BUSCADOR RECOLECTA

As is widely known, additive manufacturing (AM) allows very complex parts to be manufactured with porous structures at a relatively low cost and in relatively low manufacturing times. However, it is necessary to determine in a precise way the input values that allow better results to be obtained in terms of microgeometry, form errors, and dimensional error. In an earlier work, the influence of the process parameters on surface roughness obtained in fused filament fabrication (FFF) processes was analyzed. This present study focuses on form errors as well as on dimensional error of hemispherical cups, with a similar shape to that of the acetabular cup of hip prostheses. The specimens were 3D printed in polylactic acid (PLA). Process variables are nozzle diameter, temperature, layer height, print speed, and extrusion multiplier. Their influence on roundness, concentricity, and dimensional error is considered. To do this, adaptive neuro-fuzzy inference systems (ANFIS) models were used. It was observed that dimensional error, roundness, and concentricity depend mainly on the nozzle diameter and on layer height. Moreover, high nozzle diameter of 0.6 mm and high layer height of 0.3 mm are not recommended. A desirability function was employed along with the ANFIS models in order to determine the optimal manufacturing conditions. The main aim of the multi-objective optimization study was to minimize average surface roughness (Ra) and roundness, while dimensional error was kept within the interval |Dimensional Error|=0.01. When the simultaneous optimization of both the internal and the external surface of the parts is performed, it is recommended that a nozzle diameter of 0.4 mm be used, to have a temperature of 197 °C, a layer height of 0.1 mm, a print speed of 42 mm/s, and extrusion multiplier of 94.8%. This study will help to determine the influence of the process parameters on the quality of the manufactured parts., Peer Reviewed

The main aim of the present paper is to study and analyze surface roughness, shrinkage,
porosity, and mechanical strength of dense yttria-stabilized zirconia (YSZ) samples obtained by
means of the extrusion printing technique. In the experiments, both print speed and layer height
were varied, according to a 22 factorial design. Cuboid samples were defined, and three replicates
were obtained for each experiment. After sintering, the shrinkage percentage was calculated in width
and in height. Areal surface roughness, Sa, was measured on the lateral walls of the cuboids, and
total porosity was determined by means of weight measurement. The compressive strength of the
samples was determined. The lowest Sa value of 9.4 m was obtained with low layer height and
high print speed. Shrinkage percentage values ranged between 19% and 28%, and porosity values
between 12% and 24%, depending on the printing conditions. Lowest porosity values correspond
to low layer height and low print speed. The same conditions allow obtaining the highest average
compressive strength value of 176 MPa, although high variability was observed. For this reason,
further research will be carried out about mechanical strength of ceramic 3D printed samples. The
results of this work will help choose appropriate printing conditions extrusion processes for ceramics., Peer Reviewed

El trabajo expone la propuesta de una metodología para la obtención y verificación de modelos quirúrgicos de tejidos duros (huesos), que sugiere el uso de varios softwares (RadiAnt, SolidWorks, MeshMixer), tanto para la visualización y el procesamiento de imágenes médicas (archivos DICOM), como para la edición y modificación de los archivos STL requeridos para la impresión 3D de modelos con la tecnología de fabricación por filamento fundido. La metodología se ha validado a través de la obtención y verificación de modelos impresos de las falanges proximal y distal y de un hueso metacarpiano de un dedo pulgar., Agradecemos al Centro de Cooperación para el Desarrollo (CCD) de la UPC por su apoyo económico al proyecto 2023-B011 “Transformación de la práctica quirúrgica en un hospital de Holguín (Cuba) mediante la incorporación de la fabricación aditiva a la obtención de modelos quirúrgicos”. Esta investigación también fue financiada por la Agencia Estatal de Investigación de la Gobierno de España, a través del proyecto PID2020-115647RB-C21, “Obtención de prótesis para sustitución de tejido óseo mediante impresión 3D por extrusión y posterior sinterizado". También agradecemos al estudiante Óscar Rodríguez Valentín, así como a los compañeros Alejandro Domínguez, Ramón Casado y Héctor Sanz, todos ellos del DEM de la UPC, por su colaboración en el desarrollo del trabajo.

AM technologies have been developed for different applications in sectors such as aeronautics, automotive, or healthcare. Additionally, the range of materials that can be 3D printed has increased considerably since these technologies began to be used in the 80s of the XXth century. Nowadays, it is possible to use both polymers and composite materials (ceramic-filled, metal-filled, etc.) in extrusion technologies, both with fused filament fabrication (FFF) and with direct ink writing (DIW). Unfortunately, even though 3D printing technologies offer much more freedom than conventional manufacturing technologies (molding, machining, etc.), before printing it is necessary to optimize the process, regarding the printing parameters that are recommended with each material. In addition, post-processing techniques are often required. This study aims to show not only the different parameters that are to be considered to optimize material extrusion 3D printing of ceramic materials, mainly regarding dimensional accuracy and surface finish, but also the types of structures that can be manufactured, as well as the challenges that are nowadays faced regarding 3D printing of ceramics., The authors would like to acknowledge Alejandro Domínguez and Ramón Casado for their help with the experimental tests. This research was funded by Agencia Estatal de Investigación of the Spanish Government, via the project PID2020-115647RB-C21, “Obtención de prótesis para sustitución de tejido óseo mediante impresión 3D por extrusión y posterior sinterizado"., Peer Reviewed

