One of the central patents controlling production of a specific type of 3D printer expired yesterday, and the news has the 3D printing community buzzing. The patent concerns selective laser sintering (SLS), a form of additive manufacturing that offers some significant advantages over other techniques. Today the cost of an SLS printer can run as high as $250,000, but the hope is that this patent expiration will dramatically reduce that figure.

It might seem extreme, but the claim isn’t without evidence. After the expiration of the patent for fused deposition modeling (FDM), an enormous open source movement appeared almost overnight. What had once been a corporate oddity became a popular DIY project, and companies arose to cater to a whole new market: the enthusiast 3D printing customer. These rickety, (relatively) low-fidelity printers found great traction with the Arduino and Raspberry Pi crowd, and their success has led directly to the low-cost, mid-range printers available today.

SLS machines can offer significant upgrades over current economy-level 3D printers because they don’t rely on a traditional extruder to control the modeling material. This slow and inherently inaccurate process imposes a fairly hard limit on resolution, and greatly restricts the materials with which we can print — or at least, it has. FDM has historically used mostly plastics, like ABS, but printing with more innovative materials like carbon fiber is now becoming a reality.

By contrast, SLS machines user a high-powered laser to fuse small particles of material, released almost as an aerosol, to the growing object. With this technology it is possible to print plastic, metal, ceramic, or glass — virtually anything that can be released as a powder and heat-fused to a growing print. If this technology comes down in price even a fraction as far as FDM has, the at-home 3D printing revolution could finally begin in earnest.

At least, some people think so. Others aren’t so sure. The patent at issue here is (as you might expect since it is expiring) quite old, and covers only the most basic principle of laser additive printing. Companies have spent nearly two decades improving the technology, and those proprietary devices are all still kept safe from start-ups and hobbyists. This patent expiration technically opens a legal path for some new company or individual to bring SLS printers to market, but those outlined in the patent may simply be too primitive to be useful.

Also at issue is the financial wisdom of entering the SLS market. Since it incorporates high-powered precision lasers, there’s no guarantee that this technology can be made anywhere near as cheap as an FDM machine; a company could well find that they have no market, with printers too expensive for hobbyists and too primitive for professionals. Additionally, any attempts to improve on SLS technology could easily overlap with patents still in effect — and the risk of unwittingly opening themselves to lawsuits could stifle innovation.

Still, many of these problems existed for FDM printers when they became fair game just a few short years ago, and today you can pick some very decent home printers for as little as $300. Even if the tech has to take a few downgrades in terms of resolution or the range of possible materials, there’s no reason the basic principle couldn’t still make its way to the open source scene. We’ve already seen tentative attempts at an open-source sintering printer (PDF), such as this one that used wax as the building material — hardly a proof of concept for printing your own replacement car parts.

The past few months have seen a reduction in momentum within the open source printing community, mostly owing to the fact that their prior rate of advancement had been unsustainably quick. With a whole new method of printing now legally available, that momentum could well be about to return.