EuroWire September 2017

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Technical article
September 2017 69
tension. Behind the levelling machine
the four tension rollers, together with the
recoiler, pull on the strip.
By means of force superposition (tension
and bending) between the groups of
upper and lower levelling rollers, the
internal tensions and shape deviations of
the strips are reduced.
To achieve a sufficient levelling effect in
the case of very thin strips with material
thicknesses of between 30 and 200µm,
the metal strip specialist has developed a
cassette with a levelling roller diameter of
8mm. For thicknesses greater than 200µm,
12mm levelling rollers are used.
Deviations are automatically detected by
a Vollmer shapemeter roll for continuous
strip shape measurement. Strip zones with
waves exert less force on the segmented
roller than flat strip zones.
Software calculates the mathematical
formula for the strip shape with the help
of the measured values and uses this to
create a 3D model.
Based on this, the necessary position
of the levelling roller supports can be
calculated and automatically adjusted.
Manual readjustment is unnecessary.
A special feature is the four adjusting axles
at the upper levelling cassette, which
ensure the ultra-precise position of the
three spatial axes. “Depending on the
initial flatness, evennesses down to one
I-unit can be achieved. This corresponds
to a 0.2mm high and 100mm long wave in
the strip”, added Mr Lüdecke.
Highly dynamic drive
for broad control
spectrum
In principle, all copper alloys are
processed on the line without restrictions,
with the strips having a wide range of
cross-sections and the tensile strength
of the material varying between 300 and
1,100N/mm². The thickness lies between
30 and 500µm and the width is between
100 and 450mm, which results in an
aspect ratio of 1:75. If the yield strength of
200 to 1,050N/mm² is added, the ratio to
be controlled for is 1:390. Due to this wide
spectrum, the strip tension is measured
directly at the decoiler and recoiler, as well
as in front of the levelling machine, and
serves as a control value for the drives.
These are equipped with highly dynamic
AC motors.
The installed capacity here amounts to
around 550kW. “Feed-in is performed
with Sinamics S120 Basic Line assemblies,
so that the regenerative energy can be
reused via an energetic recovery system
on the pull side – that is, for the motors
after the levelling machine. This leads
to significant energy savings,” added
Mr Lüdecke, pointing out one of the main
advantages of the line.
Activation is performed by fully digitalised
inverters, which are coupled to the PLC of
the line controller via Profibus L2-DP. The
actual control functions are controlled via
a microprocessor that enables not only
considerable ease of operation but also
easy start-up and maintenance.
Especially user-friendly
and safe operating
concept
The complete line bears the CE sign
and is designed in accordance with the
European Machinery Directive 2006/42/EC,
which provides for, among other things, a
protective fence for employee safety.
▼ ▼ To still achieve a sufficient levelling effect despite strips having very small material thicknesses between 30 and 200
µm, the metal strip specialist has developed a cassette for levelling rollers with a diameter of 8mm. For thicknesses
greater than 200µm, 12mm levelling rollers are used
▲ ▲ A feed-in system without a manual feeder, developed by B+S, contributes to ease of operation and the economic
efficiency of the line. The beginning of the strip is clamped in a clamping bar at the beginning of the line and
pulled through to the outfeed. This means that no pilot strip is required, and welding or the need for guide plates is
eliminated. Winding on the recoiler also takes place automatically