ASA, 0,2mm Nozzle, long prints, HOW?

[user_3182160881]

…after a total of 4 successful prints lasting over 24 hours using the simplest ASA filament and the 0.2mm nozzle (100°C bed, 272°C nozzle, and 55°C chamber), it’s failing again. I’ve only changed the filament. The print fails every time with the error “the extrusion motor is overloaded,” and this happens after about 10 hours. The nozzle isn’t clogged—I pull out the filament, trim it, and keep going—but the print is still unusable because, due to the pause in printing, the filament printed later no longer adheres well to the previously printed part (2 wall lines, 1.4% infill; the parts need to be lightweight).

What I’ve tried:

• Volumetric speed: started at 2 mm³/s, lowered to 1.5 and raised to 2.5 → no success

• Print temperature: raised to 285 degrees and lowered to 250 degrees → no success; at 250 degrees, the print fails slightly sooner

• Print bed temperature: lowered to 90°C → no success

• Chamber temperature lowered: standard for ASA is 60°C, lowered in 3 steps to 45°C → no success

• Tried different ASA filaments → no success

My conclusion is therefore that the problem seems to lie in the area of the hotend’s heat sink. As I understand it, the filament gets too hot there, causing excessive friction. This works for a while—you can also see signs of under-extrusion in the print—but eventually the filament becomes so soft that it gets compressed and thickens as a result. Eventually, it gets stuck between the heat sink and the actual melting zone. Only the 0.2mm nozzle is affected because the filament spends a relatively long time in this area with the small nozzle.

Now, of course, the question arises: what should I do?

Basically, the print head is located at the hottest spot in the printer; combined with the long print time, everything there heats up to at least the chamber temperature, probably even more due to the print bed. Combined with the low filament consumption, the filament also has plenty of time to heat up to this temperature. There’s nothing that can be done to change this—yes, it has to be ASA and the 0.2mm nozzle. That leaves improving the cooling, but how?

The new firmware is supposed to include control for an additional fan on the print head, but this fan can only circulate the hot air at the top of the chamber. What exactly is this fan for?

I’ve read that the H2D has a built-in air pump that blows dust away while the laser is in operation. This would mean that (cold) air at ambient temperature would be available at the print head. If this could also be utilized for hotend cooling during printing, the problem should be solvable almost entirely with on-board resources.

Has anyone had success with this and can share their experience?

Thank you very much.

[L0rdS474n]

One possible explanation for the extruder overload is that the printer is attempting to push more filament than the system can reliably handle. I can reproduce similar behavior with TPU when using a slightly too high volumetric flow with small nozzles. Sometimes the print completes, sometimes it fails. However, when I use well‑calibrated settings and keep the requested flow within the realistic limits for the nozzle size, it runs flawlessly.

[EnoTheThracian]

I do not print ASA so it may be complete malarky:

Are you able to add a primitive cylinder or cube in parallel to your print where you set conditions for a 5+mm/s³ flow?
Of course, it depends on what is currently governing your prints flow.

&

[CamBo]

Sounds like you might be experiencing heat creep? I thought that was the purpose of the “enhanced” cooling head fan? Its supposed direct additional airflow across the hotend heatsink.

[user_3182160881]

@L0rdS474n: what would be a realistic limit for the 0.2mm nozzle or ASA from your point of view? The profile from Bambu ASA or Generic ASA are all set to 2.0mm³/s, I was down to 1.5 already?

@EnoTheThracian additional primitive would be no problem. Could you share some details why? I don’t get it yet…
@CamBo yes, this is my suggestion. This additional fan seems to suck air through the extruder and blow it straight down towards the bed. There is a small slot where the air comes out, which is located at the bottom side of the fan cover with a certain distance to the heat sinks. No glue if this supports somehow the airflow at the heat sinks…

[EnoTheThracian]

Sure, but as I mentioned, I do not print ASA so it may be completely off on a tangent.

From your description, I understood that you suspect heat creep as the root cause of your troubles. There are however only limited options and you have already tried to increase flow (i.e.: using increased filament flow to move heat away from the cold end of the hot end).
However, while 2.5mm/s³ is 25% more than your starting flow, it is still an extremely low flow.

If you are able to add a high(er) flow object, you could try to remove the heat build up in the cold section of the hot end in each layer. Unfortunately, I have no experience about what maximum flows are achievable before the extruder overload kicks in. The default max flows do appear extremely low to me though.
Similarly, while my X1 appears to share the melting chamber characteristics across nozzle sizes, I have not delved into these characters for my H2C.

