2 in 1 out setup?

  • Hi,

    this is not per se a duet topic but i think people here are more into these experimental topics, so here it goes.
    Im trying to get a "y-splitter"/ 2 in 1 out setup going, but i cant get the stringing under control.

    I bought the splitter from triangle labs on ali and mechanically the filament path works very well. My extruders and slicing also works as supposed.

    The only issue I still have is the stringing that happens when one filament gets pulled out. To combat that I tested different materials like PETG. Some people say that it tends to string less, however after 2-3 days in open air (we have 85%ish moisture in the air) it strings just like PLA.

    Then I build a whole filament drying system, incl a food dryer and "sealed" box that manages to keep the moisture around 45%. I have tested two different PLAs so far and just burning of some filament with a lighter and pulling it apart shows that there is a difference between open air filament that strings a lot and the same material dried that doesnt.

    However in the extruder no matter what retract script I use (fast-, slow pull, breaks etc) I still get a lot of stringing.

    What keeps me from giving up is that prusa with his 4 way splitter must have found a reliable way of doing that, but my talks with prusa support have not been fruitful at all.

    So is anyone tinkering with such a system and wants to share some experiences?


  • Yeah, I spent 3 months failing with a v6 hotend. I recently switched to a lite6 geometry and that fixed the problem.

    I was having some issues with an occasional jam happening on the full E3Dv6 geometry. I switched to a Lite6 - the type of geometry where the PTFE goes all the way to the nozzle, and all my problems have disappeared. The main problem is pushing the little strands of filament on the tail of the pull back into the cold v6 heat break, but with the lite6 it is extremely more tolerant because it goes directly to the hot nozzle.

    Prusa and Prometheus both have a customized v6 heatbreak with a larger bore and they use a precision filament guide tube.

    Consult the graphics at the bottom of: http://www.trianglelab.org/3856-2/

    FYI, these pictures are from different toolchange scripts that I have been running. It is entirely possible to do this without the strands you see, Kraegar's scripts work great for me with a lite6. The dragon was done with a v6 and a ram-purge. There was 1 jam that I caught, paused, and cleared. The lizard was after I switched to lite6. It is extremely more tolerant of the poorly formed filament end.

  • Intresting. I saw the recomendation from trainangle labs but I cant use a lite6 setup because I use the duet smart effector which uses a custom v6 heatsink, so there is no simple way to switch without rebuilding my whole effector.

    I also tested the retract scripts from the trainagle page and some others ones but i can see no difference in stringing.
    Could you repost the pics. I can only see links which are broken, I would like to try your scripts anyway.

    I redrying some petg samples and I have some unopened e3d asa filament. Getting rid of the stringing would be easier that hardware changes πŸ˜„

    In general it sounds like the lite6 solution you suggest is also what prusa and prometheus did, so seems the way to go.

  • I did play around with that system for a while but did not manage any worthy prints before deciding two colours just wasn't worth the hassle or multiply print times by a factor of 8, but Kraegar on here did a lot of work. He found a filament shaping method which was very reliable which went like this, on tool change, retract the filament a short distance, pause, then unretract it almost fully but not quite, this packs the tail down and makes it less likely to catch when re-fed, then fully retract and load the other filament. You can try it by hand. The long retract to get the filament clear has to happen as fast as your extruder can do it, to prevent the tail hardening before it gets pulled clear.

    There's a thread on here https://www.duet3d.com/forum/thread.php?id=1010&p=1 with a lot of detail. My issue was grappling with the firmware and having the right tool selected, and then what happens when I'm just doing most of my day to day printing with just one extruder

  • Great, ill get on that thread right away. thx

  • Can't seem to embed the pictures. Here's the link: https://imgur.com/a/Sp7ys

    PETG strings more in all of my experiences, but I will say that I run it on the higher end of its temp range for better layer adhesion.

    Kraegar's scripts should prevent the loose extrusion you see in my pics.
    The lizard is what happens when you do a straight up pull like TL's scripts. It goes, but there's molten plastic in the nozzle, and when you feed the new filament, an air bubble in between it and the molten mass causes that to get pushed out.
    His script has a tiny bit of dribble because of the pull, wait, push. I deviated from his script because I was have stringing/ other under-retraction artifacts on toolchange and wanted to try the straight up pull. I want to revert to his scripts but increase the 3 to a large value like 4-6mm retract. Will see.

    My scripts are… interesting... Start with Kraegar's and adjust as needed. Mine are all variations from his including additional wait times, different distances, a different purge location, etc... Simple will be good for you to start.

    BTW with the v6 I was originally running, I only had a moderate success rate with his scripts.

    "Lite6 geometry" is not what prusa and prometheus did. That would have been the easy way out. They created custom v6 heatbreaks that make feeding filament in easier, thus maintaining all metal.

  • Talking of which, and since this forum is a reservoir of great knowledge, why is it that e3d hotends (others may be similar) filament path opens up in the nozzle area. Why not maintain a fixed 2mm (or 1.8mm) all the way down the heatsink and into the nozzle?

  • @DjDemonD:

    Talking of which, and since this forum is a reservoir of great knowledge, why is it that e3d hotends (others may be similar) filament path opens up in the nozzle area. Why not maintain a fixed 2mm (or 1.8mm) all the way down the heatsink and into the nozzle?

    Greater surface area so effectively better/faster melting? Dunno, just a guess.

  • My first thought was that the smaller diameter of the break's ID helps the filament plug form. But if that's the case then I've got swelling because I can't get it back in thru a normal v6 break.

  • I think the reason is that the PTFE Liner on a full V6 goes to just the top of the heatbreak and I think the reason is to further insulate the filament from any heat after all you need the Meltzone to be very well defined and controlled if it was 2mm all the way thru the heatsink it would be even more important for very effective cooling of the heatsink.

    The issue with taking the PTFE all the way to the nozzle is reduced Temperature capability hence why the V6 Lite has that restriction

  • I've managed to print fairly large objects on my setup (Y-splitter, E3D V6 with Prometheus heatbreak) without issue. However, it's really hard to do if you want to keep your full metal hotend. I end up being able to only use certain brands of PLA for any print that has more than 20 layers, otherwise it just ends up jamming mid-print. If you'd like to go this way, I'd really recommend going with a PFTE lined hotend. You can use the Lite heatbreak with smart effector heatsink.

    If you still want to keep the full V6, I recommend you get a better heatbreak. Either that special Prusa one, or the one from Prometheus System.

  • @Mike I went through this train of logic yesterday, looked at the price of the Prometheus heatbreak ($25.50) vs $2 for 5pcs of the Chinese 4.1mm full thru bore breaks, and very quickly decided that I have no problem dedicating a printer (or multiple) to the y splitter and PLA.



  • I just asked prusa. They dont sell the heat break seperatly on the whole hotend and the would not be compatible with SE or the original heat sink.

    The prometheus one looks interesting though but ill try china first if guess πŸ˜„

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