A thermo fluid model for fused deposition modeling with directional thermal gradient metrics

Purpose In material extrusion additive manufacturing, temperature nonuniformity during deposition affects thermal history, viscosity evolution and temperature contrast within the deposited strand. The purpose of this study is to quantify directional temperature nonuniformity along the toolpath and through thickness for single-road fused deposition modeling, and to assess the effects of layer height and enclosure temperature. Design/methodology/approach A transient three-dimensional thermo fluid based on computational fluid dynamics (CFD) model couples creeping flow with heat transfer. The model tracks the free surface using a level set two phase mixture formulation and uses a Cross Arrhenius viscosity law. Line averaged absolute gradients Gx and Gz are evaluated for layer heights 0.25 mm, 0.50 mm and 0.75 mm under natural convection and an isothermal enclosure. Findings Under natural convection, the 0.75 mm case reaches a peak top to bottom temperature difference of 74 K, about 507 K near the surface and 433 K near the substrate. For 0.50 mm, through thickness gradients are about 10 K per mm near the melt top and 30 K per mm near the substrate. The enclosure reduces along path gradients for thinner layers but increases through thickness gradients as layer height rises. A cooling time scale based on melt volume and convective area explains this trade off. Originality/value This work introduces direction specific thermal gradient metrics for fused deposition modeling. These metrics separate along path and through thickness effects and enable controlled comparison of the simulated layer height and enclosure cases.