STEEL + TECHNOLOGY 01/2020 EXTRACT

60 | STEEL PROCESSING
Deep drawing of sheet metal
Monitoring metal sheet infeed during the
pressing process
In cold forming processes, deep drawing is considered a decisive step in the production process. optoNCDT
1420 laser triangulation sensors measure the metal sheet infeed during pressing, as this parameter is crucial for
the quality assessment of the process. Due to their robust design, these sensors are insensitive to shock and
vibration. Based on innovative sensor technology, the measured results are constantly precise even under
challenging conditions such as parts with different reflection characteristics.
optoNCDT1420 1420 sensors measure the metal sheet infeed during deep drawing
(Picture: Micro-Epsilon)
Ablank to be deep drawn is pressed
by the ram into the die (mould).
The flange of the sheet is partially
pulled inwards and distortions can
occure at the edges of the flange as a
result of the deep-drawing process,
when the material “flows“ below the
blank holder from the outer area into
the die. The distortion can be detected
as a change in distance. This value is
crucial for the quality assessment of
the pressed part.
The measurement of the distortion
is carried out using several optoNCDT
1420 laser triangulation sensors, which
are placed around the blank, either
directly installed in the die or blanholder
– or aside the die. Due to their
extremely compact design, these sensors
can be effortlessly integrated into
a small space. The arrangement is chosen
in such a way that the laser beam
is directed on the edge of the sheet,
which is between the blank holder and
the die. Due to the extremely small
measurement spot size, the laser is
able to measure extremely tight gaps
between the two tool parts of less than
one millimetre.
The measured values are transmitted
via analogue or digitally to the controller.
They allow a conclusion to be
drawn on how much material has
flowed. This enables, for example, the
pressing forces to be controlled during
the ongoing process, reducing waste,
material consumption, downtime and
costs.
Even when exposed to harsh ambient
conditions, laser triangulation sensors
from Micro-Epsilon provide reliable
measurement results. They are
rugged and can withstand high mechanical
loads such as vibration and shock.
The Auto Target Compensation (ATC)
feature rapidly compensates for different
reflections caused by high-gloss
through to dirty-matte sheet metal
parts, while enabling a smooth distance
signal.
• Micro-Epsilon
STEEL + TECHNOLOGY 2 (2020) No. 1