Residual stress and shape distortion management in polymer printing of thin-walled complex geometries

Residual stress developed during fused deposition modeling (FDM) printing of semicrystalline polymers can lead to severe shape distortion in thin-walled complex geometries. This study develops a simulation framework to investigate the thermo-mechanical mechanisms governing warpage, wrinkling, and residual stress. The simulation maps the position process using trajectory-based events coupled with transient thermal and stress analyses, creating an FDM digital twin. It incorporates progressive material activation, moving heat sources, polymer solidification capturing the glass transition and melt crystallization of semi-crystalline PLA, and evolving convective, radiative, and conductive boundary conditions. Unlike prior thermo-mechanical FDM models, this work systematically investigates the effects of seven printing parameters on warpage and residual stress with full toolpath representation of printing and considers full-field 3D validation of complex thin-walled geometries. The FDM digital twin was validated to predict wrinkling and warpage of thin-walled cubes and tessellated tubes out of polylactic acid (PLA), measured using high-resolution 3D scanning, capturing both the magnitude and spatial distribution of shape distortion. In most printing conditions, the FDM digital twin predicts maximum warpage displacements within 6%, except under a force convection condition where the deviation is above 30%. The validated digital twin of FDM printing provides a predictive tool for optimizing printing parameters, understanding residual stress formation, and improving the manufacturability of thin-walled complex polymer structures.