# Box in a box STL imports as only a single volume?

**URL:** https://www.simscale.com/forum/t/box-in-a-box-stl-imports-as-only-a-single-volume/84295
**Category:** Project Support
**Created:** [February 9, 2019, 2:13pm UTC](https://www.simscale.com/forum/t/box-in-a-box-stl-imports-as-only-a-single-volume/84295 "2019-02-09T14:13:53Z")
**Posts on this page:** 2
**Page:** 1

<div class="post-metadata">

### Author: ![mmathiasmeier](https://www.simscale.com/forum/letter_avatar/mmathiasmeier/32/5_5575768a8748004e209b776fc1b2916d.png) [@mmathiasmeier](https://www.simscale.com/forum/u/mmathiasmeier)
#### Post date: [February 9, 2019, 2:13pm UTC](https://www.simscale.com/forum/t/box-in-a-box-stl-imports-as-only-a-single-volume/84295/1 "2019-02-09T14:13:53Z")

</div>

I’m trying to do a simple CHT test, so I made a simple box in a box. I tried both splitting and not splitting the STL, but either way I get just a single volume so I can’t assign separate fluid and solid regions.

How can I make separate volumes?

Thanks

---

<div class="post-metadata">

### Author: ![jousefm](https://www.simscale.com/forum/user_avatar/www.simscale.com/jousefm/32/34908_2.png) [@jousefm](https://www.simscale.com/forum/u/jousefm)
#### Post date: [February 9, 2019, 4:30pm UTC](https://www.simscale.com/forum/t/box-in-a-box-stl-imports-as-only-a-single-volume/84295/2 "2019-02-09T16:30:07Z")

</div>

Hi @mmathiasmeier!

Can you share the project here? Makes it easier to make some suggestions on how you can proceed with your geometry.

Best,

Jousef