Hello all, I am writing here to seek advice for rectifying scarring on top surface. This is a newly purchased Bambu lab p2s. I have tried below,
I don’t think this is caused by nozzle scratching the surface as it doesn’t align with the track path when I check in the Bambu studio slicer.
A bit overextruded, so that the second last layer flaw shows up on the last layer.
Just go underextrusion by a notch, like 0.95 down to 0.85 to see if there is improvement.
It looks like the lines are are where it stops/starts extruding areas as it goes around the part. You can look at the path after slicing by using the vertical slider on the right to get to the layer and moving the the slider at the bottom of the screen to see the movement. See if it prints to one of those spots then goes to another area and then comes back. You could try using the ironing function which may take some tuning, or you could flip it over so the top side is printed on the rebuild plate for a consistent look.
Wow this seems to work, at least major improvement. it seems better now that the scars which were original there are gone
but now I am under extruding at some areas, which made some new scars
Thanks for the advice. I checked the travel path and noted that the scars do not match it. I want to see if I could solve this issue through tweaking print parameters before touching on ironing. I’m afraid activating ironing will bring a new batch of issues haha.
Now then you go half a notch, like 0.9.
If you want a bit more, you can go up / down quarter of a notch (+/- 0.025) for much better flow ratio.
Basically, you are doing fine tune (people call it calibrate) filament as you go.
You can use Orca calibrate feature to fine tune flow ratio. People recommend to calibrate filament for every single spool for the best result.
Just notice there, it goes half a notch for each piece there.
Since the geometry of those flat pieces are not exactly like the real part, I find that the calibration result is not really 100% correct for real part but most of the time good enough.
You have to take into account the tolerance of filament diameter 1.75 +/-0.05 for conventional spool. I think it’s 1.75 +/-0.03 for BBL filament. That is around +/- 3% error and +/- 2% error. So, that the flow rate 0.95 could be 0.98 for this small section but 0.92 for another section of the very same spool.
This is why you can’t control of the outcome of the top surface completely, it is either just good enough or absolute perfect. It’s like more depending on luck than skill 
Thanks so much for the detailed guidance. Once I have the time I will try it out and report back here 
