Four Conductor Sliding Ring

[pyronaught]

After a few years of dealing with my CNC heat wheel strangling itself with the power cord, I finally got around to designing a set of sliding contacts for it so that it can spin infinitely in either direction with no worry of cord strangulation. Just in time too, the insulation on the old one was just about worn through and ready to short the 120v line to the heating element. Since the wires don't move on this new one, there is nothing rubbing on the insulation to cause that problem. The fixture for holding the 28mm rotary cutting wheel on the other tool head is also 3D printed.

The hard part here was making the set of four concentric copper rings. I bet ednisley can figure out how I did that.

https://youtu.be/PE_zWWf4nv8

[jimc]

nice! what did you use for the contacts? some type of carbon brushes?

[ednisley]

figure out how I did that

Mmmm, I'd start by mining copper ore... [sigh]

Etching copper is much safer than machining it: that stuff will grab a cutter and fling itself across the shop with no warning. Been there, done that, wrecked some nice stock, won't get fooled again.

You obviously enjoyed plenty of Quality Shop Time making that tool!

[pyronaught]

figure out how I did that

Mmmm, I'd start by mining copper ore... [sigh]

Etching copper is much safer than machining it: that stuff will grab a cutter and fling itself across the shop with no warning. Been there, done that, wrecked some nice stock, won't get fooled again.

You obviously enjoyed plenty of Quality Shop Time making that tool!

Yes, in one of my attempts I epoxied a sheet of .1" copper onto a 3D printed backer, then chucked it up in a lathe with the intent of turning grooves to make separate rings. The cutter grabbed and ripped the sheet off, and also I think the heat generated weakened the epoxy as well.

So etching the rings with acid was the way to go. I still had problems masking the copper well enough to keep some acid from getting through over the long duration the etching took to get all the way through the sheet. My first attempt was the laser printer toner transfer method, but the coating that produces had pin holes that resulted in a pitted surface on the rings. I tried the Sharpie permanent marker method too, but same problem. The winning solution was to just spray paint both sides of the copper, then drill a center point and use a compass scribe to scrape circles through the paint to expose the copper where the rings needed to be separated. Once the rings separated in the acid bath they were then etched a little longer until the gap between them was about 1/16". Acetone was used to remove the paint once the etching was complete. The connecting wires were then soldered to each ring on the back side prior to epoxying them into tracks on the printed base. Another printed fixture jig was used to press the rings and sandwich them using a set of clamps.

[pyronaught]

nice! what did you use for the contacts? some type of carbon brushes?

Spring loaded test pins that are normally used for circuit board testing fixtures. They are tiny and can fit side by side on a short arm, yet still rated for up to 15 amps.

[insta]

The hard part here was making the set of four concentric copper rings. I bet ednisley can figure out how I did that.

I'm not ed, but I was going to guess witchcraft and goats blood.

[ednisley]

witchcraft and goats blood

Propitiating the Machine Shop God begins with an offering of your blood.

Around here, bleeding for 3D printing requires weapons-grade stupidity ...

[insta]

I resemble that remark.

[ednisley]

I absolutely hate seeing blood all over my fingers and having no idea what sliced me: that razor-sharp metal remains perfectly clean.

Today's projects include rebuilding a brace of fluorescent shop lights with LED tubes; those fixtures have nasty edges. I want vengeance and I want it now!

Gimme some good 3D printing action any time...

[pyronaught]

I got a bunch of nasty cuts lifting the melamine boards for making my 3D printer cabinets. Thin little chips of the plastic coating on those things overhangs the edges by a tiny amount and are razor sharp. You would think the factory saw would produce a clean edge, but for whatever reason it doesn't. I still have to wash the blood stains off.