# Problems with Cylinders (shelling and subtracting)

**URL:** <https://discourse.shapr3d.com/t/problems-with-cylinders-shelling-and-subtracting/346>\
**Category:** Modeling Questions\
**Created:** [August 12, 2016, 5:09am UTC](https://discourse.shapr3d.com/t/problems-with-cylinders-shelling-and-subtracting/346 "2016-08-12T05:09:39Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![giaa2](https://avatars.discourse-cdn.com/v4/letter/g/ea666f/32.png) [@giaa2](https://discourse.shapr3d.com/u/giaa2)\
**Post date:** [August 12, 2016, 5:09am UTC](https://discourse.shapr3d.com/t/problems-with-cylinders-shelling-and-subtracting/346/1 "2016-08-12T05:09:39Z")

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I’m trying to make a simple screw on cap for a cylinder shape

I’ve made a male screw cap (helix groove is extruded) now I’m trying to subtract that from the main cylinder to make a female (intruded groove) but I get an error message.

also when I try and shell a cylinder I commonly get an error message.

any help to avoid getting operation failure messages would be appreciated.

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**Author:** ![Istvan](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.shapr3d.com/istvan/32/23668_2.png) [@Istvan](https://discourse.shapr3d.com/u/Istvan)\
**Post date:** [August 12, 2016, 5:29am UTC](https://discourse.shapr3d.com/t/problems-with-cylinders-shelling-and-subtracting/346/2 "2016-08-12T05:29:03Z")

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Can you post a screenshot?

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**Author:** ![Istvan](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.shapr3d.com/istvan/32/23668_2.png) [@Istvan](https://discourse.shapr3d.com/u/Istvan)\
**Post date:** [August 12, 2016, 5:30am UTC](https://discourse.shapr3d.com/t/problems-with-cylinders-shelling-and-subtracting/346/3 "2016-08-12T05:30:51Z")

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One reason I can imagine is that one of the objects is a shell, and not a solid body (maybe you sweeped an edge instead of a face, or extruded the outline of a circle instead of a filling, etc.)

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**Author:** ![Istvan](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.shapr3d.com/istvan/32/23668_2.png) [@Istvan](https://discourse.shapr3d.com/u/Istvan)\
**Post date:** [August 12, 2016, 5:35am UTC](https://discourse.shapr3d.com/t/problems-with-cylinders-shelling-and-subtracting/346/4 "2016-08-12T05:35:26Z")

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Or if you have the PRO version and could post the .shapr file, then we could easily debug the issue. If you don’t want to post it in the forum, feel free to send me via email [istvan@shapr3d.com](mailto:istvan@shapr3d.com), and we will take a look at it. We handle you files confidentially.

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**Author:** ![giaa2](https://avatars.discourse-cdn.com/v4/letter/g/ea666f/32.png) [@giaa2](https://discourse.shapr3d.com/u/giaa2)\
**Post date:** [August 12, 2016, 5:43am UTC](https://discourse.shapr3d.com/t/problems-with-cylinders-shelling-and-subtracting/346/5 "2016-08-12T05:43:51Z")

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it was not a solid body.

thanks for the help