EOS Whitepaper - Additive Manufacturing Supports

1. Summary
Seasoned experts in additive manufacturing (AM)
design their parts in an optimized way for the production
method. This means, that they try to avoid support
structures wherever it is possible and choose self-
supporting geometries. But even the greatest ingenuity
does not necessarily prevent from the use of supports.
Some characteristics are simply impossible to build
without. The real challenge is to create such elements
smart and efficient. Designing support structures
therefore is an art form in itself.
The Art of supporting
metal AM parts
by Stefan Bindl, EOS GmbH
This whitepaper is for
you if you are
→→ Designing metal AM parts
→→ Seeking to design your support
generation smarter
→→ Looking to reduce your
post-build processing time
Whitepaper

2. 2
Nowadays building metal parts by additive manufacturing
requires a tremendous amount of support structures
as the designs in most cases do not really address AM
requirements. But even with specific designs for additive
manufacturing some support structures may be necessary.
Besides the boundary conditions, there are always the
same requirements for suitable support structures:
→→ Easy to remove
→→ Strong enough to hold the part
→→ Short build time
→→ Material saving
The Art of
supporting
metal AM parts
Indeed every AM engineer who is dealing with this topic
for a while knows about those. The only question arising is,
how can we get the conflict of aims solved or at least find
a suitable trade off?
By using a demo part we want to give an idea on the “Art
of supporting metal AM parts”.
Let us start with the part first: This is a design study for
a combustion chamber used in aircraft or helicopter gas
turbine engines. The entire design was dedicated to the
manufacturing method of AM, requiring virtually no
overhangs to be supported or any other geometries that
would feature any kind of support structures (see figure 1).
So far so good.
Design Study of an annular
combustion chamber
with differently shaped air inlets

3. 3
Integration of ­attachment points
Now as there was no opportunity to integrate the adjacent
module, the turbine casing, into this part some attachment
points had to be integrated. In an ideal world we would
have a closer look on the nozzle guide vane to see how we
can make use of additive manufacturing to combine both
components or at least create an advanced interface. For
this case, let’s assume for some reasons we have to stick
to the already predefined attachment points of the turbine
casing. Augmenting those, the combustion chamber could
look like this.
Design optimization to reduce
­supported ­surfaces
Now it is relatively obvious, that these overhangs will need
support structures and as they are very high above the
building platform they need to be connected to the part.
What could be done from the design was to modify the
down facing surface a bit. As this surface is going to be
rough even if using support structures we can make the
best out of it and use the surface to ensure the bolts and
nuts will not loosen during usage. In this case, some sharp
ripplets have been introduced to realize the functional
surface. In addition the support structures can be reduced
as the exposed area per layer is reduced as well. Figure 3
illustrates the new design.
Annular combustor with mounting devices
to attach to the turbine casing
Detailed view of the attachment points and the ripped downward facing area

4. 4
From obvious to smart supports
The most important question still remains open – how
can we realize the support structure in a smart way?
As can be derived from the design, the removal of the
support structures within this small gap underneath the
attachment points would require high efforts. In order to
solve this problem an additional part was created, with the
purpose of holding the supports and make it possible to
remove them. This additional block features two bottom
surfaces to be connected to the part and the top surface
to be the basis for the support holding the attachment
geometry. The block itself is designed to be self-supported
and does not require any additional supports.
Speaking about the smart way of building supports this
block has one key feature. Inside it comprises an internal
hexagon to be able to twist it after the built breaking the
supports and getting them out.
In addition to this functional integrated support assistant
some conventional support structures have to be designed.
Therefore one of the various supporting tools can be
utilized. In this case Materialise Magics was used to create
block supports.
The support in between the combustor and the support
block was designed in a way that it just holds the ripplets
in place and conducts the heat. At this location no strong
support and no really sophisticated connection to the part
is needed as the shackle grows out of the surrounding
walls of the burner.
On the other hand the support beneath the support block
needs to hold the block and withstand the impacting
recoating forces during the build. Having a circular
combustion chamber there are always some supports
and support blocks angled in a disadvantageous position.
Hence, the two supports, one on each side, feature a finer
hatch distance compared to the upper support in order to
make them stronger.
Both block supports, the upper and the lower, feature teeth
to the combustion chamber and closed walls and border
walls without teeth to the support block. This is because of
the later removal. Due to the weaker connection with the
combustion chamber it is supposed to break there and not
at the support block. As the entire supports will be broken
by twisting them an increased teeth height contributes
positively to the ease of removal.
CAD created support block featuring self-supporting geometry (left) and hexagon hole (right)

5. 5
Setting up the exposure is also a crucial step within this
support generation. The kind of exposure assigned has a
significant influence on the performance of the support
and the buildability of the part in total. The following
modifications have been made to successfully build the
part and being able to remove the support structures
afterwards.
The upper support, as it can be weak, was set to a lower
energy level to reduce the connected surface on the one
hand and to make the walls more fragile on the other. The
two lower supports have been built with the standard
EOS_External_Support parameter
The support block itself is waste material and therefore
does not need to feature highest material properties.
Therefore, the hatch distance was increased to speed up
the process by reducing laser tracks and in addition the
contours have been disabled. This has a positive effect
on build time as well as the recoater contact is decreased
because of the reduced energy introduction at the parts
borders.
In order to identify a suitable configuration of support
geometry and process parameters it might be useful to
build some test parts to evaluate different settings. In this
case this was done on an EOS M 290 (see figure 7) and the
results have been transferred to the EOS M 400 on which
the combustion chamber was finally built (fig. 8).
Additional support block featuring all support structures for the build
Getting the support out by an Allen key

6. Dr Stefan Bindl
EOS
In 2005, Stefan Bindl graduated in aerospace engineering
at the Technical University of Munich. He complemented
his engineering studies with practical experience at several
different research facilities focused on propulsion systems.
He undertook his diploma thesis on at the Institute of Jet
Propulsion at the University of the German Federal Armed
Forces in Munich, and continued working there until 2015,
first as research assistant until his doctorate in 2010,
then as team leader for the engine test facility and finally,
Stefan Bindl was professor for aircraft engine dynamics. In
2015 he joined EOS.
Contact: stefan.bindl@eos.info
EOS GmbH
Electro Optical Systems
Corporate Headquarters
Robert-Stirling-Ring 1
82152 Krailling/Munich
Germany
Phone +49 89 893 36-0
Fax +49 89 893 36-285
www.eos.info
Status 02/2017. Technical data subject to change without notice.
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