Although 3-D printing stocks were some of the best performers in 2013, the same can't be said for 2014. Generally speaking, the entire sector has fallen out of favor with investors thanks to a slew of guidance revisions, renewing concerns that the sector is grossly overvalued. The icing on the cake was when 3D Systems (NYSE:DDD) warned that it's going to take a big earnings hit in 2014 because it's increasing some expenses related to growing its business with a long-term view.

With 3-D printing stocks now well off their all-time highs, investors may start to wonder what price is too high, and how to manage the risks associated with investing in a high-growth industry like 3-D printing. In the following video, 3-D printing analyst Steve Heller sits down with the head of Motley Fool's industrials bureau, Blake Bos, to discuss 3D Systems and ExOne (NASDAQ:XONE), and how to invest in a sector that's certain to have continued volatility and looks extremely expensive on paper. (The relevant video segment can be found between 5:33 and 9:04.)

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.