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Experimental shrinkage study of ceramic DLP 3D printed parts after firing green bodies in a KILN
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The objective of this work was to investigate dimensional parameters of 3D printed parts from glass ceramic photopolymer before and after debinding and sintering in a kiln. During experiments batches of green bodies were printed with different layer thickness and curing strategy. We used 3D printer with ultraviolet LED as a light power source. The peak of intensity of the UV LED was in the range from 385 to 405 nm. DLP projector from Texas Instruments was used for mask projection. After printing, each batch of green bodies was cleaned and post-cured in a UV chamber. Then their dimensions were measured, overgrowth of each sample was calculated. Next stage of the experiment was kiln firing according to special firing schedule. Dimensions of final parts were measured again, and their shrinkage was calculated. The experiment proved the high influence of printing parameters on the overgrowth of models and almost no influence on shrinkage of parts after firing.
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... In this study, other process parameters have not affected the volumetric shrinkage. The same conclusion is reported in a study by Kovalenko et al. [40]. The influence on volumetric shrinkage should be due to other parameters, especially regarding the starting material, like solid loading and mean particle size and particle size distribution [39]. ...
Several commercial ceramic resins are nowadays available in the market of Additive Manufacturing, making more approachable ceramic stereolithography (CS) to an extended audience of users, from academic to industrial fields. Lack of knowledge in terms of material characterization and expected behavior in the manufacturing process are the main problems that involve difficulties in obtaining precise, dense, resistant, and crack-free ceramic parts. This article presents a characterization of a porcelain-based commercial ceramic resin for digital light processing (DLP), Porcelite® by Tethon 3D, and a study on the printing dimensional accuracy and cracks formation in sintered samples in dependence on the process parameters used have been performed. Two different Porcelite® resins with different solid loadings are available in the market. Rheological measurements, thermogravimetry combined with differential thermal analysis, field emission scanning electron microscopy observation, and X-ray diffraction allowed the complete characterization of the most loaded ceramic suspension. A design of experiment (DoE) approach led to planning the experimental work identifying the geometry of the samples, the process parameters, and their levels of variation to evaluate the aspects that influence dimensional accuracy when printing and crack formation during thermal treatment. The final volumetric shrinkage of components produced, respectively, with Porcelite® Bison (PB) and Porcelite® Universal (PU) is 19.3 ± 2.2% and 41.1 ± 3.6%. Solid loadings evaluated through TG–DTA are 52 wt% for PU and 72 wt% for PB. Statistical analyses highlight that layer thickness and degree of exposure influence accuracy in x- and y-directions, and for both resins, part thickness influences accuracy only in the x-direction for PB resin. Layer thickness, part thickness, and interaction are influential in the z-direction. The printed accuracy shows certain independence from the resin solid loading.
A necessidade de materiais biocompatíveis tem estimulado alternativas para proporcionar uma boa qualidade de vida para aqueles que precisam de reparos ortoprotésicos. Uma das ferramentas para reconstrução tecidual se dá pelo uso de scaffolds (matrizes de crescimento celular) obtidos por Fused Deposition Modeling (FDM), técnica de manufatura aditiva barata e acessível. Atrelando conceitos de sustentabilidade, engenharia tecidual e prototipagem rápida, a proposta deste trabalho foi a obtenção e caracterização de filamentos biocompósitos de PHBV reforçados com celulose (35 mesh) proveniente de resíduos da palmeira real australiana (1; 2,5; 5; 7,5 e 10% m/m), através de uma miniextrusora e a impressão 3D de scaffolds. Tratamento superficial no resíduo da palmeira provocou individualização e clareamento das fibrilas na celulose. A adição de fibras de celulose em meio ao PHBV causou aglomerações para maiores proporções de reforços. Todos os biocompósitos apresentaram estabilidade térmica na temperatura de processamento (100-250 °C). Apesar do aumento da banda –OH da celulose (entre 3500 e 3200 cm-1) após os tratamentos superficiais, a interação fibra/matriz foi fraca, apresentando apenas diminuição das bandas características do PHBV nos biocompósitos. Tal fato corroborou com a pequena variação de nanodureza dos biocompósitos (entre 260 e 270 MPa) em relação ao PHBV puro (262 MPa). Entretanto, a análise de citotoxicidade classificou os filamentos biocompósitos como biocompatíveis (viabilidade celular a partir de 95% após 7 dias) e a molhabilidade evidenciou a hidrofilicidade dos mesmos (ângulo de contato abaixo de 90°, chegando à θ = 56,2 ± 3,0 ° para amostra com 10% de celulose). Apesar da aglomeração das fibras de celulose 35 mesh terem impedido a impressão 3D para reforços acima de 2,5%, foram obtidos todos os scaffolds a partir de filamentos biocompósitos usando a celulose 115 mesh. Assim, os filamentos biocompósitos obtidos são promissores para aplicações em medicina regenerativa.
Ceramic green bodies can be created using stereolithography methods where a ceramic suspension consisting of 0.40-0.55 volume fraction ceramic powder is dispersed within an ultraviolet-curable solution. Three ceramic materials were investigated: silica for investment casting purposes, and alumina and silicon nitride for structural parts. After mixing the powders in the curable solution, the ceramic suspension is photocured, layer by layer, fabricating a three-dimensional ceramic green body. Subsequent binder removal results in a sintered ceramic part. Three-dimensional objects have been fabricated from a 0.50 volume fraction silica suspension.
This paper offers a review of present achievements in the field of processing of ceramic-based materials with complex geometry using the main additive manufacturing (AM) technologies. In AM, the geometrical design of a desired ceramic-based component is combined with the materials design. In this way, the fabrication times and the product costs of ceramic-based parts with required properties can be substantially reduced. However, dimensional accuracy and surface finish still remain crucial features in today's AM due to the layer-by-layer formation of the parts. In spite of the fact that significant progress has been made in the development of feedstock materials, the most difficult limitations for AM technologies are the restrictions set by material selection for each AM method and aspects considering the inner architectural design of the manufactured parts. Hence, any future progress in the field of AM should be based on the improvement of the existing technologies or, alternatively, the development of new approaches with an emphasis on parts allowing the near-net formation of ceramic structures, while optimizing the design of new materials and of the part architecture.
For the past six years, Digital Light Processing TM technology from Texas Instruments has made significant inroads in the projection display market. With products enabling the world's smallest data and video projectors, HDTVs, and digital cinema, DLP TM technology is extremely powerful and flexible. At the heart of these display solutions is Texas Instruments Digital Micromirror Device (DMD), a semiconductor-based "light switch" array of thousands of individually addressable, tiltable, mirror-pixels. With su ccess of the DMD as a spatial light modulator for projector applications, dozens of new applications are now being enabled by general-use DMD products that are recently available to developers. The same light switching speed and "on-off" (contrast) ratio that have resulted in superior projector performance, along with the capability of operation outside the visible spectrum, make the DMD very attractive for many applications, including volumetric display, holographic data storage, lithography, scientific instrumentation, and medical imaging. This paper presents an overview of past and future DMD performance in the context of new DMD applications, cites several examples of emerging products, and describes the DMD components and tools now available to developers.
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