A Simulation Study on the Effect of Particle Size Distribution on the Printed Geometry in Selective Laser Melting

Abstract

Selective laser melting (SLM) process is a powder bed fusion additive manufacturing process that finds applications in aerospace and medical industries for its ability to produce complex geometry parts. As the raw material used is in powder form, particle size distribution (PSD) is a significant characteristic that influences the build quality in turn affecting the functionality and aesthetics aspects of the product. This paper investigates the effect of PSD on the printed geometry for 316L stainless steel powder, where three coupled in-house simulation tools based on Discrete Element Method (DEM), Computational Fluid Dynamics (CFD), and Structural Mechanics are employed. DEM is used for simulating the powder bed distribution based on the different powder PSD. The CFD is used as a virtual testbed to determine thermal parameters such as heat capacity and thermal conductivity of the powder bed viewed as a continuum. The values found as a stochastic function of the powder distribution is used to analyse the effect on the melted zone and deformation using Structural Mechanics. Results showed that mean particle size and PSD had a significant effect on the packing density, melt pool layer thickness, and the final layer thickness after deformation. Specifically, a narrow particle size distribution with smaller mean particle size and standard deviation produced solidified final layer thickness closest to nominal layer thickness. The proposed simulation approach and the results will catalyze in development of geometry assurance strategies to minimize the effect of particle size distribution on the geometric quality of the printed part.

Multiphysics multi-scale computational framework for linking process–structure–property relationships in metal additive manufacturing: a critical review

“…The transient temperature distribution will naturally show different behaviour if all the above factors are incorporated. For instance, several attempts have been made to couple single-track LPBF mesoscale CFD models (with powder consideration) with the thermomechanical model [185,[216][217][218]. The predictions reveal stress concentration at lack-of-fusion voids.…”

Powder Spreading Mechanism in Laser Powder Bed Fusion Additive Manufacturing: Experiments and Computational Approach Using Discrete Element Method

“…The particle size distribution of the powder has been shown to affect the powder flow behavior and packing density of the powder bed [ 7 , 10 , 11 , 12 ]. Variations in the powder bed characteristics such as local areas with above or below-average packing densities can cause defects in the additively manufactured parts.…”