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Discrete element simulation and experimental study of powder spreading process in additive manufacturing

Research output: Contribution to journalArticle

  • Sina Haeri
  • Yuan Wang
  • Oana Ghita
  • Jin Sun

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Original languageEnglish
Pages (from-to)45–54
JournalPowder Technology
Volume306
Early online date9 Nov 2016
DOIs
StatePublished - Jan 2017

Abstract

Powders used in additive manufacturing (AM) are spread into a compact layer of particles for sintering and this process is repeated layer by layer to form the final products. Spreading of rod-shaped particles in realistic AM settings is simulated using the discrete element method (DEM) to investigate the effects of particle shape and operating conditions on the bed quality, characterised by its surface roughness and solid volume fraction. It is discovered that larger particle aspect ratios, Ar, or higher spreader translational velocities result in a lower bed quality, i.e. a larger surface roughness and a smaller volume fraction. The surface roughness increases monotonically with Ar. However, the volume frac- tion exhibits a maximum at Ar = 1.5 for randomly packed powder beds that are formed by the roller type spreaders moving at low translational velocities. It is also found that a roller outperforms a blade spreader in terms of the quality of the prepared bed at the same operating conditions. The micro-structural anal- ysis of the beds also shows particle alignment in response to the induced flow, which is qualitatively confirmed by a set of purposely-designed experiments. In addition, a shape segregation is documented for powders with mixed aspect ra- tios (Ar) such that particles with larger Ar tend to accumulate on the upper layers of the bed.

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