FLOW-3D AM is a CFD software that simulates and analyzes additive manufacturing processes such as laser powder bed fusion (L-PBF), binder jetting, and directed energy deposition (DED). FLOW-3D AM’s multiphysics capabilities offer highly-accurate simulations of powder spreading and compaction, melt pool dynamics, porosity formation for L-PBF and DED, and resin penetration and spreading for binder jetting processes, for analysis and optimization of process parameters.
FLOW-3D AM’s free surface tracking algorithm and its multiphysics models can simulate each of these processes with high accuracy. The steps in modeling laser powder bed fusion (L-PBF) processes are discussed in detail here. A couple of proof-of-concept simulations for the DED and binder jetting processes are also shown.
Laser Powder Bed Fusion
L-PBF processes involve complex multi-physics phenomena such as fluid flow, heat transfer, surface tension, phase change and solidification that significantly influence the process and ultimately, the build quality. FLOW-3D AM’s physical models simulate the melt pool phenomena at the meso-scale by accounting for particle size distribution and packing fractions while simultaneously solving for the mass, momentum and energy conservation equations.
FLOW-3D DEM and FLOW-3D WELD are used to simulate the full powder bed fusion process. The various stages in a L-PBF process are powder bed laying, powder melting and solidification and subsequently, the laying of fresh powder on the previously solidified layer, and once again melting and fusing the new layer to the previous layer. FLOW-3D AM can be used to simulate each of these stages.
Powder Bed Laying & Spreading
Using FLOW-3D DEM, it is possible to simulate the powder bed laying process by dropping a randomized distribution of particles and letting them pack, as shown in this video. One way to achieve different powder bed compactions is to choose different particle size distributions while laying the bed. As seen below, there are three different sized particle size distributions, which result in varying powder bed compactions with Case 2 giving the highest compaction.
Powder Bed Melting
After laying the powder bed, laser beam process parameters can be specified in FLOW-3D WELD to perform high-fidelity melt pool simulations. Plots of temperature, velocity, solid fraction, temperature gradients and solidus velocity can be analyzed in detail. Once the melt pool has solidified, the FLOW-3D AM pressure and temperature data can also be imported into an FEA tool such as Abaqus or MSC Nastran to analyze the stress contours and displacement profiles.
Multi-Layer Additive Manufacturing
When the first melt layer has solidified, a second layer of particles are deposited on the solidified bed. Melt pool simulations are again performed by specifying the laser process parameters on the new layer of powder particles. This process can be repeated several times to evaluate the fusing between consecutively solidified layers, the temperature gradients within the build while also monitoring the formation of porosity or other defects.
Binder jetting simulations provide insights into the spreading and penetration of the binder in the powder bed, which are influenced by capillary forces. Process parameters and material properties directly influence the deposition and spreading process.
Directed Energy Deposition
FLOW-3D AM’s built-in particle model can be used to simulate directed energy deposition processes. By specifying the powder injection rate and the heat flux incident on the solid substrate, the solid particles can add mass, momentum and energy into the melt pool. In the following video, solid metal particles are injected into the melt pool and the subsequent solidification of the melt pool on the substrate is observed.