An 8-node hexahedral mesh is automatically generated from a discrete triangulation of the CAD geometry, i.e. an STL file. For automatic meshes, the elements take an axis-aligned rectangular voxel shape, although the solver is capable of processing any general shaped hexahedron. The proprietary mesh generator is extremely optimized to efficiently deal with the distribution of surface triangles within the 3D space of their enclosed volume, to reduce both memory usage and processing time.
To accurately capture the effects of bending, hex8 meshes require a width of at least 2 elements in the bending direction. However, the geometries of additive manufacturing are typically topology-optimized within lattice type structures, and it may not be obvious to a user what the thinnest cross-section is, or where bending is important. Therefore, the best practice is to always perform a tripartite mesh convergence study to determine if the mesh is fine enough.
An isotropic h-adaptivity scheme is used to retain mesh refinement in regions where thermal or displacement gradients are large to maintain accuracy, while coarsening the mesh in other regions to reduce memory usage and processing time. The condensation and recovery method is applied for hanging nodes between varying levels of mesh refinement.
Due to the layer-wise nature of additive manufacturing, a fine mesh is only required within the top few layers. This nature allows for the mesh to be efficiently coarsened in lower regions of the print as the simulation progresses, while preserving a close agreement with the original geometry.