Schlicht Samuel, Greiner Sandra, Drummer Dietmar
Institute of Polymer Technology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Am Weichselgarten 10, 91058 Erlangen, Germany.
Collaborative Research Center 814, Friedrich-Alexander-Universität Erlangen-Nürnberg, Am Weichselgarten 10, 91058 Erlangen, Germany.
Polymers (Basel). 2022 Mar 31;14(7):1428. doi: 10.3390/polym14071428.
Powder Bed Fusion of Polymers (PBF-LB/P) is a layer-wise additive manufacturing process that predominantly relies on the quasi-isothermal processing of semi-crystalline polymers, inherently limiting the spectrum of polymers suitable for quasi-isothermal PBF. Within the present paper, a novel approach for extending the isothermal processing window towards significantly lower temperatures by applying the quasi-simultaneous laser-based exposure of fractal scan paths is proposed. The proposed approach is based on the temporal and spatial discretization of the melting and subsequent crystallization of semi-crystalline thermoplastics, hence allowing for the mesoscale compensation of crystallization shrinkage of distinct segments. Using thermographic monitoring, a homogenous temperature increase of discrete exposed sub-segments, limited thermal interference of distinct segments, and the resulting avoidance of curling and warping can be observed. Manufactured parts exhibit a dense and lamellar part morphology with a nano-scale semi-crystalline structure. The presented approach represents a novel methodology that allows for significantly reducing energy consumption, process preparation times and temperature-induced material aging in PBF-LB/P while representing the foundation for the processing of novel, thermo-sensitive material systems in PBF-LB/P.
聚合物粉末床熔融（PBF-LB/P）是一种逐层增材制造工艺，主要依赖于半结晶聚合物的准等温加工，这在本质上限制了适用于准等温PBF的聚合物范围。在本文中，提出了一种新方法，即通过应用基于激光的分形扫描路径准同时曝光，将等温加工窗口扩展到显著更低的温度。所提出的方法基于半结晶热塑性塑料熔化及随后结晶的时间和空间离散化，因此能够对不同段的结晶收缩进行中尺度补偿。通过热成像监测，可以观察到离散曝光子段的均匀温度升高、不同段的有限热干扰以及由此避免的卷曲和翘曲。制造的零件呈现出具有纳米级半结晶结构的致密层状零件形态。所提出的方法代表了一种新颖的方法，可显著降低PBF-LB/P中的能耗、工艺准备时间和温度引起的材料老化，同时为PBF-LB/P中新型热敏材料系统的加工奠定基础。
