<p>Check your settings in the slicer software you use: if you look at the sliced print carefully, you see only one line in each layer that crosses the inner section. The lines are also yellow, not green. This strongly hints that these are movement commands, not actual print commands.</p>

<p>On the other hand, you might want to carefully check in blender: at times, the normals in places get swapped inside out and then mess up the whole geometry without being visible in blender. <code>Recalculate Normals</code> can fix that at times, other times choose the messed up vertices and <code>flip normals</code>.</p>

<p>Make sure not to include voids in the model.</p>

<h2>The model in question</h2>

<p>Looking at the model, I also spotted that there was a lingering solidify modifier. Applying that resulted in this:</p>

<p><a href="https://i.sstatic.net/kl2ol.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/kl2ol.png" alt="Shell within shell"></a></p>

<p>This is a particularly bad thing. Fixing is easy though: remove the offending inner vertices. </p>

<p><a href="https://i.sstatic.net/hsf0F.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/hsf0F.png" alt="16 verts in one point?!"></a></p>

<p>Atop that, the center points are a clustered mess of vertices - surely you want to merge them into just two vertices.</p>

<p>Applying the Boolean modifier <em>now</em> created a solid shell.</p>

<p><a href="https://i.sstatic.net/zeMTV.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/zeMTV.png" alt="solid shell"></a></p>

<p>Before exporting, all other items had to be removed (deleted), then the export gives this nice model:</p>

<p><a href="https://i.sstatic.net/0byhB.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/0byhB.png" alt="[Cura slice, no scaling"></a></p>

CC BY-SA 4.0
2019-02-19T18:05:34.053Z
I cheked the slice, they are not only movement, infact they are filled iside.
Marco
CC BY-SA 4.0
2019-02-19T18:06:47.987Z
I also recalculated normals but it still remain the error.. I have no idea, I drawed this project so many times.. please help.. (and tank you for suggestions)
Marco
CC BY-SA 4.0
2019-02-20T01:02:03.137Z
@Marco then please share the model
Trish
CC BY-SA 4.0
2019-02-20T08:27:52.390Z
I added a link at the end of question.
Marco
CC BY-SA 4.0
2019-02-20T14:04:35.983Z
@Marco I did what I could... and came up with a perfectly fine model with just a few little tweaks.
Trish
CC BY-SA 4.0
2019-02-20T15:23:59.820Z
tank you for your support. I did double solidify (I had a mesh with 2 lines), so I had the first "bad thing" you notified. excluding this, I had no problem to slice the model. I don't see the clustered meshes (Verts: 1/464). a part that, I'll retry the model to understand if the error was only the double lines-screw. tank you a lot, there was a long time that i tried to understand.
Marco
CC BY-SA 4.0
2019-02-20T15:25:49.350Z
@Marco the inner shell was connected to the outer via those vertex clusters, which made the object non-manifold. It was mainly the fix of the non-manifold that eased the problems, but the simplification of the surface does yield better slicing times.
Trish
CC BY-SA 4.0
2019-02-12T01:00:01.493Z
2019-02-20T13:44:02.950Z
2019-02-20T13:44:02.950Z
Trish
<p>I'm trying to draw a strange cup, with a kind of empty handle (actually, it's not a cup, but it looks like one).</p>

<p>I need to print this object with a 3D printer, so I exported the model to 3D printing software (Simplify3D) to obtain relative G-code for the printer.</p>

<p>I can correctly export (in .stl) both parts separately (cup [a] and handle [b]), and obtain a good G-code. But when I try to match the two parts with a boolean operation, the result becomes chaotic.</p>

<p>I've added a (G-code) picture to show how the slicer creates strange triangles inside the cup; I really can't understand how to prevent it.</p>

<p>I'm designing the print using the Blender 3D software modelling tool.</p>

<p><a href="https://i.sstatic.net/BUdsI.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/BUdsI.jpg" alt="on the left theG-code, on the right the Blender model. Note strange additions of triangles inside the &quot;cup&quot;"></a></p>

<p>I've <a href="https://ufile.io/0jr9n" rel="nofollow noreferrer">uploaded my file</a> for reference.</p>

<p>The file has the bezier curves from witch I do screws in the origin. the result that I'm trying to export in stl is on the side.
Note: to have correct dimensions, I scale the model after 90° rotation on x-axis (base on bottom for printing), I then change the scale to 1:10 (bigger model), before exporting as stl.</p>

<p>I would obtain a sort of vase with an empty handle (the cylinder should work as an hole).</p>

<p>here what I do:</p>

<ol>
<li>I convert curves to meshes</li>
<li>I screw the cup (360° y-axis)</li>
<li>I screw the handle (60° after rotation -30° on y-axis)</li>
<li>I solidify the handle</li>
<li>I add 2 operations to cup, (a) solidify, (b) boolean</li>
<li>to match the two solid I adjust the solidify (a) looking to boolean result of an intersection (cup to handle).</li>
<li>when I have the right overlapping I apply (a) solidify and then (b) union-boolean (cup to handle).</li>
<li>at the end I apply a difference-boolean modificator to cup/handle with cone, to create the hole.</li>
</ol>

<p>I hope someone should explain me what I am doing wrong. I have made a somewhat simpler version <a href="https://ufile.io/0jr9n" rel="nofollow noreferrer">here.</a></p>

CC BY-SA 4.0
2019-02-12T12:54:55.557Z
Answers could be better if you share the messed up model and G-code btw.
Trish
CC BY-SA 4.0
2019-02-12T16:10:39.770Z
Make sure there are no "rogue" vertices in your handle part before combining.  I don't know Blender, but I do know that in MeshMIxer, Boolean operations only work after running the "Make Solid" command on the parts to ensure proper Boolean logic.
Carl Witthoft
<g-code><stl><blender>
Boolean operation on two objects in Blender
Marco
# Boolean operation on two objects in Blender

(Asked by: username_0 on 2019-02-11)

I'm trying to draw a strange cup, with a kind of empty handle (actually, it's not a cup, but it looks like one).

