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Research Papers

Surface Finish of Ball-End Milled Microchannels

[+] Author and Article Information
D. Berestovskyi

Schlumberger,
1200 Enclave Parkway,
Houston, TX 77077
e-mail: d.berestovskiy@gmail.com

W. N. P. Hung

Texas A&M University,
MS 3367,
College Station, TX 77843
e-mail: hung@tamu.edu

P. Lomeli

Keysight Technologies,
1400 Fountaingrove,
Santa Rosa, CA 95403
e-mail: paul_lomeli@keysight.com

1Corresponding author.

Contributed by the Manufacturing Engineering Division of ASME for publication in the JOURNAL OF MICRO- AND NANO-MANUFACTURING. Manuscript received January 25, 2014; final manuscript received September 3, 2014; published online September 26, 2014. Assoc. Editor: Sangkee Min.

J. Micro Nano-Manuf 2(4), 041005 (Sep 26, 2014) (10 pages) Paper No: JMNM-14-1003; doi: 10.1115/1.4028502 History: Received January 25, 2014; Revised September 03, 2014

This study develops a hybrid micromanufacturing technique to fabricate extremely smooth surface finish, high aspect ratio, and complex microchannel patterns. Milling with coat and uncoated ball-end micromills in minimum quantity lubrication (MQL) is used to remove most materials to define a channel pattern. The milled channels are then electrochemically polished to required finish. Assessment of the fabricated microchannels is performed with optical microscopy, scanning electron microscopy, atomic force microscopy, and white-light interferometry. Theoretical models were derived for surface finish of ball-end milling. The predicted surface finish data agree with experimental data in mesoscale milling, but the calculated data are lower than microscale milling data due to size effects. Built-up-edges, being detrimental in micromilling, can be reduced with optimal coating and milling in MQL. When micromilling and then electrochemical polishing of 304, 316L stainless steels and NiTi alloy, this hybrid technique can repeatedly produce microchannels with average surface finish in the range of 100–300 nm.

Copyright © 2014 by ASME
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Figures

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Fig. 11

Average surface finish at center of milled microchannels. Ball-end milling tools ϕ152–9525 μm, workpiece materials 6061-T6, A36 steel, NiTi, 304/316L stainless steels, in MQL condition.

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Fig. 14

Cross-sectional views of milled microchannels on NiTi alloys. AlTiN coated tool Ø198 μm, chip load 0.1 μm/tooth, speed 24 m/min, depth of cut 30 μm, and MQL. (a) 1.6:1 aspect ratio and (b) 2.2:1 aspect ratio.

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Fig. 13

Cross-sectional views of milled microchannels on 304 stainless steel. AlTiN coated tool Ø198 μm, chip load 0.1 μm/tooth, speed 24 m/min, depth of cut 30 μm, and MQL. (a) 0.3:1 aspect ratio, (b) 0.6:1 aspect ratio, (c) 0.9:1 aspect ratio, and (d) 1.1:1 aspect ratio.

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Fig. 12

(a) Micromilling of 316 L stainless steel, AlTiN coated ϕ198 μm tool, 24 m/min, 0.1 μm/tooth, MQL and (b) electrochemical polishing of 316 L stainless steel microchannels, acid solution, 2.5 A/cm2, and 400 s

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Fig. 10

Effect of tool coating on resulting burrs: (a) uncoated ϕ152 μm tool, milling 304 stainless steel, 24 m/min, 0.1 μm/tooth, MQL and (b) AlTiN coated ϕ198 μm tool, milling 304 stainless steel, 24 m/min, 0.1 μm/tooth, and MQL

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Fig. 9

Chipping of AlTiN coating layer on a coated ϕ198 μm ball-end mill. Micromilling at 24 m/min, 0.1 μm/tooth, MQL, after 12 mm of 304 stainless steel, 12 mm of 316L stainless steel, and 8 mm of NiTi.

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Fig. 8

BUEs on uncoated ϕ152 μm ball-end mill. Micromilling at 24 m/min, 0.2 μm/tooth, MQL, after machining 12 mm of 304 stainless steel and 12 mm of 316L stainless steel.

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Fig. 7

Significant abrasive wear of uncoated ϕ152 μm ball-end mill. Micromilling at 24 m/min, 0.1 μm/tooth, MQL, after machining 12 mm of 304 stainless steel and 12 mm of 316L stainless steel.

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Fig. 6

(a) SEM picture of a milled microchannel. 304 stainless steel, AlTiN coated ϕ198 μm ball-end mill, 24 m/min, 0.1 μm/tooth, MQL and (b) optical image of a milled mesochannel. 6061-T6 aluminum, uncoated ϕ3175 mm ball-end mill, 60 m/min, 5 μm/tooth, and MQL.

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Fig. 5

Topographic profile of milled microchannel: (a) oblique view and (b) top view for roughness measurement. 304 stainless steel, AlTiN coated ϕ198 μm ball-end mill, 24 m/min, 0.05 μm/tooth, MQL, and 0.18 μm Ra.

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Fig. 4

Frequency spectrum for milling with depth of cut of tool radius. Milling CP titanium, ball-end mill ϕ152 μm, spindle speed 27,238 rpm (454 Hz), cutting speed 13 m/min, feed rate 2.7 mm/min, depth of cut 76 μm, and MQL.

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Fig. 3

Frequency spectrum for milling with depth of cut of half-tool radius. Milling CP titanium, ball-end mill ϕ152 μm, spindle speed 27,238 rpm (454 Hz), cutting speed 13 m/min, feed rate 2.7 mm/min, depth of cut 38 μm, and MQL.

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Fig. 2

Frequency spectrum for rotating spindle only. Ball-end mill ϕ152 μm and spindle speed 27,238 rpm (454 Hz).

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Fig. 17

Surface profile formed in ball-end milling at the channel bottom

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Fig. 18

Validation and comparison of theoretical Ra models with experimental data. High speed steel ball-end mill, ϕ9.525 mm on 6061-T6, 4 flutes, cutting speed 15 m/min, and depth of cut 0.3 mm.

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Fig. 15

Surface profile of the channel formed in ball-end milling at particular depth OB1: (a) 3D view and (b) section view

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Fig. 16

Perpendicular section of the channel (A1B1C1)

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