<p>It's not FreeCad, it is the shape you want to create. The wall has 1.0 mm thickness. I assume that you are using 0.4 mm nozzle. With default extrusion width of 0.45, you can get either 0.9 or 1.35 mm thickness, 0.9 obviously being closer to desired.</p>
<p><a href="https://i.sstatic.net/myU4v.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/myU4v.png" alt="1.0 mm wall width" /></a></p>
<p>The other issue is, there's no space for four perimeters. So, at the point where internal perimeters end, slicer need to move external perimeters closer together, to make them fuse properly. Thus, even at 0.5 mm extrusion width you will see this collapse. To prevent this effect, you need to either use smaller nozzle that would allow for internal and external perimeters to be continuous, or change your geometry to make it compatible with FDM process.</p>
<p>Note that, if you want consistent prints, you shouldn't set extrusion width (or wall thickness, or however it's called in your slicer) to the value lower than the diameter of your nozzle. Even making it equal is risky. For this situation, I'd suggest 0.2 mm extrusion width on 0.15 or 0.18 nozzle. Or redesign.</p>
<p><a href="https://i.sstatic.net/AuepV.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/AuepV.png" alt="Wall collapse" /></a></p>

CC BY-SA 4.0
2023-12-04T06:08:10.883Z
In case I change the wall thichkness in Slicer software to 0.2mm it eliminates the problem. Is that a wrong way to solve this?
Daniel
CC BY-SA 4.0
2023-12-04T06:12:46.137Z
@Daniel wall thickness needs to be slightly larger than nozzle diameter if you want a consistent print. The same if you are lucky and nozzle is extraordinarily precise. Thus, it is a good solution, but only if you will change nozzle to 0.2 or smaller.
Mołot
CC BY-SA 4.0
2023-12-04T23:20:51.217Z
@Mołot I don´t see problems using Simplify 3D, I can have a little air gap of 0.2mm using nozzle 0.4mm.
Fernando Baltazar
CC BY-SA 4.0
2023-12-04T23:29:38.183Z
@FernandoBaltazar if your prints looks good and fuse properly with extrusion width smaller than nozzle diameter, I really want to see them. Most people can't manage that.
Mołot
CC BY-SA 4.0
2023-12-03T19:33:08.103Z
2023-12-04T06:23:02.007Z
2023-12-04T06:23:02.007Z
Mołot
<p>I designed a basic structure with FreeCAD. For the base, I started with a 40x40 mm square:</p>
<p><a href="https://i.sstatic.net/vdza8.png" rel="nofollow noreferrer" title="Screenshot of FreeCAD showing a 40x40 mm square"><img src="https://i.sstatic.net/vdza8.png" alt="Screenshot of FreeCAD showing a 40x40 mm square" title="Screenshot of FreeCAD showing a 40x40 mm square" /></a></p>
<p>And I extruded it with 6.5 mm:</p>
<p><a href="https://i.sstatic.net/Ei3kD.png" rel="nofollow noreferrer" title="Screenshot of FreeCAD's Pad parameters dialog box with a 'Length' of 6.5 mm"><img src="https://i.sstatic.net/Ei3kD.png" alt="Screenshot of FreeCAD's Pad parameters dialog box with a 'Length' of 6.5 mm" title="Screenshot of FreeCAD's Pad parameters dialog box with a 'Length' of 6.5 mm" /></a></p>
<p>Then, I added a circle sketch with a radius of 19 mm:</p>
<p><a href="https://i.sstatic.net/OPyTo.png" rel="nofollow noreferrer" title="Screenshot of a FreeCAD sketch showing a circle with a radius of 19 mm"><img src="https://i.sstatic.net/OPyTo.png" alt="Screenshot of a FreeCAD sketch showing a circle with a radius of 19 mm" title="Screenshot of a FreeCAD sketch showing a circle with a radius of 19 mm" /></a></p>
<p>And applied 5.5 mm pocket:</p>
<p><a href="https://i.sstatic.net/AIdPJ.png" rel="nofollow noreferrer" title="Screenshot of FreeCAD's Pocket parameters dialog box with a 'Length' of 5.5 mm"><img src="https://i.sstatic.net/AIdPJ.png" alt="Screenshot of FreeCAD's Pocket parameters dialog box with a 'Length' of 5.5 mm" title="Screenshot of FreeCAD's Pocket parameters dialog box with a 'Length' of 5.5 mm" /></a></p>
<p>The end result looks good:</p>
<p><a href="https://i.sstatic.net/PDbka.png" rel="nofollow noreferrer" title="Screenshot of a square base with a circular recess 3D model in FreeCAD"><img src="https://i.sstatic.net/PDbka.png" alt="Screenshot of a square base with a circular recess 3D model in FreeCAD" title="Screenshot of a square base with a circular recess 3D model in FreeCAD" /></a></p>
<p>However, <strong>any</strong> slicer I know will produce a strange shape around the middle of the sides both inside and outside:</p>
<p><a href="https://i.sstatic.net/uKOTP.png" rel="nofollow noreferrer" title="Screenshot of a sliced model with unknown artifacts at the tangent edges of the circle and square sides"><img src="https://i.sstatic.net/uKOTP.png" alt="Screenshot of a sliced model with unknown artifacts at the tangent edges of the circle and square sides" title="Screenshot of a sliced model with unknown artifacts at the tangent edges of the circle and square sides" /></a></p>
<p>There is a 1 mm thickness there, so I don't understand why are those shapes presented.</p>
<p>I'm looking for:</p>
<ol>
<li>The reason for those failed shapes</li>
<li>The  solution to eliminate them (preferably without resizing either the square or the circle)</li>
</ol>
<p>I have provided the <a href="https://filetransfer.io/data-package/ohThffuy" rel="nofollow noreferrer">STL file</a> for analysis.</p>

