# An Additively Manufactured Fe-3 Si Stator for a High-Performance Electrical Motor
## 2 Experimental Methods and Printed Material Characterization  
### Additive Manufacturing and Assembly  
In order to print the motor parts, computer-aided design (CAD) models with design dimensions provided by Arnold Magnetic Technologies (Rochester, NY, USA) were used. Due to the proprietary nature of the product, intricate details of the geometry are not disclosed. The conventional motor stator core laminates were manufactured through vacuum arc remelting of the alloy ingots, hot rolling followed by cold rolling, and stress annealing by H\({}_{2}\) followed by slitting to the required length for stamping, coating, and stacking. For the purpose of comparison, material information for conventionally processed materials that closely resembled the materials used in a conventional motor was utilized. In order to print the alloy steel for the stator core, silicon steel (Fe-3 Si) powders (particle size distribution: <45 \(\upmu\)m; source: Praxair Surface Technologies, Inc., Tonawanda, NY, USA) were used for printing with a soft magnetic composition similar to that used in conventional manufacturing of E33 alloy lamination. All samples--the Fe-3 Si stator cylinder with teeth (using the design provided by Arnold Magnetics), test specimens in the form of hollow cylinders, and solid cubes--were printed using a Renishaw AM250 selective laser-melting3D printer at the Manufacturing Demonstration Facility at Oak Ridge National Laboratory. The print parameters for the builds are shown in Table S1, adopted from the already optimized experimental process [17]. Laser power of 200 W, exposure time of 110 us, and a layer thickness of 50 um are some of the main print parameters used. The as-printed Fe-3 Si parts were subjected to hot isostatic pressing (HIP) at 1150 \({}^{\circ}\)C for 2 h at 200 MPa, with a heating rate of 30 \({}^{\circ}\)C min\({}^{-1}\) and a cooling rate of 40-50 \({}^{\circ}\)C min\({}^{-1}\)[17]. HIP offers several advantages such as a reduction in porosity, uniform compaction, and improvement in the mechanical properties of AM parts. All of the conditions were chosen based on prior empirical knowledge [16]. The HIP annealing yielded samples with densities close to the theoretical value (7.62 g cc\({}^{-1}\), measured using an Archimedes density kit). These Fe-3 Si parts are shown in Figure 1 (right). Additionally, the heat treatment relieved the internal stress in the build parts. H\({}_{2}\) annealing was used to remove carbon and oxide in the EDM-cut printed parts. A total time of 280 h was required to print the stator core in a monolithic build and an additional time of 2 h for post-processing that included machining and EDM slicing. While the 280 h printing time is quite long, several factors should also be considered which mitigate the negative impact of the long print time. First, 3D printing is capable of great concurrency. As shown in Figure 1, a great multitude of parts can be printed concurrently. This cuts down on the time per part printed. As shown in the images in Figure 1, the parts took 280 h to print, with seven parts being printed at once. This means the time per part in this case is 40 h for each stator. This is still very high compared to conventional processes or some other AM processes. However, this could be improved with larger prints printing more parts concurrently. Second, AM processes such as SLM are capable of multimaterial printing. An end goal of AM stators is to 3D print a multimaterial with a non-conducting phase and a conducting phase, with the former insulating the latter. With insulators already within the material, the necessity of lamination creation and insulation is eliminated, saving time and resources that would have been committed to such processes. Our group has already successfully printed such multimaterials, a study on which is to be published in the near future. Multimaterial printing could be achieved in two ways. One way is to premix the feedstock with both conductive material powders and insulating material powders. This is single-feed multimaterial 3D printing.