In recent memory the forum had an ad for a company making 3D models from Archicad files - can't find it today with a search, however.

Some forum members have had success.....

These outputs are getting more sophisticated since instead of producing a puckered sticky mold form for casting, the pieces are now made from sintered plastic particles and can be feasible for the short run production of complex forms.

You can use external software to convert an model from ArchiCAD into an STL file, but it'll probably be unusable to print in 3D: you need a clean simple mesh, which is completely clean:

You have to imagine that the mesh is the shell and the material will be poured inside it: there can be no gaps, no overlapping triangles, no double vertices or edges...

There is a Belgian company called "materialise", which specializes in services, hardware and software for this. They are developing their optimizing software to prepare STL files for 3D-printing since about two decades. Needless to say that it is a non-trivial task to create a clean file for 3D printing.

www.materialise.com

The software is called magics. It costs a lot.

http://archicad-talk.graphisoft.com/viewtopic.php?p=35638&highlight=#35638

And from the equine's mouth:

The method is actually quite simple. You take your model and view it in a 3D window and then you save the file in a .vrml format
I did a model that I created on an old mill building that I did rennovations on. It created the .vrml file simply and the file took with it all my colors, textures, etc. You can also use an old feature of Archicad to split the model on the x,y or z-axis so the model can be printed in sections and pieced together. The first model we printed on the Z-Corp printer came out amazingly well. It was a bit too detailed for the size I created, so I had to split my model into 2 sections and reprint it. The model is very cool, accurate and shows a lot of detail inside and out .

I'm reprinting it again and I could send you a picture of it if you want... let me know.

My company (Macdac Engineering) sells the Z-Corp printer line. Can you list my information below on the forum?
In addition, we may start working with Greg Conyngham to do training seminars in Somers, CT in the old mill building I created the model for.

Ralph

Ralph P. Guisti
V.P. Operations
Macdac Engineering
27 Quality Avenue
Somers, CT 06071
ph: (860) 749-5544 x100
fx: (860) 749-5373