Additive Manufacturing

NOV 2017

ADDITIVE MANUFACTURING is the magazine devoted to industrial applications of 3D printing and digital layering technology. We cover the promise and the challenges of this technology for making functional tooling and end-use production parts.

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NOVEMBER 2017 Additive Manufacturing FEATURE / Metal Additive Manufacturing 58 compelling. Because Elementum 3D has worked to develop other AM materials already, its team is already further along the learn- ing curve for a new material than any manufacturer could hope to be that tried to develop its own material. Given all the inputs and parameters that might be adjusted in search of controlled, successful, repeatable additive building with a new alloy, a ma- chine like the M 290 "gives us practically 1,000 different knobs to turn," he says. His company is more advanced than most in knowing which knobs to begin with, and which knobs to use in fine-tuning either the material or the process. Further, his company hopes to market the materials it develops, and this brings potential cost saving as well. It means that any manufacturer hoping to develop a new material might have the opportunity to split its expenses. If the manufacturer will allow Elementum 3D to supply the new material to other companies that might benefit from it (potentially including the manufacturer's competitors), then the chance exists to stream- line the development cost. For example, a manufacturer of industrial cutting tools recently came to the Colorado firm in the hope of devel- oping not an all-new alloy, but instead an additive material equivalent to the existing material used for that company's tooling. The manufacturer hopes to be able to 3D print tools in small quantities for special orders and prototyping using the same steel as its mass-produced products. Nuechterlein did not wish to detail the terms of the agreement with this customer, but in theory, a material such as this might rep- resent an exciting new product for other industrial tooling makers as well. Fit to Print The course of developing an entirely new AM metal or MMC could require up to 12 months, he says. There is a lot of build- ing of test samples. There is a lot of constructive failure on the way to zeroing in on precisely the properties being sought for that new material. However, in much less time— within a month—he says his company can determine whether a prospective new material is "possible and interesting." That is, whether it is viable for effective application within the laser-sintering process. If it is, then Elementum 3D's material-development work entails several stages. First, the company evaluates sourcing for the powders the material needs, looking to establish whether suppliers exist that can provide the requisite powder in both the consistency and the volume that the intended application will require. Then the team moves into making test coupons and systematically experimenting with different sets of laser settings and other build parameters to observe the effects. Mastery of the material's core properties comes first, followed by further experimentation to refine the control over the material's surface properties. Then, the company experiments with post processing steps such as anodizing and welding. Many restrictions potentially impede a material's suitabil- ity for AM, specifically DMLS. The most basic consideration Nuechterlein points to is whether the material is available in the right powder size and particle shape. The powder also needs sufficient flowability. The material needs to be weldable, he says, and weldable specifically to itself. And the microstructure of the metal as it solidifies needs to be stable and conducive for the formation of precise large-scale forms. (This last point is the factor preventing successful use of the aluminum alloy outside of the metal matrix composite.) Thus, AM is like any other manufacturing process in this respect: Some materials work well for it and some do not. Some materials are inherently more "printable" in the same way that some materials are inherently more machinable. But the exciting promise lies in the fact that the materials lending themselves to 3D printing are liable to be different from the materials lending themselves to machining. With additive manufacturing, certain materials can become "easy" that were never practical to apply before. The new MMC is an example. The composite combines the light weight of aluminum with the strength, hardness and heat resistance of ceramic, making this material a prom- ising choice not only for engines but also for applications in which high stiffness is needed for vibration control, or a low coefficient of thermal expansion is needed because of an extreme temperature range (the case with satellite parts). Yet the material's very combination of heat resistance and hardness makes it difficult and costly to machine. Additive manufacturing addresses this problem not just because it is near-net-shape (true of a molding), but rather because it is very near to net shape. A precisely controlled AM process can minimize the amount of machining to the point of making this hard-to-machine material cost-effective to apply. The AM process also makes it possible to achieve internal lattice forms and other highly complex shapes that hadn't been possible to realize in a metal matrix composite before. As a result, there is a message in this material, Nuechterlein says—an implication that offers part of the reason why he was eager to see his company pioneer this unusual material first. That message is simple, and it gives words to the realization he expects manufacturers to come to in increasing numbers. The message of this material relates to the advantage of AM that might ultimately prove to be its most important capabil- ity. With additive, Nuechterlein says, "I can have the material properties I want."

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