Which print head do you have? If it is the “standard” single extruder, print cooling is not the best with that one. There’s an “old” version and a “new” version, the new being distinguishable by two air intake slits at the front. The new is better, but according to some reports still not really good. For long bridges (i.e. filament printed without support beneath) not to sag, good cooling is required, and even then it will never be perfect. In case you encounter sagging bridges in a print where it counts, your options are:
- Get the dual extruder head - it has better print cooling. Expensive…
- Add a cooling fan to the print head - find all about it in this lengthy thread: 3DP Part Cooling Fan 5015 Replacement for Gen 1 extruder. Cheaper, but requires the willingness to tinker.
- Try going slower and/or colder
- EDIT: Forgot the obvious: Create support for longer bridges
Finally, I like this page to help with typical print issues: Print Quality Guide | Simplify3D Software