New to Fusion 360, 3D printing, design - trying to edit an .stl from Thingiverse

[BMWFan1]

There are a large number of videos and web pages showing how to edit .stl files downloaded from Thingiverse. I've watched a bunch of them. All of them I've found are at least 2+ years old and when following the instructions, I find that some of the Fusion 360 commands/options have moved, might be called something different or I'm just too stupid to figure this out.  I'm using the Personal/Free version of Fusion 360, v2.0.17954x86_64.

Might there be an recent instructional video specifically for editing .stl files that I'm just not finding? I know nothing about this type of software, but have watched 5-10 general instructional videos about Fusion 360 in addition to the many specifically for editing Thingiverse files. I am still having problems being able to successfully edit a downloaded .stl and then 3D print.

Attached is the file I'm trying to edit and then print - trying to add a wall to hopefully keep the heat from the D1 Mini out of the right side, where the BME280 temp sensor will be. 

Has the layout or operation related to Mesh/STL in Fusion 360 greatly changed with recent versions and different than 2+ years ago?

[jhackney1972]

Converted STL file to a solid body is attached.  When you finish your edit addition, right click on the body in the Browser and choose "Save as Mesh" to convert it back to a STL to send to your printer.

[BMWFan1]

Thanks for that @jhackney1972 
But when I open it in Fusion360, the units are inches and it's way too large. The overall length and width should be approx 37x88 mm.

Curious how you created that so I can be self sufficient in the future.

Another thing I ran into with your file....

I added a rectangle in the area I wanted the wall and went to extrude it up to build the wall. I can't select the rectangle and then extrude it. Fusion always wants to select the triangles instead and only allows me to extrude them. 

[TrippyLighting]

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@BMWFan1 wrote:

Might there be an recent instructional video specifically for editing .stl files that I'm just not finding?

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Edinting .stl files with CAD software, while possible, is not the best idea. .stl files contain triangulated meshes and those do not represent 3D geometry in CAD quality.

Downloading .stl files to modify then is about the worst way to learn CAD software! 

[jhackney1972 · Accepted solution]

As mentioned, using a Mesh is not a good way to model in Fusion 360.  That being said the video will show what I did to convert the mesh into a solid body and then add a feature.  The video will mention how to remove the feature I added so you can add your specific features.  Model attached.

[jhackney1972]

Well, did my last conversion work for you?  If not let me know.  If so, consider accepting my post as an Accepted Solution.

[BMWFan1]

Still working on it. But seems OK so far. It sliced in Cura, so it was a success.
Thanks.

Firing up the 3D printer now. It'll take a while to complete.

And thanks for that great video. Your explanations were very easy to understand what you were doing along the way. 

[BMWFan1]

Printed perfect. I actually started from the original file and took all the same steps you showed on the video. Thanks for that. I think it will help remembering for similar situations in the future. And I can refer back here in case my memory fails.

I shortened the plane distance you used from 25mm down to 20mm and made the height 19mm. The top fits on it perfectly. I also made another version with a chamfer on the top corner so I can pass wires through to the other side. I can use hot glue or caulk to plug the hole if needed.