Freeze-form Extrusion Fabrication (FEF) is an additive manufacturing process that extrudes high solids loading aqueous ceramic pastes in a layer-by-layer fashion below the paste freezing temperature for component fabrication. Due to effects such as the air bubble release, agglomerate breakdown, change in paste properties during extrusion as a result of liquid phase migration, etc., the extrusion force is difficult to control. In this paper, an adaptive controller is proposed to regulate the extrusion force. Recursive Least Squares is used to estimate extrusion force model parameters during fabrication and a low-order control scheme capable of tracking general reference trajectories is designed and implemented to regulate the extrusion process. The controller is implemented to regulate the extrusion process. The controller is implemented fro sinusoidal, triangular, and square reference trajectories and the results demonstrate excellent tracking performance of the adaptive extrusion force controller. Several parts were fabricated with the adaptive extrusion force controller. These results illustrate the need for extrusion force control and that variable reference extrusion.


Mechanical and Aerospace Engineering


Air Force Research Laboratory (Wright-Patterson Air Force Base, Ohio)

Keywords and Phrases

Adaptive Extrusion Force Control; Ceramic Paste Extrusion; Solid Freeform Fabrication

Document Type

Article - Conference proceedings

Document Version

Final Version

File Type





© 2008 Defense Technical Information Center (DTIC), All rights reserved.

Publication Date

01 Oct 2008