Publication: Optimización y caracterización de piezas de PLA fabricadas mediante técnicas aditivas
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2014-09
Defense date
2014-10-03
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Abstract
La impresión 3D es una tecnología que actualmente se encuentra en plena expansión. El auge
mediático que está teniendo esta reciente tecnología es también una fuente de confusión, pues
hay una gran variedad de tecnologías de fabricación que se pueden enmarcar bajo este nombre,
tanto para materiales metálicos, poliméricos o cerámicos. En este trabajo se presentan y
diferencian estas tecnologías, cuyo aspecto principal en común es la adición de material para
lograr una pieza con volumen final. Es por esto que estas tecnologías se denominan como
técnicas de fabricación aditiva.
Esta introducción sirve para enmarcar la técnica objeto de este trabajo, el modelado por
deposición fundida. Esta técnica es la que se ha desarrollado dentro del movimiento RepRap,
principal responsable de la expansión de la impresión 3D gracias a la reducción de costes que ha
propiciado. Gracias a ello, ha sido posible la compra de componentes y montaje de un modelo
Prusa i3 para la elaboración del presente estudio. Los principales materiales que se vienen
usando en las impresoras RepRap son el ABS y el PLA. Tras una presentación y comparación de
los mismos, se verá como, aunque al inicio de este movimiento el termoplástico más usado fuera
el ABS, la tendencia apunta hacia el uso masivo del PLA, debido a sus propiedades de
biocompatibilidad y medioambientales.
La necesidad de conocer las propiedades mecánicas de piezas de PLA fabricadas mediante
deposición fundida con una impresora RepRap es lo que ha motivado este trabajo. Este estudio
establece una relación entre diferentes parámetros de impresión y las propiedades mecánicas
en diferentes probetas fabricadas con este polímero biodegradable. Se estudió el efecto que
provocan en las propiedades mecánicas de las piezas variar los parámetros de velocidad de
impresión, temperatura del extrusor, temperatura de la base de impresión y uso de ventilador
de capa. Para llevar a cabo el estudio se planteó un diseño de experimentos factorial 24 a dos
niveles. Los resultados revelan la importancia de parámetros como la velocidad de impresión y
temperaturas de procesado, y la poca influencia de la temperatura de extrusor o ventilador de
capa en los resultados de tensión. Se calculó una tensión media entre todas las probetas
ensayadas de 29,5 MPa y un módulo de elasticidad de 2,7 GPa.
Para ver cómo podían afectar estos diferentes parámetros en las propiedades de las piezas y
pegado entre sus capas, se llevaron a cabo estudios sobre la densidad de las muestras, análisis
térmicos y observaciones de microscopía estereoscópica y electrónica de barrido.
Currently, 3D printing technologies are under intense development. The media hype surrounding this term is also a source of confusion and misunderstandings. There is a great variety of techniques that could be named as 3D printing, even for metal, polymeric or ceramic materials. This study gathers and explains the main additive manufacturing (AM) technologies. As the term itself says, the main common feature of these technologies is the addition of materials to get a final three-dimensional part. After this introduction, the technique used in this study can be placed and identified. This technique is named fused deposition modelling (FDM) and is the technique developed parallel to the RepRap movement, despite it was renamed by filament fused fabrication (FFF). The RepRap project has made 3D polymer-based printers available to the public due to cost reduction. This cost reduction made it possible to purchase the materials and assemble a Prusa i3 model to perform this work. RepRap printers fabricate objects primarily from ABS and PLA. This study details the main characteristics of these materials and emphasizes the tendency of fabricating increasingly with PLA and not with ABS. This is mainly motivated by PLA’s eco-friendly and biocompatibility properties. In order for PLA printed parts to be useful for biomedical, engineering and other applications, the mechanical properties of printed parts must be known. This study relates several printing parameters to some properties of the final part. The study quantifies the effects caused by the alterations of parameters such as printing speed, hot-end temperature, hot-bed temperature and the employment of layer fan. In order to do this a 24 factorial experiment with two levels was designed. Results reveal the importance of parameters such as the printing speed or hotbed temperature in contrast with the low influence of the hot-end temperature and layer fan. Results also find average tensile strength of 29,5 MPa with average elastic modulus of 2,7 GPa. Density calculations, thermal analysis, stereo microscope and scanning electron microscope (SEM) observations were conducted to evaluate the reasons of these results.
Currently, 3D printing technologies are under intense development. The media hype surrounding this term is also a source of confusion and misunderstandings. There is a great variety of techniques that could be named as 3D printing, even for metal, polymeric or ceramic materials. This study gathers and explains the main additive manufacturing (AM) technologies. As the term itself says, the main common feature of these technologies is the addition of materials to get a final three-dimensional part. After this introduction, the technique used in this study can be placed and identified. This technique is named fused deposition modelling (FDM) and is the technique developed parallel to the RepRap movement, despite it was renamed by filament fused fabrication (FFF). The RepRap project has made 3D polymer-based printers available to the public due to cost reduction. This cost reduction made it possible to purchase the materials and assemble a Prusa i3 model to perform this work. RepRap printers fabricate objects primarily from ABS and PLA. This study details the main characteristics of these materials and emphasizes the tendency of fabricating increasingly with PLA and not with ABS. This is mainly motivated by PLA’s eco-friendly and biocompatibility properties. In order for PLA printed parts to be useful for biomedical, engineering and other applications, the mechanical properties of printed parts must be known. This study relates several printing parameters to some properties of the final part. The study quantifies the effects caused by the alterations of parameters such as printing speed, hot-end temperature, hot-bed temperature and the employment of layer fan. In order to do this a 24 factorial experiment with two levels was designed. Results reveal the importance of parameters such as the printing speed or hotbed temperature in contrast with the low influence of the hot-end temperature and layer fan. Results also find average tensile strength of 29,5 MPa with average elastic modulus of 2,7 GPa. Density calculations, thermal analysis, stereo microscope and scanning electron microscope (SEM) observations were conducted to evaluate the reasons of these results.
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Keywords
Impresoras 3D, Tecnología de fabricación, Diseño asistido por ordenador, Modelado, Deposición fundida