6. Powder Directed Energy Deposition
Directed Energy Deposition (DED) is a 3D printing process in which metallic material is fed and melted by powerful energy as it is deposited. This is one of the broadest categories of 3D printing, with many subcategories depending on the form of material (filament or powder) and energy type (laser, electron beam, arc, supersonic, thermal, etc.). Essentially, it has a lot in common with welding.
This technique is used to print layer by layer, often followed by CNC machining to achieve tighter tolerances. The use of DED in conjunction with CNC is so common that there is a subtype of 3D printing called hybrid 3D printing, a hybrid 3D printer that contains both DED and CNC units in the same machine. The technology is considered a faster and cheaper alternative to low-volume metal castings and forgings, as well as for critical repairs in applications in the offshore oil and gas industry, as well as in the aerospace, power generation and utilities industries.
△DED metal 3D printing technology can quickly create a strong metal part that can then be machined to tight tolerances
●Subtypes of Directed Energy Deposition: Powder Laser Energy Deposition, Wire Arc Additive Manufacturing (WAAM), Wire Electron Beam Energy Deposition, Cold Spray
●Materials: various metals, wire and powder forms
●Dimensional accuracy: ±0.1 mm
●Common Applications: Restoration of high-end automotive/aerospace components, functional prototypes and final parts
●Advantages: High build-up rate, ability to add metal to existing components
●Disadvantages: Cannot make complex shapes due to inability to make support structures, usually poorer surface finish and precision
1. Laser Directed Energy Deposition
△3D printing metals using lasers and powdered metals
Laser Directed Energy Deposition (L-DED), also known as Laser Metal Deposition (LMD) or Laser Engineered Net Shape (LENS), uses metal powder or wire sent through one or more nozzles and melted by a powerful laser to build a platform or metal parts. Objects are built up layer by layer as the nozzle and laser move or the part moves on a multi-axis turntable. Build rates are faster than powder bed fusion, but result in reduced surface quality and significantly less precision, often requiring extensive post-processing. Laser DED printers typically have a sealed chamber filled with argon to avoid oxidation. They can also be operated with only localized argon or nitrogen when working with less reactive metals.
Metals commonly used in this process include stainless steel, titanium and nickel alloys. This printing method is often used to restore high-end aerospace and automotive components, such as jet engine blades, but is also used to produce entire components.
△Meltio M450 wire fed laser DED 3D printer, Optomec LENS CS 600 metal powder fed laser DED 3D printer and DMG Mori Lasertec 65 DED powder fed laser DED 3D printer.
2. Electron Beam Directed Energy Deposition
△Electron beam DED 3D printing
Electron beam DED, also known as wire electron beam energy deposition, is a 3D printing process very similar to laser DED. It's done in a vacuum chamber, which produces very clean, high-quality metal. As a wire passes through one or more nozzles, it is melted by a beam of electrons. Layers are built individually, with the electron beam forming a tiny weld pool into which the welding wire is fed by a wire feeder. Electron beams are the choice for DED when processing high-performance metals and reactive metals such as copper, titanium, cobalt, and nickel alloys.
DED machines are virtually unlimited in print size. For example, 3D printer manufacturer Sciaky has an EB DED machine that can produce parts nearly 6 meters long at a rate of 3 to 9 kilograms of material per hour. Electron beam DED is touted as one of the fastest, albeit not the most precise, methods of manufacturing metal parts, making it an ideal machining technique for building large structures such as fuselages or replacement parts such as turbine blades.
△Wire Electron Beam Deposition 3D Printing
3. Wire-controlled energy deposition
△Gefertec Arc Additive Manufacturing (WAAM) printing
Wire Directed Energy Deposition, also known as Wire Arc Additive Manufacturing (WAAM), is a type of 3D printing that uses energy in the form of a plasma or electric arc to melt metal in wire form and deposit it layer by layer with a robotic arm onto A surface, such as a multi-axis turntable, forms a shape. This method was chosen over similar techniques of laser or electron beam because it does not require a sealed chamber and can use the same metals (sometimes the exact same materials) as conventional welding.
Electro-Direct Energy Deposition is considered the most cost-effective option in DED technology and can use existing arc welding robots and power sources, so the barrier to entry is relatively low. But unlike welding, the technology uses complex software to control a range of variables in the process, including thermal management of robotic arms and tool paths. This technique has no support structures to remove, and finished parts are often CNC machined to tight tolerances or surface finish where necessary.
△Wire arc additive manufacturing 3D printers from Gefertec and WAAM3D.
4. Cold spray
△cold spray
Cold Spray is a DED 3D printing technique that sprays metal powders at supersonic speeds to bond them without melting and with little thermal cracking or thermal stress. It has been used as a coating process since the early 2000s, but more recently, several companies have used cold spray for additive manufacturing because it can print at speeds 50 to 100 times faster than typical metal 3D processes, And no inert gas or vacuum chamber is required.
Like all DED processes, cold spray does not produce prints with great surface quality or detail, but parts can be used directly from the print bed.
5. Fused Direct Energy Deposition
△Fused Direct Energy Deposition: Aluminum Parts Made Using Xerox's ElemX 3D Liquid Metal Printing
Fused Direct Energy Deposition is a 3D printing process that uses heat to melt metal (usually aluminum) and deposit it layer by layer on a build plate to form a 3D object. The technology differs from metal extrusion 3D printing in that extrusion uses a metal feedstock with a small amount of polymer inside to make the metal extrudable. The polymer is then removed in a heat treatment stage, while pure metal is used for molten DED. One can also liken molten or liquid DED to material jetting, but instead of a series of nozzles depositing droplets, liquid metal typically flows out of the nozzles.
Variants of the technology are being developed, and molten metal 3D printers are rare. The benefit of using heat to melt and then deposit metal is the ability to use less energy than other DED processes and the potential to use recycled metal directly as a feedstock rather than wire or highly processed metal powder.
