'extra perimeters when needed' always enforces minimum 2 perimeters #2395

curiouspl2 opened this Issue Dec 3, 2014 · 9 comments


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4 participants


Even on perfectly 90 degree perpendicular to surface objects, without infill 'extra perimeters when needed' does enforce minimum of 2 perimeters. disabling this option makes proper 1 perimeter part.


On which version of Slic3r are you seeing this behavior?


1.2.1 experimental

a4jp-com commented Dec 7, 2014

Can you try 1.2.2-dev?

a4jp-com commented Dec 7, 2014

Are you using Windows?

alexrj commented Dec 23, 2014

@curiouspl2, I can't reproduce this.
Can you provide all the usual information, with complete steps for reproducing the issue?



note this model also exposes problem with infill not anchored at perimeters (note how you can even see honeycomb infill from layers below visible in many places on screenshots)

infill problem


also a note - if external perimeter width is set above 0.8 , then everything is ok .
1.2.2 experimntal is also affected.

@alexrj alexrj modified the milestone: 1.2.3, 1.2.4 Dec 27, 2014
@alexrj alexrj modified the milestone: 1.2.4, 1.2.5 Jan 4, 2015

just tried 1.2.4 and it's also affected.
something is generally wrong about angle detection logic , because if you slice 25 to 40 fan adapter (rotated properly ofc) from here :

you get 1 perimeter result gcode file, even though it is not perpendicular to the table.
it has not very steep angle, but still it means not whole top layer lies on bottom layer, so
1)extrusion width is different - extrudate is not spreaded 100% like on layer directly below
2)bonding is very weak
3)with just a bit more steep angle effects of 1 and 2 will eventually grow enough to create holes.
'create extra perimeters when needed' theoretically should mediate that but there is no angle threshold.

extrusion compensation (the more angle the more extrudate) could help to gap this problem, and would also solve
but it is not currently implemented and even if it would be implemented - different printers with different nozzle sizes , extruder gear ratios and using various materials have various ability to overextrude - so the minimum angle varies across machine/material and should be tuneable anyway.

@alexrj alexrj modified the milestone: 1.2.5, 1.2.6 Jan 9, 2015
@alexrj alexrj modified the milestone: 1.2.6, 1.2.7 Jan 19, 2015
alexrj commented Feb 15, 2015

Good catch there. I reimplemented the detection algorithm for extra perimeters. Your test case now has the extra perimeters in a very limited number of cases, which makes sense. Further testing will tell us if this implementation is correct.
(The geometric definition of the extra perimeters logic is actually tricky since it's ambiguous)

@alexrj alexrj closed this Feb 15, 2015
@alexrj alexrj added the Fixed label Feb 15, 2015
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