Fused filament fabrication (FFF) is the most common and widespread additive manufacturing (AM) technique, but it requires the formation of filament. Fused granular fabrication (FGF), where plastic granules are directly three-dimensional (3D) printed, has become a promising technique for the AM technology. FGF could be a key driver to promote further greening of distributed recycling thanks to the reduced melt solidification steps and elimination of the filament extruder system. However, only large-scale FGF systems have been tested for technical and economic viability of recycling plastic materials. The objective of this work is to evaluate the performance of the FFF and FGF techniques in terms of technical and economical dimensions at the desktop 3D printing scale. Recycled and virgin polylactic acid material was studied by using five different types of recycling feedstocks: commercial filament, pellets, distributed filament, distributed pellets, and shredded waste. The results showed that the mechanical properties from the FGF technique using same configurations showed no statistical differences to FFF samples. Nevertheless, the granulometry could have an influence on the reproducibility of the samples, which explains that the critical factor in this technology is to assure the material input in the feeding system. In addition, FGF costs per kg of material were reduced to less than 1 €/kg compared with more than 20 €/kg for commercial recycled filament. These results are encouraging to foster FGF printer diffusion among heavy users of 3D printers because of reducing the cost associated to the filament fabrication while ensuring the technical quality. This indicates the possibility of a new type of 3D printing recycled plastic waste that is more likely to drive a circular economy and distributed recycling.

中文翻译：

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通用粒料挤出机对聚乳酸进行直接废料印刷的机械性能：与开源台式机三维打印机上的熔融长丝加工比较

熔融长丝制造（FFF）是最常见且广泛使用的增材制造（AM）技术，但它需要形成长丝。熔融颗粒制造（FGF），其中塑料颗粒直接进行三维（3D）打印，已成为AM技术的一项有前途的技术。由于减少了熔体固化步骤并取消了长丝挤出机系统，因此FGF可能是促进分布式回收进一步绿色化的主要驱动力。但是，仅大型FGF系统已经过塑料回收技术和经济可行性的测试。这项工作的目的是在台式3D打印规模的技术和经济尺寸方面评估FFF和FGF技术的性能。通过使用五种不同类型的回收原料研究了可回收的纯净聚乳酸材料：商用长丝，颗粒，分散长丝，分散颗粒和切碎的废料。结果表明，使用相同配置的FGF技术的机械性能与FFF样品无统计学差异。然而，粒度分析可能会影响样品的重现性，这说明该技术的关键因素是确保进料系统中的物料输入。此外，每公斤材料的FGF成本降低到低于1欧元/千克，而商用再生长丝则超过20欧元/千克。这些结果鼓舞了FGF打印机在3D打印机的大量用户中的普及，这是因为在确保技术质量的同时降低了与灯丝制造相关的成本。这表明存在一种新型3D打印再生塑料废料的可能性，这种废料更有可能推动循环经济和分布式回收。