Additive, Here and Now

Material Improvements

Stratasys Direct (stratasysdirect.com) is the service-provider arm of additive technology developer Stratasys. “We’re a customer from Stratasys’ point of view,” says Chuck Alexander, director of product management at the firm. Stratasys Direct uses additive technology from multiple sources as well as traditional machining and injection molding technology to create prototypes or limited production runs for its customers. “We work with a lot of end-use customers. So Stratasys will come to us and ask, ‘how can we improve?’ And we’re viewed as early adapters, so we can try things out and give feedback.” 

He offered FDM (fused deposition modeling) as an example of an additive technology that has come a long way from when it was first developed decades ago. Not only has the extrusion technology gotten more precise and reliable, the range of materials available to be used has expanded as well, which he thinks is the biggest improvement for this process. 

“FDM is a really good fit for tooling applications. The Stratasys Fortis 900 machine, for example, has a build envelope that’s 3 × 2 × 3 feet and the accuracy of FDM is well suited for fixturing and other tooling. And then there’s the breadth of materials available for the process. They recently announced a carbon-fiber-filled Nylon 12, for example. And that works well for tooling because of its strength and wear resistance.”

Alexander notes that Stratasys and other developers have begun to innovate in interesting ways in recent years, citing Ford’s use of the novel Stratasys Infinite Build system, which builds horizontally rather than vertically, and is open-ended for theoretically endlessly long builds. Ford is trying it out at printing large interior car parts at its Research and Innovation Center in Dearborn, MI. 
 

Fusion in the Lab

Jeff Schipper, director of special operations at Proto Labs (protolabs.com), illustrates one technical improvement in plastic prototyping with props: He showed two almost identical highly detailed plastic parts and explained that both were made of durable, heat-resistant Nylon 12, a material which is also used to prototype and test engine manifolds. One part is made by selective laser sintering (SLS), the other is made—and much more quickly—by HP’s recently introduced Multi Jet Fusion (MJF) process. The latter is “very fast compared to SLS,” he says, “and takes us toward the ability of making production parts in some quantity.”

Proto Labs was one of a handful of sites that tested MJF before it hit the market, working with HP’s R&D team “to fine-tune the process” of consistently producing high-quality parts. 
 

Like Stratasys Direct, Proto Labs contracts with manufacturers to make prototype and some short-run production parts through the use of additive as well as traditional technologies. MJF is now part of its offerings.

MJF uses an inkjet array to selectively apply fusing and detailing agents across a bed of nylon powder, which are then fused by heating elements into a solid layer. Once a layer is built, a fresh layer of powder is distributed on top of the previous layer and so on until the build is complete. Though the process is similar in many ways to other additive technologies such as SLS, the parts it makes have improved isotropic mechanical behavior, and generally speaking, it can make those parts more quickly than other 3D printing methods: On its website, HP cites a test that had the lead time of a sample part improve from an average of seven days using SLS to four days using MJF.
 

Speed Metal

Speed—the relative lack of it—is a primary reason why additive is still no immediate threat to traditional subtractive methods of making metal production parts, explains Richard Grylls, technical director, SLM Solutions NA Inc. (slm-solutions.us). This company is 100% focused on selective laser melting (SLM) technology—one of the additive methods that uses lasers to build up a component from a bed of powdered metal. The process makes a highly accurate, dense metal part with excellent surface finish, but does so at a rate of not pounds but rather grams of material deposited per hour.

“In general, you use our technology where you have high-value pieces of metal with reasonably low volume,” he says. Traditionally, that has meant aerospace and medical components made of titanium, Inconel or some other hard material. In automotive, using the design freedom allowed by the technique has made economic sense only in places where the volumes are low, such as in Formula One and NASCAR, and in high-end sports cars.

“Automotive has been slower in ramping up to use the technology,” he notes. “However, they are catching up, and they’re catching up fast.”

The Bugatti Chiron has two end-use components on it that are made with SLM Solutions equipment. One is a bracket that features coolant channels that would be unfeasible to machine using traditional methods, but has been made since 2016 with an SLM 280 machine. More recently, a titanium brake caliper is being made using an SLM 500. These are very low-volume parts, however. 

