Evaluation of additively manufactured thermoplastic composite magnetic field shielding for stepper motors

As stepper motors become more and more widely used in engineering systems (vehicles, 3-D printers, manufacturing tools, and similar), the effects of their induced magnetic fields present a concern during the packing and orientation of components within the system. For applications requiring security, this is also a concern as the background electromagnetic radiation (EMF) can be captured at a distance and used to reproduce the motion of the motor during operation. One proposed alternative is to use customized non-magnetic plastic shields created using additive manufacturing. Some small studies have been completed which show some effectiveness of this approach but these studies have been small-scale and difficult to reproduce. To seek a more rigorous answer to this question and collect reproducible data, the present study used full factorial design of experiments with several replications. Three materials were used: Polylactide (PLA), PLA with 25% (weight) copper powder, and PLA with 15% chopped carbon fibers. The factors of interest were infill pattern (gyroid, octet, and concentric) and shield wall thickness (10mm, 20mm, and 30mm), while the response used was strength of magnetic field at two distances (100mm and 200mm) from the motor at various angles. A total of 27 different shield designs were manufactured and tested, with a total of 1176 tests being completed. The results showed some effect, both in shielding and in increasing the magnitude of the EMF, but the effect was significantly smaller than what was shown in some previous screening studies suggesting that some previous studies had a lot of noise in the data. The replications showed excellent consistency, showing that the results are reliable. It was concluded that additively manufactured stepper motor shielding can be used effectively in some cases but is likely not the best shielding option for many scenarios in vehicles and similar applications