Hello,
I’m still a beginner in 3D printing and I’m really struggling to choose the right flow rate.
I printed PETG using 0.97 as the starting point “0” with Yolo from Orca.
The smoothest flow rate is +0.05 (so the flow rate is 1.02), but the edges are very rough.
Can you help me choose?
Thank you.
Hi, new to this software coming from Simplified 3D and printing since 2018. Is your z offset correct for your layer height? You need that to be correct before you can set Flow/Extrusion multiplier accurately. Also if there is a parameter for actual filament diameter in BLS that would need to be properly set to the measured average (with a caliper ) diameter of the filament being used at that time, as the thickness of the filament directly alters the amount of plastic output by the nozzle. BTW there will always be rough edges where the infill meets the perimeter as they must over lap for strength and you are changing direction of a thread of melted plastic. 
I have found perfectly smooth = slightly under extruded. In the past with S3D I would set the last top layer to 1% lower on the flow if I wanted it smoother as the rest of the layers under it would be well adhered, not sure how to do that in BLS as of yet.
Default bambu PETG flowrate is 0.95
I print PETG with flowrate 0.90
YMMV
I made a topic about the calibration a while ago but it seems the search isn’t great in providing the link…
With the Bambu pattern one should keep in mind that we talk about a BASIC check and that this check has some rules.
It is always best to do both rounds for the calibration, let me explain why >
The first round prints the patches around the currently set flow ratio, meaning it goes above and below it.
The second round however only goes down ! 
To get correct results try this>
From the first round select the patch where the infill lines are closed, have no gaps and that patch should either be right after one with a slight gap or if inconclusive go one higher.
Means you do not always go for the ‘best looking one’ …
You need the first patch to show slight over-extrusion if not fully conclusive or to be fully free of gaps between the lines - if in doubt use a good magnifying glass.
With the second round the flow will start with the value you picked in the first round and from there reduce the flow.
Means you should see the quality improve and pick the patch where the slight over-extrusion is gone but not the one where you can already see tiny gaps appearing between the lines.
Thank you all for your answers.
@user_3191070616
I’ve never adjusted the Z offset and don’t know how to do it. So I’ll have to look into that.
@simon14
It would really be under-extrusion for me
@user_3026326371
The patches I made were with Orca which does +0.05 to -0.05.
It is différent as Bambu does.
If you say so…
All I am saying is that the signs are clear, what you make out of the suggestions here is your decision.
I only said what I did…
If bambu calibration is better I an try this way 