Of course this neccessitates a few things:

• Increase filament max flow setting (not sure where the true max is for ASA with a 0.2mm nozzle though. You may want to run a max flow test for the nozzle with ASA.)
• Check flow for your part and, if needed, lower part speeds to bring flow back down to achieve the quality you need
• Add a primitive cylinder or cube with its own (high) speed and increased line width settings to generate a max flow driven slice. If large enough to “purge” a sufficient amount of heat/filament at each layer, you can counter heat build up in the cold end.

A completely different approach that was discussed in the forum a couple of years ago was to counter heat creep by providing additional cooling down the filament’s PTFE through a Y-splitter and a small compressor. Not sure if that went anywhere though. And what side effects are likely…

&

PS: I assume you dried the roll yourself? While I have no experience with ASA myself, other filaments tend to have very significant heat transfer difference between dry and moist.

[L0rdS474n]

You are referring to the MVS, right?
I am talking about the flow ratio.
For one of my PEBA filaments, I cannot set the flow ratio above 1, even though I would normally need around 1.2 to get correct wall thickness and dimensions. If I try to go higher, I get an extruder overload almost immediately.

So the flow ratio is the first thing I would verify.
MVS in Bambu Studio is simply an upper ceiling for volumetric flow, not a target; it is there to prevent the slicer from exceeding a safe flow rate rather than to actively push the printer to that value.

[user_3182160881]

@L0rdS474n mmh, Flow ratio is at 0.97. MVS limits the speed already, Layerheight is 0.15, which is quite high already for a 0.2nozzle. MVS at 1.7 limits the speed(set to 70mm/s) already. Do another test with higher speed. Flow test was somewhere at 4mm³/s…

@EnoTheThracian The part doesn’t limit the speed, so there should be no need for an extra primitive, right?

Thank you, guys.

[EnoTheThracian]

@user_3182160881

The part doesn’t limit the speed, so there should be no need for an extra primitive, right?

Well, if printing the part results in heat creep, we do need to think about either dumping that heat somehow and somewhere and/or about increasing hot end cooling.
Unfortunately, being an ASA print, it is also very susceptible to cooling and pauses.

That is why I proposed to consider a “heat dump” part using higher flows. However, I am wondering if a high flow prime tower could not also serve the same function. A pic of your slicer flow preview with a smooth timelapse enabled to force a prime tower could offer interesting insights.

May I also inquire as to the reason for using a 0.2mm nozzle?
Usually I use the small nozzles for great XY resolution but this does limit max flow and is usually associated with a lot of XY movement (unfortunately there’s no accounting for acceleration in the speed and flow previews). If you can afford a 0.15mm layer height, can’t you afford going to a 0.4mm nozzle with Arachne?

Gotta go. But maybe this describes better where my thoughts come from and what they intend to achieve: Extra primitive/prime tower: “Melt chamber heat through filament”, old idea about using a y-splitter and small (!) compressor: “Cold end cooling”. Again take it with a pinch of salt: I do not print ASA myself due to H&S (got the printers in my home office).
But you do not need any of that if you can go for a 0.4mm nozzle…

[user_3182160881]

@EnoTheThracian:
…well, did a test print again with higher speed. Now I see, the desired part limits the speed, as at higher speeds the edges are very poor quality and I understand the sense of a sacrifice part…
Yes, I always thought about bigger nozzle, but I try to print an rc airplane and I am not happy with the quality when using these active foaming filaments… Competitive Idea from weight and stability is ASA with 0.2mm nozzle.

let’s see, I won’t give up yet

[EnoTheThracian]

@user_3182160881

using these active foaming filaments

Oooh. I haven’t tried these yet. From what I read, they need a constant flow and speed print to ensure consistent foaming. Depending on the shape, that may actually be a factor in non-satisfactory prints with a larger nozzle?
And of course, starting to foam in the melt zone, flow is even lower in the cold end, aggravating heat creep.

&

[Bullocks]

I’d imagine constraining the nozzle’s egress [0.2mm nozzle] does some serious chaos to the foam expanding filament in the melt zone. If it can’t exit the nozzle fast enough, that gas and the nozzle is going to act like a choke, and try to propel the filament literally the other way, up and against the direction of the extruder. Overload indeed. OP didnt mention if he was using foaming or not but I would say NO for 0.2mm.

[user_3182160881]

…foaming materials, work quite well, I tried only 0.4mm nozzle there. When changing to H2D last year I need to lower the nozzle temperature to 225-227Deg to max foaming, which is a bit out of spec according to the OEM of the filament (~250Deg). The only reason I could imagine is the long hot section at these kind of nozzles. But things like overhangs or supports are really a mess compared to non foaming…
Comming back to the topic, I increased the flow (MVS to 4; speed to 120) and did again a pressure advance test which comes to much higher values than before, but with that the Part quality seems fine and it prints since 11h without any issue. Never thought that my past test of increased speed where just to conservative… Thank you guys for your input.

would it be possible to convince the slicer generating a purge tower with only one filament in use?

best regards

[EnoTheThracian]

Saw your other thread highlighting your contued troubles.

