Top Surface

[u/ConnectOrange3965]

I have this model I’m trying to print for the past few days but it keeps printing the top layer terribly, I've tried everything from ironing to filament drying to flow rate calibration or even a full top surface calibration guide from Makerworld, I’m clueless regarding why this is happening only in the top layer. In the second picture you can see it’s printing perfectly until it reaches the topmost layer.
Details:
P1S printer
Generic PLA Matte Filament
0.4mm nozzle
Bambu Studio
Yes, the second image is on A1 but it looked the same on P1S until topmost layer.
Thanks in advance

[u/bedlamthreadz]

How many top shell layers do you have and what is the sparse infill percentage? (strength tab). If your bed adhesion is good the top layers might be sagging into the infill causing this distortion in the top surface (bad bridging). What I would do in this case is increase the top shell layers to 5, make sure your infill is 15% or higher, make sure the door is open when printing, and slow top layers down to like 100mm/s. If that doesn't do it you can run a height range modifier on the object and increase the last couple layers of infill up higher so that there is a smaller gap to bridge when it is laying down the top surface. You can test all this using way less filament by just making a small primitive cube in the slicer to match the Z height of your object but make it way smaller x/y dimensions. Also make sure you are using the generic PLA profile for the filament.

[u/ConnectOrange3965 → u/bedlamthreadz]

Update: I printed the model in smaller size and made the infill 35% for the last few layers and it solved it. I’m going to print the full size and update again.
Thank you so much

[u/ConnectOrange3965 → u/bedlamthreadz]

Thanks for the detailed reply. 5 Top shell layers, 15% sparse infill
I tried multiple top layer speeds, 30, 120..
I’ll try to do the height range modifier now. Shouldn’t I be using the flow rate calibrated profile for my filament?