setup and alignment of the laser speckle imaging (lsi) instrument with the 3d printer

Visualización de la dinámica de los polímeros para optimizar la calidad de la impresión 3D

The method of 3D printing is an additive manufacturing technique in which an object is manufactured layer by layer to form the desired shape. This method has a large and diverse user-base thanks to its versatility, affordability, and ease of use. Fused deposition modeling features a moving extruder (with a diameter of hundreds of microns to a couple of millimeters) to deposit molten plastic into the desired shape1. The extruded plastic should behave in a liquid-like manner for a certain duration to achieve good fusion with the previously printed plastic and form a strongly cohesive material. However, the plastic should cool down and solidify quickly after printing to prevent the plastic from flowing away from the print location and reducing the print quality. This delicate interplay between heating and cooling has been shown to directly underpin the balance between the mechanical strength and the geometric accuracy of the final 3D-printed object2. To achieve the optimal heating-cooling balance, the plastic is extruded at a temperature just above its melting temperature, and a fan head, attached to the printer, is used to cool the plastic down quickly. An in-depth understanding of the effects of printing temperatures and cooling speeds could provide the insights required for developing advanced slicing and printing protocols that maximize the mechanical or geometric results in the areas where they are most important. Efforts to gain more insight into these processes often rely on infrared (IR) imaging, which only visualizes the surface temperature3,4,5 and does not indicate the inner temperature of the plastic. Local heating beyond the melting transition drastically increases the polymer mobility and, thus, allows polymer entanglement between the old and new material. This temporally enhanced polymer motion is a requirement for the formation of the final cohesive material6,7, but IR imaging can only measure polymer motion indirectly through the surface temperature8,9. Translating the surface temperature to layer bonding thus necessitates precise knowledge of the core-surface temperature gradient and the associated complex polymer dynamics over a range of time and length scales. A direct measurement of the layer bonding (i.e., the polymer entanglement process) would allow the visualization of the mechanism underlying bulk material cohesion without a priori information or assumptions.
To gain an understanding of the spatial and temporal distribution of layer bonding, an imaging technique that directly quantifies the dynamics of the polymers that make up the plastic filament is employed in this work. This technique, laser speckle imaging (LSI), relies on interferometric light scattering to visualize nanoscopic motions, independent of the chemical composition. Depending on the optical properties of the sample, it can accurately measure several millimeters to centimeters into non-transparent materials10,11,12, unlike IR imaging, which reports only surface temperatures8,9. These attributes have recently made speckle-based methods popular in understanding dynamic processes in a plethora of materials, although they were originally developed for medical applications10,11,12. Recently, LSI has been used to gain insight into the behavior of advanced polymeric materials such as self-cleaning liquid crystal polymer networks13,14, as well as for predicting fracture in rubber15 and for studying self-healing materials16.
The feasibility of applying LSI to 3D printing was showcased in a previous article17, where a portable LSI setup with real-time analysis capabilities was presented, and it was shown that the deposition of molten plastic results in increased polymer motion multiple layers below the current layer. In the paper presented here, systematic research into the effects of the cooling fan speed on the degree of multi-layer bonding is performed. An improved plug-and-play version of the portable instrument is used that can be operated by users without optics or programming expertise. The speckle images are analyzed in real-time using Fourier transforms17, which visualize the amplitude of the speckle intensity fluctuations. This instrument has an additional brightfield camera that is aligned with the speckle camera so that the LSI motion maps can be overlayed with the brightfield images for easier interpretation without the brightfield light affecting the motion maps. The experimental approach presented in this article can be used to gain more insight into the melting, layer bonding, and solidification of extruded plastic during the 3D printing of challenging geometries and materials.

Autor destacado: Imágenes en tiempo real de la unión en capas impresas en 3D  

Imágenes en tiempo real de la unión en capas impresas en 3D

Watch this Scientific Journal Video about Setup and Alignment of the Laser Speckle Imaging LSI Instrument with the 3D Printer at JoVE.com

Setup and Alignment of the Laser Speckle Imaging (LSI) Instrument with the 3D Printer  

Configuración y alineación del instrumento Laser Speckle Imaging (LSI) con la impresora 3D

Comience colocando la impresora 3D sobre una superficie estable para minimizar las vibraciones. Coloque el instrumento LSI junto a la impresora para que la cámara tenga una visión clara del área de impresión. Coloque el LSI ligeramente más alto que la placa de construcción de la cámara e inclínelo ligeramente hacia abajo para evitar la obstrucción de la visión.A continuación, encienda el láser y la iluminación de campo brillante y asegúrese de que estén alineados con el área de imágenes. Comience con una impresión de prueba, asegurándose de que la cámara LSI esté enfocada en el área de impresión. Durante la impresión de prueba, alinee de manera óptima la iluminación y la cámara digital y ajuste la dirección del láser para iluminar toda el área de imagen de forma homogénea.Ajuste el diafragma para que el tamaño del moteado sea ligeramente mayor que el tamaño del píxel. Seleccione los parámetros para el análisis de datos LSI en vivo, asegurándose de elegir la frecuencia que produzca el mejor contraste de imagen entre plástico fundido y solidificado. Elija la frecuencia y la duración del guardado de imágenes para preparar el instrumento LSI para capturar imágenes.

setup-alignment-laser-speckle-imaging-lsi-instrument-with-3d

Research

JoVE Journal

Engineering

Setup and Alignment of the Laser Speckle Imaging (LSI) Instrument with the 3D Printer

1.1K vistas. Comience colocando la impresora 3D sobre una superficie estable para minimizar las vibraciones. Coloque el instrumento LSI junto a la impresora para que la cámara tenga una visión clara del área de impresión. Coloque el LSI ligeramente más alto que la placa de construcción de la cámara e inclínelo ligeramente hacia abajo para evitar la obstrucción de la visión.A continuación, encienda el láser y la iluminación de campo brillante y asegúrese de que estén alineados con el ...

Video: Setup and Alignment of the Laser Speckle Imaging (LSI) Instrument with the 3D Printer  

Real-Time Imaging of Bonding in 3D-Printed Layers

In recent times, 3D printing technology has revolutionized our ability to design and produce products, but optimizing the print quality can be challenging. The process of extrusion 3D printing involves pressuring molten material through a thin nozzle and depositing it onto previously extruded material. This method relies on bonding between the consecutive layers to create a strong and visually appealing final product. This is no easy task, as many parameters, such as the nozzle temperature, layer thickness, and printing speed, must be fine-tuned to achieve optimal results. In this study, a method for visualizing the polymer dynamics during extrusion is presented, giving insight into the layer bonding process. Using laser speckle imaging, the plastic flow and fusion can be resolved non-invasively, internally, and with high spatiotemporal resolution. This measurement, which is easy to perform, provides an in-depth understanding of the underlying mechanics influencing the final print quality. This methodology was tested with a range of cooling fan speeds, and the results showed increased polymer motion with lower fan speeds and, thus, explained the poor printing quality when the cooling fan was turned off. These findings show that this methodology allows for optimizing the printing settings and understanding the material behavior. This information can be used for the development and testing of novel printing materials or advanced slicing procedures. With this approach, a deeper understanding of extrusion can be built to take 3D printing to the next level.

With a non-invasive and real-time technique, nanoscopic polymer motion inside a polymer filament is imaged during 3D printing. Fine-tuning this motion is crucial for producing constructs with optimal performance and appearance. This method reaches the core of plastic layer fusion, thus offering insights into optimal printing conditions and material design criteria.