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<p>The orange-peel phenomenon in selective laser sintering (SLS) of polyamide 12 (PA12), commonly associated with powder reuse and thermal degradation, is typically regarded as a surface defect leading to partial rejection. However, its influence on tensile performance, dimensional accuracy, and fracture behavior remains insufficiently understood. In this study, the combined effects of build orientation (horizontal, transverse, and vertical) and wall thickness (2.0, 2.5, and 3.0&#xa0;mm) on the dimensional accuracy, surface topography, mechanical behavior, and fracture morphology of SLS-manufactured PA12 samples exhibiting an orange-peel morphology were systematically investigated. Dimensional analysis revealed improved geometric consistency with increasing thickness, yet mechanical performance remained strongly orientation dependent. Horizontal and transverse samples achieved ultimate tensile strengths approaching 38 MPa and elastic moduli above 2.5 GPa at a thickness of 3.0 mm, whereas vertically constructed samples were limited to approximately 29–30 MPa and exhibited elongation at break of approximately 1.6–2.2% across all thicknesses. Statistical evaluation confirmed that build direction is the dominant factor influencing strength and ductility, whereas wall thickness primarily enhances stiffness without proportionally restoring deformation capacity in the vertical configuration. Surface topography analysis and fractographic observations suggested heterogeneous particle coalescence patterns and orientation-dependent crack propagation mechanisms. Horizontal and transverse builds exhibited cohesive fracture features with fibrillar deformation, whereas vertical specimens showed planar facets and fracture morphologies consistent with brittle-like failure. These results suggest that the orange-peel condition appears to magnify the intrinsic SLS anisotropy rather than acting solely as a superficial irregularity. Mechanical degradation under orange-peel conditions was found to be orientation sensitive and cannot be mitigated by increasing wall thickness alone. While in-plane builds may retain acceptable tensile strength under recycled powder conditions, vertically oriented components exhibit persistent ductility loss and potentially reduced mechanical robustness. These findings provide preliminary experimental guidance for the controlled use of recycled PA12 powder in SLS manufacturing.</p>

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Effect of build orientation and wall thickness on the anisotropic behavior of SLS PA12 with orange-peel morphology

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年7月10日

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  • Alejandro García Rodríguez,
  • Camilo Andrés Pérez Jiménez,
  • Nick Harritson Meza,
  • Marco Antonio Velasco,
  • Carlos Alberto Narváez Tovar,
  • Edgar Espejo Mora

摘要

The orange-peel phenomenon in selective laser sintering (SLS) of polyamide 12 (PA12), commonly associated with powder reuse and thermal degradation, is typically regarded as a surface defect leading to partial rejection. However, its influence on tensile performance, dimensional accuracy, and fracture behavior remains insufficiently understood. In this study, the combined effects of build orientation (horizontal, transverse, and vertical) and wall thickness (2.0, 2.5, and 3.0 mm) on the dimensional accuracy, surface topography, mechanical behavior, and fracture morphology of SLS-manufactured PA12 samples exhibiting an orange-peel morphology were systematically investigated. Dimensional analysis revealed improved geometric consistency with increasing thickness, yet mechanical performance remained strongly orientation dependent. Horizontal and transverse samples achieved ultimate tensile strengths approaching 38 MPa and elastic moduli above 2.5 GPa at a thickness of 3.0 mm, whereas vertically constructed samples were limited to approximately 29–30 MPa and exhibited elongation at break of approximately 1.6–2.2% across all thicknesses. Statistical evaluation confirmed that build direction is the dominant factor influencing strength and ductility, whereas wall thickness primarily enhances stiffness without proportionally restoring deformation capacity in the vertical configuration. Surface topography analysis and fractographic observations suggested heterogeneous particle coalescence patterns and orientation-dependent crack propagation mechanisms. Horizontal and transverse builds exhibited cohesive fracture features with fibrillar deformation, whereas vertical specimens showed planar facets and fracture morphologies consistent with brittle-like failure. These results suggest that the orange-peel condition appears to magnify the intrinsic SLS anisotropy rather than acting solely as a superficial irregularity. Mechanical degradation under orange-peel conditions was found to be orientation sensitive and cannot be mitigated by increasing wall thickness alone. While in-plane builds may retain acceptable tensile strength under recycled powder conditions, vertically oriented components exhibit persistent ductility loss and potentially reduced mechanical robustness. These findings provide preliminary experimental guidance for the controlled use of recycled PA12 powder in SLS manufacturing.