New Feedstock System for Fused Filament Fabrication of Sintered Alumina Parts

Only a few 3D-printing techniques are able to process ceramic materials and exploit successfully the capabilities of additive manufacturing of sintered ceramic parts. In this work, a new two component binder system, consisting of polyethyleneglycol and polyvinylbutyral, as well stearic acid as surfactant, was filled with submicron sized alumina up to 55 vol.% and used in fused filament fabrication (FFF) for the first time. The whole process chain, as established in powder injection molding of ceramic parts, starting with material selection, compounding, measurement of shear rate and temperature dependent flow behavior, filament fabrication, as well as FFF printing. A combination of solvent pre-debinding with thermal debinding and sintering at a reduced maximum temperature due to the submicron sized alumina and the related enhanced sinter activity, enabled the realization of alumina parts with complex shape and sinter densities around 98 % Th. Finally the overall shrinkage of the printed parts were compared with similar ones obtained by micro ceramic injection molding

3D Printing of ABS Barium Ferrite Composites

In this work, a process for the realization of new polymer matrix composites with nanosized barium ferrite (BaFe12O19) as ferrimagnetic filler, acryl butadiene styrene (ABS) as polymer matrix and an extrusion-based method, namely fused filament fabrication (FFF), as 3D printing method will be described comprehensively. The whole process consists of the individual steps material compounding, rheological testing, filament extrusion, 3D-printing via FFF and finally a widespread specimen characterization regarding to appearance, mechanical properties like tensile and bending behavior as well as the aspired magnetic properties. Increasing ferrite amounts up to 40 vol.% (equal 76 wt.%) cause a reduction of the ultimate stress and an increase of the magnetic polarization as well as of the energy product (BH)max in comparison to the pure polymer matrix. In addition, an extensive discussion of typical printing defects and their consequences on the device properties will be undertaken

New Partially Water-Soluble Feedstocks for Additive Manufacturing of Ti6Al4V Parts by Material Extrusion

In this work, a process chain for the realization of dense Ti6Al4V parts via different material extrusion methods will be introduced applying eco-friendly partially water-soluble binder systems. In continuation of earlier research, polyethylene glycol (PEG) as a low molecular weight binder component was combined either with poly(vinylbutyral) (PVB) or with poly(methylmethacrylat) (PMMA) as a high molecular weight polymer and investigated with respect to their usability in FFF and FFD. The additional investigation of different surfactants’ impact on the rheological behaviour applying shear and oscillation rheology allowed for a final solid Ti6Al4V content of 60 vol%, which is sufficient to achieve after printing, debinding and thermal densification parts with densities better than 99% of the theoretical value. The requirements for usage in medical applications according to ASTM F2885-17 can be fulfilled depending on the processing conditions

Printing of Zirconia Parts via Fused Filament Fabrication

In this work, a process chain for the fabrication of dense zirconia parts will be presented covering the individual steps feedstock compounding, 3D printing via Fused Filament Fabrication (FFF) and thermal postprocessing including debinding and sintering. A special focus was set on the comprehensive rheological characterization of the feedstock systems applying high‐pressure capil‐lary and oscillation rheometry. The latter allowed the representation of the flow situation especially in the nozzle of the print head with the occurring low‐shear stress. Oscillation rheometry enabled the clarification of the surfactant’s concentration, here stearic acid, or more general, the feedstocks composition influence on the resulting feedstock flow behavior. Finally, dense ceramic parts (best values around 99 % of theory) were realized with structural details smaller than 100 μm

Material development for additive manufacturing of titanium components via material extrusion

In this work, the development of a process chain to produce titanium components via Fused Filament Fabrication (FFF) will be introduced applying eco-friendly partially water-soluble binder systems. The focus of this study was the influence of different thermoplastic binder components on the properties of the feedstocks. It was found that short-chain fatty acids decrease the viscosity of the feedstocks and extraordinarily increase the flexibility of the filaments at the expense of hardness. Printing of the feedstocks showed promising results, even complex geometries could be achieved with a high level of detail. After subsequent debinding and thermal densification, titanium components were produced with a density of more than 99.9 % of the theoretical value

Feedstock Development for Material Extrusion-Based Printing of Ti6Al4V Parts

In this work, a holistic approach for the fabrication of dense Ti6Al4V parts via material extrusion methods (MEX), such as fused filament fabrication (FFF) or fused feedstock deposition (FFD), will be presented. With respect to the requirements of the printing process, a comprehensive investigation of the feedstock development will be described. This covers mainly the amount ratio variation of the main binder components LDPE (low-density polyethylene), HDPE (high-density polyethylene), and wax, characterized by shear and oscillation rheology. Solid content of 60 vol% allowed the 3D printing of even more complex small parts in a reproducible manner. In some cases, the pellet-based FFD seems to be superior to the established FFF. After sintering, a density of 96.6% of theory could be achieved, an additional hot isostatic pressing delivered density values better than 99% of theory. The requirements (mechanical properties, carbon, and oxygen content) for the usage of medical implants (following ASTM F2885-17) were partially fulfilled or shortly missed

PVB/PEG-Based Feedstocks for Injection Molding of Alumina Microreactor Components

The ceramic injection molding (CIM) process is a cost-effective powder-based near net shape manufacturing process for large-scale production of complex-shaped ceramic functional components. This paper presents the rheological analysis of environmentally friendly CIM feedstock formulations based on the binder components polyvinyl butyral (PVB) and polyethylene gycol (PEG). The prepared PVB/PEG-based alumina molding compounds were investigated with respect to their PVB:PEG ratios as well as to their powder filling degrees in the range between 50 and 64 vol.%. Corresponding viscosities and shear stresses were determined for increasing shear rates to show the effects of increased PEG content and solid loadings on them. Two single reactor components were injection molded and subsequently joined in their green state for fabrication of an alumina microreactor. The intended purpose of the alumina microreactors is their potential application as wear-resistant and hydrothermal stable multifunctional devices (µ-mixer, µ-reactor, µ-analyzer) for continuous hydrothermal synthesis (CHTS) of metal oxide nanoparticles in supercritical water (sc-H2O) as the reaction medium

3D-Printed Hermetic Alumina Housings

Ceramics are repeatedly investigated as packaging materials because of their gas tightness, e.g., as hermetic implantable housing. Recent advances also make it possible to print the established aluminum oxide in a Fused Filament Fabrication process, creating new possibilities for manufacturing personalized devices with complex shapes. This study was able to achieve integration of channels with a diameter of 500 m (pre-sintered) with a nozzle size of 250 m (layer thickness 100 m) and even closed hemispheres were printed without support structures. During sintering, the weightbearing feedstock shrinks by 16.7%, resulting in a relative material density of 96.6%. The well-known challenges of the technology such as surface roughness (Ra = 15–20 m) and integrated cavities remain. However, it could be shown that the hollow structures in bulk do not represent a mechanical weak point and that the material can be gas-tight (<1012 mbar s1). For verification, a volume-free helium leak test device was developed and validated. Finally, platinum coatings with high adhesion examined the functionalization of the ceramic. All the prerequisites for hermetic housings with integrated metal structures are given, with a new level of complexity of ceramic shapes available