Research Papers

Laser-Induced Plasma Micromachining Process: Principles and Performance

[+] Author and Article Information
Kumar Pallav

Department of Mechanical Engineering,
Northwestern University,
Evanston, IL 60208
e-mail: kumarpallav2008@u.northwestern.edu

Ishan Saxena, K. F. Ehmann

Department of Mechanical Engineering,
Northwestern University,
Evanston, IL 60208

1Corresponding author.

Contributed by the Manufacturing Engineering Division of ASME for publication in the JOURNAL OF MICRO- AND NANO-MANUFACTURING. Manuscript received January 20, 2015; final manuscript received May 27, 2015; published online June 24, 2015. Assoc. Editor: Nicholas Fang.

J. Micro Nano-Manuf 3(3), 031004 (Sep 01, 2015) (8 pages) Paper No: JMNM-15-1008; doi: 10.1115/1.4030706 History: Received January 20, 2015; Revised May 27, 2015; Online June 24, 2015

Laser-induced plasma micromachining (LIP-MM) is a novel multimaterial and tool-less micromachining process. It utilizes tightly focused ultrashort laser irradiation to generate plasma through laser-induced dielectric breakdown in a dielectric material. The plasma facilitates material removal through plasma–matter interaction spot through vaporization and ablation. The paper introduces the LIP-MM process, discusses the underlying principles behind plasma generation and machining, and proves its feasibility by describing the experimental conditions under which plasma generation and machining occur. Upon successful commercial realization of this novel process, the key benefits envisaged are micromachining with better accuracy and better surface integrity, minimal subsurface damage, relatively smaller heat-affected zone (HAZ) and low roughness in a wide range of materials including those that are difficult to machine by some of the most successful micromachining processes such as micro-electrodischarge machining (EDM) and laser ablation.

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Fig. 1

Schematics of plasma formation in the focal volume through laser-induced dielectric breakdown

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Fig. 2

Image of plasma as obtained by a CCD camera (a) super-threshold pulse energy level of 9.63 μJ, (b) near-threshold peak power density of 6.07 μJ, diffraction limited focal spot size 10.44 μm at 10 kHz pulse repetition rate

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Fig. 3

Microscopic image and transverse depth profile of a typical crater machined by four plasma discharges in stainless steel (ASTM A276)

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Fig. 4

Process schematic for plasma generation and machining

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Fig. 5

Images of plasma generated in distilled water, kerosene, and EDM oil, respectively

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Fig. 6

Dependence of the average power and the ratio of average power to pulse repetition rate on the pulse repetition rate of the incident laser beam

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Fig. 7

Experimentally determined dependence of the plasma formation probability on pulse energy at a pulse repetition rate of 10 kHz

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Fig. 8

Plasma images obtained by the high-speed camera for each laser pulse at 9.63 μJ and 10 kHz repetition rate

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Fig. 9

Plasma images obtained by the high-speed camera at different delay intervals (Δt = 0–30 ps) (9.63 μJ pulse energy and 10 kHz repetition rate)

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Fig. 10

Schematics of the formation of (a) single-pass microchannel through overlapping of craters, (b) multi-pass microchannels through lateral overlapping of single-pass microchannels, and (c) formation of 3D microfeature through machining of multipass microchannels in layers

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Fig. 11

(a) Transverse depth profile, (b) SEM image, (c) 3D depth profile of a typical microchannel machined in stainless steel, (d) Longitudinal depth profile, and (e) Histogram of the longitudinal depth profile

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Fig. 12

Microscopic image and depth profile (transverse and longitudinal) of a typical microchannel based surface textured stainless steel specimen




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