Additive manufacturing (AM) enables the production of complex geometries that are not accessible using conventional processes. During manufacture, residual stresses pose a problem of geometric stability, which affects the performance of an object printed by the 3D printing process. Residual stresses need to be anticipated in order to improve part quality. A semi-crystalline polypropylene PP polymer is used for the FDM (Fused Material Deposition) process, as it is characterized by deformability due to crystallization. Designers use numerical models to predict the thermomechanical behavior of a part printed by the FDM process, in order to find the best printing parameters. Improving these models enables a prediction close to reality. This study investigates the thermomechanical behavior of a semi-crystalline polymer (polypropylene) during a change of material deposition shape from a parallelepiped filament to a cylindrical one in a numerical study. During printing, time and temperature affect the thermomechanical properties and crystallization kinetics of polypropylene. Based on printing conditions (extrusion temperature, line weft pattern, filling, printing speed and layer thickness), the aim of this study is to investigate the effect of changing the shape of material deposition, in a numerical study, from a parallelepiped filament to a cylindrical one on residual stresses in a 3D printed part. A coupling solid mechanics, heat transfer and crystallization kinetics was considered as a Multiphysics model to predict temperature profiles, residual stresses and degree of crystallization during the FDM process. For an assessment of residual stresses during 3D printing, two samples were selected, the first for a parallelepiped material deposit and the second for a cylindrical material deposit. A choice of six points distributed over the sample enables temperature, residual stress and degree of crystallization to be analyzed and calculated, in order to study the effect of the change in deposition shape on the thermomechanical behavior of the polypropylene polymer PP. The results found in a numerical study of changing the shape of a deposit provide a reliable approach to predicting and adjusting the predicted behavior to the actual thermomechanical properties of a printed part. This change minimizes residual stresses, enhancing the development of a model that presents an accurate prediction for finding the optimum parameters to create high-quality parts.