Dual extruder pin valves

[Tim]

Continuing the discussion from the "tree frog" thread. . .

I like the idea of wire being pushed down into the nozzle alongside the filament, but is there room for it?

It occurs to me that if the dual extruder process is retracting and extruding filament by typically 6mm or more on alternating sides, then you could potentially have each wire cross-coupled to the other extruder and lightly gripping the filament, so that when the filament retracts on the left side, it yanks the pin out of the valve on the right side, and vice versa. It would be neat if you could get away with no additional electronics, solenoids, etc.

Requiring a wipe after changing extruders is a minor issue. If you can just keep the extruders from dripping all over the print, you have accomplished the main goal.

[Levi8than]

I took mine apart and measured. There is not anywhere near enough room.
The opening on the hollow threaded rod is around 1.8 mm We would need that opening to be closer to 2.1 or 2.2 mm for this to be a viable option.

We could try drilling one out and printing a custom extruder with the path added. But I don't have an extra hot end to muck with right now.

Adding the opening on the side of the nozzle isn't really an option, because it would just add an extra opening for goop to drool out of, and that's no good.

[rpollack]

come up with a reasonable plan and we'll supply some parts to use for experimentation...

[Levi8than]

Thanks Rick. That's awesome.

What does the 3mm hot end look like? Are the threads on the outside of the hollow threaded rod the same? or are the nozzles and hot end completely different? If they're the same, maybe we can just start there. I'd imagine it would work the same except be more susceptible to oozing, so pushing 1.75 down the 3mm hollow tube might be a good place to start. With plenty of room left over for the wire.

Let me think some more.

[Tim]

Adding the opening on the side of the nozzle isn't really an option, because it would just add an extra opening for goop to drool out of, and that's no good.

Is it so bad? I've been wondering about how well it could work to drill a hole into the side of a nozzle. At the time, I was thinking about using such a drill hole to inject inks or dyes into the filament, but why not a shutoff pin? But, I'm not a mechanical engineer. I'm out of my field here.

[Levi8than]

The nozzles are cheap. Around $10, try it.
But you'll need to get the angle right so that you don't hit the threaded barrel (or drill through the barrel too), and so that you do block the flow of filament.

The thin gauge stainless wire is pretty cheap, too. I think it was around $8 for a couple hundred feet last I checked. I've been trying to find pre-straightened, hardened wire, though. Possibly spring wire, something that will retain its rigidity at the bottom of the nozzle.

This may be a better option, even if it does ooze some. Going down the barrel may have the issue of the filament hardening onto our wire after retraction, which might cause a problem.... we'll have to see.

[Tim]

Is this feasible or is it just asking for too much precision alignment?

[Levi8than]

Is this feasible or is it just asking for too much precision alignment?

Neat idea. But I think I'd feel more comfortable just having 2 separate motors/solenoids.

And I think this is less easy to get working than pin valves. Though, a ball valve inside nozzle is a great idea. It would require a whole new nozzle cast. I wonder if you could order a trial version from shapeways. Does the laser printed brass stand up to heat well?

[Levi8than]

Here's what I want to try first.
I want to order the 3mm hot end barrel and plastic attachment piece from makergear. I'm going to see if Karen can introduce the parts so that I can reuse this hot end as a 1.75 mm if it doesn't work with my plug theory. If she can, then I don't mind paying for the extra parts.

I'll print my own filament path to add a path for a pin to pass through it along side the filament. A 3mm path should let me pass a 1.75mm filament + 1mm brass rod easily.
I ordered a few 1mm brass rods off amazon + a servo and the rod connectors for it. I'm going to try actuating this thing manually first then maybe move on to automating it based on the retraction settings.

I'm not sure how I'm going to machine the end of the brass rod. I'll figure out something creative. But I want to start tinkering on this.

[MG_MLS]

This released by E3D today, maybe the "Cyclops" does something like you were describing?
https://www.youtube.com/watch?v=y4bo7crrEbY