I was surprised not to see a topic on this, so here goes.
I’ve been experimenting with variations on magnet designs. One challenge I’ve faced is maximizing magnetic strength while minimizing filament depth. You can have one, but not both—or so I thought.
The Challenge
Magnetic flux strength follows the Inverse Cube Law, meaning flux strength falls off at a rate of 1/r³. Simply put, for every 1mm of outer shell thickness, the magnetic flux strength drops dramatically.
I’ve tested Halbach arrays with some interesting results, allowing me to create a nearly one-sided magnet. FYI: Most of the 3D models I found on the internet have the magnets in these arrays placed incorrectly. It makes you wonder what they were thinking.
I also discovered another trick—magnetic filament can help focus flux lines in the direction of the pole. It’s similar to how a non-magnetic steel plate transfers magnetic force when in contact with a magnet.
Looking for Feedback
This is where I’d love to hear from anyone who has used magnetic filament. I’ve only found two options:
Amolen Magnetic PLA – Works as advertised, responding to magnetic fields like metal. The downside? It’s only available online, wasn’t in stock on Amazon, and costs $30/Kg.
Protopasta’s Metal Filament – This one raises red flags. Not only is it $70/Kg, but they can’t even bother to put it on a proper spool. Who uses corrugated cardboard for a filament spool?
Does anyone know of alternatives, or has anyone actually used the Protopasta filament? Is it really worth $70/Kg on a garbage spool?
The one thing Protopasta claims that Amolen can’t do is rust when exposed to moisture, which could be useful for aesthetic details. Imagine printing Benchys that look like rusted cast iron. Yeah, that’s a great use of time and money… NOT!
Filament Friday on YouTube covered it, and the verdict was that it doesn’t support enough magnetic flux to replace real metal. That’s a shame because just imagine the creative possibilities if filament itself could be truly magnetic, rather than relying on larger and stronger magnets.
I wasn’t even aware magnetic existed !!! I’ll join your topic.
I’m shopping for some in canada now LOL
EDIT: in reviewing some of this I am VERY interested… I’m wondering if it’s more/less conductive than the copper filament they sell. This is awesome stuff, and will need a lot of testing but wow.
Yes we can literally change the shape of motors if this gets better or create a sort of print in place non-assembly version that could in theory print the outer shell and then all the wound strands in copper or something.
Yes yes I’m not a tool and have my 101 in electrical - I get the field comes from the zillion wrapped wires going round - that’s not what i’m going on about here…
Can…hmm…can we print them solid to a lesser effect is what I mean taking advantage of the two variable materials to shell everything? If yes…even if it works at like a quarter of a volt level that would be incredible as we could literally fully plastic print our 3d motors -just- for 3d stuff you know? It wouldn’t be strong or small enough to rival any metal versions or micro motors we have - but being 100% printed would already be an accomplishment regardless of the output.
Quit putting so much new stuff on my plate man - it’s already overflowing without you coming in here exciting me with magnetic filaments!!
Very interesting article and it caught my attention. So I searched and did not find neodymium filament and the research these folks did implies they came up with the formula on their own.
I don’t think that will be practical. When I did research on neodymium in order to better understand it’s properties, I learned that it’s actually manufactured under very high pressure in order to keep its molecular structure then magnetized. It’s a process more complicated than making a semiconductor wafer requiring many more steps and a whole lot of expensive equipment.
Here was the simple list:
Raw Materials needed - Neodymium (Nd), iron (Fe), and boron (B)
Melting and Alloying
Pulverization
Pressing
Sintering
Annealing
Machining & Cutting
Coating — This is the important part. I wanted to see if a larger magnet could be cut and learned they can’t after they’ve been pressed and coated.
Magnetization
This is obviously outside the scope of current 3D printing technology. It also explains why the magnets are so brittle. They have properties closer to ceramic than metal but they oxidize so quickly which is another reason encapsulating them inside a body is helpful. If you scratch the coating off a Neodymium magnet, it will peel away like dried paint and start oxidizing within hours. If you slip and let two Neodymium smack together due to their magnetic attraction, they will break like like ceramic tile, not shatter but snap in two. The stuff is very finicky.
That’s fascinating. I did not know that. While I don’t have PA-CF, I will check out some PLA-CF that I have and see if it has any magnetic properties. I don’t see how Bambu PA-CF can have magnetic properties unless it has some ferrous, Nickle or Cobalt in the material and neither Polyamide nor Carbon Fiber has these properties. That said, what else is in there that isn’t on the SDS?
There’s a thread I started when I discovered this a couple of years ago, I think. Wasn’t that long after I got my X1C. I was going to do SEM/EDX on a sample to see what its constituents were. I have to think there’s Iron in there for some reason. But I never got around to it.
My Bad. I am confusing PLA-CF which is what I had with PA-CF. I only tested PLA-CF. Truth be told, I don’t see myself following up on the PA-CF from Bambu. My curiosity just doesn’t go that far to spend $40 on a spool to find out.
This one raises red flags. Not only is it $70/Kg, but they can’t even bother to put it on a proper spool. Who uses corrugated cardboard for a filament spool?
