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What is Direct Energy Deposition Process?

This technology benefits from a high-power laser to fabricate the part in a layer- and step-wise process of sequential welding.  The high rate of the focused energy of laser source on the surface of the object under fabrication produces a melting pool into which the powder or wire material is guided. This powder and wire add material to melt pool to solidify and gradually define the object eventually.  As shown in Fig. 1, a multi-axis motion stage makes it possible to scan the cross-section, similar to the powder bed system, while continuing to add the material to the pools.  The part is placed while the nozzle or wire feed moves in three dimensions to describe a 3D final shape from the original digital file.  The part that comes out of the machine is fully functional and dense, where its strength is reportedly comparable or even better than the wrought material. 

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Fig. 1. Direct Energy Deposition and Laser Engineered Net Shape (LENS) manufacture metallic parts. The system consists of multiple or single nozzle, multi-axis motion stages, laser source, focusing lenses, powder supply system, build platform, and monitoring equipment  (image from sciencedirect.com by Bhaskar Dutta and Francis H. Froes)

The intensive thermal phenomena inherent in these manufacturing processes and the cyclic thermo-mechanical effects make these parts susceptible to distortion, residual stresses, and cracks for which post-processing is required to mitigate some of these issues and improve the part quality.  Directed Energy Deposition (DED) and Laser Engineered Net Shape (LENS) are two leading commercialized technologies in this category. 

These technologies produce melt pools that expand their applications to repair and are successfully being used for maintaining, cladding, coating, and re-storing purposes.  Due to high temperature and susceptibility to oxidation, the process is performed under vacuum or in the presence of inert gases.

Laser Engineered Net Shape (LENS), Source: optomec.com

Directed Energy Deposition (DED), Source: BeAM.com

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