CC BY-SA 4.0
2023-12-03T15:13:49.573Z
Can you include the Stl? As a link or, if it's small enough,  as a code block in the question ?
Mołot
CC BY-SA 4.0
2023-12-03T15:32:15.770Z
Also, include your slicer settings as these may be part of the problem.
agarza
CC BY-SA 4.0
2023-12-03T15:35:07.620Z
I tried more than 10 combinations of slicer settings, but those strange artifacts always stayed there. So, @agarza: if you have any idea on which settings worth trying, let me know please.
Daniel
CC BY-SA 4.0
2023-12-03T15:37:31.553Z
It could be a problem with the number of walls, the thickness of the walls, etc. Hence the reason for asking for slicer settings. We need somewhere to start.
agarza
<slicing><freecad>
Does FreeCAD produce a wrong stl for slicer software?
Daniel
# Does FreeCAD produce a wrong stl for slicer software?

(Asked by: username_0 on 2023-12-03)

I designed a basic structure with FreeCAD. For the base, I started with a 40x40 mm square:

[![Screenshot of FreeCAD showing a 40x40 mm square](https://i.sstatic.net/vdza8.png "Screenshot of FreeCAD showing a 40x40 mm square")](https://i.sstatic.net/vdza8.png "Screenshot of FreeCAD showing a 40x40 mm square")

And I extruded it with 6.5 mm:

[![Screenshot of FreeCAD's Pad parameters dialog box with a 'Length' of 6.5 mm](https://i.sstatic.net/Ei3kD.png "Screenshot of FreeCAD's Pad parameters dialog box with a 'Length' of 6.5 mm")](https://i.sstatic.net/Ei3kD.png "Screenshot of FreeCAD's Pad parameters dialog box with a 'Length' of 6.5 mm")

Then, I added a circle sketch with a radius of 19 mm:

[![Screenshot of a FreeCAD sketch showing a circle with a radius of 19 mm](https://i.sstatic.net/OPyTo.png "Screenshot of a FreeCAD sketch showing a circle with a radius of 19 mm")](https://i.sstatic.net/OPyTo.png "Screenshot of a FreeCAD sketch showing a circle with a radius of 19 mm")

