ASA with 0.2mm nozzle

Bambu Lab H2 Series Bambu Lab H2D
1

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 always occurs after a few hours of printing, usually around 8 or 10 hours. I suspect that the cold side of the hotend gets too hot, causing the filament to soften before the desired melting zone and get stuck.

Printing temperature is around 275°C, heated bed 90°C, and chamber 50°C. To counteract the filament heating (with some help of the members of this forum), I increased the print speed; the flow rate is now about 3.5 mm³/s. This allowed me to extend the time until under-extrusion to about 8–10 hours. I’ve even managed a 25-hour print this way, but the second print of the identical part stopped again after about half the print time due to a clogged nozzle.

The additional fan on the front of the print head is installed now, but seem to have no positive influence on that matter; I’ve tried various 0.2 mm nozzles, as well as different types of ASA. Unfortunately, without success. Can you please help me?

This problem only occurs with ASA using a 0.2mm nozzle; as soon as the nozzle is 0.4mm or larger, printing this material works without any issues. The cause appears to be a combination of heat (high nozzle temperature, high chamber temperature, high heated bed temperature) and the filament remaining in the print head for an extended period of time due to the small nozzle.

I’ve read that the H2D has a built-in compressor that blows dust away from the laser. Couldn’t you use this compressor to supply cooler air through a hose to cool the hotends? In my opinion, that would be more effective than this additional fan; the ambient temperature up in the chamber near the nozzle and the heated bed is likely much higher than the set chamber temperature and therefore cools less effectively than “cool” air from outside.

I would really appreciate some feedback. Thank you very much.
best regards

ASA, 0,2mm Nozzle, long prints, HOW?
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Sounds like heat creep. I would say that you just need to vent the heat from your printer, like by opening the door or something similar to stop it from getting too hot.

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…ASA needs stable temperature to handle the warping, so unfortunately this seems to be not an option.

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Most definitely should not open the door with ASA. It will cause it to warp (and emit styrene fumes into the room). For sure though it’s heat creep because of the 0.2mm nozzle. The time the filament stays in the melt zone is much higher than with a 0.4mm.

Try some of these:

  1. Drop nozzle temp to 260–265°C and retest, 275 is probably too high.
  2. Reduce chamber to 43-45°C
1 Like
5

I’m still new to 3d printing, but wouldn’t it be possible to add a pause in the gcode to cool the nozzle (keeping the chamber and bed temp stable) to address the issue? I know there may be adhesion issue when it restarts, but a slight bump in nozzle temp should help compensate, in my head at least. I know this is a bandaid fix, but if it saves a 20 hour print…

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@hyiger: thanks, and yes I did already, chamber at 45deg and the nozzle at 255 which was the lowest possible limit. This increased the warping a lot and the nozzle stucks even earlier. That is why I don’t think the heat creap is caused by the high nozzle temp, it seems for me more an issue of getting the heat away.
I mean the printhead and so the hotend cooling fan is located permanently at the hottest section of the chamber. The heat bed has almost 100deg all the time, the cooling fans blow air with above the chamber temperature and at some point the whole printhead is warmed completely, the extruder gears, the idlers, the filament and so on. This causes increased friction and than it stucks.
That is why I am thinking of how to get cooler air to the head, even at hot nozzle temps and chamber heating. Somehow the Bambu engieers did this for the laser, that is why I am hoping they will find a improvement quite fast…

@piefairy: every input is appreciated. Yypically you see a lot of signs of underextrusion before the stuck which ruins the print already before it stops…
This test was done inevitable, when the nozzle stucks and you are not directly near the printer. As the heat bed and the chamber keeps the temperature at that time, the toolhead is not cooling down. If you fix the stucked nozzle and extruder the same issue occurs only some minutes later. I see this as some kind of proove for the idea that the high ambient temp of the toolhead leads to this issue at low flow.

Thanks for your input so fare.
best regards.

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It would definitely also be worthwhile to keep monitoring the chamber temperature. 45C puts the printer in heating mode, meaning that chamber heating is switched off when chamber temp is reached, but it will not start cooling when the temperature rises above 45C.

I guess the temperature will eventually raise to 55C or maybe even higher.

Maybe placing the printer in a colder ambient environment would help to keep the chamber temperature stable at the given temperature.

Still, having the nozzle close to the build plate might make it hard to resolve this.

I had been thinking of increasing the flow rate, but have no clue if that would cause issues. The flow rate for 0.2mm is extreme low 2mm3/s for 0.2mm vs 20mm3/s for 0.4mm. I would guess 5mm3/s is still possible but never tested it.

A higher flow might help.

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Is there a reason for using such a small diameter nozzle with ASA? At lot of your issues could be solved just by increasing the nozzle size.

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@hyiger Yes, it needs to get as light as possible…

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Is this for a drone frame?

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Hi, no no drone frame, in this case a small RC EDF jet…

12

I would suggest this filament instead: ASA Aero | Bambu Lab US Store with a 0.4mm nozzle.

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@hyiger yes, I know this quite well, but I do not like it so much… Would need to adjust the Model, and even with two walls, if there is some low flow areas (horizontal faces,…) there will be defects due to the non constant flow, bridging or supports are quite bad as well. It’s quite good for simple objects from my point of view.

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I had permanent clogs or heat creeps with Bambu ASA, and tried to figure this out for six months. In the meantime, the whole problem was exactly the Bambu ASA filament.
After I switched to a common and cheap ASA filament (from Elegoo, to be exact), I never once had a problem. The prints are perfect, even with 0.06mm layer height (~0.7mm^3 flow) and 38 hours of a single print job.
(Also used the standard settings. “Generic ASA” filament profile, and “0.06mm High Quality” printing profile.)

Bambu ASA is neither dull in some places, causing under extrusion and later heat creep, or mostly full of impurities that clog the 0.2mm nozzle and even sometimes 0.4mm one.