External face not smooth

[dsanvito11]

Hi everyone,
I need help with my prints:
As you can see in the picture, the external face is not smooth and i can’t really understand why, i don’t know what to do.
In this case it was really evident, but sometimes it’s barely visible.
In the second picture you can se the object.

Thank you in advance for your help.

[mltriebe]

Slow down the outer wall to 100 or less and give it a shot.

[jonathansteury]

Hmm, that’s weird. I’ve had imperfections before too.