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Mechanical Technology — August 2016
37
⎪
Innovative engineering
⎪
The selective laser melting
(SLM) process
With selective laser melting (SLM) thin
layers of atomised fine metal powder (50
to 150
µ
m) are evenly distributed using
a coating mechanism onto a substrate
plate, usually metal, that is attached to an
indexing table that moves in the vertical
(Z) axis. This takes place inside a chamber
containing an inert gas, either argon or ni-
trogen with oxygen levels below 500 ppm.
Once each layer has been distributed,
each 2D slice of the part geometry is
fused by selectively melting the powder.
This is accomplished with a high-power
laser beam, usually an ytterbium fibre
laser. The laser beam is directed in the
X and Y plane using two high frequency
scanning mirrors.
The laser energy fully melts (fuses)
the metal powder particles to form solid
metal. The process is repeated layer after
layer until the part is complete.
SLM machines rely on STL (stereo-
lithography) files, a CAD file format cre-
ated for 3D-printing systems that slices a
CAD model into layers, allowing the part
be built slice by slice from the bottom by
fusing each 2D ‘top slice’ to the previously
fused layers below.
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Hannover, highlighted when he discussed the
use of selective laser melting (SLM) of the
first magnesium powder, Elektron MAP 43,
in lightweight designs. Gieseke outlined the
results of a study calculating the particle sizes,
processing parameters and structures required
to produce specimen components with a den-
sity of over 99%.
Challenges and solution approaches of AM
with metals in series production was dealt with
by Oliver Kaczmarzik of Concept Laser. He
examined a range of issues: how to increase
productivity; a modular approach that combines
several AM units; automated processes; the
physical separation of the construction, pre-
treatment and post-processing phases; and the
integration of AM manufacturing machines to
Industry 4.0 standards.
Both the medical technology and aviation
sectors use electron beam melting (EBM) in
the production of series parts. One of the firms
meeting the resulting increase in demand for
process and quality control solutions is the
Swedish company Arcam; and Patrick Ohldin
presented some of his company’s innovative
developments. These include a high-resolution
camera and an X-ray sensor that are integrated
into the company’s quality systems. The camera
takes images of the entire powder bed after
melting so that quality controls can be per-
formed for each layer of the process. The X-ray
sensor is able to determine beam parameters
such as position, focus and beam profile with
exceptional accuracy.
Clemens Lieberwirth from the Department
of Fluid Technology and Microfluidics at the
University of Rostock presented a further
exciting development: an extrusion-based ad-
ditive process for producing high-density metal
components known as Composite Extrusion
Modelling (CEM). It consists of two phases:
additive manufacturing of green parts from
injection-moulded metal grains; followed by
industrial sintering. CEM has demonstrated
distinct advantages over powder-based pro-
cesses in terms of material handling and
cost-effectiveness.
The new trade forum was organised by
Siemens’ Yves Küsters, who has been working
on SLM for almost ten years and was awarded
his PhD for his thesis on
‘Methodological
Parameters for a Robust Blasting Process’
.
His work at Siemens includes developing SLM
processes and materials, with a particular focus
on high-temperature alloys.
Other trade forums included for the first time
at the 13
th
Rapid.Tech were: Additive Contract
Manufacturing; Electronic Engineering; and the
Automotive Industry forum. The new conference
forums and the well-established trade forums –
Medical Technology; Dental Technology; Design;
Aviation; Tools; and Science – and the
User’s Conference provided oppor-
tunities for industry professionals to
discuss specific AM issues in depth.
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