As you can see in the photos attached, I have the problem that – repeatedly – the surface looks like that. Lowering the flow rate didn’t help. When I print it in Silent mode, the problem is a little bit less, and a mess when printed in sports mode.
I use extrudr PLA with standard settings.
Hi @Engineer,
I have some doubts/comments to try to help:
If you watch the printer laying it’s lines, you’ll see why the finish is the way it is. The filament normally doesn’t have time to dry fully before the next line is laid, so they merge together well and look smooth. However, when there are holes to negotiate, the slicer chooses to stop the long lines and go around the hole. This means the filament dries fully before the nozzle continues with the rest of the long lines, which causes a visible break in the finish. Apart from slowing down the top layer a lot, you could try adjusting the top layer line width.
Thanks so much for your answers.
What helped is lowering the temperature. A decrease of 10 degree significantly helped.
As it helped to lower the temperature my guess is that there are heat spots, but I don’t understand why. If it is too hot, shouldn’t the whole surface be bad? Moisture I think can’t be the reason since the problems always occur at the same spots.
I’m having similar problems with my top layers right now; three weeks ago everything was perfect. I’m using the same files, with the same variety of PLA filaments. It cannot be that they have ALL need drying all of a sudden (and some of this stuff I have had for months; other rolls are brand new - but ALL behave the same way).
Printing more slowly doesn’t really help - the two attached pictures were printed on the SLOW setting after having similar problems with NORMAL.
Your issue looks different from mine, as my surface is mostly great but only bad in spots. So to avoid any confusion it is better to create an own thread for your issue 
From what it looks like I would say it is over-extrusion.
Ok. Now it is clear the issue cause.
Solution: try printing using the Generic PLA (not for Bambu Filaments) filament preset without any changes. Depending on your goals requirement, you may fine-tune afterwards.
Cause:
The issue is in maximum volumetric flow rate, which BL denominates as “Maximum Volumetric Speed” and cooling, specifically the “Layer Time”. Bambu Lab’s filaments are optimized for high-speed prints, so their presets are typically unsuitable for third-party filaments. I advise you to start with the generic filament presets and fine-tune them if necessarium.
To clarify the magnitude of physical properties differences, the melt flow rate (MFR) of Extrudr PLA is 5 g per 10 min, whilst Bambu Labs PLA Matte is about eight times higher (39.4 g/10 min).
Thanks for your detailed answer. And you’re right: Changing the preset to Generic and only a bit fine tuning (lowering the temperature about 5 degrees and increasing flow rate only a little bit) brought great results.
If you reverse the lay down order and make the perimeter last from outside to in and you won’t have those lines as prevalent
The thing with these printers is since they are very fast do this sometimes.
Some filaments don’t like fast printing, I turn the heat up a few degrees, and watch the print for a few runs and see if it is straightening out. If not then it sucks but I may seem that print as messed up and try adjusting flow.
But once I get it then pretty much I know with that filament it should stay
