If the vibrations are too great, the quality
check with the vision sensor fails. "In
order to prevent vibrations, we opted
for SCHUNK linear axes with servo-
electric direct drives, which move both
dynamically and very gently," emphasizes
the experienced plant engineer. "
In addition, the entire unit can be
decoupled from the micro-vibrations
of the environment by means of an air
spring element at the moment of the
measurement, so that a highly precise 3D
measurement is possible." In addition to
the optical test, the insulation is tested
at other stations and the components
are calibrated.
Linear motor axes allow gentle
movement
The LDx series is regarded as a
benchmark in the field of high-
speed assembly. High-performance
servomotors achieve particularly high
outputs in a compact space. Almost all
modules of the LDx series are already
available as standard with absolute-
value transducers, which ensure a
repeat accuracy of 0.01 mm per axis.
They eliminate the need for expensive
reference runs when the system boots up
and after emergency stops.
In addition, the modules need neither
end nor reference sensors, reducing the
investment costs, programming effort,
and the number of cables in the cable
set. Since several freely programmable
slides can be placed on one guiding
26
profile if required, particularly compact
and cost-efficient concepts can be
implemented.
The driving force is transmitted directly
onto the slide by high-precision drive
elements, free from play, without
mechanical transmission elements. This
results in short cycle times, maximum
precision, and permanently high process
reliability. Since the modules have
almost no wearing parts, unplanned
downtime and maintenance costs are
reduced to almost zero.
LEM uses two module variants for
its application: The SCHUNK LDN is
equipped with an X profile and achieves
a maximum drive force of 250 N, and
a maximum nominal force of 120 N in
the basic version. The SCHUNK LDH,
on the other hand, is a compact Z-axis,
which is designed especially for precise
movements or controlled press-in
operations in high-speed assembly as
well as in measurement and testing
technology.
It is impressive due to the fast response
characteristics and high positioning
accuracy. The maximum driving force
is 125 N, the nominal force is 52 N.
Optionally, the axis can be supplied
with a pneumatically operated holding
brake, by which the position of the axis
is reliably maintained even in the event
of an emergency stop. The axes are
controlled with Bosch Rexroth IndraDrive
controllers as standard. The modules
are available with either an incremental
path measuring system (1Vpp interface)
or with an absolute path measuring
system (optionally with the Hiperface,
SSI or DRIVE-CliQ interfaces). Due to
these combination possibilities, the
modules are compatible with different
controllers and can thus can be quickly
and easily integrated into higher-level
controllers.
Pneumatic-free systems as a goal
From the point of view of Frédéric
Cattaneo, the trend at LEM is clearly
towards pneumatic systems. "In the
future, we will mainly build electrical
systems with electric grippers, electric
linear modules, and electric rotary
modules. The current system is an
intermediate step from pneumatics to
fully electric machines.
"The main reasons are the elimination of
valves and hoses, reduced energy costs,
cleanliness within the assembly process,
and the significantly reduced vibrations,
especially at high speeds. Instead of
radically eliminating pneumatic modules,
LEM prefers a gentle way to avoid
overworking of the user, and to ensure
maximum process reliability at all
times: Step by step, individual modules
are being replaced by mechatronic
alternatives from the SCHUNK range. In
the next step, the mechatronic SCHUNK
EGP gripper for small components will
take over the tasks of the tried-and-
tested pneumatic SCHUNK MPG-plus.
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