According to industry watchdog Wohlers Associates, the 3-D printing industry brought in about $2.2 billion in revenues in 2012 -- peanuts compared to the trillions in GDP the global manufacturing industry produces each year. Clearly, 3-D printing has a long way to grow before it'll even make up 1% of the worldwide manufacturing base. Applications involving 3-D printing will have to expand greatly in the future for 3-D printing to truly become a disruptive force in manufacturing.

In order to get some perspective on what some of the biggest opportunities are today for 3-D printing companies, I turned to Rich Stump, principal of FATHOM, a highly experienced Stratasys (NASDAQ:SSYS) reseller and 3-D printing service center. The way Stump sees it, a major driver of future 3-D printing growth will be downstream and one-off applications. In other words, finished products and customized solutions will likely fuel 3-D printing growth in the years ahead. This line of thinking aligns with Wohlers Associates, which believes the 3-D printing industry will grow by 19.3% a year through 2021 to become a $10.8 billion industry.

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Steve Heller has no position in any stocks mentioned. The Motley Fool recommends and owns shares of Stratasys. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.