Rib Geometry in FDM of Light Alloys

The present paper got the objective to propose and apply a methodology based on plastic behaviour modeling of a magnesium alloy AZ31 and on a Navier-Stokes approach to describe the rib geometry during printing by FDM (Fused deposition modeling). By the plastic modeling the rib section in terms of equivalent radius is obtained by the application of an already proposed constitutive equation under semisolid condition. The same information is obtained by the calculation of dynamic viscosity coefficient of the material under different conditions of nominal extruder nozzles that are 0.36 and 0.06 mm in radius with related extrusion velocity and internal pressure. The rib radius obtained by the plastic model is higher when the big nozzle is used compared with that given by the Navier- Stokes approach while an opposite behaviour is evidenced with the small nozzle where the apparent viscosity is higher than the one useful to describe the phenomenon. Increasing printing velocity similar rib dimensions are obtained in both cases.