Dual Extrusion Head: Heat creep discussion thread

I did some tests today with same gcode, one hotend and some environment changes.

Nozzle left:
Enclosure closed, Module closed: successfully printed
Enclosure opened, Module closed: successfully printed
Enclosure closed, Module opened: successfully printed
Enclosure opened, Module opened: successfully printed

Nozzle right:
Enclosure closed, Module closed: clogged after 10min
Enclosure opened, Module closed: successfully printed
Enclosure closed, Module opened: clogged after 40min
Enclosure opened, Module opened: successfully printed

So with my a150t I just have problems with my right hotend. And just with closed enclosure. So i think it is some heat problem. No modifications made so far.

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Interesting detail: They just published for Artisan a Q&A and a Mod’s Google Doc:

In the Modifications doc is a modification to add a heatsink fan to the DX…

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That would explain the leave the door open and use a fan followed by the use thermal paste.

Probably an opportunity to fix the latching issue too.

My guess is they’ll offer a new DX at 50% if they follow their previous updates.

Would the heat creep cause flow rates to get wonky, in the negative?

I have been having problems with the left extruder. Printing smaller objects is typically fine, but longer prints are having this weird issue where the layers arent really fusing together. I think it relates to flow rate.

On small prints with esteps calibrated, the wall thickness of a calibration print is coming out .43/.44 vs the .4, which is not a big deal, just adjust the flow rate. but if the print is longer, the flow rate is insufficent, even removing the flow rate adjusment.

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Hmm, good question. A bit of thinking on that: The insufficient cooling of the heat break lets the filament broaden more and more, starting from the heater block side, creeping up over time. One effect will certainly be that the friction of the filament against the walls will increase. In the end this leads to the nozzle clog, friction being so high that the feeder cannot push the filament any further, but instead grinds it down. In that sense “nozzle clog” is even misleading, since not the nozzle is obstructed, but the filament itself becomes the obstruction. But as the process of heat creep and filament thickening is a gradual one, I can well imagine that the feeder will also gradually start to slip, still being able to deliver some filament advance, but more and more inefficiencies coming in over time.

All just guessing of course, bt sounds plausible to me.

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For me thermal grease did not solve it. Same print that failed after 5h now failed after 2h, extrusion stopped. I’ll a) contact support, and b) build a windshield to stop warm air from being sucked in from below…
EDIT: and c) first try do do the print with the left extruder - I yet cannot rule out the filament, it’s not the best I ever had.

Also with open doors of enclosure and print head?

No, enclosure and head both closed. I do not see leaving these open as a valid solution.

Not for the Future, but maybe for a Testing purpose?

That’s very interesting. I do not see files for the mods and I would like to try the one with the fan on the module door.

Do you know how they work? Will we get mod files soon or should i dry to build on myself?

I did not see files either - not sure if they’ll follow up on that - perhaps write them a mail? Dunno… should not be too complicated to do yourself.

I use this extruder with a Prusaslicer and have never had clogged nozzles.
I wonder what in the world is different…?
My settings are 1mm of retraction, 40mm/s, and under 10mm of retraction when switching nozzles for 2 color printling. I do not allow setting the temperature low durling printing.

I have been wondering if this might be a part of the clogging problem: If you let the filament cool down, the heat creep’d parts of the filament will start sticking, and not heat up fast enough again to get moving… But that would be a poor solution - heat creep should not happen in the first place.

I added new thermal paste (the first time it was old and dry and ineffective).

in my particular case, it seems to have actually had a detrimental effect. im not ready to call it 100% on that yet, but i am having a lot of weird globules and its causing prints to fail from nozzle crashing.

perhaps the problem now lies in the fact that now that the paste is in place, the heat transfer needs to be counteracted with lower temperature printing. i am not used to printing lower then i am right now, but i will give it a whirl.

