Separation force analysis based on cohesive delamination model for bottom-up stereolithography using finite element analysis

Bottom-up (constrain-surface) Additive Manufacturing (AM) systems have been widely used in industry. Compared to traditional open-surface AM technology, properties like better vertical resolution, higher material filling rate, less production time, and less material waste make bottom-up AM technology a suitable candidate for fabrication of complex three dimensional materials with high accuracy. However during the pulling up stage, the substantial force generated between the formed part and the material container has high risk of breaking the part and therefore reduces the process reliability. In this paper, an optimization-based method is developed to model bottom-up AM process using finite element analysis (FEA). The FEA model is developed using ABAQUS to model the behavior of the cohesive delamination at the interface of the formed part and a hyper-elastic intermediate which has been used to reduce the pulling up force. An optimization model is also established to evaluate the cohesive stiffness parameters that cannot be calculated directly from closed formulas or mechanical tests. The results of this work will be used to develop an adaptive closed-loop mechanics-based system to control the pulling up process and achieve a reliable technology.