How do I keep the .stl files from being resized while exporting? I made a few models in Autodesk Inventor. When I tried to get them printed, the printer created a model smaller than the model I made in Inventor (270mm x 200mm). Is there a way to keep them from getting resized?

Here is the model in Inventor:

And here is the model being visualized by the printer driver:
.stl Basics
The .stl format has no inherent sense of which units you use. items are to scale to an ambiguous 1, which could be 1 meter, one millimeter, one lightyear or one inch. To a .stl, only the relative sizing matters. All these faces you see are compared to a line with the length of 1-unit that is
Slicer-Modeling Software interaction
The most common graphic design programs export in millimeters, but some US ones just assume inches, which is a factor of 1&quot;=25.4mm.
Cura, Netfabb, and Slic3r expect that the 1-unit line is one millimeter long - but if it is an inch instead, then the model is shrunk by 1/25.4 or to about 4% of the right size. Scaling up by 2540% one would return to the millimeter scale.
But then there are other programs that use other choices of scales. Blender for example assumes a scene is in meters by default.
Inventor
Inventor can export .stl in a variety of scales, which all just serve as how the length of the inherent but invisible 1-unit line is drawn. The default choice is centimeters, so a scaling factor of 1cm=10mm, which would explain the models being only 1/10th of the expected size in Slic3r. to change the scaling, follow the manual:

upon exporting a .stl, click Options
under Units, choose mm