During powder bed fusion processes, the laser power intensity decreases as the beam penetrates through the powder bed. The depth at which the absorbed intensity decreases to 1/e (~37%) of the initial absorbed intensity  is defined as the Optical Penetration Depth (OPD. Estimating the correct powder absorption and OPD values is critical to model powder bed fusion processes and predict the properties of the finished components.
During powder bed fusion, a laser or an electron beam selectively melts a stack of powder layers, recoated and machined in succession one after the other, to form a component.
The density of the solidified material and the surface roughness of the finished components are complex functions of the material characteristics and the process parameters.
When studying the melting and solidification processes, considering individual powder particles reveals details about several physical phenomena, for instance the relationship between capillary effects, wetting conditions and the local stochastic powder configuration. This can help elucidate the fundamental mechanisms responsible for the phenomena involved in pores formation and surface roughness development that are observed during selective beam melting .
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