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Research Papers

A Computational Model to Study Film Formation and Debris Flushing Phenomena in Spray-Electric Discharge Machining

[+] Author and Article Information
Arvind Pattabhiraman, Deepak Marla

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

Shiv G. Kapoor

Professor
Department of Mechanical Science and Engineering,
University of Illinois at Urbana-Champaign,
Urbana, 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 November 3, 2015; final manuscript received May 21, 2016; published online June 30, 2016. Assoc. Editor: Bin Wei.

J. Micro Nano-Manuf 4(3), 031002 (Jun 30, 2016) (10 pages) Paper No: JMNM-15-1076; doi: 10.1115/1.4033709 History: Received November 03, 2015; Revised May 21, 2016

A computational model to investigate the flushing of electric discharge machining (EDM) debris from the interelectrode gap during the spray-EDM process is developed. Spray-EDM differs from conventional EDM in that an atomized dielectric spray is used to generate a thin film that penetrates the interelectrode gap. The debris flushing in spray-EDM is investigated by developing models for three processes, viz., dielectric spray formation, film formation, and debris flushing. The range of spray system parameters including gas pressure and impingement angle that ensure formation of dielectric film on the surface is identified followed by the determination of dielectric film thickness and velocity. The debris flushing in conventional EDM with stationary dielectric and spray-EDM processes is then compared. It is observed that the dielectric film thickness and velocity play a significant role in removing the debris particles from the machining region. The model is used to determine the spray conditions that result in enhanced debris flushing with spray-EDM.

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Figures

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Fig. 3

Schematic of computational domain used in the dielectric spray model

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Fig. 2

Modeling methodology of spray-EDM

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Fig. 1

Schematic of spray-EDM process. 1: Nozzle with atomizer, 2: dielectric spray, 3: tool electrode, 4: dielectric film, 5: workpiece, 6: point of spray impingement, 7: carrier gas inlet, Ls: distance from droplet nozzle exit, Nl: length of nozzle unit, ds: distance of tool electrode from point of spray impingement, and α: angle of spray impingement in XY plane

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Fig. 8

Optical setup used for capturing images of dielectric film

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Fig. 9

Sample image of film between −160  and−161 mm from the point of impingement

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Fig. 4

Velocity vectors of carrier gas close to nozzle exit for 0.2 MPa

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Fig. 5

Comparison of centerline carrier gas velocity for different pressures

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Fig. 6

Droplet velocity variation for different gas pressures

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Fig. 7

Range of α to achieve spreading on target surface for different gas pressures

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Fig. 10

Simulated 3D plot of the film formed on the machining surface

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Fig. 11

Comparison of experimental and simulated values of film thickness

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Fig. 12

Comparison of film thickness for different combinations of spray parameters

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Fig. 13

Comparison of film velocity for different combinations of spray parameters

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Fig. 14

Schematic of domain and BCs for debris flushing model

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Fig. 15

SEM image of EDM crater and debris particles

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Fig. 16

Simulated trajectory of debris using stationary dielectric

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Fig. 17

Comparison of debris distribution data

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Fig. 18

Comparison of debris distribution for different spray conditions

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