MT Magazine January/February 2025

FEATURE STORY

THE EMERGING TECHNOLOGY ISSUE

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AM is generally accepted as having gotten its start in 1984, when Chuck Hull developed stereolithography – a photochemical process that uses a digitally directed laser beam to build up, layer by layer, a structure from a liquid polymer. Hull went on to found 3D Systems and released his first production machine, the SLA-1, in 1987. Whichever date you accept, this isn’t what might be considered “emerging.” Like a Horse Race Peter Zelinski, editor-in-chief of Additive Manufacturing Media, has a different perspective on the technology. For the past several years, he’s covered the global AM scene, creating YouTube videos, podcasts, websites, and a print publication – all of which means he’s been on the ground, talking with people in the industry to an extent that others can only imagine. While the array of processes encompassed by the moniker “additive manufacturing” are all advancing, he says that this is happening at different rates. Consequently, there are “jockeying moves,” as different processes come to the fore while others fall back. Zelinski says that, currently, processes like the directed energy deposition of metals and the use of granulated polymers – in lieu of spools of filament – are making strides in AM. But he points out that there is a wide array of AM technologies available to manufacturers, depending on the application – which drives process choice and material requirements. A Wide Array There is vat photopolymerization, which encompasses the original stereolithography as well as things like direct light processing. There is powder bed fusion, which has several subsets, including selective laser sintering, selective laser melting, and electron beam melting. There is binder jetting, which uses an adhesive (i.e., the “binder” that is jetted). There is material jetting – plastic or metal – where molten materials are printed and then harden as they cool. There is direct energy deposition (DED), which uses a laser to melt the powder material as it is deposited. And there are more. DED, Zelinski notes, has improved to the point that it is now capable of generating finer details and is being used to build aircraft and space components with complex inner channels. And there are cases where the build material is provided by a wire feeder, which facilitates making large “castings.” (One area where there is considerable growth in the AM field is the production of larger parts.) And along with process development goes material development, so a wide array of metals, plastics, and composites are now available for use with AM. Zelinski points out, however, that more than a small amount of material engineering is necessary; while the same material may be used to additively produce a part as in, say, molding it, microstructural changes due to the nature of the additive process may not meet the part requirement.

He says this is more pronounced in metal applications. “Is the Inconel 718 that has gone through a laser powder bed fusion the same as one that has been cast?” Given the applications where that material is commonly used, slight differences in metallurgy are not likely at all acceptable. But Zelinski makes an important point: “3D printing systems for industrial applications can do industrial work. The barriers holding back additive are numbers – for a given application, it might not be fast enough. Or the cost per part you need to get to isn’t achievable. Or the part produced isn’t precise enough without downstream steps that would add more cost to it.” He adds, importantly, “Additive technologies are advancing quickly. Numbers for it are changing way faster than the capabilities of more established technologies.” It’s what happens with an emerging technology. Still, the numbers may not work for everyone. But the number of companies for which AM is becoming more and more efficient and effective is growing.

Although the actual Apollo 13 mission occurred in April 1970, most of us probably became familiar with it during the summer of 1995, when the Ron Howard movie starring Tom Hanks was released. Among the many interesting plot points of “Apollo 13” – a testament to clever MacGyvering – is NASA’s creation of a digital twin of the spacecraft to facilitate the ground crew’s understanding of what was going on thousands of miles away in space.

So, again: an emerging technology that has been around for a while but has significantly improved thanks to recent advancements in sensors, software, and data handling. Twin Types In a sense, if we consider digital twins in the context of human twins, digital twins are both identical and fraternal. That is, identical twins come from the splitting of a single egg, which results in both embryos having the same DNA. Fraternal twins come from two eggs and two sperm cells, created at the same time but lacking identical DNA. A digital twin, created with CAD and CAE tools, is an identical model of a physical object, whether that object is a part or a system. So, the digital twin is fundamentally different than its counterpart but is engineered the same. The physical object is fitted with sensors, measured with other sensors (e.g., cameras), and set up as an IoT device. The combination of these elements provides real-time information about parameters and consequent changes to the physical object (e.g., what happens when the knob is repeatedly turned to 11?) to a digital model of the physical object. This digital twin then embodies that information to predict results, providing important data to the user, who can then improve whatever object is being modeled.