ORIGINAL ARTICLE Closed-loop automatic feedback control in electron beam melting Jorge Mireles & Cesar Terrazas & Sara M. Gaytan & David A. Roberson & Ryan B. Wicker Received: 28 May 2014 /Accepted: 11 December 2014 /Published online: 7 January 2015 # Springer-Verlag London 2015 Abstract 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 feed- back 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 manipula- tion of grain size in Ti-6Al-4V microstructure that ultimately can lead to three-dimensional control of microstructural architectures. Keywords Closed-loop automatic feedback control . Microstructure control . Electron beam melting . Ti-6Al-4V . Infrared . Additive manufacturing 1 Introduction Additive manufacturing consists of various manufacturing technologies that enable fabrication of complex parts through a layer-by-layer material addition process. The electron beam melting (EBM) process is a powder bed fusion additive manufacturing technology that shows promise for use in the rapid manufacturing of end-use metal parts. The process uti- lizes a powder precursor alloy that is deposited layer-by-layer and selectively melted to form a three-dimensional part [1]. Several materials have been processed using EBM (e.g., Ti- 6Al-4V, Inconel 625, and Inconel 718) that are of interest in the aerospace and biomedical industries [2–4]. Although part fabrication using Ti-6Al-4V has resulted in dense parts with mechanical properties comparable to wrought Ti-6Al-4V, sev- eral anomalies in microstructure are inherent to this manufacturing process, namely differences in microstructure throughout a part due to a thermal gradient within the build chamber during fabrication [5, 6]. Such uncontrolled varia- tions are not suitable when mechanically isotropic parts are needed. Although previous research has focused on optimiz- ing the fabrication process [7], variations from part-to-part, or within a single part, still exist. If a higher level of control is J. Mireles (*) : C. Terrazas : S. M. Gaytan : D. A. Roberson : R. B. Wicker W. M. Keck Center for 3D Innovation, The University of Texas at El Paso, 500 W. University Ave. Engineering Building Room 108, El Paso, TX 79902, USA e-mail: jmireles3@utep.edu J. Mireles : R. B. Wicker Department of Mechanical Engineering, The University of Texas at El Paso, 500 W. University Ave. Engineering Building Room 108, El Paso, TX 79902, USA C. Terrazas : S. M. Gaytan : D. A. Roberson Department of Metallurgy and Materials Engineering, The University of Texas at El Paso, 500 W. University Ave. Engineering Building Room 108, El Paso, TX 79902, USA Int J Adv Manuf Technol (2015) 78:1193–1199 DOI 10.1007/s00170-014-6708-4