[Off topic] all metal pla clogging

  • Hi All,

    I have a delta printer with a smart effector, a v6 titanium heatbreak (with an almost mirror internal finish) and a volcano, olssen ruby 0.4 nozzle. Aaaand have constant clogging issue inside the heatbreak when printing PLA. Only with PLA.

    -The heatbreak is almost mirror finish, and the filament seems not to stick to it at all. It's internal diameter is about 2.1mm.

    -The clog is always strongly connected to the inbound filament which is 1.74mm, measured it multiple times.
    -The clog is 6-12mm long always cylindrical as the internal of the heatbreak forms it to this shape
    -The extruder always pulls the clog back from the heatbreak on retraction, but it cannot advance it threw again to the point where it melts again.
    The extruder is a printed mk8.

    What I tried already:
    -5 different all metal heat breaks, 4 steel and 1 titanium from 4 different supplier. The titanium preforms the best.
    -Temperatures 200 - 260 degrees
    -Retraction from 1.3mm to 10mm (1.3 seems to work but the peace is unacceptably stringy I would need at least 3mm)
    -Retraction speed from 5 to 80mm/sec
    -Layer height of 0.1 and 0.2 to change the flow rate

    When the clog is formed I can push it threw the titanium heatbreak with a pliers but not the steel ones.

    I tought of getting a stronger extruder like a bondtech, but first I'd like to have your opinion .... It has been bugging me for more than a week.

    Any ideas please?

  • I’m not an expert, but heard that clogging with PLA is more prone to happen with a all metal hotend. Also did you polish the inside of the Heat break or did it come that way?

  • It was quite nice originally, so I made a try with it. It seemed better but the clogging was not completely resolved so I did polish it myself with a 2mm drill.

    Now it passes the needle test with flying colours but it is not 100% homogenous, it has an 5 - 7 mm long area which is 0.05 ... 0.1 mm wider than the other parts. I did not want to remove that much because of dimensional accuracy.

  • It's heat creep. The filament softens and swells in the area of the heat break.

    What you can do.

    A) Use the least amount or retraction possible. With too much retraction, you can pull molten filament up into or beyond the heat break where it will then cool and solidify.
    B) Print at a lower temperature if at all possible.
    C) Try a more powerful fan to increase the air flow over the heat sink.
    D) Ditch the all metal heat sinks and use the Lite version with a PTFE liner all the way through the heat break.

    "D" will almost definitely cure the problem but then you will be limited to printing at lower temperatures due to the fact that PTFE starts to degrade at around 230 degC. Which is fine for PLA, PETG, ABS etc but not for some of the more exotic filaments.

  • Thanks for the reply, understanding waht really happens helps a lot!

    I'll try to swap the fan.

    What do you think of a layer of silicone between the heater block and the radiator to reduce the radiated heat? Or will that just make the problem worse because sillicon has a higher thermal conductivity than free air?

  • 10mm retraction is way to much on a full metal. Even on bowden system, in my printer I have it between 1-2mm. What I find out is that pressure advance helps a lot with keeping the retraction low. But first check that the airflow around the heatsink is blocked like cables behind it. I personally really like the Prusa i3 MK2 solution which allows much better airflow around the heatsink, I even adopted it in my Hypercube Evolution

  • Dyzend has water cooling as an option which would surely solve the heat creep issue....

    I can’t seem to find any real reviews on the dyzend. I’m sort of skeptical about toms reviews because everything he gets is “very good” and that’s suspicious....

  • @qdeathstar E3D has water cooling solutions already too. But in my opinion this is overkill unless you a printing in a heated chamber.

  • @dragonn The 10mm was just a test, for an idea that if the retracted filament had more time to cool down ... I was flying kind of blind about the issue.

    @Qdeathstar @dragonn I'm using a smart effector, I'm not sure if a water cooling solution could work with it. Please prove me wrong 🙂

    I'm using some noname chineese 40x40x10mm fan bought from a local webshop, and just now as I paid closer attention found that it has great airflow unless I mount it, and it has to force the air between the blades of the heatsink. In this case it feels kind of crappy, so I'll buy some new fans on monday. Maybe a Sunon MB40202V1-G99 ?

  • @denke most 40mm fan tunnels for the E3D v6 are just crap because the have to much flow resistance. Maybe even mounting the fan without any tunnel would work better. I would suggest you to go with the stock 30mm tunnel and stock E3D v6 fan, I compared it to some 30x30 Sunon and the stock E3D is the much powerful.

  • @dragonn

    Not for the v6, correct? If they do that is exciting news...

  • Moderator

    40mm fans can work fine, but pay attention to the static pressure rating as well as the CFM rating. Higher static pressure is good for blowing into a restricted orifice, such as a heataink.

    I found a sunon 30mm fan that fit the bill and is actually very quiet.


  • Your setup is pretty normal, so I believe your problem is just due to too much retraction that molten PLA is pulled out into the cold zone and then got squashed by new filament.

  • @Phaedrux Thanks, I think I'll stick to the 40mm, it should be more quiet for the same effect. At least I hope. It should be easyer to find a 24V piece as well.

    @Jackal A few hours ago it happened with 0 retraction printing 40mm/s 0.2mm layer height @ layer ~60 so I lean towards insufficent cooling or bad thermal connection between the radiator and heatbreak.
    Furthermora it seems that the clogging is more probable the longer I print. If I start a new print after cleaning up a clog without cooling down, the clog almost always happens within 5 layers

  • Do you have thermal paste between the heatbreak and radiator?

  • @denke said in [Off topic] all metal pla clogging:

    Furthermora it seems that the clogging is more probable the longer I print. If I start a new print after cleaning up a clog without cooling down, the clog almost always happens within 5 layers

    That's to be expected with a heat creep issue. The longer you hold the print temperature, the further up the heat break/heat sink it'll creep. Do you really need to be able to print at temperatures higher than 230 deg C? I only ask because as I said in my first reply, the Lite version of the heat sinks with PTFE liner all the way through the heat break will almost certainly fix the problem.

  • @dragonn No, I do not. Does it make a big difference? Is there a special kind for this temp, or just some off-the-shelf cpu paste will do?

    @deckingman yes, the ptfe would limit me to 225-235 C but for eg. PET-G needs 255 for a strong layer adhesion for me.
    Hertz ABS needs 240-275 which is way up. I would essentially be limited to PLA according to theese numbers.

    If the new fan possibly with the thermal paste between the break and the radiator will not work, I'll probably snap, grab a drill and transform one of those crappy steel heatbreaks from all metal to ptfe and use that for PLA until my stock is gone.

  • @denke Yeah it makes, even E3D suggest it in they wiki https://wiki.e3d-online.com/E3D-v6_Assembly#Thermal_Compound as far I know every good cpu paste will do it too. Even seen a post on this forum where someone used solder paste and solder the heatbreak into the heatsink.

  • LOL a bit radical, but nice! 🙂

    Thank You all for your help, and you helped a lot!

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