1999 / Solid Freeform Fabrication Proceedings
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Author N. Venkataraman (a), S. Rangarajan (a), M. J. Matthewson (a), A. Safari (a), S. C. Danforth (a), A. Yardimci (b), S. L Guceri (c), (a) Rutgers University, (b) Advanced Engineering Design Center,Baxter International, Round lake IL (c) University of Illinois at Chicago
Source Solid Freeform Fabrication Proceedings, 1999, pp 351-360
Abstract Fused deposition of ceramics (FDC) is a solid freeform fabrication technique based on extrusion of a highly loaded thermoplastic binder system. The present FDC process uses filament feedstock of 1.780 mm + - 0.025 mm diameter. The filament acts as both the piston driving the extrusion process as well as the molten feedstock being deposited. The filaments need to be able to provide and sustain the pressure needed to drive the extrusion process. Failure to do this results in failure via "buckling". The filament compressive modulus determines the ability of the filament to provide and sustain the required pressure to drive the extrusion. The viscosity of the feedstock material, nozzle geometry and volumetric flow rates employed determine the pressure needed to drive the extrusion process. In this work the extrusion pressure for a particular material termed PZT ECG9 (52.6 Vol.% PZT powder in ECG9 binder) was measured experimentally as a function of volumetric flow rate and nozzle geometry. The compre ssive modulus of the material was determined using a miniature materials tester (Rheometrics, Inc., Piscataway, NJ). A process map has been developed. The map is based on the quantity delta P/E, and predicts the performance of the material in a FDC process as a function of nozzle geometry and volumetric flow rate. In general, it is observed that when delta P/E exceeds a critical value, called delta Pcr/E, there is an increased tendency for the filament to buckle. A preliminary fluid flow model for extrusion of PZT ECG9 through a FDC nozzle has also been developed using Polyflow (TM) software. The model predicts the observed trend in pressure drop with flow rate and nozzle geometry with reasonable accuracy. (Auth abstract) [References: 10]
Solid Freeform Fabrication Proceedings can be obtained from: The Solid Freeform Fabrication Symposium
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