Query: Additive manufacturing of ceramic

title: Additive Manufacturing of ceramic components by Digital Light Processing: A comparison between the "bottom up" and the "top down" approaches
abstract: A systematic study of the additive manufacturing of complex ceramic objects was carried out using two different Digital Light Processing (DLP) approaches, the "bottom up" and "top down" ones, employing the same projector as light source and a photosensitive Al2O3 based ceramic slurry. Cylindrical periodic architectures having different macro porosity, as well a bulk (dense) component in the form of a disk, were designed and additively manufactured with the two printers employing similar printing conditions. In the "bottom up" approach, the periodic detachment of the part being manufactured from the bottom surface of the vat, to enable the insertion of a fresh layer of slurry, introduced stresses and deformations in the component, leading to several problems. In the "top down" approach, the main issue is that the thickness of the printed slices is not precise and constant, due to the difficulty of the viscous slurry to uniformly wet and coat the already printed layers.

title: Process Data Based Knowledge Discovery in Additive Manufacturing of Ceramic Materials by Multi Material Jetting (CerAM MMJ)
abstract: Multi material jetting (CerAM MMJ, previously T3DP) enables the additive manufacturing of ceramics, metals, glass and hardmetals, demonstrating comparatively high solid contents of the processed materials. The material is applied drop by drop onto a substrate. The droplets can be adapted to the component to be produced by a large degree of freedom in parameterization. Thus, large volumes can be processed quickly and fine structures can be displayed in detail, based on the droplet size. Data driven methods are applied to build process knowledge and to contribute to the optimization of CerAM MMJ manufacturing processes. As a basis for the computational exploitation of mass sensor data from the technological process chain for manufacturing a component with CerAM MMJ, a data management plan was developed with the help of an engineering workflow. Focusing on the process step of green part production, droplet structures as intermediate products of 3D generation were described by means of droplet height, droplet circularity, the number of ambient satellite particles, as well as the associated standard deviations. First of all, the weighting of the factors influencing the droplet geometry was determined by means of single factor preliminary tests, in order to be able to reduce the number of factors to be considered in the detailed test series. The identification of key influences (falling time, needle lift, rising time, air supply pressure) permitted an optimization of the droplet geometry according to the introduced target characteristics by means of a design of experiments.

title: Additive Manufacturing of Ceramic Components for Facade Construction
abstract: Additive Manufacturing (AM) opens new fields of research and development in the architectural design and construction industry, enabling a geometric freedom that can result in the design of components with specific requirements and multifunctional behaviours. This work explores the integration of digital design tools and AM extrusion processes on the production of ceramic architectural components for facade construction, reshaping and expanding the boundaries of what is possible to achieve with masonry construction in a wide range of applications (opaque walls, ventilated sunscreens, and shading systems) Several stoneware prototypes were developed, encompassing different challenges such as the morphology customisation, the versatility of use, the exploitation of the maximum degree of curvature, and the optimisation of structural patterns.

title: Additive manufacturing of ceramic insulators
abstract: Ceramic samples were fabricated from alumina using traditional and additive technologies. Slipcasting technique was used to prepare sample as a traditional way, from pink alumina ceramic slurry with further drying a high temperature treatment of dried preformed ceramics. For preparation of second sample by additive route, stereolythography or SLA 3D printing was used. This sample firstly formed a so called green body ceramic from photopolymerazed slurry, that forms an organo inorganic composite with alumina as a filler. Preformed green body ceramic then undergoes a several stages of heat treatment: first is debinding process, at low temperature to rid of polymer binder and second stage is annealing at higher temperatures to fuse alumina particles together and get desired strength and porosity level. Samples were studied using GE Vtomex c 450 X ray tomography device. It allowed to compare accuracy of geometry, surface roughness and porosity of samples. It is shown that additive technology due to high accuracy of fabrication is a perspective way of precision fabrication of ceramic parts with high quality.

