来自National Taiwan University of Science and Technology使用不需要任何支持结构的融合沉积建模（FDM），具有3D打印的新晶格结构。
The shell-shaped lattice structures are based on the morphology of a sea urchin, which has a mechanically stable and load-bearing shape. The researchers aimed to emulate these properties in their printed lattice structures in order to eliminate the need for support structures, thereby reducing the amount of material, energy, and time required during the printing process, and subsequent post-processing steps.
The sea urchin-inspired lattices have been designed with specific stiffness and energy absorption properties and could have potential applications within end-use consumer products such as low-cost shoe midsoles and ski boots. The lattices could also be deployed within the automotive sector in the form of tires and automotive crush boxes, or indeed “any other energy-absorbing” structure, according to the researchers.
删除不需要的支持
使用FDM过程打印晶格结构需要一个支撑结构，以确保每个晶格元素无印刷缺陷，而不会失真或下垂。然后在通过机械或化学方法的后处理步骤中去除该支持结构。
When printing with elastic materials like TPU, the same material must be used as the support, making the removal of this support from the lattice by chemical or mechanical means near impossible due to the structure’s intricate nature. This extensive post-processing work, coupled with the extra material, energy, and processing time required to print the supports in the first place, prompted the researchers to embark upon designing stable, self-supporting TPU lattice structures that could be produced via FDM.
研究人员还希望利用特定的机械性能，例如刚度和能量吸收，以在装载和卸载结构时产生不错的压缩结果，以确保它们适合于鞋类和其他消耗能量的应用。
Previous research from China’sSoutheast Universityhas embarked upon creating an algorithm for更强，更高效的物体printed using the FDM process, using a consistent infill pattern similar to that of a lattice. Elsewhere, a team fromUC Berkeley已经开发了一种合并的方法3D打印的聚合物八位晶格成混凝土结构to act as reinforcers. The lattice structures significantly decreased the overall weight of the structure and also proved to be just as load-bearing as traditional cement.
Printing the lattices with FDM
The researchers decided upon the FDM 3D printing method due to its low operational cost and maintenance. They hope to make the FDM process more efficient through achieving higher print speeds and better build quality by removing the need for support structures when printing lattice structures.
在FDM,支持使用当晶格结构res have steep overhangs and parallel ledges. The researchers discovered that in order to print self-supporting lattices, they needed to ensure a maximum overhang angle of 45 degrees, and eliminate the structure’s parallel ledge.
The proposed lattice is made up of an interconnected network of solid struts which form basic building blocks that can then be tessellated in a periodic structure. The structure is based on a cellular design inspired by the dome of sea urchins, which is economical in materials and is able to transfer compressive stress effectively from the dome’s surface to its margin. This makes the structure stronger and more stable, and has previously been used within architectural design.
Several variations of the lattice were printed with TPU filament on aFlashforgeBeaver 3 andUltimakerFDM3D printer, with unit lattice dimensions of 8x8x8mm. The unit lattices were then tessellated into a cylinder with a diameter of 38mm and a thickness of 16 mm. After the printing of the lattice structures was complete, no post-processing steps were required, and testing of the lattices’ mechanical properties could commence.
评估晶格结构
研究人员发现，他们的3D打印的无支撑晶格结构可以提高FDM 3D打印过程的整体速度，以构建定制零件，而晶格本身为制造具有广泛量的零件的零件提供了“巨大的潜力”和大小。
Visual inspection of the 3D printed lattices found no imperfections or breaks within the structure, proving that support-free lattice structures can be manufactured for end-use products, such as midsoles and tires. The structures also exhibited a near constant energy return under cyclic loading.
According to the researchers, their structure significantly outperformed a benchmark body-centered cubic (BCC) lattice and ethylene vinyl acetate (EVA) foams in terms of energy absorption and stiffness. Additionally, the printing of the support-free lattice took three hours less than those printed with supports and removed around 11 hours of post-processing time. Printing the lattices also costs three times less than comparable structures printed with supports.
展望未来，研究人员希望他们的无支撑晶格结构可用于使用FDM的运动鞋和滑雪靴的定制中部。他们还将研究流速对使用固定喷嘴直径打印晶格的准确性的影响。
Further information on the study can be found in the paper titled“Supportless lattice structures for energy absorption fabricated by Fused Deposition Modeling”,published in the 3D Printing and Additive Manufacturing journal. The paper is co-authored by A. Kumar, S. Verma, J. Jeng.
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Featured image showsthe researchers based their lattice structures on the design of sea urchin shells. Photo via Halef/Pixabay.
