## 2 Experimental Procedures
### Feedstock and Parts Preparation  
The binder components and the powder were mixed in an internal mixer with a chamber volume of 38 cm\({}^{3}\) and counter-rotating roller rotors (Plasti-Corder PL2000, Brabender GmbH & Co. KG, Duisburg, Germany) at a rotational speed of 60 rpm, which is required for a uniform distribution of powder particles in the binder system. For all processing stages, the mixing temperature of 160 \({}^{\circ}\)C was chosen, as degradation of the low molecular binder components (PW and SA) was observed at higher temperatures, such as 170 \({}^{\circ}\)C, during the first mixing evaluations. As explained in [61], the Nd-Fe-B powder must be handled and processed in an inert environment to prevent oxidation and deterioration of its final magnetic characteristics. A 45-minute blending was performed in the internal mixer fitted with a glove box having an argon atmosphere to prevent oxidation and ensure a homogeneous mixture, as demonstrated by a constant torque value at the end of the kneading process.  
In this study, four combinations of binder components were considered to assess the effect of the binder system on rheological behavior, carbon and oxygen contamination, and magnetic characteristics. A powder loading of 55 vol.% was used in the first trials to determine the most appropriate binder formulation. Table 1 shows the binder system formulations, which cover a broad range of various percentages of the LLDPE (35-52.5 vol.%), PW (41.25-60 vol.%), and SA (5-8.75 vol.%). LLDPE is the backbone that adds strength to the molded part and helps retain the shape during solvent debinding; a higher content leads to a stronger part but a higher viscosity. PW is the flow enhancer of the binder and the soluble component; therefore, the higher the PW content is, the lower the viscosity of the binder and the less polymer to remove during thermal debinding; however, the molded part becomes more fragile. SA is the dispersant agent and viscosity modifier; the higher the SA content, the fewer agglomerates there could be in the feedstock; however, like PW, the part can become very fragile. As can be seen, choosing the appropriate range of ingredients needs to be experimentally validated. In the next step, feedstocks with the best binder system and different powder loadings (57, 58, 59, and 60 vol.%) were produced to adjust the  
Figure 2: SEM image of the jet-milled powder used for this study.  
feedback formulation and find an optimal powder loading. A higher powder content can lead to a higher density but to a substantial viscosity or unstable flow; therefore, powder content must be verified experimentally.  
After mixing, the feedstocks were cooled to room temperature and granulated in a cutting mill (SM200, Retsch GmbH, Haan, Germany). The binder system is expected to coat the alloy particles and prevent oxidation; however, an inert atmosphere is recommended during all process stages. Thus, the grinding was performed under argon, and the ground feedstocks were vacuum-sealed before further processing.  
Cylinders, 8 mm in diameter and 15 mm in height, were manufactured from each formulation by uniaxial pressing under vacuum. The pressing was carried out at 50 bar and 160 \({}^{\circ}\)C using the hydraulic vacuum press P200 PV (Dr. Collin GmbH, Maitenbeth, Germany). Uniaxial pressing was used since insufficient material was available for injection molding trials during feedstock development. Nevertheless, the pressed specimens can be used to determine that the feedstock can be debound and sintered without complications. Although the binder system can protect the produced parts from oxygen, the vacuum bags were used to store the pressed samples before debinding.