My shopmate had a TIG welder here the other day.
I took the opportunity to try welding the 3D printed metal parts I made last year:
These are intended to be coil holders, so I installed a 40 turn coil prior to welding.
Mike welding the halves together:
We used no filler rod on the theory that the infused bronze would melt and form a braze of sorts.
It worked very well:
The coil insulation didn’t survive: The coil is conductive to the casing.
I’m encouraged by the weldability. I am ordering more test parts to keep pushing this approach.
Prometheus Fusion Perfection 
TIG welding is the way to go. You can probably preserve the coil insulation by welding only a short section at a time and allowing cooling time in between welds.
A highly heat-resistant material placed between the welding joint and the metal might be in order. As you’ve mentioned before, Shapeways makes rapid prototyped ceramics. A pair of semi-circular cross section, ring shaped pieces for the inboard and outboard “seam” would protect the winding nicely.
could they print your parts, with threads, so that the one part could screw into the other?
What I am invisioning is that you have a male and a femal half of the ring. On the male half yu have threads facing out from the outer edge of the ring, and facing inside from the inner face of the ring. The female side would match this.
you would insert your coil, pul your leads through stretigacly placed holes, and then screw the other half of the ring onto the first half.
If you can attach the 6 male parts as the inner face, you would then theoretically have an easy way to replace coils if the nead arises
Very nice welds sir! To better protect the magnet wire, I’d recommend welding in spots, very, very slowly. Tack, wait, tack, wait, etc. Yes, it will take a while to finish, but better chance of the insulation surviving.
As for making them printed to screw together, it’s a good idea, but I don’t think the printing would be acurate enough to do that. Best to print it blank, and have the threads machined on/in.
Just my thoughts. :) Keep up the good work!
Oh, clamping it between two block of alum. while welding might also help too, to draw some of the heat away.
Here is a semi-educated guess though I am rusty at this: TIG I believe has a welding temp of around 3000+ degrees, so you are going to need a barrier that can resist these temps. That’s either ceramic or ceramic fiber. Even so, my instincts tell me that you will need an air gap between the wire and heat shield in the area of the weld seam, otherwise you could land with the same result. Stopping the weld process frequently and letting the donut completely cool may help. You also may have to circulate cool air through the donut while welding to prevent heat build up. Just a thought. In this case, you might try both the ceramic shield at the seam of the donut, and wrapping the wires in either Teflon impregnated fiberglass or ceramic cloth, or just buying teflon insulated wire. I don’t know what this means to your donut prototype. You may need to re-make these donuts and add volume to it to allow for this insulation. I’d try the ceramic insulating barrier along with heat resistant teflon insulated wire.
Didn’t know about ceramic cloth. Great tip.
Ceramic cloth seems rather thick and stiff.
I agree, teflon insulated wire wrapped in fibreglass or ceramic cloth. This will also stop winding flexing wearing through the enamel (which is only good for a couple of hundred volts anyway). This is what caused the coil failure in Bussards polywell.
Great work.
Steve
It might also be worth considering printing the doughnuts in one piece leaving a thin slot around the outside circumference. Then wrap the windings through the slot, press in a vice to close the slot and weld.
Steve.
Brilliant idea!