## 1 Introduction  
The ever-accelerating advancements in the capabilities, accessibilities and cost-efficiency of metal additive manufacturing (AM) platforms have sparked an interest in the electrical machine research community for developing novel three-dimensional topology-optimized 3D printed electrical machines (EM). As of yet, no research group has printed an EM with improved performance or efficiency over the traditionally manufactured EMs. In fact, fully 3D printing an EM without any assembly or post-processing during or after printing has yet to be achieved, however all the necessary components have successfully been individually fabricated: soft magnetic rotor [1, 2] and stator designs [3], gapped [4] and insulated [5] coils and metal bearings [6]. For prototyping full 3D printing electrical machines, several hybrid methods have been employed that utilize additively manufactured components, such as inserting components during printing (bearings, coils and magnets) [7] or assembling components fabricated with dedicated metal printing systems after post-production [3].  
Selective Laser Melting (SLM) printing systems have proven very capable in the creation of functional metallic parts and find employment for rapid prototyping and limited production of highly specialized parts for aerospace, automotive and astronautic sectors, where performance and mass reduction capabilities are important [8]. SLM systems are also the most widely adopted by the EM research community in the research and development of 3D printed EMs. Three distinct materials are required to be printed in parallel to successfully fabricate an EM: a diamagnetic material with high electrical conductivity (coils), ferromagnetic material with low electrical conductivity (core) and a diamagnetic / dielectric material (insulation). SLM fabrication of conductive (Cu [9], AlSi10 Mg [10]) and soft ferromagnetic (FeSi6.7 [11], FeSi6.9 [12], FeSi3 [13], Fe-Co-V [14], Fe-Ni-Si [15]) materials has successfully been accomplished, however the technology has not been used for printing insulating materials concurrently with metallic materials. The lack of insulating materials in the SLM printed soft magnetic materials has no influence on applications with a quasi-static magnetic field, such as magnetic couplers or rotors of synchronous machines. However, it is inadequate for employment in EM stator constructions, due to the extensive eddy current generated in the non-laminated structure by the rotating magnetic fields, resulting in reduced efficiency and excessive thermal heating of the machine. Employing the spatial accuracy of additive manufacturing systems, finite internal material structures with geometrical manipulation can be achieved, which have been shown to reduce the classical eddy current generation considerably [11; 13]. Introducing airgaps to the material, however, also reduces the material filling factor, which would require oversaturation to produce the same flux as in a fully dense or laminated structure.  
This paper describes the sample preparation, printing, test setup and empirical results for magnetic measurements of SLM-fabricated soft ferromagnetic silicon steel. The material properties measured are applicable for modelling novel core geometries and are a starting point for optimizing the material internal structure for reduced core losses.