Warpage (yarn production)
Distortion is the pulling of the fibers of a sliver into a finer sliver. On the spinning machines, the distortion occurs between two rotating machine parts that run at different peripheral speeds.
Roller drafting system
Principle: Two pairs of rollers, metal cylinders below, the upper roller with a flexible cover and loaded with a compression spring. The nipping lines of the roller pairs are set wider from one another than the longest fiber of the drawn belt.
While most of the fiber material is held in place by the slower roller pair, some of the fibers get between the faster delivery rollers. These push them forward, creating a thinner layer of fibers.
The capacity of a drafting system consisting of two pairs of rollers is limited, because the greater the difference in the rotational speeds of the two pairs and in the length of individual fibers, the greater the unevenness of the delivered web. In order to guarantee the quality of the sliver, the drafting devices are constructed
- from several pairs of rollers, whereby the total distortion consists of several partial distortions (as on the sketch on the right: a x b x c )
- with various auxiliary elements to control the short ("floating") fibers in the drafting area, for example:
- Straps in cotton spinning (total draft on the ring spinning machine up to about 50 times) or
- Needle bars in the drafting system for wool and long fibers, as shown in the drawing below on the right:
(1 - delivery rollers, 2 - compactor, 3 - special chain, 4 - cleaning brush, 5 - delivery, 6 - suction)
- with continuous electronic control of the band volume, combined with regulation of the draft level
Other ways of refining the sliver
Principle: The fiber band is broken up into individual fibers and then folded into a thinner band or a sliver according to a specific system. The refinement of the sliver is also called warpage.
- For example, a card is fed with around 160 million cotton fibers per minute (400 g / m). Disintegrated fibers are then spread out on the surface of the main drum so that about 10 fibers are captured per 1 cm². The material is then compressed into a tape weighing 5 g / m 2. The total delay is 400: 5 = 80
- The draft occurs in a similar way on the rotor spinning machines . The supplied sliver (fineness: e.g. 4000 tex ) is broken up and a thin sliver is created from individual fibers in the groove of the rotor. Is the peripheral speed of the rotor z. B. 200 times higher than the tape delivery, the fuse has a fineness of (4000: 200 =) 20 tex and the machine works with a total delay of 4000: 20 = 200.
When calculating the machine settings, it must be taken into account that some of the fibers on cards and rotor machines go to waste during the draft. The difference in speeds between the feed and delivery roller must accordingly be set lower than the refinement of the sliver (e.g. up to 5% on the card).
- The delay in the production of filament yarns is called drawing.
literature
- Schenek: Lexicon Garne und Zwirne, Deutscher Fachverlag 2005, ISBN 3-87150-810-1
- Kießling / Matthes: Textile specialist dictionary, Schiele & Schön Berlin 1993, ISBN 3-7949-0546-6