title: Thermal design, optimization and additive manufacturing of ceramic regular structures to maximize the radiative heat transfer
abstract: The present study is focused on the application of a ceramic tubular high temperature heat exchanger with engineered cellular architectures. Thermal design and optimization to maximise the radiative heat transfer has been investigated both experimentally and computationally. Numerical models were designed involving various arrangements of cells and their different sizes (while the total heat transfer area remains constant) They were 3D printed by Stereolithography (SLA) and subsequently sintered. Heat transfer tests were performed both with a high temperature pressure drop test and by CFD simulations on 2D and 3D models. The computational results agree with the experimental data. We found that radial heat transfer in a tube increases by 160% to 280% if a ceramic lattice is inserted, in respect of an empty tube. Moreover, the arrangement of cells and their size significantly influences the radiative heat transfer showing (for a given array) its top performances above 773 K. Geometries with large cells outside and small cells inside in the radial direction allow radiation to penetrate better through the core of the porous body. With this engineered ceramic lattices it is possible to reduce the tube length by one third to obtain more compact heat exchangers than an empty tubular solution.

title: Patent Trends in Additive Manufacturing of Ceramic Materials

title: Suitability of Biosilicate(r) glass ceramic powder for additive manufacturing of highly porous scaffolds
abstract: glass ceramic is one of the most promising alternatives to the 45S5 Bioglass(r) in terms of bioactivity, osteoconductivity, osteoinductivity, non cytotoxicity, and antibacterial properties, with significant advantages in the manufacturing of specific components of complex shapes for bone tissue application. Unlike in 45S5 glass, the crystallization does not lead to a degradation of bioactivity. In the present paper, we explored the suitability of Biosilicate(r) for the manufacturing of highly porous scaffolds (porosity of 50 80 vol% by using modern additive manufacturing technologies, such as direct ink writing (DIW) and digital light processing (DLP) Both techniques could be easily applied to fine powders of Biosilicate(r) mixed with fugitive binders. Significant densification of the struts, despite the limited powder packing, could be achieved using liquid assisted sintering, in turn, triggered by the phosphate enriched residual glass phase, already at 1000 degC. The strength to density ratio could be variously tuned (from 1.5 to 9.5 MPa cm3/g) especially with DLP derived samples, by adjusting both the firing temperature and the scaffold topology.

title: Stereolithography based additive manufacturing of lithium disilicate glass ceramic for dental applications.
abstract: With additive manufacturing (AM) on the rise in industrial production, different industries are looking for a way to benefit from the advantages over conventional manufacturing methods like milling or casting. The layer by layer approach allows the parallel construction of different complex structures with simultaneous customization of the parts, while waste material is significantly reduced. This is especially interesting for the processing of advanced ceramic materials, where often customized and single parts are required. Regarding ceramics, Lithographic Ceramic Manufacturing (LCM) provides the highest surface quality and achievable precision compared to any other AM technologies, which is necessary to meet the high demands from dental industry regarding accuracy and reproducibility. At TU Wien, we achieved expertise in printing different kinds of ceramics and glasses by using specially developed stereolithography printers based on digital light processing (DLP) followed by a thermal debinding and sintering processes. In dental industry, glass ceramic materials are widely used for customized and aesthetic restorations. This work deals with the processing of lithium disilicate via an AM technology, offering highly dense >99% full ceramic parts which meet the requirements for the use as dental restorations. With outstanding mechanical properties of over 400 MPa flexural strength, excellent translucency and accuracy, veneers, crowns and even bridges, especially for the anterior tooth area can be reproducibly printed, debinded and sintered.

title: Additive manufacturing of ceramic components
abstract: This chapter deals with the additive manufacturing (AM) of ceramic components. It shows not only the chances of this shaping route in comparison to the conventional dry, (thermo)plastic, or suspension based shaping methods, but also the challenges AM is faced with in powder technology. A variety of direct and indirect AM methods, either powder based or feedstock /suspension based, are introduced. Practical examples are given for chosen technologies, showing which AM method is suitable for which ceramic material. The contribution explains why AM of ceramic components differs from AM of metals or polymers. All ceramic AM processes are powder technological processes and need subsequent debindering and sintering steps following the AM step. The chapter gives a brief market survey and an outlook of the future development trends in this turbulent area.

title: Additive Manufacturing of Ceramic Based Materials
abstract: 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.