# CAD editing

**URL:** <https://www.simscale.com/forum/t/cad-editing/99703>\
**Category:** Using SimScale\
**Created:** [January 20, 2025, 9:54am UTC](https://www.simscale.com/forum/t/cad-editing/99703 "2025-01-20T09:54:42Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Leen\_Mohamed](https://www.simscale.com/forum/letter_avatar/leen_mohamed/32/5_5575768a8748004e209b776fc1b2916d.png) [@Leen\_Mohamed](https://www.simscale.com/forum/u/Leen_Mohamed)\
**Post date:** [January 20, 2025, 9:54am UTC](https://www.simscale.com/forum/t/cad-editing/99703/1 "2025-01-20T09:54:43Z")

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why do i always get error messages when i edit like no solid body or the facets error i have tried importing in many formats.

 ![image](https://www.simscale.com/forum/uploads/default/original/3X/c/9/c9dbadf4ac3c8352d674c03739a037abed979e71.png)  
 ![Screenshot 2025-01-17 201623](https://www.simscale.com/forum/uploads/default/original/3X/c/a/ca0fa9093a319cf4dc11be7775dd92b978b69edc.png)  
like these

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**Author:** ![nelta](https://www.simscale.com/forum/letter_avatar/nelta/32/5_5575768a8748004e209b776fc1b2916d.png) [@nelta](https://www.simscale.com/forum/u/nelta)\
**Post date:** [January 20, 2025, 11:23pm UTC](https://www.simscale.com/forum/t/cad-editing/99703/2 "2025-01-20T23:23:08Z")

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Perhaps the following will be useful:

There are two main rules which are crucial for any flow simulation:

1. Your CAD needs to be watertight: There must not be any holes except inlets and outlets.
2. Your CAD must only contain solid parts. Shells or Sheets must not appear.

Note: A sheet is a CAD geometry that is missing one or more faces.  
In other words,

> [@I cant create the External Flow Volume Mesh](https://www.simscale.com/forum/t/i-cant-create-the-external-flow-volume-mesh/93932/4):
>
> In short, a sheet body is a non-watertight geometry. It consists of faces only, and it’s completely hollow inside (i.e. it has no volume).

A few ways to do the CAD cleanup:

> [@No Solid Body](https://www.simscale.com/forum/t/no-solid-body/96093/2):
>
> - Remove small parts
> - Join surfaces
> - Create enclosed volumes from the surfaces

Also, try to import your model in a different file format. STL files are not recommended (unless for LBM or PWC simulations).

These documentation pages are useful for learning how to properly set up a CAD model :

> **[How to Find Faults in the CAD Model? | SimScale Knowledge Base](https://www.simscale.com/knowledge-base/how-to-find-faults-in-the-cad-model-2/)**
>
> This article describes some general CAD Requirements for CFD simulations and best practices on how to find faults in CAD models.

> **[CAD Preparation & Upload | Simulation Setup | SimScale](https://www.simscale.com/docs/cad-preparation/)**
>
> Learn everything you need to know about your CAD preparation and upload it into SimScale with our documented guide. Get started today!

and perhaps,

> **[CAD Mode | CAD Preparation & Upload | SimScale](https://www.simscale.com/docs/cad-preparation/cad-mode/#close-sheet)**
>
> SimScale offers a dedicated environment to interact with your CAD model and perform certain operations referred to as 'Edit in CAD mode' or 'CAD mode'.

although it may be better to fix the issue using the same CAD tool used to generate the geometry.

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**Author:** ![igaviano](https://www.simscale.com/forum/user_avatar/www.simscale.com/igaviano/32/73967_2.png) [@igaviano](https://www.simscale.com/forum/u/igaviano)\
**Post date:** [January 21, 2025, 9:40pm UTC](https://www.simscale.com/forum/t/cad-editing/99703/3 "2025-01-21T21:40:53Z")

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Hi @Leen_Mohamed, thanks for posting on the Forum and welcome to the SimScale Community 🤝

In addition to @nelta’s comments, there is an import option for STL files called ‘[Optimize for LBM / PWC](https://www.simscale.com/docs/analysis-types/incompressible-lbm/#:~:text=While%20uploading%20your%20CAD%20model%20for%20LBM%20or%20wind%20comfort%20simulations%20it%20is%20recommended%20to%20toggle%20on%20%E2%80%98Optimize%20for%20LBM%20/%20PWC%E2%80%99.).’ When selected, the CAD model is imported as a faceted geometry, which is specifically tailored for use in PWC/LBM simulations - make sure it’s toggled off.

If you’d like us to take a closer look at your project, please post a project link (**[here](https://www.simscale.com/forum/t/guide-to-clear-and-understandable-forum-posting/99461)**’s a guide explaining how).

Cheers  
Igor