EuroWire November 2016

Technical article

Double Twist

Roll Forming

Coil Pay off

Assembly into Compact Conductor

RoundWire

Roll Formed Profiles

▲ ▲ Figure 4

The process is shown in Figure 4 . Round wire is taken from large coil packs and passes through the roll form section where its shape is changed into various roll form profiles that are then assembled at high speeds by either a double twist machine or a single twist machine, depending on product size. This high-speed continuous process allows for linear speeds of 200m/ min to be achieved while producing highly compact conductors. The roll form strander is capable of producing 40 tons of 150mm 2 compact aluminium conductor in a 24-hour cycle. Conclusion Savings in production costs depend on many factors such as existing manufacturing facilities; whether the strand is currently manufactured in-house or purchased; the care and control exercised over input copper and aluminium wire; general house-keeping; and the control of high-speed double twist stranding machines. Under the most advantageous conditions savings can provide quite astonishingly short pay-back periods, but should of course be calculated for each individual application. The high performance of a roll form strander coupled with the Ceeco Bartell roll forming process will allow the cable manufacturer to reduce costs without compromising the finished conductor performance. An awareness of this and other new technologies, combined with enlightened specifications, will further enhance the development of strand design and the potential to optimise further the manufacture of stranded conductors. n

92 per cent fill factor is the best compaction that can be achieved using conventional methods. However, with the roll forming process 96 per cent fill factor can be achieved. This creates a potential saving of material of around two per cent. The productivity of the extruder relies in part on the integrity of the strand construction. This applies equally to low, medium and high voltage extrusions. Unstable strand construction not only compromises the speed of the stranding and extrusion processes, but can lead to considerable losses due to scrap and down times for both lines. Birdcaging is often the result of unstable strand design. A tightly wound conductor is less likely to end up birdcaging. The tightness of the strand is greatly dependent on the geometry of the elements. For this reason, the lay of the conductor is important. The elements of unilay/ unidirectional lay conductors are nested and, therefore, inherently have a smaller outer diameter than reverse concentric lay and SZ conductors. addition, unilay/unidirectional lay conductors self-tighten under tension. As a consequence of this self-tightening feature, the extrusion of unilay/unidirectional lay conductors is statistically less prone to birdcaging. The surface of the strand is also critical. A smooth outer layer such as one found with a roll formed layer presents a clean round profile to the extrusion process and, therefore, minimises the accumulation of conductor dust during the extrusion process. In

Ceeco Bartell Machinery Systems LLC Ceeco Bartell Products 400 Applewood Crescent, Suite 100, Vaughan, Ontario, Canada Tel : +1 905 761 3000 Email : sales@bartellmachinery.com Website : www.bartellmachinery.com

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November 2016