i»?Modern 3D printing technologies, also known as additive manufacturing, have evolved rapidly in recent years and are currently used in a wide range of engineering applications. In particular, the use of the new manufacturing techniques is leading to the development of very promising 3D electromagnetic structures for millimeter-wave (mm-wave) devices [1]. Thanks to the very compet it ive performance of 3D printing in electromagnetic structures, both the industrial and research communities are paying special attention to this manufacturing technique, a novel fabrication process for polymer, metal, and ceramic materials. The technique is an attractive option for innovative and complex part fabrication, providing improvements in customization, part compactness, and rapid prototyping as well as reduced weight, cost, and mass production lead time.