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: The model in Autodesk Inventor And here is the model being visualized by the printer driver: The model being visualized by the printer driver

  • $\begingroup$ Welcome to 3dPrinting.SE! $\endgroup$ Dec 1 '18 at 18:14
  • $\begingroup$ Luckily, it doesn't matter, since all slicing programs allow you to scale the dimensions. So long as you know at least one edge-to-edge dimension, you can handle this. $\endgroup$ Dec 3 '18 at 19:23

.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"=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 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
  • $\begingroup$ From the images he added, the model length and width are in the 100s. $\endgroup$ Dec 2 '18 at 19:37
  • 2
    $\begingroup$ @PerplexedDipole his other picture shows about 2 division lines on a prusa bed on an edge that should be 200mm. 20mm instead of 200mm is what factor? 1/10th. $\endgroup$
    – Trish
    Dec 2 '18 at 19:46

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