# Extruding Shapes with Coincident Corners

**URL:** <https://discourse.shapr3d.com/t/extruding-shapes-with-coincident-corners/38800>\
**Category:** Modeling Questions\
**Created:** [July 18, 2025, 11:29pm UTC](https://discourse.shapr3d.com/t/extruding-shapes-with-coincident-corners/38800 "2025-07-18T23:29:33Z")\
**Posts on this page:** 5\
**Page:** 1

<div class="post-metadata">

**Author:** ![JonS](https://avatars.discourse-cdn.com/v4/letter/j/9dc877/32.png) [@JonS](https://discourse.shapr3d.com/u/JonS)\
**Post date:** [July 18, 2025, 11:29pm UTC](https://discourse.shapr3d.com/t/extruding-shapes-with-coincident-corners/38800/1 "2025-07-18T23:29:33Z")

</div>

When trying to extrude shapes from a surface by sketching a grid directly on a body and then extruding different cells, I found that when there are coincident corners, a separate body gets created. These bodies cannot be combined in a Boolean operation.

The only way I found to fix this was to create either a small gap, or an overlap to remove the coincident edges. On the actual model, this created a lot of model complexity that caused failure during modeling and had issues exporting to an STL (to solve the export issue I created a custom Resolution where I increased the deviation until it would export).

The issue occurs both on my iPad and my PC.

I’ve managed to work around the problem (for one object, I had to export to a different tool, perform some edits there and re-import as a mesh) and complete the project, but this is a significant limitation when trying to create a surface texture on objects.

Is this a known issue? Is there a fix?

The example attached here shows the issue on a simplified model.

[Extruding with Coincident Corners Issue.shapr](https://discourse.shapr3d.com/uploads/short-url/5Rvn46WiYP8sWeALKz1ezSIL4hI.shapr) (42.6 KB)

 ![IMG_0201](https://us1.discourse-cdn.com/flex002/uploads/shapr3d/original/3X/8/8/88e8dd2a24c87bdae656b90cbc55cedf234a57ba.jpeg)  
 ![IMG_0202](https://us1.discourse-cdn.com/flex002/uploads/shapr3d/original/3X/f/8/f884378955d1f02eda683152c951fd7f06537df9.jpeg)

---

<div class="post-metadata">

**Author:** ![SCALEMODEL](https://avatars.discourse-cdn.com/v4/letter/s/77aa72/32.png) [@SCALEMODEL](https://discourse.shapr3d.com/u/SCALEMODEL)\
**Post date:** [July 19, 2025, 12:11am UTC](https://discourse.shapr3d.com/t/extruding-shapes-with-coincident-corners/38800/2 "2025-07-19T00:11:56Z")

</div>

I believe you are creating new body, if you click on little box icon choose Union instead of New Body.

Also when you create a new box, its trying to also union with the box next to it with zero distance so you get an error.

 ![image](https://us1.discourse-cdn.com/flex002/uploads/shapr3d/original/3X/0/4/041f1a7b097bac3ee1dd7df539915bba221671a7.jpeg)

---

<div class="post-metadata">

**Author:** ![Xdrakosha](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.shapr3d.com/xdrakosha/32/24881_2.png) [@Xdrakosha](https://discourse.shapr3d.com/u/Xdrakosha)\
**Post date:** [July 19, 2025, 6:37am UTC](https://discourse.shapr3d.com/t/extruding-shapes-with-coincident-corners/38800/3 "2025-07-19T06:37:34Z")

</div>

> [@JonS](#):
>
> Is this a known issue? Is there a fix?

It’s a known behaviour. Non-manifold bodies not allowed in Shapr3D. Only thing you can do is modify these kind of objects as you’ve described yourself.

---

<div class="post-metadata">

**Author:** ![SCALEMODEL](https://avatars.discourse-cdn.com/v4/letter/s/77aa72/32.png) [@SCALEMODEL](https://discourse.shapr3d.com/u/SCALEMODEL)\
**Post date:** [July 19, 2025, 6:46am UTC](https://discourse.shapr3d.com/t/extruding-shapes-with-coincident-corners/38800/4 "2025-07-19T06:46:50Z")

</div>

> [@Xdrakosha](#):
>
> Non-manifold bodies not allowed in Shapr3D

Also every other 3d CAD program will give you this error as well. Note that screenshot was from FUSION 360.

---

<div class="post-metadata">

**Author:** ![JonS](https://avatars.discourse-cdn.com/v4/letter/j/9dc877/32.png) [@JonS](https://discourse.shapr3d.com/u/JonS)\
**Post date:** [July 22, 2025, 1:21am UTC](https://discourse.shapr3d.com/t/extruding-shapes-with-coincident-corners/38800/5 "2025-07-22T01:21:58Z")

</div>

Thank you all for the responses. I’m surprised I hadn’t encountered (or maybe noticed) this before.