Strange perpendicular extrusions at the top and bottom of thin walls #1875

whosawhatsis opened this Issue Mar 29, 2014 · 3 comments


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I'm seeing these strange extrusion lines perpendicular to thin walls on the top and bottom layers. No idea where they're coming from, but they're putting weird edges on otherwise beautiful prints.

screen shot 2014-03-28 at 6 26 42 pm

STL, gcode, and profile:

@alexrj alexrj added this to the 1.1.1 milestone Apr 6, 2014
@alexrj alexrj added the Thin walls label Apr 6, 2014

Current master (maybe with last clipper fix) does much better job (no perpendicular artifacts), but there is artifact from medial-axis on both hollow cylinders - ends of extrusion do overlap.
gray is surface, green is medial-axis


Those artifacts kill thin-walled objects, because they're not buried inside the infill. I use a version of the classic thinwall box to verify the extrusion settings:
thinwall open box - 2 layers

That's cut down to 2 layers to reduce the clutter; normally it's 5 mm tall.

Slicing with either the default configuration or my usual one, using 1.1.1-dev (93f4fe0) produces the same extensions on one "corner" of the square:

thinwall open box - slice error layer 2

A detail view of that corner:

thinwall open box - slice error layer 2 - detail

This has become a showstopper for me, as many of the gadgets I build depend on thin walls. The binary 1.1.0 version doesn't run on Ubuntu 13.10 x86_64 (#1877) and binary 1.0.0 locks up solid with my usual configuration on that STL file.

Is there a workaround for this problem?

All the files are on my Dropbox account:

Thanks for any advice...

@alexrj alexrj modified the milestone: 1.1.2, 1.1.1 Apr 21, 2014
@alexrj alexrj modified the milestone: 1.1.3, 1.1.2 May 3, 2014
alexrj commented May 21, 2014

Fixed! And added a regression test.

@alexrj alexrj closed this May 21, 2014
@alexrj alexrj added the Fixed label May 21, 2014
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