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Just my observations but maybe they might be of help to you guys:

I have been busy dialing in CF Nylon filament and had about 20 benchys done without any clogs or heatcreep problems so far.

However when I started printing with PVA Support (or PVA Support interfaces to be exact) I suddenly had some heatcreep problems now and then.

What I have observed is that during long prints (48h+) my flow gradually decreased towards the end of the print. The prints finished but I had some strange behaviour that after a finished print the head was clogged immediately at the start of the next printjob.

Had this a few times, every time the clog reached up into the cold end, about 10mm or more.

I didnt have this problem with the PVA nozzle though, only with the one printing Nylon.

One time I changed the nozzle somewhere between two jobs and saw that inside the hotend something looking like a thin sleeve of plastic at the walls of the heatbreak had formed.

So my assumption is, that the retract at nozzle change might be the source of at least my problems.

The Nylon has the default setting of retracting 16mm at nozzle change, with standard standby temperature. So the filament retracts up into the coldend and starts sticking to the walls forming a sleeve, as long as the print is going, it doesnt fully cool down (standby temp) and still manages to extrude with ever decreasing flow, as the sleeve gets thicker. As soon as the job finishes, the temp goes down to 0° thus completely solidifying the filament and clogging the head.

The PVA has a standard retract at nozzlechange of 2mm as it is too flexible to retract further without forming a knot inside the extrudergears (tested this) and doesnt show this problem.

so my assumption is that the 16mm retract at nozzlechange is part of the problem.

I now got a 52h printjob running with Nylon retract at nozzlechange set to 2mm, hoping that this will solve the problem.
Oozing of the inactive nozzle is present, but managable as it stops as soon as standby temp is reached.

Interesting though. We got an ultimaker s5 at work, which also has a standard retract at nozzlechange of 16mm, but no problems like that. It hasnt been used very much for dual filament jobs though.

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Sorry for double post.

Some Ultimaker Users seem to have a similar problem with the 16mm retraction distance.

Raise3D for example recommends this setting:
The extruder retraction’s amount can be edited under the “Ooze” tab. Raise3D recommends maintaining the “Extruder Amount of Extruder-Switch” between 2-4mm for any standard filament types, and from 6-10mm for Raise3D Premium PLA type of filament.

Flashforge users recommend 4mm at nozzle change.

Different setups I know, but similar problem.

Did you guys have the “heatcreep” problem also with single nozzle prints, or always with dual colour prints?

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Thanks for sharing your insights! At least for me I can tell that I have the problem even with less retraction on nozzle change. The two prints that failed were with 4 mm retraction on nozzle change. I just have restarted my print, now with colors swapped, i.e. the white, dominant part of the print is now left nozzle, the smaller additions in black are right nozzle. Let’s see…

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I designed custom doors for an extra fan and I’m testing it right now.

I still need to add bottom walls and a hinge and will post stl if someone would be interested to try them.

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Yeah… thought about something like that myself, but admittedly with the price Snapmaker charges for the head, I’d expect them to come up with a solution. My right-nozzle-failed-twice-15hrs print (which in the end will most likely will end up around 18hrs) is now nearly 11h into the job and running fine so far (don’t Jinx it!) with the bulk of work switched over to the left nozzle, so it really seems that they have a systematic problem with the right nozzle cooling. If my job succeeds, I certainly will reach out to support to get their opinion on that.

Personally I think that perhaps a few slits in the front door would have been enough…

Everything coming out of my extruder is garbage right now. I think I need to go back in and remove the thermal grease. I can’t get anything to come out at all lol

The first few layers look fine then its just horrible, temperature, speed no effect lol

I am not really wanting to modify the door or remove the enclosure.

Furthermore, the DX module is alot heavier and the weight isnt balanced, I think that I need to make a support fror the DX like on the Y axis somehow. It wobbles quite a bit. I also just replaced the linear module a few days ago but no change, it sjust too bulky I think.

If your door can still be opened without removal, I would be willing to try it.

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