Heat retention modeling of large area additive manufacturing

Abstract Large Area Additive Manufacturing now enables the fabrication of structures that are dramatically more substantial than those produced with standard 3D printing. As the use of support structure is generally not appropriate when printing at these scales, understanding the limits of overhanging feature angles is necessary to establish the economic case for using large 3D printing. Additionally, understanding the physics of the process is paramount to avoiding expensive failed prints. Rapid sequential layers can result in slumping as the structure retains excessive heat when the next layer is printed. In this study, the thermal profiles of large printed parts have been experimentally measured and mathematically modeled in order to assist in the decision of whether a delay between layers is required to avoid slumping of overhanging features. The model can be used to insert additional dwell times after each layer so that the next layer of printing initiates after the previous layer is sufficiently cool such that the existing structure is appropriately solidified. Inputs to the model include the feedstock material, the number of beads in the overhanging wall, the angle of overhang and the threshold of failure represented as out-of-plane displacement from the intended geometry. The proposed thermal model can then be used with slicing software to insert pauses a priori, or can be leveraged during the print in conjunction with infrared imaging in order to provide in situ process control to improve quality and yield.