blocking travel through a void

[LoserProvocateur 0]

I'm trying to print propeller ducts (link below) where the outside tolerances are fairly lose, and a little bit of balled up TPU won't hurt anything. The inside tolerances however are critical.  The closer the prop can approach the duct, the more efficient the system is. 

I assumed this would be as simple as setting 'avoid printed parts' to off... but it seems that cura interprets this to mean the void in the duct is free to travel through.

Is there any way to block travel (and the associated stringing, and balling) through the voids in the ducts, and force travel to the outside of the part only?


https://www.thingiverse.com/thing:3351513

[geert_2 558]

In the older Cura-versions there was a setting "Combing" or something similar, which did exactly this: then the head would keep on already printed material, avoiding voids. I don't know about the most recent versions. Have you searched for that?

 

However, this will not prevent blobs in some materials (the PET that I have): material is accumulated on the nozzle during printing, and then it sags and is deposited on the print in a thick blob. If this happens near the edge, is will spread outwards. So you have to post-process anyway with some materials.