Three-dimensionally printed metals and polymers have been widely used and studied in medical applications, yet ceramics also require attention. Ceramics are versatile materials thanks to their excellent properties including high mechanical properties and hardness, good thermal and chemical behavior, and appropriate, electrical, and magnetic properties, as well as good biocompati- bility. Manufacturing complex ceramic structures employing conventional methods, such as ceramic injection molding, die pressing or machining is extremely challenging. Thus, 3D printing breaks in as an appropriate solution for complex shapes. Amongst the different ceramics, bioinert ceramics appear to be promising because of their physical properties, which, for example, are similar to those of a replaced tissue, with minimal toxic response. In this way, this review focuses on the different medical applications that can be achieved by 3D printing of bioinert ceramics, as well as on the latest advances in the 3D printing of bioinert ceramics. Moreover, an in-depth comparison of the different AM technologies used in ceramics is presented to help choose the appropriate methods depending on the part geometry., Peer Reviewed

El aumento de la esperanza de vida ha incrementado los casos de deterioro significativo de la cadera, requiriendo reemplazos articulares. Las prótesis acetabulares cerámicas, especialmente de zircona estabilizada con itria (YSZ), son adecuadas por su baja tasa de desgaste, elevada dureza y resistencia a la fractura. La fabricación aditiva ofrece una alternativa prometedora para la obtención de geometrías complejas, así como para la personalización de las prótesis. Este estudio compara dos técnicas de extrusión, fabricación por filamento fundido (FFF) e impresión directa de tinta (DIW), para producir estructuras de YSZ. El análisis termogravimétrico de las mezclas de YSZ con ácido poliláctico (PLA) (para FFF) e YSZ con plurónico F127 o con HCl (para DIW) reveló distintos perfiles de degradación térmica. YSZ+PLA mostró pérdidas de masa a 330 °C y entre 453-462 °C, mientras que YSZ+F127 presentó pérdidas a 185 °C y 350 °C. También se analizó una tercera tinta de YSZ+HCl. La reología indicó que dicha tinta no se autosustenta adecuadamente, aunque permite la impresión de formas sencillas. En contraste, la tinta YSZ+F127 mostró mejores propiedades de autosustentación. El análisis SEM mostró diferencias en la microestructura y la porosidad de los distintos materiales. Las partículas de YSZ en el filamento con PLA son submicrométricas, sin porosidad interna apreciable, mientras que las muestras de tinta tienen mayor porosidad, especialmente al emplear F127. Las probetas FFF mostraron baja porosidad volumétrica tras el sinterizado. Las tintas para DIW presentaron contracciones y densificaciones variables según su composición y condiciones de impresión. Estos resultados resaltan el potencial de la fabricación aditiva para la producción de prótesis de cadera personalizadas, proporcionando una base sólida para optimizar las propiedades mecánicas y microestructurales mediante el control de la composición de las tintas y los
parámetros de impresión., Los autores agradecen a la Agencia Estatal de Investigación la financiación del proyecto PID2020-115647RB-C21l. También agradecen a la Generalitat de Catalunya la acreditación de calidad otorgada al grupo de investigación TECNOFAB (2021 SGR 01034) y la
financiación del grupo DIOPMA (2021 SGR 00708). DIOPMA es agente certificado TECNIO en la categoría de desarrolladores tecnológicos de la Generalitat de Cataluña, y TECNOFAB pertenece a DIGIFACT (agente TECNIO).

As is widely known, additive manufacturing (AM) allows very complex parts to be manufactured with porous structures at a relatively low cost and in relatively low manufacturing times. However, it is necessary to determine in a precise way the input values that allow better results to be obtained in terms of microgeometry, form errors, and dimensional error. In an earlier work, the influence of the process parameters on surface roughness obtained in fused filament fabrication (FFF) processes was analyzed. This present study focuses on form errors as well as on dimensional error of hemispherical cups, with a similar shape to that of the acetabular cup of hip prostheses. The specimens were 3D printed in polylactic acid (PLA). Process variables are nozzle diameter, temperature, layer height, print speed, and extrusion multiplier. Their influence on roundness, concentricity, and dimensional error is considered. To do this, adaptive neuro-fuzzy inference systems (ANFIS) models were used. It was observed that dimensional error, roundness, and concentricity depend mainly on the nozzle diameter and on layer height. Moreover, high nozzle diameter of 0.6 mm and high layer height of 0.3 mm are not recommended. A desirability function was employed along with the ANFIS models in order to determine the optimal manufacturing conditions. The main aim of the multi-objective optimization study was to minimize average surface roughness (Ra) and roundness, while dimensional error was kept within the interval. When the simultaneous optimization of both the internal and the external surface of the parts is performed, it is recommended that a nozzle diameter of 0.4 mm be used, to have a temperature of 197 °C, a layer height of 0.1 mm, a print speed of 42 mm/s, and extrusion multiplier of 94.8%. This study will help to determine the influence of the process parameters on the quality of the manufactured parts., This research was financed by the Spanish Ministry of Industry, Economy and Competitiveness, grant number PID2020-115647RB-C21.