wire
2014
show
7-11 April
March 2014
183
➣➢➣
Stolberger
Stand: 09B06
Stolberger will have photographs and
information on a full range of stranding
machines, tubular stranders with bullhead,
high speed rigid stranders and designs
of pay-o s and take-ups, machines for
magnet wire, taping lines, and machines
for LAN cable.
Stolberger KMB-Maschinenfabrik
GmbH – Germany
Website
:
August Strecker
Stand: 10A21
Joining the ends of strands and stranded
conductors in front of the extruder is an
important issue in cable production. The
target is to select a quick, reliable and
economical method to ensure continuous
production.
Basically, there are two di erent methods
to weld stranded conductors in front of
the extruder.
Chamber welding method: The joint is
produced by resistance pressure welding
in a tube (chamber) which is made of
glass, ceramic or graphite. The choice
of tube material is made depending
on the strand or stranded conductor
cross-section as well as the welder’s
capacity, respectively.
For welding the two stranded conductor
ends, ie the end of the already running
cable drum and the beginning of the new
drum, are inserted into the tube in such
a way that the point of contact is in the
middle. This assembly is then inserted into
the formed grooves inside the welder’s
clamping jaws and rmly clamped.
The point of contact of the two stranded
conductor ends is brought to melting
temperature via ohmic resistance when
switching in welding current, then the
ends are pushed together and welded in
the tube by the prevailing upset pressure.
The material having become liquid is
di used evenly between the single wires
forming the stranded conductor. After
completion of the welding process the
welded strand is unclamped and the tube
is smashed.
On buttwelding machines designed for
smaller strand sizes the material is upset
via spring pressure as a rule, with the
clamping devices being opened or closed
via pedal for ease of operation – so the
operator has both hands free to handle
the strand ends as well as the tube. For
bigger stranded conductors, clamping
as well as upsetting is done. Once the
welding process is complete, the surface
of the welded joint is free of any burrs,
clean, smooth and hardly bigger in
cross-section than the original material.
Generally, welds made by means of tubes
require just a little re nishing (ie by ling),
to make their cross-section which is
slightly increased due to the process itself
pass through the inlet die of the extruder
without problems.
The chamber welding method is suitable
for regular strand constructions as well
as for ne-stranded, exible stranded
conductors as well.
Dual upset buttwelding process with
automatic
deburring:
This
welding
method is applied most successfully to
buttweld solid wires for decades already,
but also for joining stranded conductors
without any tubes. It is a proven and
well-tried process, even preferred by a
number of reputable cable manufacturers.
Contemporary extruders (XLPE) are tted
with inlet dies which allow no signi cant
tolerances in the outer diameter of the
stranded conductor. At the same time
these lines work with short processing
time. As a result there is the necessity to
produce within the shortest delay possible
welded joints of identical outer diameter
compared to the original stranded
conductor. Furthermore the welds must
be safe and reliable, ie the rst weld
must succeed optimally so the extruder’s
storage won’t run empty.
These requirements can be conditionally
ful lled
by
buttwelding
machines
working according to the chamber
welding method only. All the more as the
individual operator’s correct handling of
the complete process has an important
impact on the success of the weld.
When releasing a dual upset buttwelding
process with automatic deburring, rst
the point of contact of the stranded
conductor ends is brought to the
required welding temperature with low
pressure (welding pressure) only. Once
the material has become liquid, high
pressure (upset pressure) is switched in
and presses out of the welding zone all
heat-in uenced material, leaving just a
few tenths of a millimetre in the welded
joint. The stranded conductor’s exibility
is in uenced negatively in this short
area. Welding electrodes are tted with
knife-shaped inserts which shear o
the welding burr immediately after the
process. The still closed burr ring is torn
apart when opening the clamping device
and falls o . All motions, eg clamping as
well as upsetting and deburring, are fully
hydraulically activated.
The weld is identical in diameter when
compared to the unwelded original
material, with a welding zone that is much
shorter than on welds made according to
the chamber welding method.
Welding time is very short, too: a weld on
stranded copper conductors 1,200mm²
will only take up to a maximum 30
seconds when using a dual upset
buttwelding machine with automatic
deburring type MK 300.
Another positive side e ect on dual upset
buttwelding machines with automatic
