3D printing breaks out of its mold

The concept of 3D printing can be traced back to the 1950s, when computers were first connected to milling machines, says Neil Gershenfeld, director of MIT’s Center for Bits and Atoms. Gershenfeld pioneered the concept of fab labs—small-scale factories stocked with 3D printers and other computer-controlled fabrication tools (see the report about fab labs in PHYSICS TODAY, March 2002, page 27). Where 3D printers and other additive manufacturing technologies shine, says Gershenfeld, is in their ability to reconstruct complex digital designs.

Although various 3D printing technologies exist, they all operate under similar principles: Computer-aided design (CAD) software is used to slice a digital object into layers as thin as 10 microns; the 2D pattern of each layer is transmitted to the 3D printer, which extrudes, sprays, or spreads raw material onto a flat, horizontal platform; the material is cured, laser-sintered, fused, or bound by UV light, lasers, or electron beams. The process repeats until the object is fully formed.

Most industrial 3D printers can fabricate objects as large as a typical kitchen sink or as small as a pinhead. Some advanced CAD software allows scientists and engineers to optimize such structural properties as strength-to-mass and surface-to-volume ratios. And in the past 10 years, advances in 3D printing technology have expanded the range of usable raw materials beyond plastics to glass, ceramics, and metal.

Langer says that metal processing with laser sintering has been advanced by use of fiber lasers, which he says “offer an intense, high-quality beam that can be easily focused.” Scientists at EOS are collaborating with academic researchers on a process called micro-laser-sintering, which can print features in layers as thin as 1 micron. “We are now melting and changing the crystal structure of some metals, such as stainless steel,” says Langer. “Laser sintering is no longer just a geometry effect. Now it’s also a materials effect.”

Aerospace and medical products, such as patient-specific surgical instruments and drill guides, are among the fastest-growing segments of EOS’s customer base, says Andrew Snow, sales director of the company’s North American division. Also growing in popularity are 3D-printed medical implants, which contain complex lattice structures that support the implant’s integration with surrounding tissue. Snow adds that the need for the Food and Drug Administration’s approval has prevented the US from keeping pace with Europe, where such implants have been sold for more than four years now. Just this year, the FDA granted its first approval for the sale of a 3D-printed medical implant—a titanium hip.

Aircraft and racecar manufacturers have been among the early adopters of 3D printing, with which engineers can digitally optimize density and other structural properties to manufacture customized, lightweight components such as impellers, fuel-injection nozzles, and door hinges. “Weight equates to cost in our industry,” says Chris Wilkinson, an executive responsible for engineering development at Spirit AeroSystems in Wichita, Kansas. The company designed and manufactured a portion of the fuselage for the 787 Dreamliner, Boeing’s new carbon fiber–composite commercial airplane. Additive methods help reduce waste associated with traditional subtractive manufacturing techniques, which can leave up to 90% of expensive raw materials, such as titanium, on the floor. Wilkinson says that 3D printing “also addresses the need for rapid translation of engineering to manufactured parts.”

David Bolognino, director of General Motors’ design fabrication operations, says that additive manufacturing tools in the company’s design labs are used to produce automotive parts for preproduction models of the Chevrolet Volt, GM’s first all-electric vehicle. The technology “allows us to do very quick iterations of complicated parts and systems with supreme accuracy to reduce product development time and expense,” says Bolognino, who recalls seeing his father go from hand-chiseling wooden prototypes to becoming an early advocate of and a supervisor in GM’s rapid prototype lab. Bolognino says traditional tooling methods are still required for car manufacturers like GM to meet their mass-production needs: “At the end of the day, we have to be careful not to make parts that can’t be tooled in other ways,” he says.

Manufacturing in zero gravity is the latest venture for 3D printers. In July the entrepreneurs at Made in Space, a Silicon Valley startup, successfully demonstrated the 3D printing of a plastic adjustable wrench during a NASA parabolic airplane flight. Jason Dunn, the company’s chief technology officer, says they still have much to learn about the fluid dynamics of the process in space. Once those problems are solved, Dunn says that a space-bound vehicle would be lugging less weight because its cargo could be built in space using up to 30% less raw material. On Earth, satellites and other space equipment are made artificially heavy to withstand extreme liftoff vibrations. Dunn and his business partners are currently preparing their customized 3D printer for performance test flights funded by NASA’s Commercial Reusable Suborbital Research program aboard manned spaceflights expected to start next year (see the report about the NASA program in PHYSICS TODAY, October 2010, page 28).

Revenues from additive manufacturing technologies grew by 24.1% in 2010, according to the latest Wohlers Report, an annual state-of-the-industry publication by Wohlers Associates. The report highlights the “explosive growth of low-cost personal 3D printers,” which are primarily sold to individuals, small businesses, and academic institutions. The personal systems start at around $1000 and are used for materials science research, basic prototyping, and teaching; industrial machines can cost more than $1 million. “I’m thrilled by how many universities, community colleges, even high schools, are buying the technology,” says Wohlers.

“Kids are empowered to learn math and science when they can use a 3D printer to design an iPod holder for their bike,” says Hod Lipson, a mechanical engineer at Cornell University’s computational synthesis laboratory. He and his team use 3D printers to fabricate tiny, bio-inspired, battery-powered flying robots, dubbed ornithopters, which mimic the aerodynamic properties of hovering birds and insects. “Just a few years ago, 3D printing was an expensive technology that only large design firms could afford,” says Lipson. “Now [it is] like pencil and paper in the modern robotics lab. If we need a component, we can print it within minutes.”

Lipson and Gershenfeld say that 3D printing is just the start of the digital fabrication revolution. They are collaborating on the development of programmable materials, which Gershenfeld describes as “coded construction.” Their aim is to mimic the efficiency of molecular biological processes by applying computational error-correction techniques. “The difference between bulk raw materials and digital materials is like the difference between playing with clay and playing with Lego blocks,” Gershenfeld says. Lipson adds that the ability to assemble materials with such precision could lead to robots and machines that “respond to external stimuli in a much more sophisticated way.”