I need to print this object with a 3D printer, so I exported the model to 3D printing software (Simplify3D) to obtain relative G-code for the printer.

I can correctly export (in .stl) both parts separately (cup [a] and handle [b]), and obtain a good G-code. But when I try to match the two parts with a boolean operation, the result becomes chaotic.

I've added a (G-code) picture to show how the slicer creates strange triangles inside the cup; I really can't understand how to prevent it.

I'm designing the print using the Blender 3D software modelling tool.

[![on the left theG-code, on the right the Blender model. Note strange additions of triangles inside the ](https://i.sstatic.net/BUdsI.jpg)](https://i.sstatic.net/BUdsI.jpg)

I've [uploaded my file](https://ufile.io/0jr9n) for reference.

The file has the bezier curves from witch I do screws in the origin. the result that I'm trying to export in stl is on the side.
Note: to have correct dimensions, I scale the model after 90° rotation on x-axis (base on bottom for printing), I then change the scale to 1:10 (bigger model), before exporting as stl.

I would obtain a sort of vase with an empty handle (the cylinder should work as an hole).

here what I do:

1. I convert curves to meshes
2. I screw the cup (360° y-axis)
3. I screw the handle (60° after rotation -30° on y-axis)
4. I solidify the handle
5. I add 2 operations to cup, (a) solidify, (b) boolean
6. to match the two solid I adjust the solidify (a) looking to boolean result of an intersection (cup to handle).
7. when I have the right overlapping I apply (a) solidify and then (b) union-boolean (cup to handle).
8. at the end I apply a difference-boolean modificator to cup/handle with cone, to create the hole.

I hope someone should explain me what I am doing wrong. I have made a somewhat simpler version [here.](https://ufile.io/0jr9n)

**Tags:** g-code, stl, blender
> **Comments:**
> **username_1**: Answers could be better if you share the messed up model and G-code btw.  
> **username_2**: Make sure there are no "rogue" vertices in your handle part before combining.  I don't know Blender, but I do know that in MeshMIxer, Boolean operations only work after running the "Make Solid" command on the parts to ensure proper Boolean logic.  

---

## 1 answers

### Answer by username_1 on 2019-02-12. Score: 1

Check your settings in the slicer software you use: if you look at the sliced print carefully, you see only one line in each layer that crosses the inner section. The lines are also yellow, not green. This strongly hints that these are movement commands, not actual print commands.

On the other hand, you might want to carefully check in blender: at times, the normals in places get swapped inside out and then mess up the whole geometry without being visible in blender. `Recalculate Normals` can fix that at times, other times choose the messed up vertices and `flip normals`.

Make sure not to include voids in the model.

## The model in question

Looking at the model, I also spotted that there was a lingering solidify modifier. Applying that resulted in this:

[![Shell within shell](https://i.sstatic.net/kl2ol.png)](https://i.sstatic.net/kl2ol.png)

This is a particularly bad thing. Fixing is easy though: remove the offending inner vertices.

[![16 verts in one point?!](https://i.sstatic.net/hsf0F.png)](https://i.sstatic.net/hsf0F.png)

Atop that, the center points are a clustered mess of vertices - surely you want to merge them into just two vertices.

Applying the Boolean modifier *now* created a solid shell.

[![solid shell](https://i.sstatic.net/zeMTV.png)](https://i.sstatic.net/zeMTV.png)

Before exporting, all other items had to be removed (deleted), then the export gives this nice model:

[![[Cura slice, no scaling](https://i.sstatic.net/0byhB.png)](https://i.sstatic.net/0byhB.png)

> **Comments:**
> **username_0**: I cheked the slice, they are not only movement, infact they are filled iside.  
> **username_0**: I also recalculated normals but it still remain the error.. I have no idea, I drawed this project so many times.. please help.. (and tank you for suggestions)  
> **username_1**: @Marco then please share the model  
> **username_0**: I added a link at the end of question.  
> **username_1**: @Marco I did what I could... and came up with a perfectly fine model with just a few little tweaks.  
> **username_0**: tank you for your support. I did double solidify (I had a mesh with 2 lines), so I had the first "bad thing" you notified. excluding this, I had no problem to slice the model. I don't see the clustered meshes (Verts: 1/464). a part that, I'll retry the model to understand if the error was only the double lines-screw. tank you a lot, there was a long time that i tried to understand.  
> **username_1**: @Marco the inner shell was connected to the outer via those vertex clusters, which made the object non-manifold. It was mainly the fix of the non-manifold that eased the problems, but the simplification of the surface does yield better slicing times.  

---

