Exploring the feasibility of producing near-net-shape components with advanced properties and geometrical features via 3D printing has incrementally become the research focus of various studies. ...Digital light processing (DLP) technology can manufacture complex-structured components for various technical applications. The aims of this research were to investigate Al2O3 ceramic slurry preparation procedures to identify the ideal components to add to an in-house-developed ceramic slurry, to determine the optimal DLP printing parameters and conditions while understanding their effect on the green part properties and to evaluate the appropriate debinding regime to achieve fully dense crack-free fired parts capable of exhibiting translucent behaviours. The slurry obtained from the ball-milled powder at 800 rpm for 1 h, together with 2 wt.% BYK-145 as a dispersant and the highest achievable solid loading of 85 wt.%, showed the desired rheological and photopolymerisation properties. Full-factorial design of experiments (DOE) was employed to study the impact of the printing parameters on the density and the dimensions of the samples. Different debinding regimes were investigated and it was proven that the lowest debinding heat rate (0.2 °C/min) and longer holding times helped to reduce defects and promote densification (>99.0%), providing optimal grounds to obtain translucent fired parts.
In this work an approach for rapid prototyping and manufacturing of metallic as well as ceramic parts is presented. By using Mold Shape Deposition Manufacturing (MoldSDM), a wax mold is fabricated ...which is filled with a slurry containing the final part material in powder form. The wax mold is manufactured by first decomposing the desired part geometry into machinable compacts. In a next step the mold is built up in a series of layers by machining either the wax or a sacrificial support material. The surface quality of the final mold is only limited by the abilities of the CNC machine. After casting a ceramic or metallic slurry, the wax mold is removed and the obtained green part debinded and sintered. In this work the mechanical and microstructural properties of the parts obtained by this method are presented. The materials which have been investigated are silicon nitride and stainless steels. Due to the high mold quality the process is suitable for a variety of applications in rapid prototyping and manufacturing where parts made of engineering materials are required.
The viscosity and shear rate as a function of 2–24% volume concentration of solids was determined for alumina and kaolin slurries. A model of viscosity as a function of volume concentration of a ...dispersed phase in a matrix and a bidimensional balance of forces acting on a particle in suspension is presented. The theoretical model was compared with experimental data accomplished with a double concentric cylinders rheometer. A good correlation of the proposed model with the measured data could be verified. The forces of mechanical origin that cause restrictions to particle rotation and translation appear to remarkably influence the variation of viscosity.
Rheology of Glaze Suspensions Savarmand, Saeid; Golkar-Narenji, Mohammad-Reza; Saedi, Kourosh
Canadian journal of chemical engineering,
October 2003, Letnik:
81, Številka:
5
Journal Article
Recenzirano
Rheological properties of suspensions and ceramic glaze slurries under steady flow conditions have been considered. Colloidal forces play an important role in the rheology of such ceramic slurries. ...Since the potential function characterizes the rheology of colloidal systems, a new dimensionless group, viz. potential number, is introduced within a dimensional analysis representing the relative significance of the potential to the Brownian energy. In order to relate the relative viscosity to other dimensionless groups, a new model is proposed by the inclusion of an extra term in addition to that of the hard‐sphere theory owing to the fact that the presence of colloidal forces always increases the fluid viscosity with respect to that predicted by the hard‐sphere. Steady viscosity measurements have been carried out on ceramic glaze suspensions at different volume fractions, particle diameters, and shear rates. Experimental results have been used to modify the model relating the relative viscosity to the Péclet number, potential number, volume fraction, and maximum packing fraction.
On a examiné les propriétés rhéologiques de suspensions et de boues d'émail céramique dans des conditions d'écoulement stationnaires. Les forces colloïdales jouent un rôle important dans la rhéologie de telles boues. Vu que la fonction potentielle caractérise la rhéologie des systèmes colloïdaux, un nouveau groupe adimensionnel, soit le nombre potentiel, est introduit au sein d'une analyse dimensionnelle représentant l'importance relative du potentiel pour l'énergie brownienne. Afin de relier la viscosité relative aux autres groupes adimensionnels, un nouveau modèle est proposé par l'inclusion d'un terme additionnel en plus de celui de la théorie des sphères dures étant donné que la présence des forces colloïdales augmente toujours la viscosité du fluide par rapport à celle qui est prédite par la théorie des sphères dures. Des mesures de viscosité stationnaire ont été effectuées sur des suspensions d'émail céramique à différentes fractions volumiques, diamètres de particules et vitesses de cisaillement. Les résultats expérimentaux nous ont permis de modifier le modèle reliant la viscosité relative au nombre de Péclet, au nombre potentiel, à la fraction volumique et à la fraction de garnissage maximale.
•DLP technology was used to manufacture lattices with CAD designed struts of 200–500 μm.•The slurry prepared with the pre-treated powder showed appropriate properties for successful processing on the ...Admaflex 130.•The cure depth necessary for successful manufacturing was found to be inversely proportional to the exposed area.•DOE showed the most significant parameters that influence the dimensional accuracy were the exposure time, the exposure power and their interaction.•The broadening parameters were found to be dependent on the layer thickness as well as the energy dose and the feature size.
Digital Light Processing (DLP) technology demonstrates the potential for manufacturing parts with complex structures for various engineering applications. The purpose of this study is to evaluate Al2O3 ceramic slurry preparation techniques, establish optimal processing window and assess the manufacturability and dimensional accuracy of lattice structures with CAD strut diameters of up to 500 μm. Two preparation techniques of the ceramic slurry were investigated. The slurry with the pre-treated powder showed appropriate rheological and photopolymerization behaviour. Full factorial Design of Experiments (DOE) was conducted to generate an experimental plan and assess the influence of the printing parameters on the dimensional accuracy. Analysis of Variance (ANOVA) revealed the exposure time, the exposure power, and the interaction effect of both had a significant influence on the dimensional accuracy of lattice strut diameters. The excess cure width was found to be dependent on the feature size, the energy dose and the layer thickness.
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