Slicer not logical rendition with 1mm walls?

I am doing a design with walls around 1mm, and when i set the printer to 0.2 or 0.25 filament width, it prints empty walls with one layer of filmant at either side, amounting to 0.4 or 0.5 millimeters of plastic composing the entire wall.

If i put slic3r on 0.4mm width, it does Three!!! layers total instead of 2, with a perimiter and an infill line.

Why does 0.4 mm use 3 lines to make the walls, and 0.25 mm result in 2 and not 4 lines?


Edited 2 time(s). Last edit at 04/27/2015 05:07AM by skynetprinter.

Possibly due to rounding errors in Slic3r's computations. Another poster has however pointed out what appears to be a bug in that small gaps do not get filled if you have "detect thin walls" checked. So if you have that box checked, maybe try the same print with it unchecked.

Dave