The Role of Roller Rotation Pattern in the Spreading Process of Polymer/Short-Fiber Composite Powder in Selective Laser Sintering

Abstract

In this study, for the first time, a forward-rotating roller is proposed for the spreading of CF/PA12 composite powder in the selective laser sintering (SLS) process. The mesoscopic kinetic mechanism of composite particle spreading is investigated by utilizing the “multi-spherical” element within the discrete element method (DEM). The commercial software EDEM and the open-source DEM particle simulation code LIGGGHTS-PUBLIC are used for the simulations in this work. It is found that the forward-rotating roller produces a strong compaction on the powder pile than does the conventional counter-rotating roller, thus increasing the coordination number and mass flow rate of the particle flow, which significantly improves the powder bed quality. In addition, the forward-rotating pattern generates a braking friction force on the particles in the opposite direction to their spread, which affects the particle dynamics and deposition process. Therefore, appropriately increasing the roller rotation speed to make this force comparable to the roller dragging force could result in faster deposition of the composite particles to form a stable powder bed. This mechanism allows the forward-rotating roller to maintain a good powder bed quality, even at a high spreading speed, thus providing greater potential for the industry to improve the spreading efficiency of the SLS process.

Spreading Behavior of Non-Spherical Particles with Reconstructed Shapes Using Discrete Element Method in Additive Manufacturing

“…Chen et al examined the effect of fiber particles and found that increasing the fiber length reduces the spreadability of mixed powders and decreases the packing density [19], and they proposed a deposition mechanism and percolation effect of bimodal powder particles [20]. Cheng et al [21] and Si et al [22] examined the effect of different operation factors and mechanisms of spherical polymers. However, the investigation of non-spherical polymer particles is rather rare compared to those of spherical particles.…”

Compression-Softening Bond Model for Non-Water Reactive Foaming Polyurethane Grouting Material

“…Instead, it is discretized into interacting particle ensembles (two-dimensional disk (2D) and three-dimensional sphere (3D) are the main particle shape in space) by constructing particle ensembles into specimens of different geometries, utilizing a contact model forming interactions and iterative analysis based on Newton’s second law to make the macroscopic mechanical properties of the numerical specimen approach those of real materials [ 25 ]. Therefore, with the DEM method, the problems of discontinuities, high gradient variables, and remeshing in fracture or damage can be overcome [ 26 , 27 , 28 , 29 ]. The DEM method has been widely used to describe the macroscopic mechanical properties of materials, such as rock [ 30 , 31 ], soil [ 32 ], and concrete [ 33 ].…”