[SOLVED]
The most likely cause was incorrect tensioning of the X-axis belt (at the same time I was doing a “extruder deep cleaning”, but it didn’t seem like anything was wrong there).
That’s probably why the arrangement of the PTFE tubes had an impact on the print quality - with a certain arrangement it reduced the stress on the X-axis belt…
not “SOLVED”…
yesterday it was printing perfect, today, the same again. The same files, the same filaments (PLA Bambu Basic) and again problems with bulging egdes and some other extrusion problems like on photos above. Im getting tired… I don’t know if it could be some filament feeding problem, so once it feeds correctly on a start then the whole print come ok, and if something happened during another filament feeding on starting next print then the prints come bad? I don’t know
I had the same issue,
You can do 2 things.
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Run manual flow calibration once, and check.
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Before printing the plate, in Bambu studio, there are checkboxes for bed levelling, timelapse etc, in that section, check flow rate calibration before every print,
it will fix the issue, as it fixed mine.
yes, this works and I keep doing this from two weeks (running “flow dynamic calibration” on EVERY print), the prints are usable using this metod -much, mych better than when printing with calibration off, but still not as good as it was before problem occur -still it is treating only the symptoms instead of the cause of the problem. Before it started every print was perfect -I was not able to see difference between prints from my X1C and these from A1 (I was not even use this flow calibration check box ever before these problems starts…). Now every time I forget to turn on this function before printing, the printout comes out very bad…
Hi @akkura, we have exactly the same problem with the X1C. Our printer is just 3 months old. We had just a few dozen operating hours when the problems started. Have you made any progress on this? What does Bambu Support say about the problems? We have tried almost everything to fix this bulging corners.
I have no other solution - I have to remember to turn on “flow dynamic calibration” every time… When this options is applied the prints are acceptable (still not as good as they were before). My X1C still prints perfectly -in my case problems occur on A1. Bambu support tries to make me as a cause of the problem… their “solutions” started to be repeated in my case log so I gave up for now (unfortunately there is no personal support member assignment to the case -any new response is made by different support member -sick!) -in short: clean and lube rails, run a full calibration, swap out the nozzle, reset K value setting, clean extruder, turn off/on flow dynamic calibration
Use OrcaSlicer, calibrate pressure advance using the top line calibrations and put the K value in the filament preset.
Once per filament.
You can uncheck the dynamic calibration at the beginning of every print because both Orca and Studio will use the value in the filament preset, ignoring any K value shown on the Device tab. Both slicers use the value in the preset - only OrcaSlicer lets you see and edit the value.
Here is my five cents worth in the hope to get you guys printing again:
Please DO a full manual filament calibration so the Bambu cube comes out flawless.
NOTE the nozzle temp, flow ratio and K-factor somewhere.
Print whatever you have to print - it should work for one or more prints until your problem starts again.
Now run the manual filament calibration AGAIN.
Not to fix the problem but to see which values have to change!
Why?
If it is neither the filament, nor the general print settings that chances are it is the hardware.
Use your callipers while doing these tests to keep an eye on the filament diameter.
Trust me: Really the last thing you want is wasting hours to fix an issue that is caused by the filament not keeping the specs…
So rule the filament out as the cause early on 
Assuming it is still the same roll, same model and all…
If you have to adjust the print temp or flow ration by meaningful amounts it could indicated problems with the hotend.
This thermal grease loves to dry out and then fail.
If in doubt take it out, clean it out and replace with fresh thermal paste!
Only takes 15 minutes and if you find dried out paste or that it already crumbles chance are you fixed the issue.
Another thing that is sometimes overlooked is the inside of the hotend.
We cold pull, we hot pull, but do we ever try to look inside ?
Sometimes you can spot like flakes baked onto the wall or after a decent solvent clean damages to the melting chamber.
Rare but it happens and can be checked while doing the thermal paste.
Ok, you tried all this, the calibration finally sticks but the print still fails 
What a bummer…
But if it does it should fail differently now.
Do an infill test, like 10% rectilinear with a 3mm high cube or such.
Observe those infill lines - they should be pretty much even and solid.
Being very thin, wavy or even interrupted in some areas needs fixing.
Lower the infill speed, increase the flow for the infill if you slicer allows for or until it looks like a proper infill.
Then do observe how the bridging layer on top solid infill is done.
The bridging should be rather thin and flimsy looking but it should be complete and damage free.
The top layers, especially the last one should be both gap free and free from signs of over extrusion.
If not try a flow ration calibration based on this rather than using the standard Bambu or Orca calibration.
Especially for foaming filaments or certain filled ones this way actually provides more accurate calibration results - in terms of layer binding and surface quality.
Some filaments just need some extra attention.
Last but certainly not least: Transport issues…
Those AMS feeders bite into the filament as much as the extruder does.
The filament is forced through the teflon tubes, around tight bends and sometimes through failing push connectors.
Severe print issues often comes down to worn out tubes, build up in the knurled transport wheels and such.
Replacing worn tubes and a bit of cleaning for those transporting parts often does wonders.
After all - it is consumables we need to keep an eye on…
Hi guys,
Another one with a A1 with the same problem.
When I bought it the 4th thing that I print I realize that I thave this kind of corners…
I want to print bigger things but I dont want to send to trash detailed designs just for this problem.
should i avoid doing autocalibration at the start of every print if im usin the same filament. My corners arent that bad but i still see some bulge.
could also changing the smooth coefficent in bambuslicer help with the corners so in theory the extruder has more time to react with movement if its more gradualy?