Inside circle is not round in the toolpath preview. #2416

a4jp-com opened this Issue Dec 14, 2014 · 9 comments


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@alexrj alexrj added this to the 1.2.2 milestone Dec 17, 2014

I suspect this is intended behavior - outer surface perimeters end with a really tiny inwards movement to hide the extrusion end. Otherwise it tends to leave a noticeable seam on the surface which is problematic for dimensional accuracy.

As your part is just 5x5mm, the toolpath preview is magnified a lot...


This pattern would be on every layer if it was to hide the seamline but it is random and not on all layers or in the same place. My seam is aligned so if it was to hide the seam it should only be in one place.

Sometimes there is one bump but at other times two.

screen shot 12-21-14 at 04 21 am

screen shot 12-21-14 at 04 24 am


Well, in those images my guess would be polygon offset artefacts. Slicing vertical holes (or cylinders) at different heights will result in differently segmented circle polygons although they will have the exact same shape. The reason is that each square surface segment around a cylinder is made from at least two coplanar triangles (or even more, depending on the geometry of the model). Offsetting these irregular polygons several times can on some occasions produce artefacts like these..

alexrj commented Dec 20, 2014

Come on, those things are like 0.01mm...

alexrj commented Dec 20, 2014

(anyway, those are caused by the upstream -excellent- Clipper library, so that's not something I can fix myself)

@alexrj alexrj modified the milestone: 1.2.2 Dec 21, 2014

What is the web address of the clipper library?

Is it causing the problems with the lines going through the hexagons (honeycomb) as well?


The block.stl above is perfectly round.

screen shot 12-22-14 at 01 39 am

Slic3r 1.2.2-dev (2014-12-22nd 1:39 a.m.)

Just a note: The walking-machine.stl still has the problem.

screen shot 12-22-14 at 01 41 am

harriv commented Jan 6, 2015

Clipper library can be found here:

@alexrj alexrj added a commit that referenced this issue Jan 30, 2015
@alexrj Remove artifacts in original slices so that they're not amplified whi…
…le generating perimeters. #2561 #2416
alexrj commented Jan 30, 2015

Okay, these artifacts are now filtered out by Slic3r.

@alexrj alexrj closed this Jan 30, 2015
@alexrj alexrj added this to the 1.2.6 milestone Jan 30, 2015
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