Axial Flux Motors

An interesting introduction to this new (old) motor type:

And a question: has anyone run an axial flux motor using SimpleFOC?

Axial flux motors are standard on many mechanical disk drives due to heir extremely low profile, low cogging and high torque at low rpm. One of my tests for my boards for simple-foc is if they can drive such a motor. They were also the standard motor configuration for the old CD walkmans, and low profile floppy and CD and zip drives, whoever is old enough to remember them :). However, I’ve never had access to industrial grade high power axial flux motors. I would guess, since they were designed with 3-phase control in mind, to be a drop-in replacement as far as the control board algorithm is concerned. The board wouldn’t even know it is driving an axial vs radial motor.

Old Floppy drive motor below, 2-pole-pairs, 3-phase.


Here is another close-up

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The stators are a good choice for iron powder manufacture process.

Source: Case: Axial flux machines save space, weight and cost | Höganäs

The entire motor is easily milled on a 3-axis CNC provided you have the correct steel. Also the windings are very easily done by hand, unlike the radial flux where it’s a real pain to wind the motor. Last, but not the least, the magnet rotor can be double-sided, on both sides of the winding stator, which increases the efficiency and provides a symmetrical force. I saw somewhere a 3-d printed axial motor where the winding cores are only made of soft steel, and inserted into holes of two 3d-printed disks, and the magnets were glued outside also on two disks. Very easy to manufacture, just glue the thing together. You can wind the individual stator solenoids separately outside on a jig and press them into the 3d-printed stator disk.

Edit: You need to make the stator cores from either laminated or wire steel, else the Foucault currents will heat up the core and melt the plastic.

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The company producing the iron powder actually makes samples for CNC milling. I haven’t done a cost benefit calculation, since I don’t know the price of those coated iron spheres. They come in a specialized sealed big bag.

The powder iron ability to magnefy is highly depending on the final density. Which is why such huge pressure is needed, after which it is burned solid.

Edit: Some time ago I had a fantasy about two large electromagnets creating the pressure to create a green part, but I’m still not sure how much pressure one can make like that.

Is sintered iron powder even suitable for the magnetic cores? The eddie currents will heat it up pretty quickly and both lower the efficiency as well as overheat and melt whatever insulator comes in contact. For the cores only laminated silicon steel with very narrow hysteresis is appropriate. You can make it out of amorphous solid steel (glass steel) but that’s insanely expensive. There are companies making sintered SMC but again these are a lot more expensive than laminated components.

They claim it to be cost effective, but still don’t know the price of the powder. Tooling and all that is not cheap. They have different granular size powder. Electromagnetic components | Höganäs

Was thinking just maybe it’s possible to harvest the forces in the thermal expansion of some kind of oil. But 600 to 850 MPa is crazy pressure.

Eddy current is not an issue in coated iron powder, that’s the whole point of it.

Have you already contacted them and have they agreed to sinter you the raw SMC billets to machine? Sintering in single batches is usually no-go for companies like that.

Why would you need oil pressure? You want to liquid cool the motor?

I’m just contemplating how one can create enough pressure to do in-house SMC. OpenSMC press. The oil is for a piston. Just a fantasy :nerd_face:

The samples for CNC milling I found in a catalog somewhere. Guess it’s part of their business, to let folks try it out before going to production.

I see. This is 100% achievable, because the press you showed me is for pressing multiple shapes at the same time. If you are pressing small, one at a time billets, you can use a manual something like that:

Or something like that:

And then you can make an inductive oven to sinter the billets

Then use one of these to machine the parts

Good luck. Please don’t kill yourself.

Yeah :sunglasses:

This expansion wax, normally used in thermal actuators, has a 15 increase in volume when melted. If one was to harness this increase in volume, having a piston compress the powder in a mold. Just maybe one could do a SMC green part.

Edit: I believe the seals would be the weakest point in such a device.

A third way would be to slam a object (X mass) with high speed (X acceleration) into a mold filled with SMC powder and WHAM!

Let’s build a electromagnetic tower. Gravity is free :wink:

How much should the object weigh and to what speed should it be accelerated in order to reach 850 MPa on a 10cm x 10cm mold?

I was thinking something like a huge (tall) solenoid with a heavy iron core (Bullet), but maybe air pressure could also accelerate the mass with sufficient force.

The mas should be raised inside the tube somehow (loaded) Yeb a vertical canon pointing downwards

Alternatively you may construct a projectile and expel out of a large caliber against a solid target:


I think gunpowder is for jarheads, but non the less I agree.

Doing a quick search I found heavy duty seals rated for 200 bar. That should, I think, be enough pressure on the payload. Let’s call it The Hammer. I wonder if the mass will bounce back and if so, it probably will, to whichever height. Having a automated plug inserted to the end of the barrel, could raise the thing to loading height. This should happen while the green part in the mold is ejected and the mold refilled with coated iron powder. I wonder how many parts per hour is possible.

Edit: Maybe :thinking: there is already a mold standing by ready for punching…perhaps for a different part, who knows

In order to utilize the full stroke/length of the cylinder, a electromagnet should hold the Hammer until pressure builds up. WHAM!