NASA's JPL Makes Bi Metallic 3d Printer

The technology to 3D print a single part from multiple materials has been around for years, but only for polymer-based additive manufacturing processes. For metals, jobs are typically confined to a single powdered base metal or alloy per object.

However, researchers at NASA’s Jet Propulsion Laboratory say they are in development of a 3D printing technique that allows for print jobs to transition from one metal to another in a single object. According the JPL researchers, these gradient metals have been created previously in a lab setting but NASA’s process is the first to make usable objects that take advantage of the mechanical and thermal properties of the various metals used.

“We’re taking a standard 3-D printing process and combining the ability to change the metal powder that the part is being built with on the fly,” said Douglas Hofmann, a researcher in material science and metallurgy at JPL, and visiting associate at Caltech. “You can constantly be changing the composition of the material.”

According to the researchers, the process is based on Laser Deposition technology, in which metal powder is injected into a high-powered laser beam that melts the surface of the target object to form a small molten pool. Powder applied to this pool is absorbed and leaves a deposit as thin as 0.005 in. thick. These densely bonded layers can then be used to either build or repair metal parts.

In JPL’s technique, the build material’s composition is gradually transitioned as the print progresses. For example, the powdered build material might contain 97 percent titanium alloy and 3 percent stainless steel at the beginning of the transition. Then, in 1 percent increments between layers, the gradient progresses to 97 percent stainless steel and 3 percent Ti alloy by some defined point in the overall 3D printing process.

The main benefit — in addition to testing the metallurgical properties of new alloy compositions – is to take advantage of the differing physical properties (i.e. thermal expansion, magnetism or melting temperature) of the two or more metals in one solid component, say the researchers.

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