Rojtricot storage feeder improves quality of weft insertion technical fabrics
15th December 2008, Obertshausen
Leading builder of warp knitting machines Karl Mayer, has been using Memminger-Iro’s Rojtricot storage feeder to improve fabric quality on its weft insertion machines and particularly with fabrics for technical applications.
Warp knitting is a complex process, in which the relationship between all the processing sequences has a decisive effect on the efficiency of the process and the quality of the fabrics produced. The principles of feeding the yarn to the knitting point are very important for the quality of the fabric and therefore the process is constantly being improved.
The yarn must run with a high degree of precision from the warp beams and has to reach the processing point at a precise tension and should not be damaged in any way by the processing sequences. If necessary, the delivery of individual yarns can be specified by experienced specialists.
This is a particular requirement on warp knitting machines with parallel weft insertion. When using high-performance production machines, all 24 or 30 weft yarns taken-off from the weft-yarn creel must be inserted absolutely uniformly over large fabric widths and this applies to every type and count of yarn. Synthetic yarns, either in the form of monofilament yarns, twisted or untwisted multifilament yarns, or textured yarns, must lie as perfectly in the fabric as wool or cotton yarns do. Furthermore, increasingly more technical, special yarns have to be processed efficiently and accurately.
If weft stripes are formed during insertion of the yarns, the fabric will fail the quality criteria. There are many reasons for undesirable stripiness, but they can often be traced back to the yarn package. Irregularities in the yarn being delivered, such as different package diameters, differences in the package build, or irregular yarn finishes, can no longer be compensated for by simple braking systems.
The efficient operating principles of storage feeders can help to solve these problems. The yarn lengths, which are processed by the operations of the weft laying-in device, are first taken off from the package, wound individually onto a storage device, and delivered at the same tension as required.
Memminger-IRO is one of the best known manufacturers of storage feeders and the company, which specialises in yarn-feed technology, has been supplying high-quality products to knitting companies for more than 40 years including Karl Mayer.
Rojtricot storage feeder
Karl Mayer Malimo uses the Rojtricot storage feeder from Memminger-IRO on its warp knitting machines with parallel weft insertion. This high-precision yarn delivery system was optimised especially to cater for these types of machines. This device is especially suited for use with high yarn speeds. It has a stationary spool body to prevent undesirable, additional yarn twisting and has a switch for setting the rotational direction for S or Z twist yarns.
The spool body also has a device for transporting and controllably separating the yarn windings, which is an important requirement when processing difficult yarns. A braking system at the end of the spool body ensures that the yarn tension is uniform. The braking system is available in two versions, i.e. with a ‘natural or synthetic brush’ or with ‘metal lamellae’ to enable the brake to be set optimally for the different types of yarns and counts. If the metal lamellae braking rings are used, the correct setting of the twist direction of the yarns must be taken into account. With yarns having a high twist, the storage feeder must run with the yarn twist. For yarns with less twist, it is recommended that the storage feeder should run opposite to the twist direction.
An important advantage of the Rojtricot is that it operates without interruption, i.e. without any stops and starts, as long as yarn is required. This increases the quality of the fabric considerably, improves machine efficiency and reduces downtime.
MSUS Weft Insertion System
The Karl Mayer MSUS weft insertion principle features a universal weft insertion process for all kinds of yarn materials, yarn counts, and machine speeds. Twenty four or thirty weft yarns are infinitely and simultaneously laid around the hooks of transport chains as a function of the system used (P2 system / P3 system). The weft yarns are clamped in the transport chains and fed to the knitting area. After interlacing in the stitch course, the weft yarns are cut-off directly beside the outer compound needles.
P2 system used in machine models RS MSUS, RS MSUS-V
The weft carriage moves in both axes i.e. in x-axis (inserter movement lengthwise to the weft carriage support) and in y-axis (racking movement of hook chain). Gentle treatment supposed, the mechanical construction ensures high yarn counts and high tensile loads.
Using the RS MSUS-V machines, very dense, semi-open or open structures can be fixed to nonwoven fabrics. This Raschel machine allows force-absorbing yarns oriented in 0° and 90° directions to be mechanically bonded with a web by knitting yarns during the knitting process. The stitch-forming knitting yarn system fixes the other yarns layers according to pattern and mostly stretched onto the pre-bonded web. Karl Mayer claims that the oriented reinforcements ensure remarkably high tear resistance values for composite fabrics which can be exactly adapted to the field of application.
In knitted geocomposites, the yarn layers maintain reinforcement and support features and the webs offer erosion protection, separation and filtration. A wide variety of yarn types and yarn counts contributes to the versatility of the RS MSUS-V this machine with web feed. Applications include geotextiles, coating substrates, secondary carpet backings, construction textiles and agricultural and greenhouse textiles.
P3 system used in machine models HKS MSUS, RS MSUS, RS MSUS-G, RSP MSUS
The movements of axes have been segregated. The weft carriage moves in x-axis (inserter movement lengthwise to weft carriage support). A racking device is used to move the y-axis (racking movement of hook chain).
The parallel movement of individual elements ensures high machine speeds along with gentle treatment of fibrous material.
According to Karl Mayer the HKS MSUS machines sets the benchmark for efficiency, economy, and excellent fabric quality. The HKS MSUS high-performance automatic warp knitting machine with parallel weft insertion is available in one-guide bar or two-guide bar configuration.
Offering the possibility to process a great variety of yarn materials and yarn counts, these machines can manufacture a wide range of products for various fields of application. Karl Mayer says that the HKS MSUS is just the right machine for the production of interlining articles ranging from sheer to thick and sturdy structures, using plain yarns, textured yarns and spun yarns. Parallel weft insertion fabrics are also suited for making lightweight and yet dense coating substrates. Applications include interlinings, coating substrates, curtains, surgical bandages, furnishing fabrics, adhesive tapes and outerwear.
Author: Billy Hunter