So, did BlackMagic3D fail to make a useful thing because they haven't worked/researched hard enough, or the idea of 3d-printable ferromagnetic material is doomed from the beginning?
I don't have the answer, but I have a guess. To make something go smoothly through extruder, one needs to put quite a lot of plastic into it. A wild guess will be 60% by volume has to be plastic.
Ferromagnetic particles can have permeability that is very high. But it probably doesn't matter how high it actually is, because as it is mixed with non-magnetic material, the gaps between particles will probably become the dominant reluctance of the system, and will totally determine the permeability. So, it will probably make little difference to mix in particles with a permeability of 100 or of 100000. It will look more like a gapped inductor with a huge gap of 60% or so of length of magnetic circuit. That is, like made of material having permeability of about 1/60%, i.e. about 2.
So, to me it looks like the idea of making 3d-printable ferromagnetic material by adding metal powder to plastic is fundamentally doomed. But I would love to be proven wrong on this opinion.
PS. Do you think a material with permeability of 2 is useful for something? Post a comment! So far, I haven't invented any application.