Update: 123D beta 5 uses the proper units for exporting STL files, so the scaling operation is no longer necessary.

As I noted previously, objects in STL files created by Autodesk’s new 123D CAD program are not correctly scaled when loaded into ReplicatorG (at least not for me, I’m using the public beta from a few weeks ago).  Eyeballing it, I guessed the object in RepG was about 1/10 the size defined in the 123D model.

To test this hypothesis, I designed a rectangular prism, 50 mm by 25 mm by 10 mm (yes, the temptation to go 90x40x10 was strong).  Results follow:

Calibration object designed in 123D, 5 cm long, 2.5 cm wide, and 1 cm high.

I saved this object in 123D as an STL file, loaded it into RepG, and applied a 10x scale.  I printed it on a Makerbot Thing-O-Matic:

123D calibration object printed.

(You can see the final layer didn’t finish, because I forgot to put more feedstock into the printer; fortunately there was enough to print all the layers)

I measured the printed object with my digital caliper, and the ground truth dimensions (maximum) are: 49.7 mm in length, 25.0 mm in width, and 10.2 mm in height.

Pretty darn good!