Purpose

Powder bed additive manufacturing processes are widespread due to their many technical and economic advantages. Nevertheless, the disposal of leftover powder poses a problem in terms of process sustainability. The purpose of this paper is to provide an alternative solution to recycle waste PA12 powder from HP multi jet fusion. In particular, the opportunity to use this material as a dispersion in three-dimensional (3D) printed clay is investigated.

Design/methodology/approach

A commercial fused deposition modelling printer was re-adapted to extrude a viscous paste composed of clay, PA12 and water. Once printed, parts were dried and then put in an oven to melt the polymer fraction. Four compositions with different PA12 concentration were studied. First, the extrudability of the paste was observed by testing different extrusion lengths. Then, the surface porosities were evaluated through microscopical observations of the manufactured parts. Finally, benchmarks with different geometries were digitalised via 3D scanning to analyse the dimensional alterations arising at each stage of the process.

Findings

Overall, the feasibility of the process is demonstrated. Extrusion tests revealed that the composition of the paste has a minor influence on the volumetric flow rate, exhibiting a better consistency in the case of long extrusions. The percentage of surface cavities was proportional to the polymer fraction contained in the mix. From dimensional analyses, it was possible to conclude that PA12 reduced the degree of shrinkage during the drying phase, while it increased dimensional alterations occurring in the melting phase. The results showed that the dimensional error measured on the z-axis was always higher than that of the XY plane.

Practical implications

The method proposed in this paper provides an alternative approach to reuse leftover powders from powder bed fusion processes via another additive manufacturing process. This offers an affordable and open-source solution to companies dealing with polymer powder bed fusion, allowing them to reduce their environmental impacts while expanding their production.

Originality/value

The paper presents an innovative additive manufacturing solution for powder reuse. Unlike the recycling methods in the body of literature, this solution does not require any intermediate transformation process, such as filament fabrication. Also, the cold material deposition enables the adoption of very inexpensive extrusion equipment. This preliminary study demonstrates the feasibility and the benefits of this process, paving the way for numerous future studies.

中文翻译：

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粉末床工艺中的废聚合物增强粘土糊的 3D 打印

目的

粉末床增材制造工艺因其众多技术和经济优势而得到广泛应用。然而，剩余粉末的处理在工艺可持续性方面存在问题。本文的目的是提供一种替代解决方案，从 HP 多射流聚变中回收废 PA12 粉末。特别是，研究了将这种材料用作三维 (3D) 打印粘土中的分散体的机会。

设计/方法/方法

重新调整商业熔融沉积成型打印机以挤出由粘土、PA12 和水组成的粘性糊状物。打印后，将零件干燥，然后放入烘箱中以熔化聚合物部分。研究了四种不同 PA12 浓度的组合物。首先，通过测试不同的挤出长度来观察浆料的可挤出性。然后，通过对制造部件的显微镜观察来评估表面孔隙率。最后，通过 3D 扫描对具有不同几何形状的基准进行数字化，以分析在该过程的每个阶段出现的尺寸变化。

发现

总体而言，证明了该过程的可行性。挤出测试表明，浆料的成分对体积流量的影响很小，在长时间挤出的情况下表现出更好的一致性。表面空腔的百分比与混合物中所含的聚合物分数成正比。从尺寸分析可以得出结论，PA12 降低了干燥阶段的收缩程度，同时增加了熔融阶段发生的尺寸变化。结果表明，z轴测量的尺寸误差总是高于XY平面的。

实际影响

本文提出的方法提供了一种替代方法，可通过另一种增材制造工艺重复使用粉末床融合工艺中的剩余粉末。这为处理聚合物粉末床熔融的公司提供了一种负担得起的开源解决方案，使他们能够在扩大生产的同时减少对环境的影响。

原创性/价值

本文提出了一种用于粉末再利用的创新增材制造解决方案。与文献中的回收方法不同，该解决方案不需要任何中间转换过程，例如灯丝制造。此外，冷材料沉积能够采用非常便宜的挤压设备。这项初步研究证明了这一过程的可行性和好处，为未来的众多研究铺平了道路。