What is the Skirt Setting For?

[KenW]

I’m trying to get my head around the various options in Cura (and presumably apply to other slicers). In Bed Adhesion, there are choices of none, raft, brim, and skirt.

Raft I understand, and this seems to be the most reliable but also means the underside of the printed object needs some clean-up. It prints a platform for the actual print to stand on, creating a large surface area to grip the bed, and also (effectively) a buffer zone of (I think) four layers to iron out any first-layer print defects, and to even out irregularities in the bed surface.

Brim I understand, this creates a surround around the actual print, adding grip but without coming under the actual print so the underside is clean (surface of the bed notwithstanding). It stabilises the perimeter of the actual print by being in contact with it, and obviously consumes a lot less filament than raft.

Unless I’m mistaken, Skirt is a brim but with a gap surrounding the actual print footprint. I can see that eliminates any minimal clean-up of a brim, but I do not understand how (being not in contact) it can contribute anything to bed adhesion. My observation is that it prints the skirt, and then tries to print the perimeter of the actual print, but because there is nothing to constrain it the first line is very likely to pull away from the bed and corrupt the print (ditto the skirt itself, but that doesn’t matter so much).

What gives?

[CrazyIvan]

Build Plate Adhesion you mean.

Yes, I've just looked at the preview of my current project with it set to skirt, and I agree it does not seem to serve any useful purpose for my Tina2, with perhaps the exception that it gives the flow of filament chance to stabilise. I've noticed the first several inches of print tend to be thinner to start with, and the initial nozzle wipe it does is nowhere near enough to clean the barrel (as it were).

It would be good to get comments from users of other printers, with different experience.