You were aware, I hope, that the popularization of 3D printing is happening now, rather than 20 years ago, is because the previous generation of patents is expiring?

(at least that's what I heard, anyway. havent done my due diligence and actually checked. maybe that's worth a blog post itself, if true.)

Groundnut:

The first available 3D printers were produced in the early 1980s. Because those patents were issued under the existing law of the time, they all would have expired around 2002.

Other issues unrelated to the technologies of the machines may be the drivers for the expansion of the use of the machines. New materials, reductions in cost of the materials and machines, and faster processors are all contributing to the expansion of this technology. Fundamentally, as happens with many patented technologies, the first 3D printers were never going to penetrate the market widely because the necessary technologies to reduce cost and expand applicability were unavailable. By the time those technologies became available, the first 15 years of 3D printer patents were already expired.

It does not appear that there is any relationship between expiration of patents and growth of 3D printing. Indeed, it may be that patents in this area are growing - not on the machines, but on the technologies that make the machines truly useful.