Karl Mayer: Uniquely flexible and profitable: Weft insertion reinvented

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    “We were able to record a super response. Especially on the first day of the fair, the number of visitors was surprisingly high”, Vice President Sales Hagen Lotzmann sums up with satisfaction. The reason for the high visitor interest were innovative machine features: the new VARIO WEFT laying system, a solution for stabilising the edges, monitoring of the weft tension and a central suctioning device. The WEFTTRONIC® II G was shown at ITMA in a working width of 213″, the best-selling working width for the production of geogrids.

    More patterning freedom
    Above all, VARIO WEFT delighted customers by revolutionising weft patterning. The innovation makes changes of weft pattern extremely simple, fast and flexible. The electronic solution requires no mechanical intervention during threading in and has no limitations in terms of repeat length. In addition, there is considerably less selvedge waste.

    The basis for this advantage package is a newly developed patterning principle: Whereas weft carriage and transport chain used to work with a weft insertion according to the desired pattern, now a full threading in is always used. A stop-and-go operation of the transport chain and a new movement curve of the supporting sinker ensure that the yarn is fed according to the pattern. If a weft yarn is to be inserted into the fabric, it is guided to the knitting elements by the circulating transport chain and brought into the engagement area of the slider needles by the supporting sinker. If a free space is to be created in the fabric, the transport chain stops and the supporting sinker dips under the weft yarn. “The flexibility which VARIO WEFT offers in weft patterning is completely new for our customers. In the discussions on this during the ITMA, potentials were discussed and thought processes initiated. We are expecting many new product ideas, and we will be on hand to help our customers implement them,” explained Hagen Lotzmann.

    Lower costs and environmental impacts
    With the elimination of the vacant positions in the transport chain, the waste generated here is also eliminated. In the conventional process, the weft yarns are passed by the empty positions, and the yarn sections running in the direction of work have to be disposed of, with negative effects on costs and the environmental balance. The relative yarn waste is greater the more positions have to be bridged and weft threads inserted, i.e. the more open the grid is. When considering the absolute savings potential, however, the count of weft yarns in the fabric must also be taken into account.

    For example, with a weft threading in of 5 full, 10 out, about 61 % less material is needed. This results in about 38,000 EUR less costs and about 256,000 kg less CO2 emissions per year. In the case of denser grid designs with an threading in of 2 full, 2 out, the material saving is lower at just under 46%, but the absolute annual saving in costs is higher at around 40,000 euros and in CO2 emissions at almost 270,000 kg.

    Stable selvedges
    Another innovation of the WEFTTRONIC® II G stabilises the fabric selvedges and uses the weft yarn ends for this purpose. The weft yarn ends sticking out at the sides of the mesh selvedges are mechanically and by means of air flow returned to the warp knitting elements and firmly integrated into the mesh structure by means of a stitch.

    Due to the thus consolidated fabric ends, the grids can be better fixed during the finishing process – an advantage especially for medium-weight and heavy geotextiles. This allows the shrinkage behaviour of the warp knitted fabric to be adjusted in a controlled manner and its quality to be improved. The consolidated selvedge structures can also open up new areas of application, for example in the fields of slope stabilisation and safety nets.

    Controlled yarn tension
    To maximise fabric quality, the WEFTTRONIC® II G has been equipped with a weft tension monitoring system. The new solution keeps an eye on every single yarn and triggers actions when threshold values are exceeded or undershot: first a warning, then the machine is stopped.

    When resetting to new patterns, the weft tension can be easily adjusted and controlled, thus improving the reproducibility of the product quality. In addition, the tension data can be stored for control and traceability of production orders.

    Automatic suction in non-stop operation
    A new device for suctioning off selvedge waste, the CSD 600, focuses on increasing machine efficiency. The innovation continuously picks up the weft waste during machine operation and uses operational stops for fully automatic emptying, without any manual intervention. In addition, less electrical energy is required compared to the previous solution with one suction cabinet on each side of the machine. The savings potential is around 8 %.

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