In the following video, 3D printing specialist Steve Heller and Motley Fool industrials analyst Blake Bos share their biggest takeaways from attending RAPID 2014, a 3D printing-focused conference held in Detroit.

Throughout RAPID 2014, Blake and Steve were struck by the sheer number of metal 3D printers from a host of different vendors, including Arcam, 3D Systems, ExOne, EOS, and many others. What Blake and Steve found particularly interesting was the level of competition for a product only expected to move hundreds of units per year. According to Wohlers Report 2014, 348 metal 3D printers were sold in 2013, representing an increase of 75.8% over 2012 activity.

Granted, a metal 3D printer can easily cost upward of $500,000, meaning there's potentially hundreds of millions in revenue at stake for leading metal 3D printing vendors.

As far as opportunities for investors, Arcam is the only pure-play metal 3D printing company, which recently reported strong earnings and uses a metal 3D printing technology called Electron Beam Melting, or EBM. EBM is currently a less popular metal 3D printing technology than direct metal laser sintering, or DMLS, which is employed by 3D Systems, EOS, and Renishaw, but the hope is that the uses for EBM will be expanded in the future.      

Additionally, investors looking to get more diversified exposure to the 3D printing industry at large, including the rapidly growing metal 3D printing space, could consider 3D Systems for their portfolio. However, investors considering 3D Systems should also be aware of the risks associated with the company, as well as the fact that it recently experienced execution issues.

Check out the video below to hear Blake's and Steve's biggest takeaways from RAPID 2014. A full transcript follows the video.

Blake Bos: Blake and Steve here, folks. We're in Detroit, Michigan. What are we doing here, Steve?

Steve Heller: We're at the Big M/RAPID 2014.

Bos: The Big M, folks. It's huge.

Heller: Largest additive manufacturing-focused conference -- that's 3D printing, for you readers, folks.

Bos: For 3D printing nerds like us, it's nirvana. We've got all the companies here. We've got ExOne, we have Arcam, we have 3D Systems, Stratasys, Incodema...

Heller: EOS.

Bos: EOS. Yes, it's too many to name. We talked to them all. We got a bunch of good information, and we're going to wrap it all up for you right here, folks, give our biggest takeaways of the two days we've spent here so far.

I'll let you lead it off, Steve. What's your No. 1?

Heller: Let's go M for Metals.

Bos: Yes, M for Metals.

Heller: Big focus on metal 3D printing. Particularly, direct metal laser sintering seems to be the prevailing technology. That's the technology that General Electric is using to 3D-print its LEAP engine fuel nozzle, which will be pioneering larger-scale manufacturing runs -- 40,000 units a year -- which will be an industry first.

Bos: Yes, that's definitely an industry first. The majority of the industry right now -- 3D printing, additive manufacturing -- is plastics. But from what we learned here, metal is where it's at. That's where the growth engine is at. That's where everybody wants to be.

Heller: Exactly, yes. Wohlers Associates put out their report [on the state of the industry]. In 2013, unit growth for metal 3D printing was up about 75% from 2012 levels.

A lot of that actually had to be attributed, though, to Morris Technologies coming offline. They were purchased by General Electric, and they were the largest metal 3D printing service provider in the space. Now the industry is replenishing that demand, so there might have been a boost in demand for 2013.

Bos: Some super-normal demand last year.

Heller: Right, I would say it's abnormal. I'd be interested to see how it follows through in 2014 and beyond.

Bos: It definitely seems like it's growing, from people we talked to. The investor in me, when I hear this about direct metal laser sintering and everybody wanting to get in and the big growth rates, I'm like, "Oh, I want to invest in it. How do I make money off this?"

Let's take that for the investors. Can we make money off this? Is there any way?

Heller: Yes, I think there's a few ways to think about it. 3D Systems, obviously, through their Phenix acquisition is definitely something to think about -- although right now it is a small percentage of their revenue, so is it a big enough tail to wag the dog?

To be determined, but it's definitely a company you should look at. I think they're competitive in the space. We definitely got that. We spoke with the reps. Their printer is almost in parity with the competition.

Bos: Yes, they have a good product, but like you said, we're talking 300 printers.

Heller: 300 printers a year.

Bos: That's small. That's still really small.

Heller: The whole industry is competing for 300 printer sales a year. That's really...

Bos: And Stratasys sold, what, over 4,000 last year?

Heller: Yes. They have the largest install base in 3D printing, but that includes plastics. That also includes MakerBot, which has over, probably 50,000 printers by now.

Bos: But it shows how small the unit number is for metals.

Heller: Exactly. It's super-small. These are almost $500,000-and-up machines, so a very specialized industry. A lot of aerospace -- it seems to be almost all aerospace right now.

Bos: Yes, very aerospace driven, from who we talked to.

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Blake Bos owns shares of Apple. Steve Heller owns shares of 3D Systems, Apple, and ExOne. The Motley Fool recommends 3D Systems, Apple, ExOne, Renishaw, and Stratasys. The Motley Fool owns shares of 3D Systems, Apple, ExOne, General Electric Company, and 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.