDM drilling and (b) variation of gap distance and fluid pressure inside the gap during vibration-assisted micro-EDM

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