And applied 5.5 mm pocket:

[![Screenshot of FreeCAD's Pocket parameters dialog box with a 'Length' of 5.5 mm](https://i.sstatic.net/AIdPJ.png "Screenshot of FreeCAD's Pocket parameters dialog box with a 'Length' of 5.5 mm")](https://i.sstatic.net/AIdPJ.png "Screenshot of FreeCAD's Pocket parameters dialog box with a 'Length' of 5.5 mm")

The end result looks good:

[![Screenshot of a square base with a circular recess 3D model in FreeCAD](https://i.sstatic.net/PDbka.png "Screenshot of a square base with a circular recess 3D model in FreeCAD")](https://i.sstatic.net/PDbka.png "Screenshot of a square base with a circular recess 3D model in FreeCAD")

However, **any** slicer I know will produce a strange shape around the middle of the sides both inside and outside:

[![Screenshot of a sliced model with unknown artifacts at the tangent edges of the circle and square sides](https://i.sstatic.net/uKOTP.png "Screenshot of a sliced model with unknown artifacts at the tangent edges of the circle and square sides")](https://i.sstatic.net/uKOTP.png "Screenshot of a sliced model with unknown artifacts at the tangent edges of the circle and square sides")

There is a 1 mm thickness there, so I don't understand why are those shapes presented.

I'm looking for:

1. The reason for those failed shapes
2. The solution to eliminate them (preferably without resizing either the square or the circle)

I have provided the [STL file](https://filetransfer.io/data-package/ohThffuy) for analysis.

**Tags:** slicing, freecad

> **Comments:**
> **username_1**: Can you include the Stl? As a link or, if it's small enough,  as a code block in the question ?  
> **username_2**: Also, include your slicer settings as these may be part of the problem.  
> **username_0**: I tried more than 10 combinations of slicer settings, but those strange artifacts always stayed there. So, @username_2: if you have any idea on which settings worth trying, let me know please.  
> **username_2**: It could be a problem with the number of walls, the thickness of the walls, etc. Hence the reason for asking for slicer settings. We need somewhere to start.  

---

## 1 answers

### Answer by username_1 on 2023-12-03. Score: 3

It's not FreeCad, it is the shape you want to create. The wall has 1.0 mm thickness. I assume that you are using 0.4 mm nozzle. With default extrusion width of 0.45, you can get either 0.9 or 1.35 mm thickness, 0.9 obviously being closer to desired.

[![1.0 mm wall width](https://i.sstatic.net/myU4v.png)](https://i.sstatic.net/myU4v.png)

The other issue is, there's no space for four perimeters. So, at the point where internal perimeters end, slicer need to move external perimeters closer together, to make them fuse properly. Thus, even at 0.5 mm extrusion width you will see this collapse. To prevent this effect, you need to either use smaller nozzle that would allow for internal and external perimeters to be continuous, or change your geometry to make it compatible with FDM process.

Note that, if you want consistent prints, you shouldn't set extrusion width (or wall thickness, or however it's called in your slicer) to the value lower than the diameter of your nozzle. Even making it equal is risky. For this situation, I'd suggest 0.2 mm extrusion width on 0.15 or 0.18 nozzle. Or redesign.

[![Wall collapse](https://i.sstatic.net/AuepV.png)](https://i.sstatic.net/AuepV.png)

> **Comments:**
> **username_0**: In case I change the wall thichkness in Slicer software to 0.2mm it eliminates the problem. Is that a wrong way to solve this?  
> **username_1**: @username_0 wall thickness needs to be slightly larger than nozzle diameter if you want a consistent print. The same if you are lucky and nozzle is extraordinarily precise. Thus, it is a good solution, but only if you will change nozzle to 0.2 or smaller.  
> **username_3**: @username_1 I don´t see problems using Simplify 3D, I can have a little air gap of 0.2mm using nozzle 0.4mm.  
> **username_1**: @username_3 if your prints looks good and fuse properly with extrusion width smaller than nozzle diameter, I really want to see them. Most people can't manage that.  

---

