"An additive manufacturing process called Freeze-form Extrusion Fabrication (FEF) was developed in this study to fabricate complex ceramic parts that require the use of sacrificial materials. The aqueous paste of alumina (Al₂O₃) was used as the main material, with solids loadings as high as 50 vol. % and water as the main liquid medium. Methyl cellulose, with a 10 vol. % solids loading and 90 vol. % water content, was used as the sacrificial material. The freeze-form extrusion machine has multiple extruders (extrusion devices) capable of fabricating parts from multiple materials without mixing them. The dynamic process of extruding alumina and methyl cellulose was characterized using an empirical first-order model with the ram velocity as the input and the extrusion force as the output for alumina and methyl cellulose pastes. After modeling the dynamics of extruding alumina and methyl cellulose pastes, a General Tracking Controller (GTC) was applied in order to achieve a consistent paste deposition with a constant extrusion rate for extrusion of both the part and sacrificial materials. This controller also performs Extrusion on Demand (EOD), which starts and stops the paste extrusion on demand and facilitates the switching process between different materials while fabricating complex parts. Freeze-drying was used to remove the water content after building parts from alumina and methyl cellulose pastes. Finally, the parts were debinded to burn out the methyl cellulose binder and sintered to densify the ceramic part"--Abstract, page iii.
Leu, M. C. (Ming-Chuan)
Landers, Robert G.
Mechanical and Aerospace Engineering
M.S. in Manufacturing Engineering
Missouri University of Science and Technology
xi, 83 pages
© 2012 Diego Armando Garcia Montaño, All rights reserved.
Thesis - Open Access
Library of Congress Subject Headings
Ceramics -- Extrusion
Feedback control systems
Print OCLC #
Electronic OCLC #
Link to Catalog Recordhttp://laurel.lso.missouri.edu/record=b9638224~S5
Garcia Montaño, Diego Armando, "Fabrication of complex ceramic parts with sacrificial material using freeze-form extrusion fabrication" (2012). Masters Theses. 5302.