Three-dimensional finite element analysis simulations of the fused deposition modelling process

Fused deposition modelling (FDM) is a layer-manufacturing technology that has been widely used for rapid prototyping applications in product design and development. Owing to the intensive energy, rapid cooling, and phase changes, parts made by FDM and other layer-manufacturing processes deviate from the designed geometry, and some require laborious post-processing. Most severe form inaccuracies such as curl, warping, and delamination are attributed to the residual stress accumulations during prototype fabrications. This study investigates the FDM process, which consists of complicated heat and mass transfer phenomena coupled with mechanical loading and phase changes. A finite element analysis model using element activations has been developed to simulate the mechanical and thermal phenomena in FDM and further used for residual stress and part distortion simulations. The model has also been used to study the tool-path effects on the FDM process. Tool-path patterns affect the residual stresses in not only the magnitude but also the distribution which shows stress concentrations aligned with the primary direction of the tool path. Measured prototypes from the experiment show that the part distortion centre shifts distinctly owing to different tool-path patterns, which is consistent with the residual stress characteristics in the simulations. From the simulations, it is also shown that the short-raster tool path results in higher residual stresses, and thus possibly larger distortions, than the long-raster and alternate-raster patterns, both having similar stress distributions and distortion features.