SLM technology is slow because “we didn’t have much laser power,” Grylls said. The process maintains its precision and finish quality by relying on no more than 700-W laser power, where some other methods may use a 3-kW laser to make a courser part, but make it more quickly. SLM Solutions is making up the difference by using multiple low-powered lasers to increase the deposition rate. The SLM 500, for example, has four 700-W lasers. 

“It’s still not quite there in terms of raw pounds deposited per hour, but it's approaching what machines using higher powered lasers can do. In about three years, the industry standard has gone from having 400 W of laser power to 2.8 kW—a seven-fold increase. That directly correlates to maybe a five-fold increase in deposition rate,” he said. And that means that “there are some huge application areas for parts—especially in automotive—that would have been completely uneconomical earlier.” 
 

Throughput Improvement

According to Jon Walker, the designated automotive specialist at EOS North America (eos.info/en), the average cost per part of an additive-made component—across their various materials and technologies—has come down around 20 percent. “And that’s a number that’s probably going to continue on a similar curve,” he says. EOS has been doing a number of things to keep the trend going. 

First, the company is partnering with materials makers to develop additive materials that more closely align with the automotive industry’s needs. “All of the metal materials we’ve offered to date are medical implant grade or aerospace grade—and those would be overkill for most automotive and other industries like agriculture,” he explains.

Second, they are improving the throughput of the machines. On the metal side, the company’s M400-4 machine uses the same four-lasers-are-better-than-one approach cited by SLM Solutions to improve build speed to about 3.5 times what it was with the single laser approach. But along with that, the company is focused on improving the throughput in other ways.

He cited the example of the P500 machine for printing plastics, which launched last year. It has a faster build rate but also better material recyclability, “so you can use more recycled powder per build,” as well as robotic loading and unloading. “And it has the world’s first machining-center-style cast bed inside a 3D printer,” for temperature management, enabling preheating and consistent builds, 24/7. 

“Now that the process of building a part has been matured, we’re picking off the low-hanging fruit, where there were other shortcomings within the process.” Those include powder handling efficiency, ease of use, and ease of automation. “We’re taking a process that works and now enabling people to run it around the clock,” Walker says.

Additive Materials Becoming More—
and Less—Specialized

The materials used in additive are improving in two directions at once. On one hand, more specialized materials are being developed to broaden the range of parts that can be built. Examples include Nylon 12 CF, the carbon-fiber filled version of the already versatile nylon material used in FDM and other processes, mentioned above. But there are many more: 

Under-the-hood polymer-based offerings from DSM (dsm.com), for example, include the Arnitel ID 2060-HT filament, which the company says is easy to weld, is suitable for applications such as hot and cold charge air ducts; and Somos Taurus, which the company says is the first SLA material to bring a combination of thermal resistance, mechanical strength and impact performance that previously has only been achieved in AM using techniques such as FDM and SLS.

On the other hand, in the interest of cost savings, additive technology developers are striving to make equipment that works effectively with less-specialized materials. 
“Additive is probably still only 0.05 percent of the overall powdered metal industry,” EOS North America’s Jon Walker explains. “All of the metal additive processes to date have depended on powdered metals specially made for those processes—they need each particle to be close to perfectly round spheres. It’s a very tiny niche within the powdered metal industry, and making it is a very labor-intensive process, where they need to use gas atomization instead of water or something else that might be more common. That begins to show why the powder has been so expensive.”

In response, EOS is beginning to partner with materials developers to design materials “that are more commonplace, and already come in at a lower cost per part. We’re working with them to learn how to let lower-cost materials work on the EOS platform that has traditionally required a more specialized material.”

Stratasys and other companies are taking the same approach, according to Chuck Alexander, director of product management at Stratasys Direct. The recently released Stratasys F123 series uses a thermoplastic material that is “closer to the pellet shapes used in injection molding,” he says. “If you can use a material that is already manufactured in large quantities, it's much less expensive.”

Prototype exhaust vent made via FDM with Somos-Taurus for high thermal resistance and mechanical strength.