Abstract
Alumina ceramic feedstocks with ethylene vinyl acetate and stearic acid as an organic binder were prepared and shaped by a commercial 3D filament printer. Rheological properties and the ability of ceramic feedstocks to be processed into filaments and shaped by the fused deposition modeling/filament (FDM/FFF) technique were investigated.The addition of stearic acid affects the viscosity as a function of shear rate in a complex way. Analysis with rheological models shows that while using a small amount of stearic acid, a viscosity plateau at low shear rate (cross model) can be observed. At high stearic acid content, a yield point (Herschel-Bulkley model) occurs, as the stearic acid content surpasses the amount needed to cover the powder surface. The stearic acid also influences the properties of the solidified filament, making it more brittle and less flexible.Thin wall structures were printed, debinded and sintered to demonstrate the shape stability and fusion between the layers. Ring-on-ring bending tests of sintered discs show that the printing defects are the primary concerns that determine the strength of sintered samples.
Highlights
Fused filament fabrication (FFF) is a well-established additive manufacturing technique
The ceramic material is fed to the printer in the form of a thermoplastic filament, which is pushed into the hot zone via a roller drive
Where wB is the percentage of all organic binders in the feedstock, wSAB is the percentage of stearic acid in the binder and BET is the specific surface area of the CT3000 alumina powder
Summary
Fused filament fabrication (FFF) is a well-established additive manufacturing technique. The filament must possess certain mechanical properties in order to be suitable for the FFF printer It must be strong and hard enough to avoid shearing due to pinching from the drive wheel [1] and stiff enough to avoid buckling between drive wheels and the hot zone of the ex trusion die. The 3D printing of ceramic filament depends on the rheological behavior of the feedstocks, the mechanical properties of the filament, the geometry of the filament, the design of the machine, the processing parameters and the printing head [1]. The filament must be bent between the spool and the printing head, which is another reason why certain flexibility of the filaments is required Another important parameter that determines the efficiency of the fi lament to be extruded without buclikng is the ratio between compres sive modulus, E to the apparent viscosity, ηa. Disc structures were printed and sintered to measure the biaxial bending strength, and the microstructure was examined
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