Communications of the ACM
Bespoke Additive Manufacturing
Additive manufacturing (also known as three-dimensional printing) is an inevitable successor to traditional subtractive manufacturing, since it saves on material costs and simplifies automation of the manufacturing process.
Credit: 3D Systems Inc.
Additive manufacturing (AM), also known as rapid prototyping and three-dimensional (3D) printing, is enabling on-demand customization of components to start making major contributions to the manufacturing supply chain, giving rise to a new era of personalized items, the market for which, together with replacement parts and prototyping, could total over $160 billion by 2026.
While it may never completely replace traditional subtractive manufacturing — which, like a sculpture starts with a solid block and machines-away unneeded material — AM is an inevitable successor to many subtractive jobs, since it saves on material costs and simplifies automated manufacturing.
"I doubt we'll see additive manufacturing replace entire industries, but it could disrupt some supply chains. Manufacturers will mostly use it for replacement parts, urgent orders, as well as for customized components," said Pierce Owen, principal analyst of smart manufacturing at Oyster Bay, NY-based market research firm ABI Research. "We already see additive manufacturing adoption in aerospace for fuel nozzles and interior components, and in most other industries for prototypes, but customized items are also on the rise, including prosthetics, implants and surgical/anatomical models in medicine and dentistry, custom components in the automotive aftermarket, and midsoles in one-off or small-run customized footwear." ABI, Owen said, forecasts that in 2026, "Manufacturers will use additive manufacturing to produce $24.5 billion-worth of aerospace and defense parts and components, $14.2 billion of healthcare and dentistry-related parts and products, and $163.4 billion in total production value across all industries."
According to Stefaan Motte, vice president and general manager of additive manufacturing vendor Materialise NV of Leuven, Belgium, Materialise was "instrumental in getting 3D printing accepted by traditional industries. We demonstrated that 3D printing can be more economical than traditional manufacturing for bespoke items. We started working with Sonova (a Swiss maker of hearing solutions) to automate the personalization of hearing aids by scanning the inner-ear shapes of patients, then 3D-printing an exact fit. Our solution was so cost-efficient that 3D printing is now cheaper than traditional ways of personalizing hearing aids, leading to widespread adoption of 3D printing by all the bespoke hearing aid suppliers."
Materialise also is working with Hoya eyewear to personalize eyeglasses that use lens-centric designs that perfectly fit the face of the wearer.
Additive Applications
Other applications of additive manufacturing can be seen in a broad array of industries.
In aerospace, for example, jet engine parts can be produced on demand; in one instance, Motte said, 12 additively manufactured jet engine parts were used to replace 200 subtractively manufactured components, boosting both speed of manufacturing and the overall reliability of the aircraft.
All the major automotive makers use 3D printing for rapid prototyping, as well as to produce production parts. Major auto racing teams in competitions from Formula 1 to NASCAR are designing/manufacturing bespoke performance engine parts to give them a winning edge. In the automotive aftermarket, innovation abounds with bespoke accessories for automotive interiors from companies like Ai Design.
Even shoemakers Nike and Adidas are getting into the act with customized footwear. Nike used a SLS (selective laser sintering) 3D printer to make custom spiked soles for the Zoom Superfly Flyknit shoes it created for Olympic gold-medal-winning American sprinter Allyson Felix. Adidas last year introduced its Futurecraft shoe, which it produces using Redwood City, CA-based Carbon's speedy continuous liquid interface production (CLIP) technology to 3D-print Futurecraft soles.
AM is also breaking into professional markets. Dental offices are switching to 3D printers after using computer numerical control (CNC) equipment to make bespoke dental appliances for patients right in their offices. Companies like Datron, MecaNumeric, Reitel, Roders Tec, and Roland have mature machining hardware and software for creating dental appliances in the dentist office that sells for as little as $20,000. Unlike 3D printers, however, CNC uses subtractive manufacturing techniques: starting with solid block of material, which is sculpted away to form the finished appliance (from crowns to implants to bridges). Their superior accuracy compared to first-generation additive manufacturing techniques led dentists to favor their use, despite their higher cost and the waste of subtracted materials.
With the ongoing evolution of 3D printers, the cost of making bespoke dental appliances is down to as little as $10,000. For instance, equipment from EnvisionTEC of Dearborn, MI, at starting prices as low as $10,000, makes use of digital light processing (DLP) techniques to create all varieties of dental appliances. Using million-pixel digital micromirror devices (DMD), EnvisionTEC can image an entire layer of an object simultaneously or scan the exact shape of teeth inside the mouth in three dimensions. Then, as with CNC, the dentist has time to prepare the tooth for the appliance, a crown for instance, while it is being 3D printed and prepared for placement.
SLA using scanning lasers, instead of DLPs, images 3D layers one pixel at a time, albeit requiring longer build times. Likewise SLS can create metal dental appliances, but not with the high resolution of laser-based SLA or the speed and resolution of DLP. Nevertheless, professionals are already using these 3D printers, costing $5,000 to $50,000, to create personalized medical and dental prosthetics including orthodontic models, crowns, bridges, denture frameworks, night guards, bonding trays, and surgical drill guides.
Texas Instruments, creator of the DLP subsystems used by 3D printer manufacturers, recently expanded its line of "Pico" controllers with high-resolution 3D printers selling for under $1000. The key was using less expensive Pico DMD chips, originally designed for portable pocket projectors.
TI systems and marketing manager for DLP products Srikanth Gurrapu said the "immediate market" for the new printers is professional and industrial, and we believe this scalable product portfolio will drive innovation in mainstream 3D printers and 3D scanners for high speed and high resolution at very affordable end system price points."
In the near future, 3D-printed medical appliances will be coming to an operating room near you. For instance, damaged bones can be regrown inside patients with scaffolds that are 3D-printed to their exact specifications, then implanted so bone growth will follow their predefined shapes, after which the scaffold itself naturally biodegrades, according to Benjamin Schultz, a research associate at the University of Wisconsin-Milwaukee. Said Schultz, "I am currently producing magnesium-alloy bone scaffolds that are bioresorbable. The metal scaffold itself is cast from a 3D-printed mold that provides the shape of cancellous bone, providing a sort of template for bone to grow. Such scaffolds are implanted to aid in healing of large injuries to bone, where a section of bone has been removed or lost."
One goal of 3D printing in medicine is the construction of replacement organs. For instance, Indiana University School of Medicine is home to a $9-million research project with Lung Biotechnology (a wholly owned subsidiary of Silver Spring, MD-based United Therapeutics) to 3D-print new internal organs for the more than 110,000 people awaiting a transplant. That project, already underway, uses pig liver cells genetically engineered to be compatible with human hosts, then 3D-prints them into the shape of a human liver. After proving the functionality of these livers in the lab, the researchers plan to implant them into the 20 patients that would otherwise die each day while awaiting a liver donor.
R. Colin Johnson is a Kyoto Prize Fellow who has worked as a technology journalist for two decades.
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