In the Freeze-form Extrusion Fabrication (FEF) process, extrusion-on-demand (EOD) refers to the ability to control the start and stop of paste extrusion on demand and is vital to the fabrication of parts with complex geometries. This paper describes the development of EOD for ceramic FEF through modeling and control of extrusion force, selection of appropriate process parameters, and a dwell technique for start and stop of extrusion. A general tracking controller with integral action is used to allow tracking of a variety of reference forces while accounting for the variability in the paste properties. Experiments are conducted to model the process and tune the controller. The developed technique for EOD is demonstrated to fabricate a number of cross sections and three-dimensional parts from alumina paste.

Meeting Name

20th Annual International Solid Freeform Fabrication Symposium (2009: Aug. 3-5, Austin, TX)


Mechanical and Aerospace Engineering

Research Center/Lab(s)

Intelligent Systems Center


This research was supported by the U.S. Air Force Research Laboratory through the Center for Aerospace Manufacturing Technologies (CAMT), contract #FA8650-04-C- 5704, at the Missouri University of Science and Technology (Missouri S&T), and by CAMT Industrial Consortium whose members consist of Boeing, General Dynamics, Spirit AeroSystems, GKN Aerospace, Siemens, KMT Waterjet, the Product Innovation and Engineering, Spartan Light Metal Products, and the Third Wave Systems. The research was also supported by Missouri S&T’s Intelligent Systems Center.

Document Type

Article - Conference proceedings

Document Version

Final Version

File Type




Publication Date

05 Aug 2009

Included in

Manufacturing Commons