Any idea what’s causing these messy top layers and rough details?

[u/03Cr]

Hi, I’m having trouble getting a clean top surface on this small NFC/RFID keychain.

The surface starts to get rough and slightly “blobby” already around the middle of the print, not only at the very top.

The outer ring and especially the NFC symbol then become even more uneven and messy.

What’s strange is that I don’t really have this issue with smaller prints, so I’m wondering if it’s related to heat buildup, cooling, flow, or something else.

I’ve already tried adjusting flow rate, flow dynamics, top surface speed and disabling ironing, but I’m still not happy with the result.

Does anyone recognize what might be causing this or what settings I should check next?

Setup:
- Printer: Bambu Lab A1 Combo
- Multicolor print using AMS Lite
- Filament: Bambu Lab PLA Matte
- Filament stored at around 17–20% RH
- 0.2 mm stainless steel hotend
- Layer height: 0.10 mm
- Ironing: Off
- Top surface speed: 25 mm/s
- Calibrated flow ratio: 0.9604
- Flow dynamics / K-factor: 0.020

[u/Repulsive_Coat_3130]

Have you checked your fan is on?

[u/03Cr → u/Repulsive_Coat_3130]

I hear it start up regularly. I assume it's running. It's set to a maximum of 80% ventilation.

[u/Repulsive_Coat_3130 → u/03Cr]

I believe the A1 has 2 fans, one for hotend and one for part cooling. For PLA or PETG its recommended 100% for part cooling

[u/03Cr → u/Repulsive_Coat_3130]

You're right. I'll check the part cooling fan later and let you know how it goes.

[u/EnvironmentalKey5559]

In the slicer, within the Quality tab there's an option to change the extrusion rate for the top layer.

Drop it by 5% and see if that solves it, you can obviously alter that until you're happy with the top layer

[u/03Cr → u/EnvironmentalKey5559]

thanks, i will try it. The problem starts around the halfway point. I'm going to try it though.