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Printing Ferrites

Posted by terribleperson 
Printing Ferrites
August 19, 2013 03:47PM
Disclaimer: I don't have any experience with 3D printing or mills, and little understanding of the behaviour of magnets. If I did, I probably wouldn't be posting this here. I am, however, quite a fan of 3D printing. I believe it's the future. So I'm trying to do my little bit to help.

Recently Hackaday featured a 3D printed stepper motor. Of course, while neat, it didn't have many practical applications, because really the only things that were 3D printed were structural parts. It still required normal electronics, and permanent magnets housed in the plastic rotor. However, someone in the comments mentioned that steppers with permanent magnet cores often used ferrite.

Ferrites are magnetic ceramics whose primary component is iron(III) oxide. Iron(III) oxide is pretty cheap. You could make dozens of steppers with five dollars worth of iron(III) oxide. The problem is the binder. Most commercial ferrites use strontium carbonite, barium carbonate, or cobalt. I don't know much about magnets, but I'm assuming there's a reason all those binders are metallic. That's why I'm posting here. I'm hoping there's some way to print iron(III) oxide containing cements, ceramics, or even plastics that can still be permanently magnetized.

The reason I want to be able to print ferrite should be pretty obvious. As far as I can tell, stepper motors are a major component of the price of most repraps. If people with a 3D printer could print the permanent magnet rotor, wind the copper themselves, and print a plastic shell, I imagine the price would come down quite a bit.

edit: Plus, if we could 3D print stepper motors, we could use motors with the optimum capabilities for a given design, rather than shaping a design to fit the available motors.

Edited 1 time(s). Last edit at 08/19/2013 03:48PM by terribleperson.
Re: Printing Ferrites
September 02, 2013 06:46PM
Hard to see how to beat 15€/servo at the wages many people have! Also, not sure if you'd get similar quality ferrites at all, i mean you'd have a medium for the stuff to go into, thinning it, and 'getting the magnetization in'.

However, i like the idea of the ability to make those things by itself, and we dont quite know where it leads a-priory. For instance, it'd probably be able make some shapes better.

Of course, it might be a good idea to start with more regular ceramic, so you know what we have?

To be honest i dont know much about this at all.. According to wiki there is possibly a powder you can start with. Presumably you can mix this powder with some ceramics people are using now, at least to some extent. But even then during baking you need significant magnetic fields to actually magnetize it, that possibly doesnt sound very easy.(and has to be at sufficient temperature) Depends on how strong the field has to be and if permanent magnets can provide the field from outside/withstanding the temperatures.

Then(well maybe you want a plan before, if the above is hard) you probably want to try maximize the density of the actually magnetizing bit. Not sure how to do that either, i dont know how this stuff affects the flow during it being laid down and how ceramic bonds work. (So dont take me too seriously)

There is also the point: afaik neodynium magnets arent all that expensive at this point. They might have enough 'magnetization density' that an approach using those might be plain better. Basically just improving on Chris Hawkins design? For instance putting the magnets closer together, and instead of separate spools, have pegs sticking radially outward.
Re: Printing Ferrites
March 02, 2015 08:22AM
My first thought when it comes to this is making sure that the magnetic field is uniform, otherwise (in layman's terms) your magnetic material isn't really magnetic. You want a magnet's microscopic regions to all be aligned in same direction otherwise it will be less magnetic (more diamagnetic). Now you have a material that is not as responsive to the stepper motor's movements (since it is less magnetic) and more resistant to an external magnetic field (the technical term for magnets is reluctance) so it's not as efficient either.

You could probably print some ferrite and it might work, but it probably won't be nearly as good as commercial ferrite production. The Wikipedia article you posted says that there is a fairly complex process of making ferrite magnets (melting at high temps, milling, pressing, external magnetization, and then heated again).
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