RE: Print Scar ... What's the reason?
That is the z-seam, created when the nozzle moves from layer to layer with FFF printing. You can adjust the position under Print Settings->Advanced->Seam position. Aligned and Nearest will attempt to tuck it into a corner, but on cylindrical prints, it has to go somewhere. Rear will align it on one side where it might be hidden or sanded after printing. Random distributes it around the print, but often creates unsightly zits.
If you calibrate your slicer filament settings, you may be able to reduce the size of the seam. It looks like you're over-extruding a bit which accentuates it.
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RE: Print Scar ... What's the reason?
@bobstro
Wow, that was a stunningly informed reply. Thank you!