The U.S. Patent and Trademark Office in Alexandria, Va., recently hosted a fascinating display of technology. 3D Systems (NYSE:DDD), Stratasys (NASDAQ:SSYS), and other top companies involved in additive manufacturing, or 3-D printing, displayed their wares in the same room.

Fool analyst Rex Moore was at the conference, and chatted with Stratasys engineer Jim Comb. In this installment of our series, Jim explains the differences between Stratasys -- after its merger with Israel's Objet -- and other 3-D companies.