<p>I have a Tronxy P802E, which works pretty well for me. I currently use Ultimaker Cura 4.1.0.  However, I occasionally get a weird problem where the walls in certain parts of certain prints will be highly porous.</p>

<p><a href="https://i.sstatic.net/RMI8x.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/RMI8x.jpg" alt="porous print wall"></a></p>

<p>Contrast the following similar, yet non-porous, structure elsewhere in the print:</p>

<p><a href="https://i.sstatic.net/VrYQ1.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/VrYQ1.jpg" alt="non-porous print wall"></a></p>

<p>(Note, though, that you can see porosity in the wall of the triangular structure on the right.)</p>

<p>I've printed this twice - once with retraction enabled, and once with retraction disabled.  Porosity occurred to the same degree, and <em>in the same places</em>.  It's neither a jam nor general underextrusion, because it occurred on every z-layer in the same set of xy places, but <em>not</em> in other xy places.  It makes me wonder if there's something about the order that Ultimaker Cura codes the structures to be printed in, that causes this problem - like if it's e.g. transitioning from one wall to an opposing wall after infill, triggers low extrusion, or something like that.  I further wonder if it's a problem in gcode or something that occurs in the physical act of printing.  Has anybody seen this before?  Have they solved it?</p>

<p>Oh, this may or may not be unrelated, but when I've watched the infill, I notice that there's frequently little gaps just before or after crossing another infill line.  I may make a separate question about that, eventually, if it's not related to this.</p>

CC BY-SA 4.0
2019-07-31T01:03:13.673Z
If it's random, it could be underextrusion as a result of the gear slipping or the filament being dirty, If it is always in the same zone, then it could be that the bed wasn't level.
user77232
CC BY-SA 4.0
2019-07-31T12:07:19.630Z
Could you please add some printing parameters like temperatures, speeds and e.g. filament type (PLA/ABS/...). Look into ["*Helpful Templates / Help us help you!*"](https://3dprinting.meta.stackexchange.com/questions/395/helpful-templates-help-us-help-you) for more hints to enhance your question with additional specific information.
0scar
CC BY-SA 4.0
2019-07-31T15:38:05.200Z
If it's always in the same part of the print,  go into Cura and select Layer View to see if the slicing algorithm is not producing a solid wall.  What you show looks almost like failed "bridging" of the roof surface there due to no wall at all existing beneath.
Carl Witthoft
CC BY-SA 4.0
2019-08-02T07:24:33.337Z
Try examining GCode in another software. But most software does not take extrusion into account. Ot might be possible for Cura to miscalculate extrusion in those places.
Cem Kalyoncu
<ultimaker-cura><underextrusion>
Walls are sometimes porous
Erhannis
# Walls are sometimes porous

(Asked by: username_0 on 2019-07-31)

I have a Tronxy P802E, which works pretty well for me. I currently use Ultimaker Cura 4.1.0. However, I occasionally get a weird problem where the walls in certain parts of certain prints will be highly porous.

[![porous print wall](https://i.sstatic.net/RMI8x.jpg)](https://i.sstatic.net/RMI8x.jpg)

Contrast the following similar, yet non-porous, structure elsewhere in the print:

[![non-porous print wall](https://i.sstatic.net/VrYQ1.jpg)](https://i.sstatic.net/VrYQ1.jpg)

(Note, though, that you can see porosity in the wall of the triangular structure on the right.)

I've printed this twice - once with retraction enabled, and once with retraction disabled. Porosity occurred to the same degree, and *in the same places*. It's neither a jam nor general underextrusion, because it occurred on every z-layer in the same set of xy places, but *not* in other xy places. It makes me wonder if there's something about the order that Ultimaker Cura codes the structures to be printed in, that causes this problem - like if it's e.g. transitioning from one wall to an opposing wall after infill, triggers low extrusion, or something like that. I further wonder if it's a problem in gcode or something that occurs in the physical act of printing. Has anybody seen this before? Have they solved it?

Oh, this may or may not be unrelated, but when I've watched the infill, I notice that there's frequently little gaps just before or after crossing another infill line. I may make a separate question about that, eventually, if it's not related to this.

**Tags:** ultimaker-cura, underextrusion
> **Comments:**
> **username_1**: If it's random, it could be underextrusion as a result of the gear slipping or the filament being dirty, If it is always in the same zone, then it could be that the bed wasn't level.  
> **username_2**: Could you please add some printing parameters like temperatures, speeds and e.g. filament type (PLA/ABS/...). Look into ["*Helpful Templates / Help us help you!*"](https://3dprinting.meta.stackexchange.com/questions/395/helpful-templates-help-us-help-you) for more hints to enhance your question with additional specific information.  
> **username_3**: If it's always in the same part of the print,  go into Cura and select Layer View to see if the slicing algorithm is not producing a solid wall.  What you show looks almost like failed "bridging" of the roof surface there due to no wall at all existing beneath.  
> **username_4**: Try examining GCode in another software. But most software does not take extrusion into account. Ot might be possible for Cura to miscalculate extrusion in those places.  

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## 0 answers

