How to print an electric motor | Hacker News Reader

How to print an electric motor

spectrum.ieee.org

167 pointstomcam34 comments

On a similar note, Fishman produce a range of electric guitar pickups that use stacked PCBs for the sense coil, rather than the traditional loop of enamelled copper wire. It's not necessary (and it's undoubtedly more expensive), but it gives them far more precise control over inductance.

https://www.youtube.com/watch?v=oZSS13d3vZs

https://www.fishman.com/products/series/fluence/

Uh ... cool! He says "48-layer circuit board", so my initial guess is those are not super-cheap, no. I think a regular PC motherboard (which is not a very simple board) has 8-10 layers. 48 is a lot.

Another cool video of a high performance 3D printed halbach array brushless DC motor:

https://youtu.be/YsSm65DAcCg

The author posted up all his design files and has extensive documentation and instructions.

(Note that most of the housing is 3D printed while you still need bearings, coil and magnets etc). But still very cool what is possible and opens endless customization opportunities.

Very neat. I wonder how the small magnets are retained when the rotor is stationary. The big ones slide in but the small ones are just pushed into place. Once the whole thing is moving they get pushed out but when it isn't moving the stator will suck them in.

I'm assembling this right now, and the stator doesn't pull them out - it seems like the magnets on either side help keep them in place.

Amazing maker build. Just watching the video is sheer pleasure.

This is cool, but I'm quite concerned about efficiency. There are much smaller motors that can release 4 times the energy of this one.

> "I’ve been able to almost double it by adding a ferrite sheet to the back side of the stator coils to contain the coils’ magnetic field lines."

I never heard of a ferrite sheet, completely awesome! I liked the article, but IMO the title is a little misleading. What I gathered is that he 3d printed the rotor only. I'm assuming the actual 4 layer pcb was etched. The rotor was still wound manually. The hall sensor still soldered by hand.

The print notion implies production automation, which is my only gripe. His hackaday has a more accurate title "PCB Motor".

doesn't PCB stand for "Printed Circuit Board"? So it's still mostly printed.. The rotor is 3d printed, and the stator is manufactured via PCB techniques. I understand what you mean regarding it not being totally printed though.

While “PCB” does mean “Printed Circuit Board”, it’s kind of a misnomer. The word “printed” doesn’t really accurately describe the process used to make PCBs.

They're standard printing techniques, just not "squirt something out of a nozzle" printing. With the exception of drilling and through-hole plating, the processes used in PCB manufacture would be entirely familiar to any experienced printer.

Depends what type of PCB[1] we're talking about.

[1] https://www.nano-di.com/dragonfly-2020-pro

Lithography is a printing process. Machines that make single copies without plates or masks is a newer use of the word.

You can automatically solder the sensor, and I don't know what you mean about winding the rotor. All you have to do is snap some magnets into it.

It's completely automatable, but then so is a normal motor. This isn't about automation.

However I agree that the title is misleading. The 3D printing is by far the least interesting thing about this motor.

There's also a related but different type of pcb motor that relies on the piezoelectric effect instead of magnetism: https://www.youtube.com/watch?v=uFZsH62ewYo

Fascinating motor design. I wonder how much torque is lost using a hall sensor vs backemf. It is my intuition that backemf would be more precise than hall sensor, but I don't know much about motor design. Would it be worth adding circuitry to amplify the backemf signal?

I doubt the claim that printing a coil on PCB is cheaper than winding wire coils. At any rate you have to print the design on PCB , etch it join those double side PCBS. It cannot be cheaper.

You can build a coil winding jig to automate the winding process too..

Yup absolutely, plus the amount of conductor you can use is limited on a PCB. It is cool but not cheaper.

When IEEE claims cheaper, they certainly don't mean in terms of Joe basement hobbyist complementing his next Arduino weekend hack.

At production scale--starting in the low 100s by rough estimate--and presuming motor specs satisfy application requirements, cost per unit would quickly approach rock bottom.

PCBs are super cheap. If you design one which is of a common type - 2 or 4 layer, FR4, 1.6mm etc, the price per unit is very low. There's lots of Chinese board houses now that will produce 100x100mm boards for 50c a board if you buy 10! That's $5 including postage to have a double sided PCB made. 4 layer is slightly more expensive at lower quantities, but once you get more than a few hundred made you're looking at under $1 a board.

If you want to make a product cheaply, doing it in a way that makes use of the electronics production process is a really good way to start. Compared to implementing your own mechanical designs and manufacturing process it's really, really easy and cheap.

Instead of using permanent magnets, why not create two PCBs which rotate wrt eachother?

That’s actually a really big deal, right? If we can 3d a motor were way closer to a self replicating 3d printer.

The only thing actually 3d printed here is ridged container for holding the permanent magnets in place. PCB electromagnets are not new and multilayer interconnect PCB boards have been around for 30 years. A real 3d printed electric motor would be quite a feat indeed.

That has me wondering if kind of a hybrid solution could work, like a 3D printer that can also pick and place components mid-print. That could be a reliable way to deal with the permanent magnets, since presumably there isn't going to be a way to print out any material that would magnetize itself reliably.

I think there’s a way to make motors without permanent magnets

Indeed. An electromagnet is a magnet! However usually these are quite weak even with iron cores.

Quite weak? Electromagnets can be as powerful as you want in a given space provided you can cool them and you can avoid saturating the core.

I more mean in reference to using them as an opposing magnetic field for using in an electric motor. Like suppose he simply put two PCB electromagnets together. What would you expect the force to be?

I'm sorry I read your comment as a general statement on electromagnets. Yes, two PCB based electromagnets are not going to be able to make a very dense magnetic field. The major reason is that the current carrying capacity and cooling will be lousy. But a sizeable electromagnet made from a copper coil and a half decent core material will happily lift your car.

There is a solution for "printing" magnetic domains in a base magnet, maybe a printable material could be devised such that later on a "magnet writing head" could create whatever magnets are needed.

https://youtu.be/drD416THU7Y

People are working on such an hybrid: https://hackaday.io/project/963-firepick-delta-the-open-sour...

(the project seems dormant, though)

The tech has existed for a while to embed components inside PCBs --- inserting them into voids during the lamination process. Small discretes (capacitors, resistors etc) up to full magnetics are being embedded in production.

Example of an embedded magnetic in a board-mount DC-DC converter-- https://twitter.com/hubmartin/status/906768773180530689

You can print pneumatic (or hydraulic) motors. You will need pneumatic pump or an other source of compressed air to power them, of course.

PS. You can also 3d print electro-static motors, but they require high voltage, blades, and doping. See https://www.youtube.com/watch?v=oMK0dEKWJdY , https://www.youtube.com/watch?v=OHMpbJIXWtE .

Also, regular electric brushless motor 3d printed: https://www.youtube.com/watch?v=-6ikMRXNs9s .

I hope, this will inspire someone.

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