Warp Knitting Preparation
Technical modifications on creels and warping machines for processing technical yarns
Fig 1.:Horizontal balloon limiter
Out of all the textile materials, technical yarns are the most responsible for performance. They must match the end-use requirements exactly, can be processed into geogrids, tarpaulins, advertising substrates, 3D textiles, all kinds of nets, and reinforcement substrates for example, and, above all, they are extremely strong. Yams with counts of 1100 dtex and above provide maximum strength characteristics, but they also require special handling throughout all the processing stages. Yarn guiding forms the focus of steps taken to modify and adapt the warp preparation
technology developed by KARL MAYER.
In contrast to their large circumference, the thick yarns have a relatively small contact area on the package surface, and therefore do not adhere well to each other. The result is that individual yarn layers can slide between the back wall of the package and the package disc at the take-off points. They become entangled there, and can cause yarn breakages. This problem can be solved by having a foam rubber cover on the package disc and the spring-loaded contact points at the package (Fig. 2).
The high weight of the technical yarns also makes it necessary to make further
Fig.2 : Package
disk with foam rubber cover
design modifications. Projecting yarn balloons are produced during take-off at high speeds, and these can catch on each other. If the machine stops as a result of a yarn breakage, the yarn ends fall to the floor and pull the entire wound package along with them. This can be avoided by using balloon limiters. The horizontal limiters consist of intermediate plates arranged horizontally between the rows of packages for catching the yarn ends (Fig. 1). The
vertical balloon limiters prevent the yams from jumping uncontrollably Into the yarn guide of the yarn tensioners. KARL MAYER's top balloon limiting devices have a cylindrical shape, completely surround each package, and ensure that the yams do not become entangled with each other or in the yam guides of the yam tensioner (Fig. 3),
Consequently, as soon as the machine is switched on, it can be run at maximum speed and the yams are delivered in an orderly manner to the yam tensioner. The KFD-AIR is used in this case (Fig. 4). This yam tensioner is designed especially for processing filament 'yarns and technical yams from 50 to 3000 dtex or 167 to 1000 dtex, it can produce yam tension levels of 10 to 90, M or from 30 to 230 M when processing these types of yams, absorbs yam tension peaks by air damping of the compensating lever, and is resistant to contamination. When processing coarse monofilament yarns with diameters above 0.3 mm, the KFD-AIR should also be fitted with a special cover. This prevents the rigid yarns from jumping out of the guide devices during take-off. If the yarn is too heavy for overhead take-off, the use of a special take-off roller is recommended. This guarantees tangential unwinding and controls the yarn tension as well, and thus replaces the KFD yarn tensioner. The principle of tension compensation is based on the increase and decrease of the braking force during take-off, by the rise and fall of a metal ring moving in a magnetic field (Fig. 5). This system operates extremely accurately and permits take-off speeds of up to 400 m/min for a maximum package weight of 6 kg to be achieved.
In addition to ancillary equipment needed for guiding the technical yarns, the machine used for warping them also has to be equipped with special devices. These include a roller unit with a more efficient motor and larger roller diameters. The resulting larger contact area of the yarns on the roller surface, in combination with the higher motor efficiency, enables the high tension level needed between the roller unit and the warping machine to be established. A pressure roller also ensures that the warp beam produced has a smooth, uniform surface. KARL MAYER Textilmaschinen GmbH offers a variety of raschel and high-performance tricot machines with and without weft insertion facility for processing the beams into custom-made technical textiles. Table 1 gives an overview of the warp preparation
technology recommended for the specific warp knitting machines.
All in all, this represents custom-made technical expertise from one and the same manufacturer!