Deactivate combing in first layer I noticed a problem with the combing feature. When I print the first layer with combing set to “not in skin” the extruder does not retract on the first layer. That leads to ugly oozing strings in the visible parts of the prints and also to other problems. E.g. if I want to print a model with tiny circles in the first layer (like for screw holes) the circles get easily pulled away because the extruder is not retracting. At first I thought I’m having sticking problems with the first layer, but I improved that a lot and my prints are perfectly fine now, when I turn off combing completely. In that case the extruder is retracting as desired and the circles stay in place. But turning combing off isn’t always a good option. Sometimes large prints take so much longer and may even have little marks in the visible surfaces where the retractions happened. So I don’t want to turn combing off completely just to be sure the first layer is okay. I saw this behavior with a lot of different models now, so I’m sure, Cura doesn’t always handle the first layer as skin. Setting combing to “not in skin” does definitely not help.

Here are two pictures of the first layer of a print. The first one with combing turned off. You can see the light blue travel lines which mean, the extruder is retracted.

And the second one with combing set to “not in skin” where you can see the dark blue lines. The extruder is not retracted there which produces the described problems.




Updated question to answer:

Thanks a lot for explaining that to me. But I’m afraid the problem still persists. The value of “retraction minimum travel” was at 0.8 mm, which should be fine I assume. Now I’ve set it to zero, just to be sure. The extruder does still not retract as you can see in the picture below. 



But when I turn combing off completely, the retraction is happening. So I think it is a problem with the definition of “skin” for the combing mode “not in skin”. The bottom layer doesn’t seem to be treated as skin. By the way, I’m running the latest version of Cura of course (4.6.1).
If you set it to Not in Skin it will not comb and as such it will retract. Retraction travel moves are shown as light blue lines


  Light blue are retraction moves.  Dark blue are non-retracting moves.  Both types are non-extruding moves.


In that respect you would expect that if you set Combing to Not in Skin, it will retract and move to the other position:



If you wouldn't comb at all, you would see the same:



If you would comb all layers, so no retractions, we would expect dark blue lines:



Basically, Cura does exactly what it needs to do as seen in the screenshots, I cannot place/reproduce the screenshots in the question. To explain this (as commented below by @R..) another setting or settings may have caused preventing retraction like the Retraction Minimum Travel (retract_min_travel) in Cura.