Sustainability the Key Question for Additive Manufacturing

6K Additive’s UniMelt microwave plasma system. (All images provided by 6K)

Sustainability is the hot topic companies can no longer ignore. Sidelining positive action indefinitely and “greenwashing” just won’t cut it anymore. Regardless of how successful a product is, or what application may be ideal for your product, the question “Is it sustainable?” is being posed more and more. And while many organizations aren’t quite anxious enough yet to fork out premium prices to protect the environment, governments are imposing more regulation.

Sustainability headlines dominate the media; must address their approach to sustainability in order to future-proof their success.

Choices and Questions

This leaves many businesses between a rock and a hard place. How do they achieve ambitious environmental targets, embody the ecological poster child their customers and investors want to be seen supporting, yet remain competitive on pricing—which is still the principal factor most businesses base their buying decisions on? Everyone knows sustainability costs. But does it have to?

While many companies would happily shift to sustainable business models, ensuring that ethos follows throughout the supply chain can be daunting if not downright implausible. In additive manufacturing (AM), for instance, the case is often made that the process is sustainable because it’s digital production—you only produce what you need, so there’s no waste. And the ability to share files digitally across the world means production stays local, alleviating hefty, CO2-burning transportation requirements.

But what most are not aware of is that AM metal materials production, a critical component in the supply chain, is environmentally unfriendly. If you start a manufacturing process using materials that already have a high environmental cost, can you really claim to be working sustainably?

6K Additive’s sustainable AM ​​powder solution drives the full circular economy utilizing machining scrap, used powder, support structures and failed builds as their feedstock.

Most people will agree it’s time to get supply chains working sustainably. The big question is: If the AM industry shifts to a more sustainable material production method, is it going to cost more?

Addressing Supply Chains

Focusing on metal additive manufacturing, it’s clear change is needed because the incumbent processes used to manufacture materials are not sustainable. The metal powders used in most AM processes are produced by either gas atomization (GA) or plasma atomization (PA)—and regrettably come loaded with a sizable environmental price tag before manufacturers even got started. With low yields and high waste, both processes expend prodigious quantities of energy.

6K Additive’s metal AM powder

GA is the most common technique for creating metal AM powders. It operates by heating metal or alloy into a molten melt stream. The stream is then engaged with high-velocity gas. This breaks the material into molten particles that typically range from 1 to 250 µm.

Laser powder bed fusion is by far the most widely used technique for metal AM and typically requires particle sizes in the range of 15-45 µm for its powder. In the GA process, therefore, a large percentage of the particles produced are viewed as scrap due to their size. The impact of this is an extremely low yield, with materials produced that have little to zero value—burdening the usable, correct-size powder with significant environmental and economic cost.

The other popular method is PA. This process uses wire as feedstock, which is melted by plasma torches using a similar gas stream to that used in GA. The issue with this process comes from the need to turn raw materials into wires as a feedstock. There is a surprisingly small number of metals that can be economically produced in wire form, restricting the variety of AM powders available using this method. The available materials are often sourced from countries like China and Russia; for manufacturers in North or South America or Western Europe, this additional step adds a great deal of time and energy, contributing to a negative carbon footprint as well as increased cost. PA is more efficient than GA, producing about 30 percent of the desired 15-45 μm yield size, but still produces waste and—again—cannot claim to be a sustainable process.

Given the conflict between Russia and the Ukraine, the issue of a domestic supply chain has become even more important. US military bone yards have a year of supply of nickel and titanium in the form of scrap material. 6K Additive’s ability to use these materials—as highlighted by the company’s recent Defense Logistics Agency award to convert scrap material from military vehicles—is the ideal solution to mitigate supply chain and national security risks for AM powder production.

Building a Circular Economy with Innovative Technology

6K Additive’s goal is to help eliminate wasteful, unsustainable material production by replacing it with advanced high-performance materials produced from sustainable sources—without the expected higher price.

Using the world’s first industrial-scale microwave plasma—its proprietary UniMelt system—6K Additive has developed a process that uses scrap as feedstock and produces extremely high yields—as much as 98 percent depending on the alloy. The UniMelt process also uses less energy in producing metal additive manufacturing powders, addressing all the environmental shortcomings of gas and plasma atomization processes.

Many of the factors that make the 6K process sustainable also make it cost effective, allowing 6K Additive to offer competitively priced powder while still achieving an environmentally friendly product. By using feedstock from the manufacturing process—including used AM powders, AM support structures, non-conforming 3D prints and certified chemistry machining scrap—6K Additive can source materials economically, without relying on overseas sources. 6K Additive provides an additional benefit to its customers by allowing them to essentially profit twice in the process by selling scrap feedstock material to 6K and receiving credits against premium metal AM powder purchases, creating a valuable and sustainable circular economy.

A scanning electron microscope (SEM) image of 6K Additive perfectly spherical tungsten powder.

Not only does 6K Additive recycle waste material and put it back into the supply chain, but it produces less waste, too. 6K’s proprietary preprocessing enables near-100 percent yield within any targeted particle size distribution—whether creating powders for MIM, laser or e-beam powder bed fusion, or binder-jet processes. And, of course, less waste also means more economical production.

6K Additive has the added benefit from scale: As additive manufacturing scales to predicted production levels, prices will naturally improve. Both atomization processes will still be beholden to extremely low yields, foreign feedstock prices, fuel prices from overseas, and purchases dictating cost and ultimately price to their customers.

With all the sustainability and cost benefits, users might wonder about the performance of the materials produced by 6K Additive. Unlike atomization processes, 6K’s UniMelt process does not use high-velocity gases to disintegrate molten metal flow. It uses a uniform plasma and lower gas volume, which significantly reduces the risk of gas entrapment in the particles—resulting in highly dense, less porous powder. The outcome is powder particles that are highly spherical with no satellites, no internal porosity and high flowability with a higher tap density. In turn, premium AM powder produces premium parts, so it’s also less likely to be failed parts that add more waste to the manufacturing process.

The UniMelt process also works with an unlimited number of materials, including next-generation, engineered alloy spherical powders that have not been possible to produce previously. This creates more choice for manufacturers than ever. For instance, key materials in demand for military and space application are refractory metals like tungsten or rhenium. By using multiple feedstock sources, the UniMelt process can produce these sought-after alloys for additive manufacturing powders at production scale. This ensures users who are developing new applications in areas such as hypersonics, space and rocket development have access to additive manufacturing.

6K Additive’s technology illustrates that sustainability doesn’t have to be too costly, negatively impact performance or reduce the options available to manufacturers. Designers and manufacturers are presented with a whole new set of production-grade advanced materials that are cost-effective, sustainable and can even form a circular economy.


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