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Freeform Fabrication of Functional Silicon Nitride Components by Direct Photo Shaping

Published online by Cambridge University Press:  10 February 2011

S. Ventura
Affiliation:
SRI International, 333 Ravenswood Avenue, Menlo Park California 94025
S. Narang
Affiliation:
SRI International, 333 Ravenswood Avenue, Menlo Park California 94025
P. Guerit
Affiliation:
SRI International, 333 Ravenswood Avenue, Menlo Park California 94025
S. Liu
Affiliation:
SRI International, 333 Ravenswood Avenue, Menlo Park California 94025
D. Twait
Affiliation:
Honeywell Ceramic Components, 2525 West 190th Street, Torrance, California 90504
P. Khandelwal
Affiliation:
Rolls-Royce Allison, P.O. Box 420, Speed Code W-05, Indianapolis, Indiana 46206-0420
E. Cohen
Affiliation:
University of Utah, Department of Computer Science, 3190 Merrill Engineering Bldg., Salt Lake City, Utah 84112
R. Fish
Affiliation:
University of Utah, Department of Computer Science, 3190 Merrill Engineering Bldg., Salt Lake City, Utah 84112
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Abstract

This paper describes a new multilayer solid freeform fabrication process, “Direct Photo Shaping” (DPS), where visible digital light projection is used as a maskless tool to build images on photocurable ceramic dispersions (ceramic powders in photopolymerizable liquid monomers) by flood exposure. For each layer, the projected image is changed according to the CAD data describing the object being built and solidification takes place by photocuring the exposed areas. Multiple layers are dispensed and photocured to fabricate the object of interest. A final rinse with a suitable solvent allows the removal of any uncured ceramic dispersion. The porous free formed “green” ceramic object can then be fired and sintered into a highly dense ceramic part. Digital Light Processing™ technology (developed by Texas Instruments) enables SRI International to project digital, high resolution, high brightness, high contrast visible light to photocure and form components with a good degree of accuracy. This paper describes the Direct Photo Shaping process and its advantages, and how DPS is being applied to the fabrication of ceramic (Honeywell AS800) gas turbine components for military and commercial applications. ASS00 test specimens with flexural strength in excess of 800MPa were fabricated by DPS. A first-stage AS800 turbine vane for the Rolls-Royce Allison Model 501-K industrial gas turbine was fabricated by DPS and tested in a gas-burner test rig at 1204°C. Initial tests show that ceramic samples with optimized surface finish (comparable to that achieved by ceramic bisque machining) can be fabricated by applying a pixel anti-aliasing filter along the boundaries of the sample projected slice images.

Type
Research Article
Copyright
Copyright © Materials Research Society 2000

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