EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

3D printing has become an attractive manufacturing possibility due to its continuous development over the last years. One common used technology in 3D printing is the digital light processing (DLP) process. It is based on the photopolymerization of photo-curable resins and offers the advantage of high-resolution prints. But due to its complex nature, a robust prediction of the process induced influences on the printed part is challenging. In this work, a step by step simulation strategy is proposed to predict mechanical and geometrical properties based on the used process parameters. The simulation enables modelling of the process-specific layer by layer curing and the resulting effects such as shrinkage due to crosslinking, residual stresses and curing-dependent mechanical properties. The degree of curing in each layer is calculated based on an autocatalytic model, which was fitted using photo DSC measurement results. The model accounts for the dependency of the curing rate on temperature and light intensity. The light intensity is calculated depending on the distance between light source and the respective element in the layer, to account for a gradual curing across the layer thickness. The shrinkage and the cure-depending mechanical properties were determined based on shrinkage tests and dynamic mechanical analysis measurements. The elaborated models are implemented as a UMAT subroutine in the commercial FE software Abaqus 2019 (Dassault Systèmes Simulia Corp, Providence, RI.). A graphical user interface (GUI) was created to allow for a simple set up of the simulations and first validations of the simulation approach were performed based on specifically designed geometries exhibiting pronounced processing effects.