Introduction:
MTT120 Additive Manufacturing is a
Masters course in Additive Manufacturing processing which has been successfully
running at Chalmers for several years now. Students are encouraged to come up
with interesting and novel concepts that could showcase the applications of
this technology to the industry. In this case, a group of students from 2020 AM
course (comprising of David Johansson, Erik Tjärdahl, Martin Ohlsson,
William Höglind, Simon Lundin, Lars Wihler) designed and developed a Copper
waveguide filter for 10GHz frequency. The part was then printed by EOS, Finland
in pure Cu and tested here at Chalmers by David Johansson. Now, David answers
some questions for us about the components they designed.
Questions:
What is the application
of these waveguide filters?
Waveguides are capable
of transferring large amount of power at higher frequencies with little
attenuation. A filter’s purpose is to extract only certain frequencies and
reject the rest. It might be used in communication infrastructure, radar
equipment etc.
How is this AM produced
component better than conventionally produced counterparts?
A filter like this has a
very complex internal geometry and would traditionally be made from multiple
parts. And one of the main contributors to losses in waveguide systems is
coupling between those parts. So, you would have to have very flat surfaces and
lots of fasteners to ensure a good connection. By utilizing AM technology, we
can eliminate these surfaces and reduce the amount of fasteners needed.
However, making such a simple component as we did is not the most exciting part.
Since AM allows more 3D approach and the ability to merge multiple components
into one, we can build an entire feed chain. Combining filters, splitters and
antennas into one part reducing weight and improving performance.
Are there limitations to
the AM design? How can it be improved according to you?
The part we printed had
a very rough surface of Ra=20µm, this is too rough for frequencies higher than
10Ghz as the attenuation would be too great. This could be improved using a
different AM technology designed for smaller parts or by using good post
processing treatments if possible.
Picture1: CAD design of the component with cut section
design
Picture 2: Simulated vs actual values for frequency
showing an actual loss of -0.7 dB is observed and the frequency for lower cut
is seen to be 9.977 GHz instead of 10 GHz which is close to commercially
available stock part.
Picture3: Picture of
actual component after printing and post processing. Printed in pure-Cu