Shape accuracy in stereolithography: A material model for the curing behavior of photo-initiated resins

Shape distortions and internal stresses can limit the range of application of generative manufacturing techniques. These effects are caused by materials transformations during the production process which typically involves a layer-by-layer generation of complex components. In the case of stereolithography, shape distortions and residual stresses are caused by the polymerization shrinkage and the temporary local heating of the resin during processing. The complex interplay of increasing stiffness, decreasing flowability, and volumetric changes due to polymerization shrinkage and thermal expansion during the curing reaction was described with a four-parameter Burgers model. In order to obtain the required parameter set for the model, dedicated mechanical experiments as well as thermal and volumetric analyses of the resin were carried out. The Burgers model can be used in finite-element-simulations of the building process of a component. Experiment s and simulations yielded qualitative similar results for a »diagnostic H« component. Future work needs to focus in increasing the efficiency of the simulations in order to be able to model more complex structures.