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TECHNICAL PAPERS

A Simulation-Based Correlation of the Density and Thermal Conductivity of Objects Produced by Laser Sintering of Polymer Powders

[+] Author and Article Information
M. Kandis, T. L. Bergman

Department of Mechanical Engineering, 191 Auditorium Drive, University of Connecticut, Storrs, CT 06269

J. Manuf. Sci. Eng 122(3), 439-444 (Nov 01, 1999) (6 pages) doi:10.1115/1.1286558 History: Received February 01, 1999; Revised November 01, 1999
Copyright © 2000 by ASME
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References

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Martinez-Herrera,  J. I., and Derby,  J. J., 1994, “Analysis of Capillary-Driven Viscous Flows During the Sintering of Ceramic Powders,” AIChE J., 40, pp. 1794–1803.
Bellehumeur,  C. T., Bisaria,  M. K., and Vlachopoulos,  J., 1996, “An Experimental Study and Model Assessment of Polymer Sintering,” J. Polym. Eng. Sci., 36, pp. 2198–2207.
Kandis,  M., and Bergman,  T. L., 1997, “Observation, Prediction, and Correlation of Geometric Shape Evolution Induced by Non-Isothermal Sintering of Polymer Powder,” ASME J. Heat Transfer, 119, pp. 824–831.
Kandis,  M., Buckley,  C. W., and Bergman,  T. L., 1999, “An Engineering Model for Laser-Induced Sintering of Polymer Powders,” ASME J. Manuf. Sci. Eng., 121, pp. 360–365.
Whitaker, S., 1977, A Theory of Drying in Porous Media, in Advances in Heat Transfer, J. P. Hartnett, and T. F. Irvine, Jr., eds., Academic Press, New York, pp. 119–203.
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Figures

Grahic Jump Location
A diagram of the SLS process is shown in (a) while a micrograph of a cross section of an SLS part formed from polycarbonate powder is included in (b). The white regions correspond to high density, fused powder while the dark regions are highly porous. Reprinted with permission from Ind. Eng. Chem. Res. 1993 , 32, 2305–2317. Copyright 1993 American Chemical Society.
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A schematic diagram of laser-induced sintering of powder showing the coordinate system and the HAZ forming and sinking into the porous powder bed
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The predicted part shape (solid lines) and isotherms (dashed lines) following laser processing of (a) the first layer, t=2.4 s, (b) the third layer, t=7.2 s, and (c) the final layer at t=9.6 s. The location of the four irradiation sites are indicated by the vertical lines. The final part shape with its internal ϕ distribution is shown in (d) where the bottom, outer white regions correspond to ϕc≥ϕ>0.6, while the dark regions are 0.6≥ϕ>0.4, and the remaining inner white regions are 0.4≥ϕ. The isotherms (outer to inner) correspond to temperatures of 50°C to 250°C at 50°C increments.
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The predicted part shape with its internal ϕ distribution for (a) the base case simulation and (b) the alternating beam scanning simulation. Porosities are denoted as described in Fig. 3.
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The predicted part shape with its internal ϕ distribution for the simulation (a) using 10 percent less laser beam power (135 W/m) and (b) using 10 percent more laser power (165 W/m). Porosities are denoted as described in Fig. 3.
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The predicted part shape with its internal ϕ distribution for the simulation (a) N=3 and (b) N=5. Porosities are denoted as described in Fig. 3.
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The predicted part shape with its internal ϕ distribution for the simulation using a top hat (flat) beam intensity distribution. Porosities are denoted as described in Fig. 3.
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Porosity distributions of the 1.5 mm×0.3 mm specimen corresponding to (a) Fig. 5a, (b) Fig. 5b, (c) Fig. 6a, (d) Fig. 6b, (e) Fig. 7a, (f ) Fig. 7b, and (g) Fig. 8. Porosities are denoted as described in Fig. 3.
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Dependence of keff/ks on the ϕ̄ of the specimen.

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