Generation of Porous Structures Using Fused Deposition

The Fused Deposition Modeling process uses hardware and software machine-level language that are very similar to that of a pen-plotter. Consequently, the·use of patterns with poly-lines as basic geometric features, instead of the current method based on filled polygons (monolithic models), can increase its efficiency. In the current study, various toolpath planning methods have been developed to fabricate porous structures. Computational domain decomposition methods can be applied to the physical or to slice-level domains to generate structured and unstructured grids. Also, textures can be created using periodic tiling of the layer with unit cells (squares, honeycombs, etc). Methods 'based on curves include fractal space filling curves and.change of effective road width Within a layer or within a continuous curve. Individual phases can also be placed in binary compositions. In present investigation, a custom software has been developed and implemented to generate build files (SML) and slice files (SSL) for the above-mentioned structures, demonstrating the efficient control ofthe size, shape, and distribution ofporosity.Mechanical Engineerin

Mechanical and Rheological Properties of Feedstock Material for Fused Deposition of Ceramics and Metals (FDC and FDMet) and their Relationship to Process Performance

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 feedstockbeing 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 ofthe filament to provide·and sustain the required pressure to drive the extrusion. The viscosity ofthe feedstock material, nozzle geometry and volumetric flow rates employed determine the pressure needed to drive the extrusion process. In this worktheiextrusion pressure for a particular material termed PZT ECG9 (52.6 Vol.% PZT powder in ECG9i~inder) was measured experimentally as a function of volumetric flow rate and nozzle geometry.rhe compressive modulus ofthe material was determined using a miniature materials tester (Rheoinetrics, Inc., Piscataway, NJ). A process map has been developed. The map is based .on the quantity MIE, and predicts the performance of the material in a FDC process as a.functioIl.ofnozzleg~ometry and volumetric flow rate. In general, it is observed that when MIE exceeds a critical value, called APcr/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™ software. The model predicts the observed trend in pressure drop with flow rate and nozzle geometry with reasonable accuracy.Mechanical Engineerin