# Unable to Shell 3mm due to "Self-intersection" on G2 Loft (plus potential asymmetry issue)

**URL:** <https://discourse.shapr3d.com/t/unable-to-shell-3mm-due-to-self-intersection-on-g2-loft-plus-potential-asymmetry-issue/40169>\
**Category:** Modeling Questions\
**Created:** [January 20, 2026, 10:05am UTC](https://discourse.shapr3d.com/t/unable-to-shell-3mm-due-to-self-intersection-on-g2-loft-plus-potential-asymmetry-issue/40169 "2026-01-20T10:05:22Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![gluhy](https://avatars.discourse-cdn.com/v4/letter/g/46a35a/32.png) [@gluhy](https://discourse.shapr3d.com/u/gluhy)\
**Post date:** [January 20, 2026, 10:05am UTC](https://discourse.shapr3d.com/t/unable-to-shell-3mm-due-to-self-intersection-on-g2-loft-plus-potential-asymmetry-issue/40169/1 "2026-01-20T10:05:22Z")

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**Description of the issue:** I am designing a protective wire cover for automotive use, intended to be 3D printed in resin. I require a wall thickness of approximately **3mm** to ensure durability against vibrations.

I am encountering a blocking issue when trying to apply the **Shell** command to my main body. The error message is: _“The face couldn’t be offset because the offset surface would result in self-intersection or regions of tight curvature.”_

**My Workflow & Goal:** I have successfully modeled this part before using a “messy” workflow (modeling the base and top as separate solid blocks with details, then boolean unioning them — see the attached **black render** ). However, for serial production, I am trying to optimize the workflow to be cleaner and more parametric:

1. Create the main form (Loft).

2. Shell the entire body.

3. Add cuts/details last.

**The Geometry Setup:**

- **Base:** A rectangular profile (dimensions are fixed as this is a press-fit connector for a plug).

- **Top:** A loft connecting the base face to a top oval sketch.

- **Loft Settings:** Start Continuity: None, **End Continuity: G2** , **End Magnitude: 2**.

**Observations & Questions:**

1. **Asymmetry:** When editing the Loft, I noticed that the white control points are **not symmetrical** left-to-right (see attached screenshot with control points). Could this slight twist/asymmetry be causing the Shell calculation to fail?

2. **Curvature:** Is the “End Magnitude: 2” creating internal geometry that is too tight for a 3mm offset? I am open to adjusting the curvature (G1 or lower magnitude) as long as the transition remains visually smooth.

3. **Best Practice:** Is my approach (Body → Shell → Details) the recommended workflow for this type of part in Shapr3D, or should I stick to my previous method of booleaning solid chunks?

**Attachments:**

- Screenshot of the Shell error.

- Screenshot of the Loft control points showing asymmetry.

- Render of the final goal (black part) created with the old workflow.

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**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:** [January 20, 2026, 2:01pm UTC](https://discourse.shapr3d.com/t/unable-to-shell-3mm-due-to-self-intersection-on-g2-loft-plus-potential-asymmetry-issue/40169/2 "2026-01-20T14:01:03Z")

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> [@gluhy](#):
>
> However, for serial production, I am trying to optimize the workflow to be cleaner and more parametric:
> 
> 1. Create the main form (Loft).
> 2. Shell the entire body.
> 3. Add cuts/details last.

Can you share the project with the “main form”, so I can try/play with it?

My quick tests show it can be done:

 ![image](https://us1.discourse-cdn.com/flex002/uploads/shapr3d/original/3X/b/b/bbe40af964ef61217f9404641ff149cf8baf4c1d.jpeg)  
 ![image](https://us1.discourse-cdn.com/flex002/uploads/shapr3d/original/3X/9/b/9b454560fe23b57357ba5a373580432f20e40610.jpeg)

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**Author:** ![Oregonerd](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.shapr3d.com/oregonerd/32/8012_2.png) [@Oregonerd](https://discourse.shapr3d.com/u/Oregonerd)\
**Post date:** [January 21, 2026, 12:01am UTC](https://discourse.shapr3d.com/t/unable-to-shell-3mm-due-to-self-intersection-on-g2-loft-plus-potential-asymmetry-issue/40169/3 "2026-01-21T00:01:42Z")

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Try the bottom section only, the one seen in the last pic. Then simply look inside and choose the face and extrude it out?

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**Author:** ![Oregonerd](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.shapr3d.com/oregonerd/32/8012_2.png) [@Oregonerd](https://discourse.shapr3d.com/u/Oregonerd)\
**Post date:** [January 21, 2026, 12:02am UTC](https://discourse.shapr3d.com/t/unable-to-shell-3mm-due-to-self-intersection-on-g2-loft-plus-potential-asymmetry-issue/40169/4 "2026-01-21T00:02:33Z")

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Like making a container then punching the bottom out.