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T
he cheapest versions are cast, but
those for well-heeled customers
are cold-forged and pre-
cision-machined using CAD
modelling and water-jet cutting machines.
Aluminium wheels are the pride and joy
of prestige-conscious drivers. Their
unquestionably good looks also have a
small disadvantage: more and more of
the wheel interior is exposed to the
critical gaze. This means that the hubs, in
particular the brake discs, are exposed to
the ravages of time. Even with the most
exquisite alloy wheels, rusty steel will
spoil the picture.
It is therefore fortunate that dedicated
developers from Kirchheim in Southern
Germany have found an elegant solution
to the problem. The injection machinery
manufacturer Sprimag
Spritzmaschinenbau GmbH & Co. KG
protects brake discs with lacquer
technology to prevent corrosion,
transforming them into a feast for the eye
of motorists – including those driving the
premium brand Audi. The clever feature
of this process: proportional pressure
control valves type VPPM controlled via
Profibus by a valve terminal MPA are used
to regulate the spray pressure so finely
during the lacquering process that there
is no need to mask the friction surface of
the discs to protect them against lacquer
mist. This innovative solution reduces the
consumption of lacquer with semi- and
fully-coated brake discs and makes the
finishing process quick and cost-effective.
Minimised overspray
At the heart of the lacquering process is
the perfect implementation of computer
programs by pneumatic components.
Within the brake disc feed system, a laser
probe identifies the type of brake disc
and sends this information to the PLC.
The system controller sends the
appropriate data packet with the
necessary parameters for the product
specific spray pressure to the
proportional valves VPPM. The cascade
control system for these valves, with
integrated multi-sensor control, adjusts
the atomiser air, the spray jet and the
pilot air to optimum settings and reduces
overspray. This is the amount of lacquer
which escapes during spraying
applications into the environment in
Eye-catching discs
They look their best
when they are at rest. It is particularly when the vehicle
to which they are fitted is at a standstill that lacquered brake discs attract the
eyes of car fans. At Audi, sophisticated technology from Sprimag and Festo is
generating some striking impressions in the automotive“underworld”.
Powerful valves:
A dozen proportional valves VPPM regulate the
spray pressure precisely.
Fine nozzle:
No need for protective masking of brake discs which are
to be only partly lacquered.
Lacquering brake discs