A scanner with which to port them into a computer if they are not digital
A 3D CAD program that allows you to build over a backdrop you import
If the CAD program does not output .stl files you need a conversion program...
I've been told that some of the 3D scanning options can be temperamental and not consistently reliable. It was not specified if this problem was software or hardware related.
IMHO 3D printing has tremendous potential in so many diverse industries. The current bio-medical 3D printing research studies are an amazingly "WOW!" application that possibly can benefit so many people.
From an O gauge industry standpoint, since Lionel is currently using 3D printers to design products and some parts, I would hope that Lionel would create and sell their version of K-Line's 0-31 2-truck Shay locomotive coupler bracket/guide to be used on the recent Lionel 2 truck Legacy Shays.
