TLDR: don’t put too much trust on bambu profile and filaments…
I trusted Bambu too much for their profiles and filaments, then I got this with PLA Matte, Desert Tan, which is freshly dried at 55C for 8Hrs :
The walls are perfect, the bottom layers are perfect, it’s just the top layer that is underextruding by a visible amount.
- I initially thought that it might be my HF nozzle finally had some clogging after I abused it so much with all sorts of CF/GF/Sparkling… filaments. So I did lots of cold pulls to clean it thoroughly.
No, the problem continues.
- Then I swapped to a relatively unused HF nozzle.
No, the problem continues.
- I re-did the K value tests manually, got 0.021 which is reasonable and close to default value.
No, the problem continues.
- I measured the filament’s size with Mitutoyo caliper, 1.73mm, not bad. 1.73mm means that the flow would be 97.7% of what it’s meant to be. So you need to boost up the flow ratio. 1.73/1.75 = 0.98857, square it you get 0.97727, and flow ratio = area size length of extrusion, and area size we have right now is 97.7% of what it should be, so flow ratio needs to be boosted.*
No, the problem continues.
- As a desparate grasp, I tried to do the flow calibration on the A1 mini which is using a H2D standard 0.4mm nozzle. This is to rule out if I have anything mechanically wrong with my H2D.
No, the problem continues, even on the A1 mini. But the relief is that at least it’s not my extruder giving up.
- I tried to print with PLA Basic then.
The problem disappeared. So it’s the filament all along.
It’s super weird, but I guess the moral of the story is, don’t put your trust on Bambu’s filaments and profiles too much, do your own flow rate calibration… I guess.
Also this is a quite common issue for PLA Matte it looks, I asked around and some others are having similar issues with PLA Matte. Is the default flow rate too low?
(my manually calibrated flow rate is 1.01)
Similar here. In my case it’s - educated guess - friction inside the tubing and some residue of previous prints with Bambu Silk+ or PETG HF (I know > cold-pull… ). However, sometimes the H2D isn’t in the mood of printing…
I have been having the same issue with gray PLA Matte. I didn’t realize it was an issue with matte material specifically. I ended up going to 1.03 and it mostly went away, but randomly crops up.
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Not the friction, I printed on a1 mini with the filament wedding almost directly to the tool head with very short tube, still the same result. Then I boosted the flow rate to 1.01, everything is fixed.
Unfortunately, yes — you’re confirming what I’ve been saying for a while: everything related to Bambu Studio and the H2D has only been vaguely sketched out by BambuLab, from filament calibrations to print profiles, both generic and Bambu’s own. And on top of that, they think it’s a priority to integrate paid services like Helio. Poor us…
I don’t think it has anything to do with H2D. It’s the same on other machines.
Sure and I understood your message.
Was simply sharing what I discovered in my specific scenario, which is tubing and the mood of my printer 
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I have been having the same issue, 3 different PLA matte rolls.
It looks like they noticed too, default FR for Matte on X2D is now 1.006.
but ONLY for the standard nozzle with standard extruder. The other 3 - remains at 0.98. @SupportAssistant I wonder if this is an error?
Same man. Specifically the matte gray too. I have used matte black and no issue. Any pla basic, metal, pla+ no problems either which is why I thought it was me. Spent the last 2 days ruling everything out from nozzle clog, extruder gear, filament path constriction, ensuring my filament is dry, eventually checking other PLAs again and it runs perfect and it’s not just a single matte grey roll either, I swapped out through 2 other matte gray rolls just to see and same result. Just finished flow rate calibration and bumped it from current default P2S profile of 1.02 to 1.0666. Much Better, but still some minor gaps between the fill lines and the walls especially near corners on the first layer so bumping initial layer flow rate up 2%. Never once in my 3 years of using almost exclusively Bambu printers and Bambu filaments has this happened I have always been a big proponent and supporter of bambu default filaments settings for bambu brand filaments to be always spot on but it missed the mark by a lot on matte grey PLA.
