Print, Aim and Shoot: What Does a Plastic Handgun Mean for the Future of 3-D Printing?

A University of Texas at Austin law student has demonstrated to the world that any ambitious tinkerer can make a handgun almost entirely out of 3-D printed parts. Cody Wilson’s revelation is not likely to lead to an arsenal of plastic zip guns anytime soon, but it does raise a number of hairy questions about a technology that, until now, has been highly touted as central to the future of manufacturing in the U.S.

Images and video of Wilson posing with and firing his “Liberator” handgun have made the rounds on the Internet in recent days. It’s a stark contrast to the image that 3-D printing, or “additive manufacturing,” proponents have pursued thus far, where the world benefits from robotic prosthetics, replacement hips and other biomedical wonders manufactured layer by layer out of molten plastic or metal, as dictated by a CAD (computer-aided design) file.

Wilson’s gun consists of 15 parts assembled after being printed individually in a Stratasys Dimension SST machine out of white ABS plastic—a polymer made from the chemical compounds acrylonitrile, butadiene and styrene. Only the gun’s firing pin (a common nail) and an obligatory piece of steel embedded in the handle—so that it does not violate the Undetectable Firearms Act (pdf)—are metal. Wilson has made the design files needed to create the Liberator—that fires standard handgun rounds—available as a free download for anyone interested in replicating his work.

Wilson positions himself as a protector of civil liberties—in particular “popular access to arms”—and has founded a nonprofit called Defense Distributed to further this goal. His libertarian views are not unlike those of free, open-source software advocates or hackers who take down Web sites and pick apart popular software like Windows to prove they are not as secure as they appear—except for the small detail that he wants to empower people to make devices that can harm or kill other people. (He’s also published blueprints for 3-D printing part of an AR-15 semiautomatic rifle.)

Technically speaking, Wilson’s so-called “Wiki Weapon” pushes the boundaries of 3-D printing capabilities, especially those of lower-end systems not able to work with anything stronger or more durable than ABS plastic. Although the Liberator currently fires only a single shot, better materials as well as improved designs and post-processing techniques might ultimately lead to a weapon that can shoot multiple rounds without breaking down.

To learn more about the potential impact of Wilson’s work on the world of 3-D printing, Scientific American spoke with Ryan Wicker, director of the University of Texas at El Paso’s W. M. Keck Center for 3-D Innovation. Wicker shared his thoughts about Wilson’s invention, the technical challenges of making a 3-D printed gun and the reality that the unbridled creativity promoted by 3-D printing was destined to take a darker turn.

[An edited transcript of the interview follows.]

What was your reaction when you learned that someone had printed nearly all of the components needed to assemble a handgun using a 3-D printer?

This story has been developing for months, if not years, so it was pretty anticlimactic. I probably first became aware of what [Wilson] has been doing when Stratasys went in and confiscated the printer they leased to him [in October. I have been hearing for years about people using 3-D printers to make parts for guns. In the evolution of 3-D printing it’s certainly natural for things like this to happen.

Are there specific challenges to making a working firearm using 3-D printed parts?

Building the parts with a high level of dimensional accuracy would be one challenge and the material performance would be another. A firearm experiences a high-energy impulse in the chamber, where the gun components start off at ambient conditions but are subjected very quickly to higher temperatures and pressures. This sudden change can compromise the structural integrity of the gun, even possibly making it explode.

What is the significance of Wilson making most of his gun parts out of ABS plastic?

ABS is an inexpensive polymer typically used by the type of 3-D printer that he used. There are plastics that are stronger, more durable and perform much better than ABS, but those higher-end materials require higher-end machines than what he had.

Why is ABS the standard plastic for lower-end systems?

ABS is just a commodity, a commonly used plastic that the automotive industry has used for years to create injection-molded parts. Different 3-D printing systems work differently, but [Wilson’s] uses an extrusion-based process that’s analogous to a hot-glue gun. ABS’s extrusion temperature [the point at which the polymer starts to deform and can be squeezed out into layers] is lower than other, more capable plastics. It doesn’t require a more expensive system that can [operate at] higher temperatures.

Why not use a more durable plastic?

Stratasys offers a more expensive plastic called Ultem, which potentially would be a better performer than ABS for this application. But you can’t print this type of high-end material using the low-end [$20,000] industrial printer that [Wilson] used. You need a high-end machine that costs anywhere between $100,000 and $400,000 to be able to use those better plastics. Although it’s not possible now, that doesn’t mean someone couldn’t develop the capability to work with better plastics on low-end systems.

Other than the materials that can be used, what limitations do lower-end 3-D printers have at this time?

Another limitation is accuracy. These machines don’t have the temperature control of higher-end systems, and consequently the dimensional accuracies suffer. The more expensive industrial systems take into account how much a part will change as it goes through the process of being made. Better temperature control enables a printer to better adjust for changes in the material as it is layered, solidifies and shrinks. If you don’t take those changes into account, some layers might be farther apart, creating voids that prevent the finished product from being as strong as it could be.

All of these things can be overcome. There are lots of people working in their homes on inexpensive desktop systems [like those MakerBot produces] who are going to be geeky, experimenting and optimizing their systems. They’ll write their own code and figure out how to compensate for their equipment and materials. That’s what my students do. There is some knowledge that you have to develop to use these systems optimally.

As inventors develop this knowledge, are there concerns that more of them will experiment with 3-D printed weapons?

3-D printing is not the only enabling technology here. 3-D printers may be a little less complicated to use than [some computer numerical control (CNC) systems that manufacturers use to make tools], but you still can buy a CNC machine today and use that to build weapons. In fact, I would be much more scared of people who have expertise in machine shops [making weapons] than I would of someone using a 3-D printer.

And, even if you don’t print the parts for the weapons yourself, there’s an entire industry that makes parts on demand today using 3-D printing. You can upload your file online without even speaking with anyone and pay for it with your credit card.

How soon will higher-end 3-D printers capable of using better materials become affordable for hobbyists and inventors?

I don’t know how much the cost can come down for some high-end systems because they are big machines and they use more expensive industrial components, which limits how much the price can be reduced. And the price of high-end systems may not be the limiting factor for hobbyists because they can take a desktop system [like those made by MakerBot] and supercharge it, and there’s no technical reason you couldn’t use it to print a weapon.

How would you supercharge a desktop 3-D printer to give it that capability?

I may enclose it so that I can reach higher temperatures and work with [stronger, more durable] materials. I might also do this by modifying the printer’s heater to make the printhead hotter.

People are less likely to modify an industrial system because companies like Stratasys don’t give you access to their printer’s source code. MakerBot and other desktop printer–makers do. That means I can write my own code to change things on these lower-end systems but I can’t [change] that on a Stratasys system. Even the materials used by industrial systems are controlled. A canister of material used in a Stratasys printer even has a microchip that knows what and how much material it contains.

What impact will Wilson’s experiment have on 3-D printing?

It concerns me a little, but I think this type of project was inevitable. We would all like these technologies to be used for the benefit of society, and I believe these benefits far outweigh the risks. There are lots of wonderful examples—customized hearing aids, 3-D printed electronics and even shoes as well as [efforts to print artificial human] organs. The government will ultimately decide whether the technology should be regulated, but I see these technologies completely disrupting the way we make products, and bringing innovative, entrepreneurial manufacturing work back to the U.S. We’ve traveled too far down the road to turn back at this point. With these technologies, the future is limited only by one’s imagination.

Follow Scientific American on Twitter @SciAm and @SciamBlogs. Visit ScientificAmerican.com for the latest in science, health and technology news.
© 2013 ScientificAmerican.com. All rights reserved.