Mechanisms and elimination strategies of overhang closure failure during support-free laser powder bed fusion
Laser Powder Bed Fusion (LPBF) is a promising technique for manufacturing components with complex geometries. However, its application is limited for critical engineering parts featuring enclosed interior overhangs due to the necessity of sacrificial support structures. Thus, achieving support-free...
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| Main Authors: | , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Elsevier
2025-08-01
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| Series: | Materials & Design |
| Subjects: | |
| Online Access: | http://www.sciencedirect.com/science/article/pii/S0264127525007488 |
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| Summary: | Laser Powder Bed Fusion (LPBF) is a promising technique for manufacturing components with complex geometries. However, its application is limited for critical engineering parts featuring enclosed interior overhangs due to the necessity of sacrificial support structures. Thus, achieving support-free LPBF for such structures is highly desirable but remains challenging, primarily due to printing failures at overhang closures. In this study, representative bridge structures with varying overhang lengths were designed and printed. The results identified two distinct failure modes: the fracture at the closure under high laser energy densities of 67–146 J/mm3, and the deposit loss near the closure region under a low energy density such as 40 J/mm3. These findings demonstrate that the unsupported overhang closure cannot be reliably printed using uniform process parameters. To overcome this issue, a novel adaptive process strategy was developed, employing region-specific laser energies to enhance the structural strength and mitigate the thermal stress at the overhang closure. Using this approach, an unsupported overhang closure with inner circle diameter of 84 mm incorporating a single-layer overhang length of 1.83 mm at the closure (over 60 times of the layer thickness of 0.03 mm) was successfully printed. The unique findings from this study provide new insights into the failure mechanisms of overhang closures and advance the potential for support-free LPBF in manufacturing components with prominent enclosed overhang features. |
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| ISSN: | 0264-1275 |