# Trying to use Union to merge objects

**URL:** <https://discourse.shapr3d.com/t/trying-to-use-union-to-merge-objects/28859>\
**Category:** Modeling Questions\
**Created:** [November 11, 2023, 5:29am UTC](https://discourse.shapr3d.com/t/trying-to-use-union-to-merge-objects/28859 "2023-11-11T05:29:46Z")\
**Posts on this page:** 9\
**Page:** 1

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**Author:** ![Dayton3D](https://avatars.discourse-cdn.com/v4/letter/d/7bcc69/32.png) [@Dayton3D](https://discourse.shapr3d.com/u/Dayton3D)\
**Post date:** [November 11, 2023, 5:29am UTC](https://discourse.shapr3d.com/t/trying-to-use-union-to-merge-objects/28859/1 "2023-11-11T05:29:46Z")

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In the attached file, I have the four slices joined together by a cylinder at the top. I can use Union to join one slice with the cylinder, but after that all I get is “Boolean Operation Failed”. What am I doing wrong? All five objects intersect at the top.

[Support\_01.shapr](https://discourse.shapr3d.com/uploads/short-url/1niWb3FC9gkfweiJitBxE7qfbIJ.shapr) (18.8 KB)

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**Author:** ![TigerMike](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.shapr3d.com/tigermike/32/32650_2.png) [@TigerMike](https://discourse.shapr3d.com/u/TigerMike)\
**Post date:** [November 11, 2023, 6:14am UTC](https://discourse.shapr3d.com/t/trying-to-use-union-to-merge-objects/28859/2 "2023-11-11T06:14:08Z")

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For some reason Shapr3D does not like the sharp points. I don’t know if it’s a Parasolid issue or a Shapr3D issue. Anyway, it works if you extend the small cylinder upward above the sharp points.

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**Author:** ![Dayton3D](https://avatars.discourse-cdn.com/v4/letter/d/7bcc69/32.png) [@Dayton3D](https://discourse.shapr3d.com/u/Dayton3D)\
**Post date:** [November 11, 2023, 2:51pm UTC](https://discourse.shapr3d.com/t/trying-to-use-union-to-merge-objects/28859/3 "2023-11-11T14:51:59Z")

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Thank you Mike, good catch.

Another question related to this. I’m new to 3D printing, but before I made the cylinder and the slices monolithic and exported it to the printer, the slicing algorithm didn’t require supports, but now it does. No big deal, other than a waste of filament. Do you see anything obvious I could change to avoid this? It added support under the peak.

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**Author:** ![TigerMike](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.shapr3d.com/tigermike/32/32650_2.png) [@TigerMike](https://discourse.shapr3d.com/u/TigerMike)\
**Post date:** [November 11, 2023, 5:25pm UTC](https://discourse.shapr3d.com/t/trying-to-use-union-to-merge-objects/28859/4 "2023-11-11T17:25:04Z")

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Do you intend to have that open dome feature throughout the platform? Meaning 12 domes instead of just the one at the corner?

If so, I would do a test print of the one dome corner without supports. If it prints fine, great. If it fails, which I think it will, do it again with supports. After that, remove the supports to see how well the underside is. If all good then do the final print of a 12 dome platform. The part is not very big and the amount of filament for supports is negligible in my opinion. Besides, a bit of wasted filament is worth the learning and experimenting experience. Good luck.

 ![test platform](https://us1.discourse-cdn.com/flex002/uploads/shapr3d/original/3X/c/f/cf0d1f7f0b10db044ce495963ad6de21f883a045.jpeg)

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**Author:** ![Dayton3D](https://avatars.discourse-cdn.com/v4/letter/d/7bcc69/32.png) [@Dayton3D](https://discourse.shapr3d.com/u/Dayton3D)\
**Post date:** [November 11, 2023, 5:38pm UTC](https://discourse.shapr3d.com/t/trying-to-use-union-to-merge-objects/28859/5 "2023-11-11T17:38:02Z")

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Sounds good, thank you. The dome will be in all twelve circles, but it’s a one time thing so I’ll leave the supports in. I just wasn’t sure if my drawing was flawed somehow, but after printing it, it seems rock solid.

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<div class="post-metadata">

**Author:** ![Dayton3D](https://avatars.discourse-cdn.com/v4/letter/d/7bcc69/32.png) [@Dayton3D](https://discourse.shapr3d.com/u/Dayton3D)\
**Post date:** [November 12, 2023, 4:14pm UTC](https://discourse.shapr3d.com/t/trying-to-use-union-to-merge-objects/28859/6 "2023-11-12T16:14:47Z")

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Mike, could you give me a quick explanation how you cut away that corner? I managed to do it, but it was a hack and I’m sure there is a better way.

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**Author:** ![TigerMike](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.shapr3d.com/tigermike/32/32650_2.png) [@TigerMike](https://discourse.shapr3d.com/u/TigerMike)\
**Post date:** [November 12, 2023, 5:24pm UTC](https://discourse.shapr3d.com/t/trying-to-use-union-to-merge-objects/28859/7 "2023-11-12T17:24:12Z")

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I created a couple of construction planes and used **Split Body**.

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<div class="post-metadata">

**Author:** ![Dayton3D](https://avatars.discourse-cdn.com/v4/letter/d/7bcc69/32.png) [@Dayton3D](https://discourse.shapr3d.com/u/Dayton3D)\
**Post date:** [November 12, 2023, 8:13pm UTC](https://discourse.shapr3d.com/t/trying-to-use-union-to-merge-objects/28859/8 "2023-11-12T20:13:28Z")

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Perfect, thank you. I’ve got to get better versed in construction planes.

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<div class="post-metadata">

**Author:** ![Dayton3D](https://avatars.discourse-cdn.com/v4/letter/d/7bcc69/32.png) [@Dayton3D](https://discourse.shapr3d.com/u/Dayton3D)\
**Post date:** [November 17, 2023, 5:45am UTC](https://discourse.shapr3d.com/t/trying-to-use-union-to-merge-objects/28859/9 "2023-11-17T05:45:25Z")

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Mike, another question.

In the model above, is there a way to grab the bottom edge of the slices and rotate them while leaving the top stationary, creating something like a pinwheel effect? Or is that something I would have had to plan for ahead of time?