A multiphysics modelling framework for part-scale digital light processing vat photopolymerization simulation

Digital light processing (DLP) 3D printing is a vat photopolymerization-based additive manufacturing technology widely used for fabricating polymer parts with high resolution and fast printing speed. However, predicting geometric distortion and residual stress remain challenging because layer-by-layer photopolymerization process and subsequent UV post-curing involve coupled irradiation, chemical reaction, heat transfer, and mechanical deformation. In this work, a multiphysics modelling framework is developed by integrating irradiation, photopolymerization, thermal, and mechanical models to capture curing behaviour, residual stress evolution, and part distortion during DLP fabrication and post-curing. The framework is assessed using two benchmark examples from the literature by comparing predicted curing profiles, stress distributions, and warpage with published experimental and numerical results. To enable efficient part-scale simulation, an equivalent irradiance model (EIM) is introduced, in which multiple physical layers are combined into a single lumped layer while preserving the cumulative print-through exposure effect. For a 3D mounting bracket, the EIM reduces the simulation time from 25.5 h to 48.6 min, corresponding to an approximately 31-fold speedup. The proposed framework is further applied to simulate post-curing and an industry connector structure, demonstrating its capability for efficient DLP process simulation within the resin system and process parameters investigated in this study.