Critical Influences of Particle Size and Adhesion on the Powder Layer Uniformity in Metal Additive Manufacturing

04/18/2018
by   Christoph Meier, et al.
0

The quality of powder layers, specifically their packing density and surface uniformity, is a critical factor influencing the quality of components produced by powder bed metal additive manufacturing (AM) processes, including selective laser melting, electron beam melting and binder jetting. The present work employs a computational model to study the critical influence of powder cohesiveness on the powder recoating process in AM. The model is based on the discrete element method (DEM) with particle-to-particle and particle-to-wall interactions involving frictional contact, rolling resistance and cohesive forces. Quantitative metrics, namely the spatial mean values and standard deviations of the packing fraction and surface profile field, are defined in order to evaluate powder layer quality. Based on these metrics, the size-dependent behavior of exemplary plasma-atomized Ti-6Al-4V powders during the recoating process is studied. It is found that decreased particle size / increased cohesiveness leads to considerably decreased powder layer quality in terms of low, strongly varying packing fractions and highly non-uniform surface profiles. For relatively fine-grained powders (mean particle diameter 17 μ m), it is shown that cohesive forces dominate gravity forces by two orders of magnitude leading to low quality powder layers not suitable for subsequent laser melting without additional layer / surface finishing steps. Besides particle-to-particle adhesion, this contribution quantifies the influence of mechanical bulk powder material parameters, nominal layer thickness, blade velocity as well as particle-to-wall adhesion. Finally, the implications of the resulting powder layer characteristics on the subsequent melting process are discussed and practical recommendations are given for the choice of powder recoating process parameters.

READ FULL TEXT

page 4

page 6

page 8

page 13

page 14

page 19

page 21

research
04/18/2018

Modeling and Characterization of Cohesion in Fine Metal Powders with a Focus on Additive Manufacturing Process Simulations

The cohesive interactions between fine metal powder particles crucially ...
research
06/09/2023

Novel Simulation-Inspired Roller Spreading Strategies for Fine and Highly Cohesive Metal Powders

When fine powders are to be used in powder bed metal additive manufactur...
research
06/22/2022

SR-DEM: an efficient discrete element method framework for particles with surface of revolution

Many granular products have the shape of surface of revolution (SR), typ...
research
05/18/2010

From granular avalanches to fluid turbulences through oozing pastes. A mesoscopic physically-based particle model

In this paper, we describe how we can precisely produce complex and vari...

Please sign up or login with your details

Forgot password? Click here to reset