Meccanica Magazine n. 4

ENG
3D Bioprinting: the new frontier of additive manufacturing for
biomedical and pharmaceutical research
The RocWAAM-Robotic Wire Arc Additive Manufacturing project
kicked-off at the Department of Mechanical Engineering of the
Politecnico di Milano, under the scientific lead of Prof. Barbara
Previtali. The aim of the project is to develop the WAAM system, the
deposition process, and sharing the know-between the partners.
The implemented WAAM system will make use of the new Cold
Metal Transfer - CMT arc welding technology. Integrated to a sixaxis
robotic manipulator, the metal additive manufacturing of large
components with great geometric freedom will be possible through
an advanced degree of automation
The RocWAAM project will develop the WAAM process for
applications in the fields of die-making, civil construction, and
energy, while comparing this new technology with other families
of additive manufacturing processes as well as the conventional
manufacturing processes that it replaces. The research on the
subject will be built by giving particular emphasis to the topic of
sustainability which represents one of the main forces towards the
industrialization of the process. The team brings together the main
leaders in hardware development, ABB and Fronius that have an
established ten-year collaboration in the field. The two companies
integrated the WAAM cell in our laboratories. The BLM Group will
provide the comparison with the alternative laser metal deposition
(LMD) and laser metal wire deposition (LMWD) technologies. The
3 end-users in the team will provide the application cases to
explore different materials and geometries. Fontana Group for
the automotive die-making, Edilanzutti for the civil construction,
and Baker Hughes for the energy sector will provide distinct case
studies to allow testing the process on different scenarios.
WAAM technology uses the same operating principle as arc welding,
in which an electric arc is used as a source of heat to achieve the
melting of the metal that is supplied in the form of wire. Different
possible configurations can be recognized depending on how the
electric arc is triggered. In the case of the MIG / MAG configuration,
used in our laboratory, the electric arc is ignited between the wire,
which is coaxially fed by the welding torch, and the component. The
partnership with Fronius and Arroweld offers the opportunity to use
their proprietary CMT method. Using CMT it is possible to generate
an oscillation of the electric current thanks to the retraction of the
wire. In fact, in this configuration, the wire (positive pole) is pushed
out until the contact with the piece (negative pole) generates a short
circuit, at this point the wire is retracted. As the wire moves away
from the piece, the value of the voltage and consequently of the
electric current are varied. This strategy allows you to have a more
precise control over the heat input and to manage drop detachment
in a more controlled manner. By transferring these advantages to
additive manufacturing, where the control of thermal accumulation
becomes particularly relevant not only for the aesthetics but also for
the functionality of the component.
With the introduction of WAAM technology in our laboratories, the
additive manufacturing research capabilities of DMEC are further
enriched.
meccanica magazine
67