Alexandria University Faculty of Engineering Textile Department
Slub yarn
Moustafa Abdeltwab
Introduction Slub yarn is a yarn containing varying thicknesses which is produced by changing the speed of the bottom rollers on the spinning frame. We can achieve the various size and irregularity of slub yarn by slightly modifying the production process. Slub yarn began to be used in the creation of slub silk. It is generally used to make upholstery, lace, net curtains and house hold fabrics. It is widely been used to produce denim fabrics and more vivid casual wear.
Abstract How to get sub yarn , and get its properties.
Definition a yarn with thick and thin sections alternating regularly or irregularly.
Structure A simple slub yarn structure is composed of two parts, the base part and the slub part. Figure 1 indicates the geometrical parameters of the two parts. The appearance of slub yarn is influenced by the length and linear density of each constituent part. The boundary of the base part and slub is defined as half of the height of the trapezoid of the slub.
Procedures: There are several methods to get slub yarn : a) PRODUTION OF SLUB YARN ON ROTOR SPINNING MACHINE. There are several methods for producing slub yarn on Rotor spinning machine.
b) Production of slub yarn by feeding additional material.
By means other the sliver feed roller (15) as mentioned in the method of feeding additional material on the Ring spinning machine. The first (the base sliver) was fed continuously, while the second additional sliver was fed intermittently with the computer, it was possible to program the movement of the additional sliver feed.
c) Production of slub yarn by excess feeding method. The variable speed of the sliver feed roller was achieved by use of a special unit (15), called (GOE unit stands for ground slub Open End) produced by Swiss manufacturer. It was made up of two parts. One part was the mechanical drive system for the sliver feed roller, consisting mainly of a servomotor with accessories, and was built in to the Rotor spinning machine. The other part, standing by the side of the machine, was a computer. With the computer, it was possible to program the movement of the sliver feed roller. Hence a basic speed could be chosen and, from this,
higher speeds during various times and with various time intervals could be set. The resulting slubs according to a set program have constant or different thickness, length and spacing.
But this method has some limitation in the slub formation. The slub thickness is limited and cannot produce slub shorter than Rotor circumference. The working principle of the slub yarn device in Rieter(16) is based on a variable, motor driven feed of sliver into the rotor and a constant yarn delivery to the bobbin. The slub yarn device is fully integrated into the existing machine electronics. The system does not require any space for extra control units. The machine parameters as well as the slub system settings can be entered on the machine control panel. The slub programming software and SLUBLink memory card for data transfer from PC to the Rotor spinning machine are included in the standard equipment. The slubs can be programmed at regular or irregular length and spacing.
Capio(17) has long been involved in the manufacture of equipment for the production of slub yarn. On the Open End Rotor spinning machines by means of the Capio device is controlled pneumoelectronically. It has the same limitation of Swiss manufacturer.
d) Production of slub yarn by the pressurized air method. Slub yarn (13) is produced on Rotor spinning machines by partly blocking the evenly distributed fibre flow in the fibre transport channel by injecting pressurized air achieved by using a nozzle, which can be located at different places in the fibre transport channel, and the direction of the nozzle can be perpendicular to the fibre flow or against or with the fibre flow at different angles. The diameter of the nozzle and the air pressure can be varied with certain limits. This method causes a periodic accumulation of fibres, which constitute the slub, i.e., some fibres are held
back for a time while the rest are forming a yarn. The thick places are created when material is let free, i.e., when the air injection is stopped or the mass of accumulated fibres is large enough to overcome the resistance of a continuously blowing air jet. The thin places are created when some material is held back, i.e., during the accumulating period. The pressurized air method can produce slubs shorter than the Rotor circumference, but it is difficult to obtain effects longer than the Rotor circumference.
e) Production of slub yarn by combination of excess material and pressurized air methods. Because of the limitation of the excess material method and the pressurized air method, it was decided to accumulate the two methods to remove this limitation.The combination occurs when the blowing of pressurized air (18) was controlled by the GOE computer. When the feeding of the excess material begins, blowing starts, and, when feeding of the excess
material stops, blowing stops. The intention with blowing is to divide the GOE effects into smaller ones. That means that the blowing should start and stop in phase with the formation of the GOE effects. When the feed roller starts feeding excess material, blowing also commences. But, since the material has to pass along a part of the opening roller before reaching the air barrier, and this takes some time, blowing will, to begin with, affect the normally fed material. On the other hand; when excess feeding stops, the blowing stops and the excess fed material on its way between the feed roller and nozzle will not be affected. Investigations have been made in order to find out the importance of the above mentioned out of phase blowing. One way was using a time rely set to give a proper time delay for the opening and closing of the air valve. Another method was to build in an extra volume of air between the air valve and nozzle. Since it took some time to fill this volume when the air valve was opened, the blowing began later. When the valve was closed, the extra volume of air had to pass through the nozzle, and the blowing ceased later. The time delay could be varied by varying the air volume. A third way was to
program the time delay directly from the GOE unit. It could, however, never be stated that the out of phase blowing had any significance on the appearance of the yarn or its mechanical properties.
Different types of slub yarn Slub over slub with different length & thickness For the preparation of this type of yarn in the same duration of overfeed the amount of overfeed is varied many times depending on the different thickness of slub required. Fig 3 Multicount yarn Each slub in a slub yarn can be extended to make a multicount yarn, ie, multicount yarn is a yarn in which the count of yarn changes at intervals along its length. In
multicount yarn the yarn count changes within a pattern repeat, the yarn twist remains unchanged and the yarn twist multiplier changes due to the yarn sections with different count(6). Multicount effect is a special kind of effect produced by synchronised draft and twist variation with control devices. Multicounts are produced with a second servomotor connected to the front roll(4). Multicount yarn can also have short slubs in each count and this type of yarn is known as Multicount - Multislub yarn. Multicount yarn are presently in great demand for denim yarns(7). In practice, a pattern repeat for multicount yarns consist of 2 to 5 yarn counts(6). The length of the yarn sections in the individual counts is between 0.5 and 5 metres. For denim, short length effects are interesting, as they can be seen in the trouser leg or in sleeve. The long yarn effects are more seldom, and they are rather used for home textiles. Multi-twist yarn
In this type of yarn, the yarn count remains unchanged, but the yarn twist changes and the yarn twist multiplier changes. These different twist levels 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, which causes the colour effects. Combination of multicount & multi-twist In some cases both methods are combined. The yarn count changes within a pattern repeat, the yarn twist changes & the yarn twist multiplier also changes.
Applications
:
modern fashion and have been gaining more importance in the clothing sector, especially denim, and in furnishing and draperies. Demand for complex
fabrics with distinguishing characteristics is increasing, conquering larger shares of the textile market.
Conclusion There is a great demand of slub and multicount yarns in suiting, shirting, denim and home textiles especially in coarse count and with the help of latest technology it is possible to produce the yarns like slub, multicount, multi-twist and combinations of multicount & multi-twist with the help of various attachments and machines available in a controlled and reproducible manner as per the effect requirement.
Refrences: 1. Wilson, I, Before the Flood, Orion, London, 2001. 2. Wayland Barber, E, The Mummies of Ürümchi, Macmillan, Basingstoke, 1999. 3. de Saint-Aubin, C G, Art of the Embroiderer, 1770 (loc. Museum of London).
