Layer starting at overhang issue

[mikk36 0]

Hey,

I noticed that at times, Cura decides that it's a good idea to start printing in plain air, which means that there are either worms sticking out of the printed object or support structure, that isn't really supporting, because its edge isn't where it's supposed to be.

I illustrate this with a small snapshot of the generated g-code.

http://dl.dropboxusercontent.com/u/54281287/curaOverhangLayerStartIssue.PNG

The issue is that when ending the retraction, the plastic comes out just a bit too late for it to grab onto the layer below it, so it'll just fall into the inner wall of the support structure, whereas if it started laying down the plastic in the same direction as the previous layer before it, it sticks just fine and it can end the layer just fine over the overhang.

Would it be possible (or is it already?) to force Cura to not start layers in such manner that it will lose the first segment until it reaches some previous layer in its path?

 

[gr5 898]

Your example shows bridging. Cura is starting a "bridge" right at a un-rectract. This is not common so it seems like a bug/feature that hasn't been thought about much in the past.

Cura doesn't always properly detect bridging. When it does, the behavior is a little different. I'm not sure if Cura failed to detect bridging here or if it *did* detect it but allows a un-retract. Daid will have to comment.

An obvious fix would be to add some infill. Also if you do thinner layers it might help on this particular design. Also doing a thicker shell (.8mm is two shell passes. Better than .4mm - one pass).

 

[mikk36 0]

That isn't bridging, that's support structure generated by Cura itself. The real model is the curved part on the right.