Department of Textiles
D.K.T.E. Society’s Textile and Engineering Institute, “Rajwada”, Ichalkaranji-416115 Maharashtra, India
Developments in spinning have generated many yarns structures like fancy yarns, intend for different domains and end use. In these yarns, irregularities like neps, knots, loops and snarls of different size and shape are arranged with varying distance between them. One of the well-known and most popular fancy yarns is the slub yarn. As an example of a textile issue that was once considered a defect, slub yarn has proven to be an advantage in some instances. There are different types of slub yarns exists viz. normal slub yarn, multi-count, multi-twist, reverse slub, and slub on slub which are discussed in this paper.
Keywords- slub yarn, multi-count, negative slub, slub on slub.
1. Introduction to Spun Fancy Yarn
2. Slubbing Effects
There are four basic of Fancy effects: slub, multi-count, multi-twist, and reverse slub. The various combinations among these four can create infinite yarn and fabric designs.
2.1. Slub Yarn
Slub yarns contain slubs/thick places at predefined intervals along the length of the yarn. Slub can be defined by its length and diameter. The distance between two slubs is called a pause. Slub length and pause length determine the slub frequency, i.e. the number of slubs per unit length. In slub yarn, the dimension of the slub (length and diameter) can be the same as shown in fig.1.
|Figure 1: Slub Yarn |
Slub Yarn is a yarn containing thick places of different thickness and length that are achieved by the programmed acceleration of back and middle rollers in case of ring spinning and the feed roller in the case of rotor spinning. Slubbing effects are produced via a program controlled drafting system using a servomotor which varies acceleration of back and middle rollers in case of ring spinning, at the same time maintaining the front roller at a constant speed. This controlled acceleration produces variation in slubs (or flames) count (TSlub), spacing (or pause) length (Lpause) and spacing count (Tpause).
To create a slub is as simple asserting its length in millimetres, its thickness (multiplier) as a percentage of the base yarn and the pause (distance between one slub to the next) in millimetres. The random variation of thickness, length and pause gives a wide range of effects, ensuring the use of slub yarns in many applications like denim, shirting, knitwear, casual wear, ladies dress material and also in curtains and upholstery.
2.2. Multi-Count Yarn
In principle, the multicount yarn consists of different yarn counts one after another along the same yarn path. Each Slub in a Slub-yarn can be extended to make a multicount yarn. The multicount yarn consists of different yarn counts of random sequence. Twist multiplier of the yarn remains unchanged in spite of varying the draft. The multicount effect is obtained through a draft variation to modify the count and the front roller speed to modify the twist. With the electronic drafting system drive using servomotor, both draft and twist can be varied in a controlled manner. Slubs of different thickness, length and twist are incorporated into the yarn during the manufacturing process of yarn.
|Figure 2: Multi-Count Yarn |
2.3. Multi-Twist Yarn
In this type of yarn, the yarn count does not change, but the yarn twist is changed. Different twist levels obtained will create variations in the yarn’s dye intake, thus creating a special fabric appearance. The twist difference causes a colour change in the fabric. Yarn sections with different twist absorb the colour particles differently. The yarn section which receives more twist has lower dye uptake and vice a verse. This causes the colour effects.
|Figure 3: Multi-Twist Yarn |
2.4. Slub on Slub
In this yarn, the diameter may vary infinite times on every single slub according to its length. So each slub may have any shape and drawing.
|Figure 4: Slub on Slub |
2.5. Injected Slub Yarn
Injection slub yarn is a specialized fancy yarn and it is made up of two different materials, one for slub portion and the other for base yarn. Both the material will be dissimilar in nature, colour and character. The basic principle behind the production of injection slub yarn is, slub portion will be injected at random over the continuous running of base yarn. In this process, two yarns are twisted together and short fibres are injected into the form-locking connection. These injected slubs are produced and located in just the right places. Its length, thickness, and distance can be varied to create different structural effects on the fabric.
2.6. Negative Slub
As the slub, the negative slub or reverse slub is obtained with a drafting variation that, in this case, is negative and reduces the yarn thickness. Here slub formation is without changing the front roller speed, for a perfect distribution of the twist on the yarn.
|Figure 5: Reverse Slub Yarn |
There is a great demand of slub yarns in suiting, shirting, denim and home textiles. With advanced technology now it is possible to produce a different variant of slub yarns in controlled and reproducible manner.
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