export> stl> EXPORT STL, blender keeps saving the wrong file 5 hours now I have this mesh opened in blender that I been trying to export as a stl file. 5 hours blender every time exports the WRONG file. A file that is not even loaded into the editor. a file that I didn't open.
Select is not an ambiguous word. File, export, stl, these words have ONE and only one definition. it's really hard to misspell FILEX.STL, only one button with the label EXPORT STL.
Of course, there are plenty of things that I can double-check 5, 10, 20 times, including the MANY posts on this and other sites telling how to go FileExportStlFilenameButton....
I'm a programmer so I already have parts of my scalp where the nerves are dead from pulling my hair out. I've seen glitches that you wouldn't believe. I've never seen anything like this.
the .blend file I'm trying to export as STL is a quad mesh whereas the .stl image that blender keeps exporting is a triangle mesh which the quad mesh is derived from.
I loaded a triangle mesh, converted it to quad mesh, saved it as a blend file. quit blender, restart blender, load the quad mesh file, check it carefully yeah that's a quad mesh alright. export the quad mesh image as FILEX.STL. run my CAD program, open filex.stl and what do I see, the ORIGINAL triangle mesh file which I know is impossible. spend 4 more hours checking every conceivable way to verify that blender has the right file, to no avail.
STL format only supports triangles.


  STL file format wiki
  
  STL (an abbreviation of "stereolithography") is a file format native to the stereolithography
  CAD software created by 3D Systems. STL has several
  backronyms such as "Standard Triangle Language" and "Standard
  Tessellation Language".
  
  An STL file describes a raw, unstructured triangulated surface by the
  unit normal and vertices (ordered by the right-hand rule) of the
  triangles using a three-dimensional Cartesian coordinate system. 


A simple test would be to export and re-import cube or plane, and note the triagulation.

Related Triangles to quad for 3D printing