Numerical Study of the Impact of Shear Thinning Behaviour on the Strand Deposition Flow in the Extrusion-Based Additive Manufacturing

This paper investigates the influence of shear-rate dependent viscosity on the strand deposition flow during Extrusion-Based Additive Manufacturing. Extrusion-Based Additive Manufacturing, also known as Fused Deposition Modeling (FDM), is a manufacturing method in which material is joined layer by layer into a 3D object. A solid filament is heated above the melting point and extruded through a nozzle to form a strand. The process is modelled within the paradigm of Computational Fluid Dynamics as an isothermal Generalized Newtonian fluid flow. The power law is used as the constitutive relation between the shear-rate and the viscosity. A sensitivity study of the model’s input parameters (power-law index and consistency index) is made. The simulations are performed varying two process parameters: the vertical distance between the substrate and nozzle exit as well as the relative horizontal velocity between the substrate and nozzle. The model is used to investigate the cross-sectional shape of the strand after the deposition and the force exerted on the substrate by the material extruded from the nozzle (the printing force). Under the tested conditions, we find a neglible change in the cross-sectional shape and the printing force behaviour when varying the power-law index and the consistency index. Thus, it is concluded that the Newtonian fluid model provides a sufficient approximation to simulate the deposition flow under the given assumptions.