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Research Papers

Manufacturing of 316L Stainless Steel Die Mold by Hot Embossing Process for Microfluidic Applications

[+] Author and Article Information
J. Zhang

e-mail: jie.zhang@femto-st.fr

T. Barrière

Femto-ST Institute,
Applied Mechanics Department,
UMR 6174 CNRS, ENSMM,
Besançon Cedex 25030, France

Contributed by the Manufacturing Engineering Division of ASME for publication in the JOURNAL OF MICRO- AND NANO-MANUFACTURING. Manuscript received April 7, 2013; final manuscript received September 18, 2013; published online November 6, 2013. Assoc. Editor: Don A. Lucca.

J. Micro Nano-Manuf 1(4), 041003 (Nov 06, 2013) (10 pages) Paper No: JMNM-13-1019; doi: 10.1115/1.4025554 History: Received April 07, 2013; Revised September 18, 2013

Hot embossing process has emerged as a viable method for producing small, complex, precision parts in low volumes. It provides several advantages such as low-cost for molds, high replication accuracy for microfeatures and simple operation. The adaptation of this process for producing high fidelity hot embossed feedstock based metallic powders without the need for machining of the die mold is outlined. This was achieved through a combination of powder metallurgy and plastic hot embossing technologies to produce net-shape metal or hard materials components. In this paper, the manufacturing of molds that are suitable for the production of microfluidic systems using the replication technique is discussed. Variations of parameters in the replication process were investigated. An experimental rheological study was performed to evaluate the influence of the mixing parameters on the rheological behavior and thermal stability of 316L stainless steel feedstock. The effects of the solid loading on the feedstock rheological properties and tolerance control as well as mechanical properties and microstructures were investigated.

Copyright © 2013 by ASME
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Figures

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Fig. 1

Schematic illustration of manufacturing process chain of microstructured mold inserts combining the hot embossing process and powder metallurgy processes

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Fig. 2

(a) Scanning electron micrograph and (b) particle size distribution for 316 L stainless steel powders (d50 = 3.4 μm) used in the related investigations

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Fig. 3

(a) Brabender mixer equipment, (b) mixing chamber with maximum capacity of 55 cm3, and (c) front view of mixing chamber and twin-screw with dimensions

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Fig. 4

SEM micrographs of SU-8/Si master mold: (a) and (b) trench connected to reservoirs

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Fig. 5

(a) Pattern geometries of the elastomeric die cavities mold, (b) sketch of a microfluidic pattern used in the study, (c) and (d), 3D topographies imprint of elastomeric die cavity mold realized by casting of a Sylgard 184

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Fig. 6

Schematic of the hot embossing process for manufacturing 316 L stainless steel die mold

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Fig. 7

TGA curves of the binder and the binder components (PW 55%, PP 40%, SA 5%) in nitrogen atmosphere for kinetics rate of 10 °C/min

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Fig. 8

Mixing torque versus time profiles associated to the different solid loadings realized at 170 °C and 50 rpm

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Fig. 9

Mixing torque versus time profiles associated to the different rotor speed realized at 210 °C and solid loadings of 60%

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Fig. 10

Viscosity of the 316 L stainless steel feedstock with solid loading equal to 60 vol. %, tested at different temperatures

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Fig. 11

3D topographies imprint of 316 L stainless steel replicas with solid content 64 vol. %, obtained by hot embossing process at different forming temperatures

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Fig. 12

2D topographical profiles of 316 L stainless steel replicas with solid content 64 vol. %, obtained by hot embossing process at different forming temperatures and the elastomeric mold, in X–X direction (Fig. 5(c))

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Fig. 13

Photographs of the microfluidic tools after (a) embossed and (b) sintered steps, produced using 316 L fine stainless steel feedstocks (solid loading: 64%)

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Fig. 14

Effects of kinetics sintering temperature on shrinkages for a final sintering temperature eq. to 1360 °C in X–X direction

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Fig. 15

Optical micrographs of the sintered microstructured stainless steel samples for different final sintering temperatures: (a) 1100 °C, (b) 1200 °C, (c) 1300 °C, and (d) 1360 °C

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Fig. 16

Effect of sintering temperature on the sintered density (dwell time 60 min, 10 °C/min)

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Fig. 17

Effect of solid loading on the sintered density (dwell time 60 min, 1250 °C)

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Fig. 18

Hardness variations as a function of sintering temperature

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Fig. 19

Effects of thermal debinding and sintering on the surface roughness in hot embossing process

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