Printing in 3D involves sending a designfile to a printer that then forms a solid version of that object by slowly building it up in layers of plastic.
Engineers working for car companies and using networked computer-aided design terminals still file their ideas directly to the server for the chief designer to approve rather than bouncing them around among colleagues for collective improvement.
Presumably, to obtain the design for a widget will be as easy as downloading a song (both legally or illegally) because the design is all software, a small file that a CAD program would handle, for example.
As part of my job, I reported alarming inadequacies: in one case high-grade equipment (ASME III, class 1) was operated in nuclear power reactors with no accepted safety file, regardless of a previous accident and a half-dozen failures in achieving acceptable design results.
One group calling itself Defense Distributed hopes to create a file for a gun capable of shooting a .22 caliber bullet and may upload its final design to Thingiverse.