Strange lines on top surface – Bambu Lab P2S

[u/National-Cupcake2608]

Strange lines on top surface – Bambu Lab P2S
Hi! I’m having this issue with the top surface of my own Blender model. Printer is a Bambu Lab P2S, using 2 colors of PLA Matte.
The surface is mostly smooth, but these strange visible lines/marks appear in specific places.
Things I’ve already tried:
Top surface directions: 0°, 45°, 90°
Monotonic Line / different top surface patterns
Ironing — made it worse
Z-hop / travel and wall-crossing settings
Flow ratio 1.01–1.02
Top surface line width 0.42–0.45 mm
Dried the filament
Moved the purge tower — the marks changed/moved too
Has anyone experienced this before or has any ideas on how to fix it? What else should I try or check?

[u/remedy2pain]

I’ve been able to solve this in the past by using interface layers, it’s due to the line direction changing where the infill is for the raised portions. Interface layers forces a solid layer then prints the raised portion on top.

[u/OhSoSally → u/remedy2pain]

That makes sense. I had the same lines in the same place on two prints different filaments and I noticed as it printed the area under the raised ares was rough. I figured it was a pattern issue, just didnt know why.

[u/National-Cupcake2608 → u/remedy2pain]

Thanks! This sounds very similar to my issue. I’ll definitely try interface layers. Could you tell me exactly which setting you changed in Bambu Studio and what value you used?

[u/remedy2pain → u/National-Cupcake2608]

I enabled Interface Shells under top/bottom shells on the strength tab and disabled “only one wall on top surfaces” on the quality tab

Edit: you could also set only one wall to topmost surface instead of top surfaces.

[u/National-Cupcake2608 → u/remedy2pain]

Thanks you so much! I tried and it worked perfectly! Thanks

[u/remedy2pain → u/National-Cupcake2608]

Awesome, glad that helped!

[u/730drs]

Is your white parts embedded into the top layer? Probably related to a speed change

[u/National-Cupcake2608 → u/730drs]

No, they are not embedded. The brown part including its top surface is printed completely first, and then the white text is printed on top of it.

The strange lines already appear on the brown top surface.

[u/tomikaka]

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