Directed energy deposition (DED) is one of the ASTM accepted additive manufacturing technologies. In operation, focused energy, (from a laser beam, for example) is directed at a powder material (usually metal) while it is being deposited onto a surface. When the energy and the powder meet, just as the powder hits the surface, the powder is melted and fused onto that surface.
Other names for DED include Laser engineered net shaping, directed light fabrication, direct metal deposition, and 3D laser cladding.
Usually, a DED system has a nozzle that is mounted onto a multi axis arm. The arm moves in multiple directions to deposit the melted powder. Typical applications are to build geometrically complex shapes and to repair existing parts.
The process can be used with polymers, ceramics but is typically used with metals, in the form of either powder or wire.
The vendors of DED include:
BeAM, an Addup Co., uses a deposition nozzle mounted on the z-axis of a DED dedicated CNC machine for up to 5 axes of freedom for the deposition. The DED dedicated CNC machine uses traditional CNC controls and ISO g-codes familiar to a traditional manufacturing workforce.
Optomec offers its LENS directed energy deposition (DED) systems. The company recently announced a new LENS Laser Deposition Head (LDH 3.X), with a variable optics system that can create three discreet focused spot sizes to accommodate changes in laser power. The LDH 3.X supports a range of laser powers from 500 W to 3 kW to ensure optimal DED processing across a range of parts and applications.
One of the newer materials Optomec can work with is copper, which can be a challenge due to the material’s high reflectance. The infrared wavelengths on most standard, laser-based AM systems are not readily absorbed by copper, so it can be difficult to establish a melt pool as the laser energy is reflected back into the source. Optomec engineers developed process parameters to account for thermal conductivity differences, as well as changes in absorption and have demonstrated efficient DED builds with pure copper.
Copper is often used in heat exchangers and industrial applications in aerospace and chemical processing. The Optomec systems can also handle alloys of copper such as bronze, brass and cupronickel.
Sciaky’s electron beam (EB) gun deposits metal in the form of wire feedstock, layer by layer, until the part reaches near-net shape and is ready for finish machining. Gross deposition rates range from 7 to 25 lb (3.18 to 11.34 kg) of metal per hour, depending upon the selected material and part features. The company also offers a dual wirefeed system, which lets users combine two different metal alloys into a single melt pool to create “custom alloy” parts or ingots. The mixture ratio of the two materials can also be customized. Users can alternate between different wire gauges for finer deposition features (thin wire) and gross deposition features (thick wire).
Polymer materials can also work with a DED process. AREVO, based in Silicon Valley, California, developed a technology to enable polymer DED. This process uses a “wire” or filament of carbon fiber impregnated with a thermoplastic polymer matrix.
DED does have some limitations. Depending on the system, Parts produced may have low resolution. The surface will usually require some secondary machining.
Because of the deposition process, DED is not a suitable means of creating support structures, which can limit parts with certain geometries, such as, overhangs.
