Name: Setup and Alignment of the Laser Speckle Imaging (LSI) Instrument with the 3D Printer
Uploaded: 2023-09-01T12:20:00
Duration: 1 min 25 s
Description: 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

可视化聚合物动力学以优化 3D 打印质量

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.

作者聚焦：3D 打印层中粘合的实时成像  

3D 打印层中粘合的实时成像

Our research aims to improve layer bonding during 3D printing. We use a method called laser speckle imaging to visualize the bonding process in real time. These insights will guide the optimization of printing conditions, hopefully leading to enhanced material design and performance.Currently, the layer bonding is studied using infrared imaging techniques that visualize this plastic*surface temperatures. To study layer bonding with infrared imaging, it is assumed that the inner temperature and the surface temperature is equal. Also, the complex relationship between temperature and the plastic fluidity has to be known.We've adapted laser speckle imaging for the use of 3D printing and have shown how to easily obtain deeper understanding of the layer bonding. Our LSI approach measures the polymer motion inside the plastic, visualizing the layer bonding without any assumptions. The technique is also non-invasive, easy to use, and has an excellent sensitivity.The method shown in this research can be used to study 3D prints or patterns that are challenging. The results can be used to understand how the setting should be changed to improve the print's quality.

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  

激光散斑成像 （LSI） 仪器与 3D 打印机的设置和对准

首先将3D打印机放置在稳定的表面上，以最大程度地减少振动。将LSI仪器放在打印机旁边，以便相机可以清楚地看到打印区域。将LSI放置在略高于相机构建板的位置，并将其稍微向下倾斜以防止视线障碍。接下来，打开激光和明场照明，并确保它们与成像区域对齐。从测试打印开始，确保LSI相机聚焦在打印区域。在测试打印期间，以最佳方式对齐照明和数码相机，并调整激光方向以均匀地照亮整个成像区域。调整光圈，使斑点大小略大于像素大小。选择实时LSI数据分析的参数，确保选择在熔融和固化塑料之间产生最佳成像对比度的频率。选择图像保存的频率和长度，以准备LSI仪器捕获图像。