248 Prakt. Met. Sonderband 52 (2018) 
matrix (usually PA12 or PPS). Traditionally they are produced via injection molding, 
calendaring, compression molding and extrusion [1-4]. Additive manufacturing (AM) is novel 
manufacturing technique that enables production of parts directly from CAD model without 
the use of expensive molds. The material is deposit in X-Y direction in layer-upon-layer 
fashion and thus creating third dimension. The main advantages of AM are possibility to 
produce parts with complex geometries that are not possible with traditional manufacturing 
techniques and low-cost production of small batches. Fused deposition modeling is widely 
adopted AM technique that works by heating the thermoplastic material above its softening 
point and deposit it on building platform [5, 6]. Huber et. al. recently showed that is possible 
to produce NdFeB bonded magnets with desktop FDM 3D printer, but they achieved poor 
magnetic properties (Br 310 mT) compared to injection molded bonded magnets. 
Furthermore, since highly filled PA11 compounds are brittle it is challenging to wind the 
filaments on the spool [7]. Li et. al. used Big Area Additive manufacturing (BAAM) to produce 
bonded magnets. They achieve magnetic properties compared to injection molded bonded 
magnets (Br 510 mT, (BH)max 43,5 kJ/m?), but the BAAM technique is only useful for the 
production of larger magnets with low accuracy [8]. Compton et. at. used direct-writing 3D . 
printing to produce Nd-Fe-B bonded magnets with epoxy-based thermoset binder and 40 : 
vol. % MQA powder [9]. Ja¢imovi¢ et. al. used Selective Laser Melting (SLM) to produce Co 
sintered magnets from MQP-S powder. With fine tuning of processing parameters, they % ha 
achieved slightly better magnetic properties that injection molding references (Br 590 mT, we 
(BH)max 45 kJ/m®) [10]. In the present study we developed filaments for 3D printing based fee 
on thermoplastics matrix with the NdFeB content up to 92 wt. %. Developed filaments offers 
superior magnetic properties and can be winded on spool and thus easily processed. Fu 
fiat 
2. EXPERIMENTAL PROCEDURE BE 
For compounding of filament for 3D printed polymer bonded magnets, the commercial melt 55 Im 
spun powder (MQP 14-12, Magnequench) was selected as the magnetic powder. The MQP Re: 
powder is a multimodal mixture of Nd-Fe-B particles having plate-like morphology with ih 
average particle size of 250 um. It is specifically designed for high magnetic flux and high res 
temperature application, such as automotive motors and sensors. This material is produced irs 
by employing a proprietary rapid solidification process followed by a milling process and fez DC 
heat treatment. The magnetic characteristics of the powder are: B,=850 mT, (BH) max = 120 
kJ/m* and Hei= 1050 kA/m (Hai -intrinsic coercivity) [11]. As a polymer binder the PA12 
(Orgasol 2002 D NAT 1) was provided by Arkema (France). PA12 have average particle J RES 
diameter of 20 pm and melting point of 177°C. To improve the processability, thermal 
oxidation resistance and mechanical properties of polymer bonded magnets, the MQP The mag 
powder was treated with 3-Amino-propyl-tri-ethoxy Silane coupling agent by simple Shape, ty 
immersion of powders in aqueous solution of coupling agent. The excess solution was other han 
decanted and with Silane treated powder was dried in vacuum furnace at 80°C for 2 hours. andinterf 
Additionally, before mixing the PA12 with MQP powder, the PA12 was also dried to achieve Se and 
constant weight. The PA12 was dried four hours in a convection oven at 80°C. The desired magnefic 
amounts of MQP powder was dry mixed with PA12 and other additives and lubricants in a eNd-Fe 
Turbula Shaker-Mixer to achieved the homogenous mixture of magnetic and polymer wre: 
powders. The Turbula Shaker-Mixer is specially designed for exact powder blending of fe gr ~ 
extremely heavy powders with very light ones (pvar=7, 62 g/cm? and ppar2=1,03 g/cm®). To Tre: 
ensure homogeneous distribution of magnetic particles the filament was prepared using two- Be ooo 
step process. First the granules were prepared that were then used for preparation of the nigga 
filament.