Wall thickness/horizontal fusing

[ViennaBlood 2]

After some testing it appears that Cura is not fusing multiple walls properly.

I set the nozzle diameter to 0.4mm and extrusion width to 0.4mm. Then I set numer of walls to 3. This results in a calculated wall thickness of 1.2mm.

If I read the generated G-code correctly the traces for this wall are 0.4mm apart.

I also tried it the other way around: I set wall thickness to 1.1mm, with an extrusion width of 0.4mm (hoping this would cause cura to "crush" the walls together, fusing them). In the resulting G-code the walls are 0.4mm apart, producing a 1.2mm wall.

This means that if my extrusion multiplier is properly calibrated those 3 walls are barely touching. Test prints seem to confirm this - unless I set the extrusion multiplier to overextrude by more than 5% wall adhesion is very bad.

So it seems Cura is relying on overextrusion and/or wobble to fuse the walls.

Slic3r seems to do this differently and offers a very good explanation of this problem here: http://manual.slic3r.org/advanced/flow-math (sections "Extruding on top of a surface" and "Spacing paths")