Alignment of Magnetic Particles in Functionalized Magnetic 3D Printer

Abstract

Additive manufacturing via 3-D printing technologies have become a frontier in materials research, including its application in the development and recycling of permanent magnets[1,2]. In-situ alignment during 3D printing of magnetic materials has opened new horizons for manufacturing of complex permanent magnets[3,4]. Based on our former work[3], we will present a multiphysics model that couples fluid dynamics and electromagnetic interactions, to predict the degree of alignment (DoA) of a polymer bonded magnet printed under applied field. We have developed a mathematical model which predicts the flow of magnetic particles in a viscous fluid through a nozzle under applied magnetic field. A particle-fluid interactive fluid flow simulation is performed to model the flow regime of molten bonded magnet. The interactions between the drag, inertial, and magnetophoretic forces are analyzed to predict the particle trajectory. Torque balance is performed between the drag torque, magnetic torque on particles from the applied field, and torque from particle-particle interactions. The torque balance is coupled with the flow simulation to predict the degree of rotation of magnetic particles during printing. Experimental validation of the DoA predictions (exp = 0.62 and theory = 0.634) was performed using 65vol.% NdFeB+SmFeN in Nylon12 3D printed samples with variable alignment field (Fig.1a). The model is parameterized to predict the impact design and operating parameters including alignment field, magnetic loading fraction, and particle size. The results demonstrate an increasing alignment field with higher loading fraction magnets (Fig.1b). This work is supported by the Critical Materials Institute (CMI), an Energy Innovation Hub funded by the U.S. Department of Energy (DOE), Office of Energy Efficiency and Renewable Energy, Advanced Manufacturing Office. Ames Laboratory is operated for the U.S. Department of Energy by Iowa State University of Science and Technology under Contract No. DE-AC02-07CH11358. Figure 1. a) DoA prediction for 65vol.% NdFeB+SmFeN in Nylon12 before and after printing with 0.15[T] field, and b) DoA vs. field for NdFeB+SmFeN in Nylon12 with different magnetic loading fractions.