Hi Adan, .stl files don't have any way to mark what units the file is in. So probably simplify3d is making a guess and is ending up using a different unit system than what you actually used.

There may be an option in simplify3d where you can tell it what units were used in the .stl file, either that or you'll need to find out what units it is expecting and switch your unit system in MoI to that before exporting to .stl . Probably it's expecting either mm or inches.

- Michael