Electron beam freeform fabrication
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Electron Beam Freeform Fabrication (EBF3) is an additive manufacturing process that builds complex, near-net-shape parts requiring substantially less raw material and finish machining than traditional manufacturing methods. It uses a focused electron beam in a vacuum environment to create a molten pool on a metallic substrate.
NASA Langley Research Center (LaRC) originated (EBF3) technology development. The Additive Manufacturing Process was primarily developed and engineered by Karen Taminger, material research engineer for NASA LaRC. EBF3 is a NASA-patented additive manufacturing process designed to build complex, near-net-shape parts requiring substantially less raw material and finish machining than traditional manufacturing methods. There is a history of over a decade of successful collaboration with other NASA centers (JSC, GRC, GSFC and MSFC), Federal agencies and the U. S. aerospace industry. EBF3 is a process by which NASA plans to build metal parts in zero gravity environments; this layer-additive process uses an electron beam, and a solid wire feedstock to fabricate metallic structures. The process efficiencies of the electron beam and the feedstock make the EBF3 process attractive for in-space use.
Since 2000, a Team of Researchers at the NASA LaRC have led the fundamental research and development of this technique for additive manufacturing; which is cost-effective, “green” manufacturing technology, for metallic aerospace structures. Additive manufacturing encompasses processes in which parts are built by successively adding material rather than by cutting or grinding it away as in conventional machining. Additive manufacturing is an outgrowth of rapid prototyping techniques such as stereolithography, first developed for non-structural plastic parts over thirty years ago.
The operational concept of EBF3 is to build a near-net-shape metal part directly from a Computer Aided Design (CAD) file without the need for molds or tooling dies. Current computer-aided machining practices start with a CAD model and use a post-processor to write the machining instructions (G-code) defining the cutting tool paths needed to make the part. EBF3 uses a similar process, starting with a CAD model, numerically slicing it into layers, then using a post-processor to write the G-code defining the deposition path and process parameters for the EBF3 equipment. It uses a focused electron beam in a vacuum environment to create a molten pool on a metallic substrate. The beam is translated with respect to the surface of the substrate while metal wire is fed into the molten pool. The deposit solidifies immediately after the electron beam has passed, having sufficient structural strength to support itself. The sequence is repeated in a layer-additive manner to produce a near-net-shape part needing only finish machining. The EBF3 process is scalable for components from fractions of an inch to tens of feet in size, limited mainly by the size of the vacuum chamber and amount of wire feedstock available.
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