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3-D printers can fabricate objects that traditional manufacturing tools could never cook up. The question now is whether they can generate profits that justify the hype swirling around the industry.

3-D printing has become one of the most talked-about technologies. Stock prices of the four publicly traded makers have soared, and shipments of desktop printers used by hobbyists and small businesses have increased dramatically. With the final companies reporting earnings over the past week, investors got a better idea of where this rapidly growing industry is heading.