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The print is very solid except for the 4 walls.

From the top, I can slide a paper down to the bottom. This is ONLY between the walls, the rest of the print is solid. The filament is PLA 1.75 mm.

But the bottom is solid, no gaps.

I have checked the usual problems on Ultimaker troubleshooting photo gallery, but I can find anything similar.

Any advice to fix this would be very welcome.

3d print wall separation

Print settings:
cura settings 1 cura settings 2 cura settings 3

0scar
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theMouse
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6 Answers6

5

To fix this, I had results with the following way:

  • Change your extrusion width from being equal to your nozzle size (0.4 mm) to slightly larger (I use 0.45 mm). That way you better combat the shrinking of the filament.
  • Having the Print thin walls setting activated to force the printer to print intermediary walls if there are areas where less than the prescribed wall thickness for a single wall fills in spaces that are as a result of the wider outer walls left. The result for a 1.2 mm wall, the central part is a 0.3 mm zigzag.
  • Lower the extrusion temperature a tad as hotter filament shrinks more on cooling! For PLA about 200 °C is my sweet spot.

Additionally, there are extra steps that could be taken:

  • Finally, you could play around a little with the extrusion multiplier to try to get rid of the tiny bit of under extrusion you have.
  • Calibration could help too.
fractious
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Trish
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4

I've experienced this too, especially with flex modified PLA filament. For that, fixing underextrusion and increasing temperature made it go away. Sadly Cura has no option to overlap walls slightly (if printed in the right order, this could be done without affecting dimensional accuracy) except possibly the outer one, so you really have to get extrusion rate calibrated right or this will happen.

R.. GitHub STOP HELPING ICE
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4

Now that print settings are shared we can see that this problem is not related to too fast printing (only 20 mm/s) or too low print temperature (210 °C should get PLA fluid enough). To explain this, a low temperature and too fast printing cause under-extruded lines.

There are 2 other causes that might be worth investigating:

  1. Under-extrusion. From the top layers one can see that there may be insufficient material printed. Calibration of the extruder helps in this respect.
  2. Inaccurate positioning. This may for instance be caused by loose belts or a mechanical defect.
0scar
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0

Look for the horizontal expansion setting in Cura. By default it should be zero. The description includes this:

Positive values can help compensate for too big holes.

The "holes" here includes these gaps. You can set it to something very small (ie: .01 or .03, probably no more than .05) and that will likely be enough to get it to fill in those gaps.

Unfortunately, I only have a little direct personal experience with this setting, hence the probably/likely weasel words, and I can't give much real guidance on exactly how big or small you can go with this.

Joel Coehoorn
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0

I had the same problem, through multiple models and different brands of PLA. I fixed it by setting the Material "Wall Flow" parameter (both inner and outer wall) to 102%.

Note: The outside dimension is still accurate.

0scar
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user1493362
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-1

I know this is an old post but I had this problem in Cura 5.8 and found it was because I was using the concentric setting for my walls. It seems to be a bug in this version. I changed to lines and the problem went away. Before finding this was the issue I had tried upping my extrusion rates and line width all to no avail. Did not have this problem in previous versions. I wasted 4 rolls of filament on two bass guitar bodies before figuring this out.

Bill Hubbell
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