Earlier this year at the Additive Manufacturing Strategies (AMS) event in New York City, I participated in two discussions: “Emerging Alloys and Metallic Materials for AM” and “Moderating the Future of DED (directed-energy deposition) and WAAM (wire arc AM).”
The technologies have a lot in common. For starters, each requires the manufacturer to qualify its processes prior to serial production, which means they must be repeatable and reliable. If not, it’s unlikely that the business will be commercially viable. Feedstocks also must be consistent; inconsistency can lead to myriad downstream problems, including poor part quality and headaches for process engineers.
I specifically said “part,” not “print.” The latter is merely a shape and a step in a long, complex process. Traditional manufacturing principles stress designing for the process. For AM, however, design must encompass the entire process, starting with materials and printing but also consider thermal treatment, machining, chemical post processing, volumetric and dimensional inspection, and mechanical testing.
To successfully implement any 3D-printing technology, there must be a balance between technical and business sides. While a robust business case is a good start, qualification built on a poor business case will lead to less-than-desirable results. The qualification process and technical requirements need to inform the business case, and, in some instances, each may need to be challenged.
We also need to recognize that AM is still in its infancy. As a materials engineer, I look at available feedstocks and ask how they can support broader growth. Future success requires consistent, affordable feedstocks. On the metals side, these typically come as powders or wire. Thanks to many decades of welding, wire is generally high quality and readily available. Powders are a different story.
Because AM is relatively new, creating industry specifications isn’t easy. That’s why we, as an industry, must support and continue the methodical, ongoing development of new specifications. At the same time, current specifications should be constantly evaluated and revised as needed.
For example, we currently have 16 approved AMS specifications for metal powder. But when you consider that there are at least 50 aluminum alloys and more than 2,000 approved AMS specifications for bar stock alone, it’s clear our work is cut out for us! Alloys have long been developed for specific processes, and it makes little sense to continue using ones invented decades ago for traditional manufacturing processes like hot forming and casting. Certification of AlSi10Mg in 3D printing is difficult because it doesn’t have an Aluminum Association designation like 7075 or 6061, whereas Ti-6Al-4V titanium is still Ti-6Al-4V even in powder form.
The point is simple: AM will succeed faster if we don’t have to innovate on materials and processes at the same time. Once we have a robust method for creating new process and material specifications, developing materials better suited to the AM process will become easier.
In addition, we need new production methods for the metal powders used in AM. The conventional method—atomization—is both expensive and requires a skilled workforce. The economics of atomization also limit the number of materials available in powder form. Most powders today are produced through water atomization, but these are generally unusable with AM. Worse, the plants producing AM-friendly powders using gas and plasma atomization will be at capacity in the near future; without their expansion, AM’s growth is limited.
Lastly, AM requires special skills, and the global workforce is yet to catch on. Engineers are still mastering design for casting processes, so how can they be expected to design for AM? As Paul Gradl, principal engineer at NASA, often says, NASA buys parts with a pedigree—emphasizing the end-to-end lifecycle. This encompasses all design aspects: microstructure, geometry, feedstock, inspection, post processing, and certification. Again, parts not prints.
I look forward to meeting AM’s many challenges, whether it’s addressing the requirements of DED-style processing or learning about new materials and processes. Engineers optimize. It’s what we’re taught to do. So I say: “Bring it on.”
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