To all those saying that it didn't happen, or that it wasn't a bubble since 3D printing is a bigger industry now than it was then: yes there definitely was a bubble, seen both in company valuations, in media coverage, and in VC beliefs. It looked like this (see the 10x spike around 2013-2014, which reverted completely by 2015).
And yes, obviously the tech has improved a lot since, and so has the revenue it drives. In fact, *3D printing revenue growth has closely tracked analyst projections from 2013, over an entire decade*. Yet there was a large bubble regardless.