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Modeling of the Microscale Selective Laser Sintering Process

In addition to the experimental μ-SLS test bed being developed in the NDML, new molecular scale models are under development to quantify and certify the μ-SLS process. Modeling of the μ-SLS process is challenging because most macroscale models of SLS contain assumptions that are no longer valid when the size of the particles being sintered is smaller than the wavelength of the laser used to sinter them. Therefore, in modeling the μ-SLS process we must account for the wave nature of light and cannot rely on the ray tracing models commonly used to model the SLS process. Also, heat transfer in the μ-SLS process is dominated by near-field radiation due to the diffraction of the light off the nanoparticles in the powder bed and the ultrafast lasers that are used in the μ-SLS system. This means that the assumptions of heat transfer by conduction and far-field radiation in the macroscale SLS systems are no longer valid for the μ-SLS system. Finally, the agglomeration of nanoparticles in the powder bed must be accurately modeled in order to precisely predict the formation of defects in the final parts produced. The figure on the left shows a simulation of the formation of the nanoparticle powder bed, which aligns well with the measured particle distribution in the actual powder bed. Overall, the goal of this modeling effort in the NDML is to predict the quality of a part produced for any given processing conditions in order to produce parts that are “born certified” and do not require post fabrication testing.