Abstract

Having excellent permanent conductivity among all of its conductive fibres, metal wire exhibits electrostatic charging or discharging during various industrial processes because of friction, separation or conduction between objects. In the electronics industry in particular electronic product are becoming smaller, and are sensitive to sudden electrostatic discharging without any protecting device. The electrostatic discharge generates signal interference, resulting in the incorrect function of the electric facility or other breakdown. Therefore electrostatic protection and electromagnetic shielding are important In this investigation, complex core spun yarn is fabricated in a ring spinning frame. The novel attachment is done in G5/1 ring frame The spun yarn has various counts, twist alpha and cover materials. The effects of the parameters on the yarn characteristics of the complex core spun yarn are investigated.

Key words: core yarn, spinning tension, geometry, core-sheath ratio

1 INTRODUCTION

When core spun yarn is spun, the core material should be fed into the center of the drafted zone and the roving is spread to generate a well covered and a spinning effect. The guide device is installed on the roller- weighing arm to feed core material stably to the center of the roving. The guide device incorporates a guide pulley, and will move with the wire to prevent creating additional friction between the metal wires and feeding device.

1.1Effect of Process variables on Ring Core-spun Yarn Properties

The process variables that affect the core-spun yarn properties are:
1.Core sheath ratio
2.Pre tension applied to the core material
3.Spinning draft
4.Number of roving feed and Twist

1.1.1 Core- sheath Ratio

It has been found that decreasing sheath content will increase the strength of the core-spun yarn. Apart from this there is an improvement in the extension and the evenness properties. In the case of core-spun sewing threads, a 2: 1 ratio of core sheath gives poor core coverage, and may raise the problem of stripping off the sheath during the sewing, whereas, with a 1:1 core sheath ratio the striping off problem reported to minimize.

1.1.2 Pre-tension to Core Material

The pre-tension is needed to regulate the geometrical position of the filament. This input tension varies with the twist factor, size and the quality of the filaments used. There are methods for optimizing the tension of the core filament in the core spinning process. Colored filament was passed over a tension device of attachment and fed before the nip of the front roller of the ring frame. The pre-tension was gradually raised until the colored filament is completely covered by the cotton fibres, and this value was taken as the optimum input tension. It was approximately 10% of the breaking load of the core yarn. An introduction of a compensatory tensioner can be reducing the tension variation. An extension of 1 % to the core filaments while feeding to the ring frame ensures no buckling or curling of sheath fibres. Core yarns are usually pre- tensioned to an extension of around 5-10% for flat continuous filaments yarns, about 30% for textured yarns and up to 400% for an electrometric core. If insufficiently tensioned, the filament will either periodically appear at the yarn surface, grin through or become wrapped around the fibre ribbon as the ribbon being twisted.

1.1.3 Spinning Draft

Spinning drafts can be varied to obtain the required yarn count based on the core the sheath ratio.

1.1.4 Number of Roving Feed

The possible ways of feeding the core material at the front roller nip with respect to roving are:
Filament at the center of the roving
Filament at the sides of the roving
Filament on the top of the roving
Two-rove feeding (Filament at the center of the rovings) provides better core positioning and control during spinning influences the structure and properties of core-spun yarns.

1.1.5 Twist

Adequate cohesion obtained in individual yarns at high twist rates and it minimizes the sheath slippage. In addition to this, the filament pre-twist in opposite direction to the ring twist reduce the sheath slippage. The extension of the core-spun yarn tends to reduce at higher twist levels.

2.0 MATERIALS AND METHODS

The following spinning frame parameters are recommended for use in the production of core spun yarns containing viscose fiber.

2.1 Gauge

The distance between the spindle center lines is the gauge of the spin frame. To reduce the occurrence of sheath damage due to balloon contact with separators, 75 mm and 82.5 mm gauges are recommended for fine and coarse count core spun yarns, respectively.

2.2 Spin Geometry/Spin Ratios

Proper spin geometry is important to control spinning tension and reduce the occurrence of break backs and core breaks during spinning. Generally, it is better to use a large bobbin diameter with a small ring diameter specifically a ring diameter to bobbin diameter ratio of 2:1. A maximum bobbin length to ring diameter ratio of 5:1 should be used to ensure that the angle of pull is greater than 30 degrees. Longer bobbins relative to ring diameter lead to higher tensions. This rule should be followed for cotton, synthetic, and blended yarns to help prevent core breaks, scuffing of the fibers, and dyeing problems.

