EOW March 2014

wire 2014 show

7-11 April

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

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 : www.stolberger.com

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

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March 2014