Direct Energy Deposition covers a range of different technologies.
This technologies are mainly applied for repair processes but they
are getting used more and more for direct part production.
The energy source can be a laser or an electron beam.
The build material is metal and it comes in form of powder or wire.
The machines are usually based on a 5 (+) axis CNC system but
industrial robots also more and more used.
Laser based energy deposition
Laser based energy deposition is also known as Laser Cladding
and Laser Metal Deposition (LMD)
Most of the systems are powder fed systems also called blown powder systems.
A nozzle / head is the core component of the system. This head has multiple jets
to supply the build material and a shielding gas. The laser beam is guided via an
optic fiber into the head. The laser window is positioned in the center of the head.
The head is mounted in the chuck of a CNC- multi axis machine or on a industrial robot.
This way the head can be moved with constant distance over the work piece. The angle of deposition
can be adjusted according to the geometry of the work piece. Shielding gas is released out
of the jets to create locally an inert atmosphere in the work area. When the laser is switched
on it heats up the work piece locally. The work piece eventually melts and the build material is
added to the gas stream. The powder particles heat up when they are injected into the laser beam.
The material fully melts and adds to the melt pool. When the head moves the material solidifies and
creates a weld track.
Another weld track is placed next to the one created previously until the whole work area is covered
with a layer of new material. The next layer is applied on top of the previous layer and the part gains thickness.
Depending on the machine setup only the head or also the work piece is moved.
Moving head and work piece is beneficial as it offers more angles for the deposition.
The resolution of laser energy deposition systems varies depending on the
nozzle/head. This is set by focus diameter/ spot size and the jets for material used
resulting in different melt pool sizes. Commonly post machining is applied.
The materials for laser based direct energy deposition processes are usually
gas atomized metal powders. All kind of metals can be processed as long
they can be gas atomized and be welded by laser.
Nickel based super alloys, Stainless steels, Tungsten Carbides are just some
of the materials most commonly processed.
What are common applications?
Laser based Direct Energy Deposition is preferably used for repair processes.
However it can also be used to create entire parts starting on the build plate.
Wear resistant coatings
One main application is the deposition of wear resistant coatings.
Tungsten carbide can be deposited on tips of drilling equipment.
Tubes can be coated on a set-up like lace. The work piece rotates and the
head moves along the work piece creating wear-resistant protective layer.
Rebuilding of turbine components
Components of gas turbines are oftentimes made of nickel-based alloys.
This components are usually created by casting. The casting process can
lead to a geometric deviation of the part compared to the nominal model.
During the process the workpiece may deform even further ending up
with a more or less individual shaped. This is why hand welding and brazing
techniques are oftentimes applied for repair and refurbishment of this parts.
Using Laser based Direct Energy Deposition for reconditioning and repair of
such kind of components offers several advantages:
– It allows a repair with the same as the base material of the component
– It can be integrated in a adaptive-machining process, accommodating the individual shape of the part
– It reduces the need for high-skilled labor and as well the chance of failure by human error
– The build up as well the post machining can be performed on one machine
Near net shape manufacturing
Parts can be additively build up close to their final shape.
Subtractive machining can be applied in a second step on the same machine.
This video from DMG MORISEIKI shows the benefits of such a hybrid process [LINK]
Electron beam based Energy Deposition Systems
Electron beam based Energy Deposition Systems are usually wire fed.
The machine is in a huge vacuum chamber. A nozzle is moved in gantry system.
The nozzle is feeding the material in form of wire. A electron gun is mounted
pointing towards the wire outlet.
The electron gun heats up and melts the substrate.
Material is added in wire form. When the head moves a weld track is created.
The next weld track is always placed next to the previous track until the substrate
is covered with a layer of new material. The next layer made of weld tracks can be
applied and the part grows.
High deposition rates makes this process suite able to build up larger structures.
Some machines have machine work areas of several square meters.
Near net shape manufacturing for Aviation industry
SCIAKY is a manufacturer of electron-beam based Energy Deposition Systems.
Sciaky calls its’ technology Electron Beam Additive Manufacturing (EBAM) process.
The material is added as a wire and the electron gun has power of up to 40 kilowatts.
See here a video how large scaled components are manufactured near net shape.
This process offers great advantages compared to CNC machining of large parts
for aero industry.
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