2.3 Top Cot Hardness and Load

Softer front rolls with lower nip pressures are recommended to reduce probability of core damage in the front nip. Therefore, the lowest Shore hardness front roll and load spring feasible without jeopardizing yarn quality should be installed. Front rolls with Shore hardness of 65 to 72 have been used with success, along with roll loads of around 30 pounds of force (lbf).

2.4 Drafts

The draft of the core determines the power of the yarn and also affects the coverage (how uniformly and tightly the sheath covers the core). Due to the unique load-elongation response of viscose fiber, higher drafts are recommended, as compared to spandex core spun yarns. The winding denier of viscose fiber on the spools is the same as the stated denier. There is no pre-drafting during fiber production. Therefore recommended drafts are machine drafts with no need for pre-draft calculations.

2.5 Travelers

Selection of traveler weight is critical to control spinning tensions and core coverage. Proper traveler weight selection requires some experimentation to ensure balloon stability and good bobbin build and density. The lower retractive force of viscose fiber dictates lighter traveler weights than those typically used in spinning soft core yarns.

2.6 Spinning Speed

Selecting spindle speed is a function of frame geometry, ring diameter, twist multiple, traveler type, and yarn count. For example, finer yarns spun on smaller rings using lighter travelers can run at higher spindle speeds. Conversely, lower spindle speeds are required for coarser yarns spun on larger rings using heavier travelers. As a general rule, traveler speeds Below 23 m/sec are recommended for core spun yarns containing viscose fibre.

2.7 Filament Centering

As with all core-spun yarns, care must be taken to maintain the core filament in the center of the sheath fibers. Alignment should be set accurately at the start of spinning and checked periodically. The V-guide used to position the sliver should have little to no side-to-side movement which may effect the centering of the core fiber.

2.8 START UP PROCEDURE FOR CORE SPINNING:

For quality yarn production, the following start up procedure is recommended:
1.Verify that all rolls, v-guide and creels are free of any fiber, roving or yarn wraps. Any laps that occur during spinning should be removed prior to piece up of the broken end.
2.Make sure the roving traverse is disengaged.
3.Set the ring rail movement for a fast up stroke and slow down stroke. This motion is preferred for lower ends down rate, better balloon stability, and longer traveler and ring life.
4.Insert the appropriate gears for the target yarn count, twist and core draft.
5.Install the lowest shore A front roll and load spring feasible without jeopardizing yarn quality.
6.Install the recommended traveler.
7.Creel in the appropriate roving.
8.Creel in the core. Spools should be handled with care to avoid scuffing, denting or brushing. Spools that have been bumped or dropped should be checked for damage prior to installation in the creel.

9.Piece up the yarn and verify core position. The v-guide or roving should be adjusted so that the core is centered in middle of the roving ribbon.
10.Run approximately 100 meters of yarn, collecting 4 bobbins to verify that yarn count, twist level and core draft are correct.
11.Begin core spinning.

2.9 CORE MATERIAL SPECIFICATION:

Diameter of the copper wire is 0.05mm.
The package weight is 600 grams.
Package diameter 8.5cm.

2.10 SHEATH SPECIFICATION:

The rayon roving size used in this study was 240gr/30yd.
The length of the fibre is 38mm.
Denier of the rayon fibre is 1.2denier
The count of the cover material is 10 Ne
The twist levels are 14, 19 twist per inch (TPI) according to various twist alpha .

3.0 RESULTS AND DISCUSSIONS

Test results of copper core yarn with 14 tpi (SAMPLE I)

Test results of copper core yarn with 19tpi (SAMPLEII)

As the part of the study, a successful attachment was fabricated and installed in G5/1 ring frame; the working performance was observed and found satisfactory. Two twist levels were tried and the single yarn strength tested in TENSOMAXX TESTER, with 500mm gauge length, pre-tension at 0.5cN/tex and at a speed of 5000mm/min.

Literature cited

1.Shawney.Special purpose fabrics with core spun yarns-Indian journal of fiber and textile research-dec-1997
2.Balasubramaniam,Properties of core spun yarns-Journal of textile institute T534-61-1970
3.Babaarslan, Method of producing polyester/viscose core spun yarn containing spandex using modified ring frame-Textile research journal, April 2001
4.Ramasamy, Developments of core spun sewing thread-SITRA,vol.43,No 45,August 1998
5.Ching-Wen Lou. Process of complex core spun yarn containing a metal wire-Textile research journal,75(6),466-473(2005)

To read more articles on Textile, Fashion, Apparel, Technology, Retail and General please visit www.fibre2fashion.com/industry-article