One Drop at a Time: Xerox 3D Prints with Liquid Metal

Xerox’s 3D liquid metal printer can print intricate, robust parts in a matter of hours. (Image courtesy of Xerox.)

With a 2021 fiscal budget of $161.4 billion dollars and a battle force of 298 ships, the U.S. Navy boasts some of the most advanced technology being implemented today.

Less impressive, though, is the fragility of its supply chain. Outside of the U.S. Navy’s gargantuan size and the huge distances that need to be connected, there is a critical lack of flexibility in the supply chain itself. In 2019, Navy Secretary Richard Spencer, had warned of how the current supply-chain structure is a proverbial house of cards.

“Many contractors were reliant on single suppliers for certain high-tech and high-precision parts, increasing the likelihood they would have to be procured from geostrategic rivals [Russia and China],” said Spencer.

A chart representing the U.S. Navy’s entire fleet. Arranging for new or replacements parts for such an immense, mobile fleet not only costs an inordinate amount, but can also waste a lot of valuable time. (Image courtesy of Naval Graphics.)

To meet such a massive, time-sensitive demand strain, the U.S. Navy has turned to 3D printing on board their ships as a potential recourse. By 3D printing metallic end-user parts, not only would the Navy curtail dependence on competing nations—it would augment the efficacy and flexibility of the supply chain itself.

A Metal Printing Foundry

In a strategic collaboration with Xerox, the Naval Postgraduate School (NPS) has received a 3D liquid metal printer dubbed ElemX. Such a collaboration will grant NPS faculty and students the opportunity to fully explore the efficiency of 3D printing metal equipment on demand. Moreover, such a collaboration will prompt research into the full potential of Xerox’s 3D printing solution not only for the various U.S. defense sectors, but for aerospace, automobiles, heavy machinery, and even oil and gas.

“As the Department of the Navy’s applied research university, NPS combines student operational experience with education and research to deliver innovative capabilities and develop innovative leaders with the knowhow to use them,” remarked Ann Rondeau, President of NPS and a retired Vice Admiral. “This collaborative research effort with Xerox and the use of their 3D printing innovations is a great example of how NPS uniquely prepares our military students to examine novel approaches to create, make, prototype and manufacture capability wherever they are.”

ElemX predominantly uses aluminum as its building medium. On top of being light, versatile, and durable, aluminum is also cost-effective: a ton of aluminum costs a little over $2,000. More importantly, it is highly resistant towards corrosion and oxidation—no doubt, a vital quality for metallic equipment in oceanic settings.

Standing at 6.88ft (2.1m) and 8.86ft wide (2.7m), ElemX is paired with a propriety AI software that assists in designing the needed component. Once the part has been fully designed and given its specifications, the printing can commence.

ElemX’s AI software allows the user to design precise parts with intricate geometries. (Image courtesy of Xerox.)

In the first stage, a coil of aluminum wire is gradually fed into a heated reservoir that can reach temperatures as high as 815^oC (1500^oF). With a melting point of 660^oC (1220^oF), the aluminum wire melts rapidly. The liquefied aluminum is then collected in a specially designed ceramic nozzle called the ejection chamber.

The aluminum wire melts in the heated reservoir and collects in the ejection chamber. (Image courtesy of Xerox.)

The ejection chamber is ensconced inside an electromagnetic coil. Once this coil is energized, the magnetic field produced is strong enough to push inwards at the liquid aluminum, squeezing it inside the ejection chamber. This process whereby magnetic field is used to manipulate liquid metal is known as magnetohydrodynamics (MHD). In a manner similar to how a ketchup bottle works, every time the magnetic field is energized, a droplet is squeezed out of the ejection chamber and onto a collection tray below.

Using the principles of MHD, the magnetic field squeezes out the liquified aluminum one drop at a time. (Image courtesy of Xerox.)

These droplets collect in a series of layers on the tray. Molten aluminum takes around five minutes to cool, and solidifies in roughly fifteen minutes. Thus, as the ejection tube continues to dispense liquid aluminum, the drops can accrue relatively quickly into the desired shape. In fact, the rate at which the aluminum droplets are discharged is variable, with a maximum ejection capacity being a mind-boggling 1,000 drops per second. As such, the production rate can be accurately calibrated based on the job requirement.

ElemX can print parts as large as 300mm x300mm x127mm (11.8in x 11.8in x 5in), and even then, it takes only about four hours to print. The simpler the part is in its design, the faster ElemX will be able to print it. Additionally, given how ElemX marries 3D printing with AI designing software, the printed product requires little to no post-processing, curtailing production times even further.

The 3D printed parts can be simple or intricate. (Image courtesy of Xerox.)

Leaving It in the Dust

3D printing that uses MHD on liquified metal is the brainchild of a father-and-son start-up called Vader Systems. In 2019, Xerox acquired Vader Systems (did Xerox have the higher ground?) as part of an initiative to carve its own slice of the $8 billion 3D printing industry. Prior to Vader Systems’ innovation, the various metal 3D printing methods employed powdered metals, out of which powder bed fusion (PBF) remains the most common. In PBF, layers of powdered material are piled on top of each other in the desired shape and then fused together via high-intensity lasers or electron beams. Direct energy deposition (DED) is another form of metal 3D printing whereby powdered metal is forced through a feeding nozzle onto a building platform where it is melted using a heat source (laser or electron beams).

A closer look at how DED works. Interestingly, metal wires have also been used in DEDs instead of powder, but the main drawbacks have been the exorbitant price of such DEDs as well as the rudimentary nature of the parts that could be printed. (Image courtesy of Rapid Prototyping of Biomaterials, 2nd Edition.)

Though innovative in its own right, using powder for 3D printing has severe drawbacks. For one, the powder form of many metals and polymers is considered ultra-fine particles (UFPs). Exposure to UFPs can lead to a variety of adverse health effects including asthma, nausea, lung damage, heart diseases and even strokes. Another drawback of powdered materials is that UFPs can enter the printer itself, and damage or clog its various mechanic and electronic systems. Repairing or replacing such parts is often not only cumbersome but expensive. More importantly, powdered emissions are often combustible and, if left unchecked, pose the risk of explosive hazards.

Working with powdered material is a health risk that requires specialized protective equipment, stringent regulations, and thorough cleaning. (Image courtesy of Canadian Metal Working.)

By substituting powder with an aluminum wire, Xerox is not only circumventing virtually all the safety hazards posed by metallic powder, but offering an expedient, cost-effective solution for the U.S. Navy.

As noted by Colonel Todd Lyons, Vice President of the NPS Alumni Association and Foundation: “This is one way to bend the cost curve so that the DoD [Department of Defense] is not spending a thousand dollars for every dollar that a peer competitor spends.”