WCN Spring 2011

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WCN Issue N° 44 26
speed between wire and contact
pulley changes with every diameter, no
optimal adjustment is possible. This
fact reduces the lifetime of the contact
pulleys, increases production costs
and causes surface damage.
The Niehoff single drive system for
contact pulleys has proved its worth
on the market.
This system enables speed setups
adjusted to each individual wire
diameter, which can be stored in a
recipe administration in the PLC.
This is even a must in the annealing of
alloy wires, which are used more and
more in the automotive industry.
Wire compensating device
A dancer or wire compensating device
appears to be quite simple. But here
are also some features which have
a positive effect on wire quality, for
example a swivelling laying arm in
order to avoid wire bundle crossing
on the way to the spooler. Another
example is the automatic adjustment of
the wire tension towards the spooler, ie
the control of the wire tension via load
cell. Operator mistakes are reduced.
Selection of the right guide pulleys
The selection of suitable guide pulleys
also has important influence on wire
quality. Basically, in multiwire drawing
lines only pulleys with cylindrical base
should be applied with sufficient space
to allow all wires to run in parallel.
The application of incorrect pulleys
with insufficient base or V-shape
pulleys cause the wires to overlap
and this in turn leads to different wire
speeds in the wire bundle.
The wires in the bundle are stretched
to different extents, a fact that can
only be compensated by increasing
the wire tension in the dancer.
This in turn means a loss of wire
elongation and an increase in electric
resistance leading to a reduced
conductance of the conductor.
The economical meaning of this will be
explained at the end.
Take-up systems
In order to prevent the wires in the
bundle from overlapping and crossing
it is essential to take care for the
correct installation of the spooler,
even if this might be logistically
unfavourable.
How to define poorly wound
spools?
In addition to incorrect winding
tension, most of the serious mistakes
occur at the switchover points of the
wire traverse.
Selection of guide pulleys
Pulley bottom width (L):
As large as wire diameter x
number of wires
Correct
Wrong
Too small bottom with
causes:
different running diameter
different wire speed
higher winding tension for
compensation necessary
3.3 Take-up system
Pintle type spooler
Wire path to spooler
Good
Not
ideal
Wire compensating device (dancer)
swivelling traverse pulley,
wires do not cross
• Load cell for indication of adjusted wire pulling force
• Automatic adjustment of wire pulling force, depending
on finish wire diameter