Abstract

Selective laser sintering (SLS) is a powder bed fusion technology that uses a laser source to melt selected regions of a polymer powder bed based on 3D model data. Components with complex geometry are then obtained using a layer-by-layer strategy. This additive manufacturing technology is a very complex process in which various multiphysical phenomena and different mechanisms occur and greatly influence both the quality and performance of printed parts. This review describes the physical phenomena involved in the SLS process such as powder spreading, the interaction between laser beam and powder bed, polymer melting, coalescence of fused powder and its densification, and polymer crystallization. Moreover, the main characterization approaches that can be useful to investigate the starting material properties are reported and discussed.

Highlights

  • Powder bed fusion (PBF) processes are a widely adopted family of additive manufacturing (AM) technologies capable of producing three-dimensional (3D) parts showing unprecedented geometric complexity and good mechanical properties

  • The results showed that both polyamide 12 (PA12) and PS powders formed defect-free layers; on the con- such as the density, the packing trary, the TPUpacking layer was not continuous, showing defects

  • The results showed that polyamide 12 (PA12) powders reflected only 5–6% of the incoming laser energy at the bed surface, yielding an absorption coefficient of 0.94

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Summary

Introduction

Powder bed fusion (PBF) processes are a widely adopted family of additive manufacturing (AM) technologies capable of producing three-dimensional (3D) parts showing unprecedented geometric complexity and good mechanical properties. Polymer and composites parts with complex geometry can be fabricated without the use of supports or molds, making SLS a cost-effective alternative to other additive technologies (i.e., fused deposition modeling or stereolithography), or more conventional ones such as injection molding [1] These advantages have encouraged the use of SLS in several contexts, from prototypes to the fabrication of spare parts and small series in automotive and aerospace fields, to customized prosthesis for biomedical applications [1].

Schematic
Selective Laser Sintering Process
Powder
Interparticle Forces
Temperature and Humidity
Optical Properties of Polymeric Powders
Graphical
The “Melt Pool”
Main Process Parameters Involved in the Formation of the Melt Pool
Powder Properties Affecting the Melt Pool
Evaluation of the Melt Pool
Evaluation the
Binding Mechanisms in SLS
Models of Viscous Sintering
13. Schematic
Experimental Evaluation of Coalescence
Conclusions and Future Perspectives
Powder Spreading
Laser Motion and Irradiation
Thermal Diffusion
Polymer Viscous Flow and Particle Coalescence

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