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This has happened a few times whenever I print with the white PLA (Hatchbox 1.75 mm). It seems that the print job produces smooth sidewalls for most of the part but at a certain point and above, the walls become rough as if the alignment is off or something. I've attached a picture to show the issue. Does anybody have any insight?

Problem demonstration

I'm using a Printrbot Simple Metal and some of the print settings are listed below:

  • Slicer: Slic3r
  • [First] Layer height: 0.2 mm
  • Perimeters: 2
  • Solid Layers [top/bottom]: 3
  • Infill: 25%
  • Fill pattern: Rectilinear
  • Top/Bottom Fill pattern: Concentric
  • Perimeter speed: 30 mm/s
  • Infill speed: 80 mm/s
  • Travel speed: 150 mm/s
  • Acceleration (perimeters): 1000 mm/s2
  • Acceleration (default): 3000mm/s2
  • Default extrusion width: Slic3r chosen
  • Print temperature: 220°C

I've noticed in the Slic3r rendering that the affected area seems to be the point where the infill switches from 25% to solid as seen in the included picture. If this is the problem, is there any way to enforce solid infill a few layers below this to eliminate the awkward transition, or specify a smaller extrusion width at this point?

Screenshot of infill switch

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  • $\begingroup$ Thanks for the suggestions Itamar Green and lz42. I went back and printed the top of the part (slicing just below the referenced area in the Slic3r preview above) after lowering the print temperature to 210 degC and tweaking some Slic3r settings until the extrusion path appeared continuous on each layer (unlike above). I also changed to concentric fill pattern from rectilinear and adjusted the infill width until the preview artifacts disappeared. I think the modifier mesh approach would be best to fine tune the parameters as necessary for different layer regions so I accepted lz42's answer. $\endgroup$ – Ryan Neph Feb 20 '17 at 19:28
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If you want to change settings on some area of your part check out modifier meshes in Slic3r.

It looks like to0 much heat is delivered when solid infill starts and some melting occurs. See 3D Printing Problems #22: Extrusion Temperature Too High.

You can try:

  • Lower extrusion temperature
  • Lower filament flow
  • Improve part cooling
  • Lower print speed
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  • $\begingroup$ wow, I had always wondered if that type of setting override was possible in slic3r but I guess I never looked hard enough. Thanks for the tip on modifier meshes! I'll do some test printing to check my temperature setting too and update this post when I have some conclusions $\endgroup$ – Ryan Neph Feb 19 '17 at 16:09
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Slic3r has an option of

Solid infill threshold area 

which is the area that when you pass it (and start printing smaller than it), the infill becomes solid.

If you set it to a smaller number (or 0), then your infill won't become solid and the problem will vanish.

Source: Slic3r Manual - Infill Optimization

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  • $\begingroup$ That's definitely a useful suggestion @Itamar Green. For this part I tried settings with 100% infill and concentric fill pattern and the pictured area still has an awkward transition where the software tries to adjust the infill width to fill with a single extrudate instead of the two extrudates for the layer before it. I'll keep this tip in mind in the future though. $\endgroup$ – Ryan Neph Feb 20 '17 at 19:42

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