Automatically turn on fan on overhang only?

Hi,

During the calibration process I had some issue with overhang that I solved adding a fan.
As I am printing ABS, I would like to turn on the fan only for overhang/bridge and not for the entire print.

Is there any option to do so in Slic3r, Cura, ou Kisslicer?

Thanks

link to slic3r documentation

Hi,

Thank you for answering.
You were right. At some point during the calibration process I modified the cooling settings of slic3r and it wasn't working correctly. I restore the defaults and here are the results:
from left to right: my old cooling settings (0.25mm), defaults slic3r setting (0.25mm), defaults slic3r setting (0.1mm)
from bottom to the top: 230°C, 225°C, 220°C, 215°C, 210°C, 205°C, 200°C (printing ABS)
Prusa I3 temp test by Ray Ishido, on Flickr
Prusa I3 temp test by Ray Ishido, on Flickr

Wow, I didn't realize the cooling settings made that much difference for abs. Out of interest, what settings were you using that produced the first print?

I used the same setting for the three prints (bed temperature at 120°C and noodle from 230°C to 200°C), except that the fan was turn off for the left one.

I added this fan duct as close as possible to the nozzle and set a min/max of 0%/100% in slic3r

I was worried that the extra cooling produces some kind of delamination or weaken the print but that wasn't the case.
The only care that must be taken is that the fan does not cool the bed more than 3°C. If that occurs Marlin stop the print. That's the reason why I configured the fan to be turned off for the first 4 layer at 0.25 and first 10 layer at 0.1

Thanks Ray, I'll keep this in mind for things to experiment with.

James.