EoW September 2009

technology news

Double twist stranding of instrumentation cables

The pre-twister VVD180 has been developed for the cost-effective produc- tion of insulated wires, pairs, quads and cable cores with 5- or 7-conductor design and three or more films applied in the S or Z twist direction by double twist stranding machines. The pre-twist devices enable the application of tapes under a reduced, controlled and constant tension. The devices can accommodate tapes made from all kinds of films used for data and special cables. The speed can be infinitely controlled. The VVD pre-twisters are designed to handle stranded products with a maximum diameter of 10mmor 15mm. Double twist stranding machine DSI 631 is used for a wide conductor cross-section range and a maximum strand diameter of 8mm. The lay length can be freely adjusted from 8mm to 180mm with a lay length tolerance of less than ±0.5% of the effective lay length. The DSI 631 and the larger version DSI 1001 are designed to cable insulated conductors into pairs or quads and to strand conductor pairs into LAN cables and other special cables, with or without back twist. Depending on the respectivemachine version up to three films can be applied. An important feature of the DSI stranders is the single bow design that results in a significantly reduced energy consumption and noise emission. Three-phase drive technology and non-contact machine data transfer reduce maintenance to a minimum. All production parameters are set using the machine’s HMI touch screen display where they are clearly visible, together with service and maintenance messages. Maschinenfabrik NiehoffGmbH& Co KG – Germany

Maschinenfabrik Niehoff has developed the DSI series of double twist stranding machines, and additional equipment which can be combined tomanufacture all types of data and special cables, including LAN cables of all existing categories and even future generations. An example application of the versatility of Niehoff’s double twist stranding lines is the manufacturing of instrumentation cable for the petrochemical industry. In this case, the cable consists of two flexible conductors with polyethylene insulation, two fillers and a drain wire (ground). During the stranding process, the inner part of the cable has to be wrapped with three film layers. All elements of the cable are assembled in one process on a stranding line which is composed of three payoffs type ATP 630, three payoffs type ALB 600, a pre-twister type VVD 180, and a DSI 631 type double twist stranding machine. ATP 630 tangential payoffs are designed for the uncoiling of cables, insulated single conductors, pairs and quads with a maximum diameter of 4mm. Each payoff is driven by a dancer-controlled spool drive with adjustable wire tension; the maximum haul-off speed is 300m/min. In this case, the units were used to payoff the two flexible insulated wires and the ground wire. The ALB 600 longitudinal tape payoffs with tape forming are driven by a dancer-controlled AC motor; they are designed to enable an easy and rapid film insertion and tensioning. The film tension can be adjusted separately and the forming tools for overlapping either on the right or left can be quickly exchanged. The payoffs can be operated with payoff spools or film disks and are suitable for films with a maximum width of 40mm and a maximum thickness of 65µm. The maximumhaul-off speed is 300m/min.

Fax : +49 9122 977 155 Email : info@niehoff.de Website : www.niehoff.de

DSI 631 type double twist stranding machine ▲ ▲

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EuroWire – September 2009