Moldable Iron Powder

A long-term back-burner project just got my attention when I found out that Home Depot sells magnetic paint.

The project is a levitating globe thingie, designed as a control systems trainer that lets the student program the control rules in C and see how different control strategies lead to different sorts of system performance.

The paint got me thinking -- if they can make latex paint with iron powder in it, can I buy some sort of plastic resin with iron powder in it and make my own custom magnetics on the cheap?

So: does anyone know of an iron-powder/epoxy (or whatever) mix out there that you can buy, or an iron powder material that you can mix with your own resin to mold soft magnetic materials out of?

I'm looking to build some cores, and maybe have some made at a low volume if the prototypes work. I do _not_ need super high permeability -- the air gap in this is so big that according to the FEA program I'm using there's not much difference between core material with a relative permeability in the hundreds vs. iron (with relative permeability in the thousands).

Thanks.

Reply to
Tim Wescott
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Interesting! What is it called, and is there a web reference?

Reply to
PeterD

Don't know about the power, but I've used these people for sample cores. Fast service and good product. They might be able to find you some powder.

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Reply to
Jim Stewart

Searching on "magnetic paint" on the Home Depot or Rust-Oleum sites should get you there.

Reply to
Tim Wescott

Hi Tim, There are a lot of iron filled epoxies out there. Two names that come to mind immediately are Moglice and Devcon. I recall Dave Trumper at MIT had a nice mag-lev demo that used a photocell as feedback.

Reply to
jeff

If you buy casting resin, rather than laminating resin, you can cast thick sections without it getting too hot. You also can reduce the accelerator ("catalyst") to keep it cooler but that's risky business, because, if you go below the tolerable threshhold, the resin won't cure hard at all.

Casting resin is widely available from resin suppliers. It's usually much clearer than laminating resin.

Iron powder has been used to fill epoxy for making short-run forming dies. There have been entire books published about using filled epoxies (aluminum-filled, mostly, but also stone aggregate and iron) for dies and similar applications, but I haven't read one since around 1980, so I don't know what's current.

Reply to
Ed Huntress

"Tim Wescott" wrote in message news:hbmdnfVvIcn3SpfWnZ2dnUVZ_hj snipped-for-privacy@web-ster.com...

in the 80's i did some casting using polyester resin. i was hired to make reproductions of the ornaments on the cast iron buildings in soho, new york city. i was kinda making it up as i went so i have no idea of the longevity of the stuff i made. i mixed iron powder into the resin before adding the hardener. the finished castings *actually DID look* like cast iron, i was amazed. they even rusted. thing is the iron powder is heavy and would settle to the bottom of the casting if you had a long curing time. i mean, not all of it, but it generally tended to start settling to the bottom, even in the mixing bucket, and even with heavy doses of "thixotropic powder" etc. but it was cool. and they did look like cast iron. i never thought to touch a magnet to them, i'd bet they were magnetic. i got the iron powder from some sort of scientific materials supply house, but i bet you could probably find a place that sells it much cheaper. i'm sure there must be lots of information out there about adding metal powders to resin castings. in my case, you're not supposed to use polyester resin to do castings, it heats up and i think i've heard it can even catch fire. i fudged it so i opened the molds when the resin was cured enough to hold it's shape but before they got too hot. i worked in fiberglass mat/fibers before closing the mold (polyester is brittle and would snap like ice if you don't have some sort of reinforcing material in it.) when i was in college ('78~'82) there was a guy there who was making larger than life size castings (of human figures) in polyester that had (lots) of bronze powder mixed in. i think they called it "cultured bronze". looked, more or less, like bronze. no idea there again of the longevity. i'd think there'd be no problem mixing in iron powder. (but then again i don't really know you're trying to do, i'd imagine if you were trying to cast lucite ALL the iron would settle to the bottom before it cured.) good luck. let's see some pics. ("cores", huh?)

b.w.

Reply to
William Wixon

Thanks Jeff. That gave me the keywords I needed.

Goodness but it's expensive stuff, at least from McMaster. Gotta think about this again, maybe.

Reply to
Tim Wescott

It's either soft iron, or it needs a strong field to polarize it. How is it used? (IIRC, the permeability of ceramic magnets id low, so they support large gaps too.)

Jerry

Reply to
Jerry Avins

From what I found searching, it's soft. that is, magnets are attracted to it, but it's not attractive on its own.

Jerry

Reply to
Jerry Avins

Right. I'm looking for an armature material for an oddball electromagnet

-- big, light (well, relatively), and capable of supporting a significant AC component without wasting it all as heat.

Reply to
Tim Wescott

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nothing came up with the suggested search terms however.

Reply to
PeterD

Not exactly iron powder, but you can buy a 10lb bag of #7 steel shot for $21.99.

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Finer steel shot is used in shotblasting (like sandblasting). There are many suppliers, don't know what a bag of that goes for. Google and a couple of phone calls might be enlightening.

Reply to
Don Foreman

Ferrite powder is manufactured (it's a component of copier toner, among other things). You might call Fair-Rite and see if they can sample you a bottle. Failing a commercial source, fabricate a ball mill and grind some yourself. Without knowing the magnetic requirements, I cannot say if ferrite will work for you.

Kevin Gallimore

Reply to
axolotl

Fuck you.

Gunner

"Aren't cats Libertarian? They just want to be left alone. I think our dog is a Democrat, as he is always looking for a handout" Unknown Usnet Poster

Heh, heh, I'm pretty sure my dog is a liberal - he has no balls. Keyton

Reply to
Gunner Asch

Might try picking these up, too:

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?sequence=1 PDF files worth reading. (Found them using David's name, above.)

Jon

Reply to
Jon Kirwan

Look for sintered metal in a magnetic material. I think some magnets are made with sintered iron.

Reply to
Bill McKee

I wish this had come up 5 months ago, when I was taking down Ceromet/MPP in Anaheim, California.

I could have gotten you guys a few thousand pounds of iron powder for free.

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If you want a few pounds..maybe I can get it from another company if I ask nice and they want a service call.....

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Gunner

"Aren't cats Libertarian? They just want to be left alone. I think our dog is a Democrat, as he is always looking for a handout" Unknown Usnet Poster

Heh, heh, I'm pretty sure my dog is a liberal - he has no balls. Keyton

Reply to
Gunner Asch

Hell, NO! They're clearly liberals. They lollygag around the house expecting their human servants to deliver pre-chewed food to their face and schlep away their shit, while they mutilate the furniture, piss all over everything, and sneer at you.

Hope This Helps! Rich

Reply to
Richard the Dreaded Libertaria

:LOL..

Ill have to change that sig..you make sense.

Gunner

"Aren't cats Libertarian? They just want to be left alone. I think our dog is a Democrat, as he is always looking for a handout" Unknown Usnet Poster

Heh, heh, I'm pretty sure my dog is a liberal - he has no balls. Keyton

Reply to
Gunner Asch

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