Zhang Yongjie, Moon Seung Ki
Singapore Centre for 3D Printing, School of Mechanical & Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore.
Materials (Basel). 2021 May 28;14(11):2907. doi: 10.3390/ma14112907.
Fused filament fabrication (FFF) is increasingly adopted for direct manufacturing of end use parts in an aviation industry. However, the application of FFF technique is still restricted to manufacturing low criticality lightly loaded parts, due to poor mechanical performance. To alleviate the mechanical performance issue, thermal annealing process is frequently utilized. However, problems such as distortion issues and the need for jigs and fixtures limit the effectiveness of the thermal annealing process, especially for low volume complex FFF parts. In this research, a novel low temperature thermal annealing is proposed to address the limitations in conventional annealing. A modified orthogonal array design is applied to investigate the performance of ULTEM™ 9085 FFF coupons. Further, the coupons are annealed with specialized support structures, which are co-printed with the coupons during the manufacturing process. Once the annealing process is completed, multiscale characterizations are performed to identify the mechanical properties of the specimens. Geometrical measurement of post annealed specimens indicates an expansion in the layering direction, which indicates relief of thermal stresses. Moreover, annealed coupons show an improvement in tensile strength and reduction in strain concentration. Mesostructure and fracture surface analysis indicate an increase in ductility and enhanced coalescence. This research shows that the proposed annealing methodology can be applied to enhance the mechanical performance of FFF parts without significant distortion.
熔融长丝制造（FFF）越来越多地被用于航空工业中直接制造最终使用部件。然而，由于机械性能较差，FFF技术的应用仍局限于制造低关键性、轻载部件。为了缓解机械性能问题，热退火工艺经常被采用。然而，诸如变形问题以及对夹具和固定装置的需求等问题限制了热退火工艺的有效性，特别是对于小批量复杂的FFF部件。在本研究中，提出了一种新型低温热退火方法来解决传统退火中的局限性。采用改进的正交阵列设计来研究ULTEM™ 9085 FFF试样的性能。此外，试样采用专门的支撑结构进行退火，支撑结构在制造过程中与试样一起共打印。退火过程完成后，进行多尺度表征以确定试样的机械性能。退火后试样的几何测量表明在分层方向上有膨胀，这表明热应力得到缓解。此外，退火后的试样拉伸强度有所提高，应变集中有所降低。细观结构和断口表面分析表明延展性增加且聚结增强了。本研究表明，所提出的退火方法可用于提高FFF部件的机械性能而不会产生明显变形。
