Investigation on the Spreading Behaviour of Sand Powder Used in Binder Jet 3D Printing

TL;DR

This study models the spreading behavior of cohesive sand powder in binder jet 3D printing, analyzing how particle size, jamming, and surface roughness affect layer uniformity and spreadability.

Contribution

It introduces a Discrete Element Method model to analyze spreading, focusing on jamming, empty patches, and the effects of surface roughness in binder jet 3D printing.

Findings

Large particles are harder to spread due to jamming.

Empty patches vary in size and shape within the spread layer.

Roughness and gap height influence spreadability and layer uniformity.

Abstract

The spreading behaviour of cohesive sand powder is modelled by Discrete Element Method, and the spreadability and the mechanical jamming are focused. The empty patches and total particle volume of the spread layer are examined, followed by the analysis of the geometry force and jamming structure. The results show that several empty patches with different size and shapes could be observed within the spread layer along the spreading direction even when the gap height increases to 3.0D90. Large particles are more difficult to be spread onto the base due to jamming, although their size is smaller than the gap height. Size segregation of particles occurs before particles entering the gap between the blade and base. There are almost no particles on the smooth base when the gap height is small, due to the full-slip flow of particles. The difference of the spread layer and spreadability between the cases with rough and smooth base is reduced by the increase of the gap height. An interesting correlation between jamming effect and local defects (empty spaces) in the powder layer is identified. The resistance to particle rolling is important for the mechanical jamming reported in this work. The jammed particles with a larger size ratio tend to be more stable.