Fabing magnetic materials

I apologise for my simplicity here, but from the discussion on forrest Higgs board, i've put up this basic plan. Using a solenoid to aligned magnetic particles is the way that it's been put forward, the problem with a solenoid is that particles are exactly aligned only when they are deep inside the solenoid itself, after that the flux lines tend to diverge outwards in a sort of oval shape. So the basic Idea I think is to set it up so that a slurry gets driven into the solenoid, the solenoid turned on, the solenoid turned off and then the aligned slurry is driven out the main piping again. Most likely into some sort of mold where it can harden. it is absolutely possible to make fine magnetite harden at low temperatures, since this is my normal day job (pelletising the stuff)

The main problem with this plan is that a thick slurry will undergo deformation as it passes through the feed tube. Distorting the alignment of the particles at different rates depending on their distance to the wall of the tube (it's a side effect of viscocity)

Attached are some very very basic drawings I've probable got the whole wrong idea, but maybe they will get more talking done in the forums and the blogs.

Forgive me if my questions are completely ridiculous... I know very little about this stuff.


won't the particle alignment change even more during transfer into a mold? does the ratio of the feed tube diameter to the mold diameter have an impact on the distortion of the alignment? or am I totally in left field?

could you put the slurry into a mold and then drop a solenoid around it, then power it on... move to the next mold.. etc..

[codesushi.com]


I probably just need to do some remedial reading on magnetism... and magnet fabrication.

You're right on that one. The main idea I had for a mold was based more around it being pretty much being a cylinder so that the particles won't de-align when you squish them out(ie, they would basically stay in a cylinder shape. It probably is a better way to do it using a solenoid the way you say though. It would be good to fab the molds first, fill them, then attach the solenoid and power it up. The main issue I think is that it takes a while to solidify large magnets when you're not just melting them together. I've done experiments on pieces roughly the size of the magnets we want, and at room temperature it can take a day or two for non polymer binders to make fine magnetite get some hardness into it.

It would probably be easy to do these one at a time and solenoid them while they cure, but I think your turntable idea is the way to go if we can use a polymer binder to make hardening really fast.

"It would probably be easy to do these one at a time and solenoid them while they cure"

do the particles tend to lose alignment if they are not under a constant magnetic field during a slow cure?

I wonder how things change if you were to let the molds cure some percentage, say 50%, and then apply the solenoid for the first time...

or.. maybe the turntable system could rotate through the molds until they all cure.. 10 minutes each... 6 molds.. one 10 minute magnetic field per hour...

... 'magnetic fabbing' is pure high-tec and high-power ...

VAC in Germany builds crazy shaped magnetic objects with NdFeB-granules embedded in resin - AFAIK they use magnetic fields with 5 to 7 times more force then the finished objects should have!

It's much easier to fab the non-magnetic body/housing and insert NdFeB-magnets.

Here a sample of a magnetic-ferrofluidic pump where i inserted linear magnets in the feeding tube and quarters of ring-magnets in the spindle:


The thinner ring-magnet on top has a diameter of 40mm, a hole of 22mm and is 3mm thick.

The parted ring-magnets in the spindle has the same shape, but 5mm thick ...

Viktor

Damn! That's beautiful stuff, Viktor!

that is a very cool looking doodad you have there!

So that thing pumps ferrofluid purely through the force of magnetism?

besides the power required for the "mother" is there anything else super tricky about the process?

... nope - the ferrofluid is the sealing medium settling along the linear and the spiraling magnet-rails.

I designed the pump for transporting gasses or fluids which didn't mix with the ferrofluid or when inserting two separating membrane-tubes in the slit between spindle and tube for pumping blood

Imagine fluid half-ropes along the magnetic rails, maybe 7mm wide and 4mm high.

When i insert the spindle in the feeding tube there remains a slit of 2mm between the surfaces, so the ferrofluid trays are compressed and overcrossed.

Between the overcrossed ff-trays remains rhombic areas, which are sealed against each other with the ferrofluid and can withstand 0.4 bars pressure per ff-sealing.

With the design of 3 windings against 4 linear segments i have 10 to 12 rhombic segments in spiral sequence but only 3 sealings along the tube so the maximum pressure between inlet and outlet is 1.2bars (remember: 3 x 0.4bar) - with a longer design and more windings along the tube you can stack/add the 0.4bars per complete windings for more pressure-difference.

Beside - this prototype is powder-bed-fabbed from starch, i have another one (a bit smaller) which is fabbed from gypsum powder with green colored glue-inc, but i hadn't insert magnets, so it's in the original state after printing - i'll post a photo when home again ...

Viktor

ferrofluid blood pumping...
seems to be a nice hobby

No, honestly; that's impressive!

'sid

... atached is a photo with the fabbed parts of both prototypes - the creme-coloured is built from starch, the greenish one should be from gypsum powder with some green colour in the glue-ink ...

The basic idea was a high-precise gas-pump with airtight and 'eternal' sealings.

When some guys asked for a peristaltic blood-pump, which didn't smash the blood-cells, then i simply inserted two thin elastic and concentric tubes in the slit, so the ferrofluid trays could enclosure a volume of blood (or another liquid or gas) without having physical contact to the transported medium.

The main advantage of this design was the 'super-soft' squeezing of the embedded rhombic volumes through the tube, so there isn't the danger of smash, shred or tear up blood-cells, what's the main reason for thromboses in surgery ...

Viktor

Edited 1 time(s). Last edit at 07/30/2008 03:06PM by Viktor.

... look at the image of the motor-parts on the second side of the PDF-file: [www.modellbahn-west.de]

Maybe it's an idea for designing and printing/wiring own motors?

Viktor

Edited 1 time(s). Last edit at 08/25/2008 02:40PM by Viktor.