Closed-loop automatic feedback control in electron beam melting

An infrared (IR) camera has been installed in an additive manufacturing Arcam A2 electron beam melting (EBM) system for improved layer-by-layer monitoring and feedback control of the EBM build process. Previous research demonstrated that temperature variations present during an EBM build (e.g., part/powder bed temperature elevates as build height increases) produce microstructural differences leading to variations in mechanical properties. Currently, the EBM system allows for process parameter modification (beam current, beam speed, beam focus, heating time) during fabrication. Modification of processing parameters can help achieve full spatial and temporal control of temperature that could lead to controlled microstructural architectures in EBM-fabricated parts. Furthermore, an automatic feedback control loop can help produce desired mechanical properties with limited user intervention. In this research, an automatic feedback control system was developed to acquire data used to create a temperature matrix of the part/powder bed surface, record information from each layer, and use the recorded information as an input to a software interface. Upon analysis of input data, the software interface communicated with Arcam's EBM interface to change necessary parameters automatically on-demand. Results show successful manipulation of grain size in Ti-6Al-4V microstructure that ultimately can lead to three-dimensional control of microstructural architectures.