ASA with 0.2mm nozzle

Dear Babulab Team, I’ve been using an H2D for about a year now (~1,240 printing hours). The machine runs great so far, but there’s one thing I haven’t been able to figure out, and I’d like your help with it. I want to print a few lightweight parts made of ASA using a 0.2mm nozzle, but unfortunately, this usually results in under-extrusion, which causes the extruder motor to overload or the hotend to clog. The parts are quite large, so the print time ranges from 15 to 25 hours. The problem alw…

While I do hope that Bambu comes back to you with a workable solution, there’s this last-ditch approach I mentioned above.

@EnoTheThracian

A completely different approach that was discussed in the forum a couple of years ago was to counter heat creep by providing additional cooling down the filament’s PTFE through a Y-splitter and a small compressor.

I first came across this here:

Extruder cooling strategies?

I’d actually been giving this some thought. I tried doing PLA support on a PETG print and it gave me fits. The PLA would load in a printhead that had been printing PETG, in a build chamber that had been printing PETG, with predictable results. I was thinking I could force air down the tube the filament follows to get to the print head. It wouldn’t be a lot of air, but it would be cool air, and it’d vent right into the area where the filament usually blobs-out and jams the extruder. Something l…

And another quick mention (including product) here:

Heat Creep causing extruder blocks - "FIX"

@user_3026326371 The actual fix will be cool down the extruder but not affecting the chamber temperature. And the best solution I can find is to add an extruder cooler, I picked it up from x2hammer, it channels the air directly into the extruder by using the filament tube and cools the extruder ONLY. It simple solves my issue for good.

I think this is the one.
Extruder Cooler - Pioneer Edition - MartilloTech
A bit on the pricey side though. It’ll probably be much cheaper to get a simple fan, design a shroud to funnel the air into a PTFE and then route it through a dedicated Y-splitter straight to the extruder.

Unfortunately, that is the only case where I have come across this approach to counter heat creep.

&

Addendum: The E3D hotends appear to be better regarding heat creep in those posts above. While there’s no .2 available for the (yet), they also seem to cause a color issue for the nozzle detection.
The diamondbacks are however reported to be superior anyway. Quite pricey though.
DiamondBack HotEnd for Bambu Lab H2D, H2C, H2S & P2S – E3D

[user_3182160881]

@EnoTheThracian
Thanks for your input. This is what I had in mind. Did not know that there are products already…The Martillo Tech product is on the pricey side and the shipment to Germany is the next 60bucks…
I wonder how to thighten the tube on that side where the filament is comming from, this would have much less resistance for the air than the way to the print head and most of the air would go this way… The other thing is, the issue occurs in my case in the “cool side” of the hotend. Not in the extruder or die filament path in the print head. So I guess a separate air hose to the printhead for additional cooling of the “cool side” of the hotend could may also do the job…
An aquarium pump I do have here, with that I could play around a bit. Lets see.

best regards.

[EnoTheThracian]

@user_3182160881

I wonder how to thighten the tube on that side where the filament is comming from, this would have much less resistance for the air than the way to the print head and most of the air would go this way…

I think that is pretty simple. I assume you are (also) using a 4-in-1 connector? Or you can print a Y-splitter from MakerWorld. Both options give directionality to the flow so I’d expect the majority of the air to go towards the extruder. Of course, the problem is a bit further down, but the air will be significantly colder and I also do not think that you need a lot of airflow as you are already managing 15h.

@user_3182160881

So I guess a separate air hose to the printhead for additional cooling of the “cool side” of the hotend could may also do the job…

That is another idea which may very well be worth a try.
Do you have an H2S, C or D? I have a C so I know I could either use the other PTFE path or maybe the air assist tube and inlet of the Laser module. From what I see in the wiki, the S does seem to also have the inlet for the air assist tube.

&

PS: Habe mal auf Englisch weiter gemacht da es für andere vielleicht sehr interessant sein kann

[user_3182160881]

…its a H2D in my case. Yeah, lets stick to english here, otherwise we would miss some input most likely

[EnoTheThracian]

Sorry for the really, really late thought. But it is also really, really simple:
Have you considered countering heat creep by printing without the silicone nozzle sock? To increase overall hot end cooling?

I am currently addressing an in-print extruder overload issue with my .2 nozzles with PETG as a support interface. It stopped recurring quickly when I forgot to replace the silicone sock…

[user_3182160881]

thanks for the idea, and no, I did not tried this yet. I put it on my list…