Build Orientation Optimization Problem in Additive Manufacturing Ana Maria A.C. Rocha 1[0000-0001-8679-2886] , Ana I. Pereira 2[0000-0003-3803-2043] , and A. Ismael F. Vaz 1[0000-0002-9972-7474] 1 Algoritmi Research Centre, University of Minho, 4710-057 Braga, Portugal arocha@dps.uminho.pt,aivaz@dps.uminho.pt 2 Research Centre in Digitalization and Intelligent Robotics (CeDRI), Instituto Polit´ ecnico de Bragan¸ ca, 5300-253 Bragan¸ ca, Portugal apereira@ipb.pt Abstract. Additive manufacturing (AM) is an emerging type of pro- duction technology to create three-dimensional objects layer-by-layer di- rectly from a 3D CAD model. AM is being extensively used by engineers and designers. Build orientation is a critical issue in AM since it is associated with the object accuracy, the number of supports required and the processing time to produce the object. Finding the best build orientation in the AM will reduced significantly the building costs and will improve the object accuracy. This paper presents an optimization approach to solve the part build orientation problem considering the staircase effect, support area charac- teristics and the build time. Two global optimization methods, the Elec- tromagnetism-like and the Stretched Simulated Annealing algorithms, are used to study the optimal orientation of four models. Preliminary experiments show that both optimization methods can effec- tively solve the build orientation problem in AM, finding several global solutions. Keywords: Design Tools, Additive Manufacturing, 3D printing, Opti- mization, Build Orientation 1 Introduction Traditional manufacturing methods involve a solid block of material being carved, or shaped, into the desired product, where block parts are being successively re- moved in different ways. Additive manufacturing (AM) has emerged in the last decades becoming an alternative to the traditional subtractive manufacturing. It is a technology that builds 3D objects by adding ultrathin layers of material, one by one, for fabricating the desired product. Additive manufacturing processes involve the use of three-dimensional (3D) computer-aided design (CAD) data to create physical models. One of the greatest