Control-oriented modeling and repetitive control in in-layer and cross-layer thermal interactions in selective laser sintering

Abstract

Although laser-based additive manufacturing (AM) has enabled unprecedented fabrication of complex parts directly fromdigital models, broader adoption of the technology remains challenged by insufficient reliability and in-process variations. Inpursuit of assuring quality in the selective laser sintering (SLS)AM, this paper builds a modeling and control framework of thekey thermodynamic interactions between the laser source and thematerials to be processed. First, we develop a three-dimensionalfinite element simulation to understand the important featuresof the melt-pool evolution for designing sensing and feedbackalgorithms. We explore how the temperature field is affectedby hatch spacing and thermal properties that are temperaturedependent. Based on high-performance computer simulation andexperimentation, we then validate the existence and effect of periodic disturbances induced by the repetitive in- and cross-layerthermomechanical interactions. From there, we identify the system model from the laser power to the melt pool width and builda repetitive control algorithm to greatly attenuate variations ofthe melt pool geometry.