Magnetics Business & Technology - March/April 2024 - 34

TECH TIPS
Removing the Bottleneck in Welding Electrical Conductors for EVs
Motor stator with 192 welds
The need to increase the rate of joining electrically conducting
components has become critically important in the electric
vehicle sector as it is emerging to be the bottleneck of manufacturing,
according to Alex O'Farrell, development engineer
with Cambridge Vacuum Engineering. As a maker of welding
machinery, the UK-based company works close to the subject.
In a recent presentation prepared for the 75th International
Institute of Welding Annual Assembly & Conference in Tokyo,
O'Farrell made his case for electron beam welding technology,
highlighted here.
The short focal depth of field of a welding laser also creates a
high failure rate in the manufacturing, it requires high precision
of machines in the manufacturing line to ensure the parts are
prepared and held accurately at the correct working distance
so that the weld executes correctly, repeatably. These drawbacks
experienced when laser welding copper are issues that
are not relevant, however, to electron beam welding, says
O'Farrell.
Electron beam welding suffers no reflectivity issues to prevent
it coupling into materials, the focal depth is multiple times longer
and is rapidly adjustable during the process as the focusing
is performed by electromagnetic coils, he maintains.
Copper hairpins for EV manufacturing
The components of significance are electrical connectors and
wires which can be sub-millimeter thick foils or several millimeter
thick rectangular section wires. The material most used for
these components is copper due to its low cost, high electrical
conductivity, and plentiful availability. The high thermal
conductivity of copper and low thermal input required for the
components in proximity of the joining processes leads most
manufacturers to choose laser welding for their high throughput
manufacturing.
Laser welding of copper is challenging primarily due to the
wavelengths of commercially available lasers typically being
red and infrared, these do not easily couple into copper due to
the high reflectivity.
The reflectivity also contributes to limit the beam angle of
incidence, meaning the process must integrate mechanical
repositioning of the welding head.
34 Magnetics Business & Technology * March/April 2024
The rapid speed of beam positioning by electromagnetic coils
and commercial availability of significantly higher beam power
supplies are the most important advantages in allowing electron
beam to process hundreds of copper welds per minute.
The rapid rate of processing means the seconds taken for the
vacuum chamber to evacuate ready for welding become negligible,
furthermore, the fact that the welds are performed in a
vacuum chamber mean the resulting weld has no porosity and
impurities in the connection, optimizing electrical performance
and vehicle efficiency.
A builder of both laser
beam and electron
beam welding machines,
Cambridge can tailor
them with numerous
customizations for
specific manufacturing
requirements. In June, it
launched a new electron
beam welding machine
for electric vehicle components
including batteries,
shunt resistors, motor
stators, hairpins and
invertors. For more info
and O'Farrell's presentation,
see www.camvaceng.com.
Electron beam welding system from
Cambridge Vacuum Engineering
www.MagneticsMag.com
http://www.camvaceng.com http://www.MagneticsMag.com
Magnetics Business & Technology - March/April 2024

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