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www.us-tech.com Pr o duc t io n
3D Printing Powder Optimization Improves Part Quality
By Del Williams T
he global 3D printing metals market is expected to reach $3 billion by 2025, according to Grand View Research. However, to take full advan- tage of this growth and produce high-quality parts efficiently, powder
producers, 3D printer manufacturers and others must ensure the consistent, repeatable quality of the metal powders used in the process. Applications for 3D printing range from aerospace, defense and automo-
tive to medical and jewelry. The metals involved include aluminum, titanium, stainless steel, cobalt-chrome, copper, or nickel, as well as precious metals, such as gold, silver, platinum, and palladium.
Optimizing Powder Quality Most metal powders used in 3D printing, such as iron, nickel, cobalt, alu-
minum, and titanium alloys, are produced by gas atomization. In this process, a feedstock is melted in a crucible before it is ejected from a nozzle into a high- pressure gas stream. This breaks the molten metal into fine particles, typi- cally under 50 to 150 µm in size. While the metal powders pro-
duced by this process are typically spherical in shape, it is also important to address the porosity of the surface of the particles to improve “flowabili- ty.” Otherwise, the powder can clog or slow during the process, affecting the speed and quality of printing. “For reliable 3D printing produc-
tion, the powder must flow continuous- ly and smoothly,” explains George Paf- fendorf, director of operations at Advanced Powder Solutions (APS), a con- tract manufacturer with extensive powder expertise. APS is the in-house test- ing and engineering arm of GEMCO, a manufacturer of tumble blending and vacuum tumble drying equipment. The attractive force between tiny, submicron-size particles also increas-
While metal powders are typically spherical in shape, it is important to address the porosity of the surface to improve “flowability.” Otherwise, the powder can clog or slow during the process, affecting the speed and quality of printing.
es as the particles become smaller. From a quality standpoint, metal particle porosity can also reduce the
load bearing, fracture toughness and fatigue properties of the finished part. Under cyclic stress conditions, it can also lead to cracks and part failure. To eliminate porosity and enhance flowability, Paffendorf says a growing
number of proactive powder suppliers, as well as 3D printer manufacturers, are adding a heat treatment step to the manufacturing process that involves tumble dryers to achieve a more consistent, high-quality product.
Reconditioning Powder It is also important to efficiently reuse any unused metal powder at the
bottom of the tray for the next print job, because it is costly and cannot be wasted. When this is necessary, vacuum tumble blenders, like those from GEMCO, can be used to re-blend the powder in with new material. Advanced tumble blenders are designed to apply even turbulence in all
corners of the mix. This is accomplished through a combination of macro and micro blending that produces a better distribution. Macro blending is achieved by rotating the shaped vessel, allowing the
material bed to fall away from the vessel’s walls. The blender moves at a pre- cise speed, with the vessel wall at a precise angle, so that the material cas- cades over itself. There is no additional force from paddles, plows or spiral rib- bons — just gravity. While this occurs, micro mixing, if needed, simultaneously proceeds with
agitator blades located in the mixing zone center of the vessel, where fine pro- cessing in the material happens. Together, the macro and micro mixing even- ly expose each particle to six times more active blending per revolution than traditional mixers. Although the industrial 3D printing market primarily involves metal
powders, the addition of a heat treatment step can improve part quality and manufacturing productivity in markets where plastic or resin-based powders
are utilized as well. Contact: Advanced Powder Solutions, 301 Smalley Avenue, Middlesex,
NJ 08846 % 800-654-3626 E-mail:
sales@okgemco.com Web:
www.okgemco.com r
March, 2020
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