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Directed Energy Deposition
ISO/ASTM definition: “directed energy deposition, —an additive manufacturing process in which focused thermal energy is used to fuse materials by melting as they are being deposited. “Focused thermal energy” means that an energy source (e.g., laser, electron beam, or plasma arc) is focused to melt the materials being deposited.”
Directed Energy Deposition or DED can also be known as (in alphabetical order):
➢ 3D Laser Cladding
➢ Cold Gas Dynamic Spray*
➢ Cold Spray*
➢ Direct Laser Deposition or DLD
➢ Direct Laser Fabrication
➢ Direct Metal Deposition or DMD® (DM3D Technology, LLC)
➢ Directed Light Fabrication or DLF
➢ Electron Beam Additive Manufacturing or EBAM ™ (Sciaky, Inc.)
➢ Electron Beam Freeform Fabrication or EBF3
➢ Focused Ion Beam Direct Writing or FIBDW
➢ Metal Powder Application or MPA (Hermle Maschinenbau GmbH)
➢ Laser Chemical Vapor Deposition or LCVD
➢ Laser Consolidation or LC 
➢ Laser Deposition Welding
➢ Laser Engineered Net Shaping or LENS® (Sandia National Labs), 
➢ Laser Metal/Melting Deposition or LMD
➢ Laser Powder Forming
➢ Laser Rapid Forming
➢ Powder Fusion Welding
➢ Shape Welding
➢ Shape Deposition Manufacturing or SDM
➢ Three-Dimensional Welding
➢ Wire Arc Additive Manufacturing or WAAM
*An additive manufacturing process in which kinetic energy is used to fuse materials by plastic deformation as they are being deposited. “Kinetic energy” means the energy contained by the material that is being deposited at high velocity and is released at the time the material contacts a solid surface.
From 1994-1997 in New Mexico USA, Sandia National Laboratories developed a new AM technology which they called LENS. It differed quite a bit from all other AM technologies at the time and spawned a number of similar processes like DMD, which was commercialized in 2002 by POM Group based in Michigan USA. These other processes use many different names in an attempt to differentiate themselves; DLD, LC, LMD, DLF and more, but can be understood the same as LENS. LCVD is a completely different process from LENS and has its origins in the 1980s, but it wasn’t used to build actual 3D parts until the early 1990s. Three-dimensional welding has its roots in 1960s Germany where parts were built up using welders, but it wasn’t specifically used in AM until in the 1990s. In 2002, engineers at NASA developed a system that uses electron beams and solid wire feedstock to create parts that could potentially be made in space without gravity called EBF3. Since 2013 researchers have been investigating the use of cold spray techniques in AM as an alternative to thermally based fusion methods.
Figure 1: Example of a directed energy deposition system’s basic components, LENS (top) and EBF3 (below)
Directed energy deposition processes look very different between each method, but the premise is the same in each case. First, there is a focused area of intense energy, usually a thermal energy source like a laser, electron beam, or TIG welding torch. A feedstock material is introduced into that intense energy area causing it to bond to the surrounding material. This feedstock can be introduced either through blowing powder into that area like with the LENS or cold spray process, by pushing a solid wire into that area like with EBF3 and WAAM, or by introducing a special gas into the build chamber like with LCVD or FIBDW. The bonding mechanism varies in each process as well. In LENS and related methods, the powder enters into a melted pool of material and initially sticks to it and then melts to join the melt pool which will then cool and solidify. With EBF3 and WAAM, the wire melts and binds to the previous layers and then cools and solidifies. With LCVD and FIBDW, either a laser or an ion beam heats a spot on the build surface to a high enough temperature to thermally decompose a halide gas compound. This special gas then deposits half of itself onto the build surface, while the other half combines with a reducing chemical in the air like hydrogen to form a secondary gas compound. With the cold spray process, material is deposited at very high velocities onto the build surface and then plastically deforms and bonds onto the part.
Several different processes fall into this category, so advantages depend on the process. With the powder blowing method, powders can be changed or mixed mid-build thus creating multiple materials in a build, even creating a gradient between two different materials in the same build. This can also occur in LCVD or FIBDW by evacuating the build chamber from one gas, and putting in a different one thus making multiple materials possible. LENS type processes are able to aid in the repair of damaged parts that normally could not have been repaired using traditional methods. It can roughly add material to the damaged areas which are then cleaned up and machined to tolerance afterwards. Some of these processes like EBF3 and WAAM can also be used to develop near net shape parts that can then be machined to final tolerance without the traditional waste associated with subtractive manufacturing from a solid block. Some of these processes can also be used in space without the need for gravity like EBF3 and cold spray.
Again disadvantages range between processes. All of these processes require material to be deposited one spot at a time, and cannot do entire layers all at one time; tool paths are needed to complete each layer. Consequently build speeds are limited and somewhat slow. LCVD is especially slow due to the decomposition process and limited material deposited by it. These processes do not lend themselves to create support structures, so certain geometries with overhangs may not be created. Resolutions are generally very low and have a rough surface finish that may need post-processing like machining to get tight tolerances.
 “ISO/ASTM 52900:2015(en), Additive manufacturing — General principles — Terminology,” International Organization for Standardization (ISO), Geneva, Switzerland, 2015.
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