Multi-physics simulation of a material extrusion-based additive manufacturing process: towards understanding stress formation in the printed strand

The application of material extrusion methodologies in the fabrication of thermoplastic components frequently entails many notable challenges, such as shrinkage, warpage, and delamination. During the extrusion process, there is an uneven cooling gradient between the layers. As a result, this causes a component to be distorted. This deformation is observed as the corners of a component rise above the printing bed. However, printing a single-layer strand and then submerging it in hot water results in a noticeable distortion. This issue is explained, and it is investigated using simulations and experiments. The primary objective of this study is to conduct a numerical simulation of the extrusion process, with a specific emphasis on analyzing the stresses in the printed strand. The simulations are conducted utilizing the finite element approach, where the arbitrary Lagrangian-Eulerian method is employed to solve the free surface. Stress analysis entails solving the non-isothermal thermo-mechanical flow problem. The material extrusion process is simulated using generalized Newtonian and viscoelastic models. The present work aims to examine the spatial distribution of stresses inside the printed strand and its corresponding cross-sectional area. This study investigates the impact of several printing process parameters on stresses in the printed strand, including bed temperature, nozzle temperature, and printing speed. An experimental investigation was undertaken to examine the influence of printing speed on the degree of bending shown by the printed strand, with the aim of corroborating the results obtained through simulation. This study's findings provide valuable insights into the stresses experienced by the printed strand.