Fused filament fabrication of thermoplastics in high vacuum without convective heat transfer
Abstract In-space additive manufacturing (AM) offers significant potential to expand human space exploration beyond low Earth orbit and the moon. Although extrusion-based AM has proven feasible in zero gravity, the functionality of such a process in orbit-like vacuum conditions with practically no c...
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| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Nature Portfolio
2025-07-01
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| Series: | Scientific Reports |
| Subjects: | |
| Online Access: | https://doi.org/10.1038/s41598-025-13181-2 |
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| Summary: | Abstract In-space additive manufacturing (AM) offers significant potential to expand human space exploration beyond low Earth orbit and the moon. Although extrusion-based AM has proven feasible in zero gravity, the functionality of such a process in orbit-like vacuum conditions with practically no convective heat loss remains barely explored. To this end, a Fused Filament Fabrication (FFF) system was designed that successfully operated in high vacuum at 10− 4 mbar where convective heat transfer is negligible. Polylactic acid (PLA) tensile specimens were fabricated in three orthogonal print orientations under high vacuum conditions. Tensile testing, scanning electron microscopy, and micro-computed tomography were employed to assess tensile strength, elongation at break, void content, and the effects of vacuum on thermal dissipation. The objective was to evaluate how the vacuum environment influences the anisotropy of mechanical properties in printed parts. The absence of convective losses improved the layer bonding strength of specimens printed in the vertical (z) direction with load applied perpendicular to the filament strand orientation (V90), compared to specimens printed in horizontal (x or y) direction with load applied perpendicular to filament strand orientation (H90). This was attributed to the considerably slower cooling process in the case of V90 specimens. Moreover, thermal insulation provided by the vacuum environment had a beneficial influence on heat break and hot end. In vacuum, the set extrusion temperature was closer to the temperature measured at the tip of the nozzle. This study also identifies a temperature undershoot during decrease in hot end temperature in the printing process, which adversely affected interlayer adhesion. The findings indicate that the current PID-based hot-end control requires optimization to enhance the temperature control rate and minimize thermal deviations. These insights contribute to a deeper understanding of thermoplastic processing under convection-free conditions using fused filament fabrication (FFF). |
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| ISSN: | 2045-2322 |