Features
Login | Register 
Clip this Page |Discuss this Page |Email this Page |Print this Page
Spinning & Weaving
  Filament weaving on unconventional looms

Unconventional or shuttleless weaving machines have gained high popularity in the recent years. The yarn supply for weft is utilised directly without need for conversion into pirn. There are four principles of weft insertion on these machines. Each type has its own merits for different types of production. A considerable amount of filling waste is made during weaving on these machines.

Suitability of different machines

Projectile weaving machines

These machines are mainly used for spun yarns made of cotton, rayon, polyester, etc and also their blends. It is also possible to effectively weave filament yarns. The technical aspects relating to warp yarns remain the same irrespective of whether it is shuttleless or shuttle looms. Some of the recommended weft yarn counts are given in Table 1 below.

 

Table 1. Recommended weft counts

________________________________________________________________

Type of material                        Range of yarn counts

1. Rayon staple                           6s - 36s Ne

2. Spun synthetic fibres               18 - 70s Ne

3. Continuous filament                70 - 270 Denier

_________________________________________________________________

Popular types of projectile weaving machines (such as Sulzer Ruti) incorporate the following special features so as to enable successful weaving of filament yarns

a) Feeding of the warp yarns from the warp beams to temple without deflection.

b) Whip roll filament weaving machine is hard chromed and polished.

c) The drop wires are lesser in thickness so as to minimise friction, and also the points of contact are hard chromed.

d) Three wheel types of temple, which only engage at the selvedge zone, are used.

e) The tucking needle is redesigned so as to modify its motion during selvedge formation. It remains stationary for a short duration after gripping an end, till the healds are almost closed. Also the tuck in needles are pointed at their edges and are highly polished and chromed. Straight needle tucks the thread quite close to the edge of the fabric. Melt selvedges are also available on these machines.

f) The gripping surface of the projectile is highly polished and slightly curved at the ends, so that the individual fibrils are not ripped off. The same is applied to projectile feeders.

g) All the eyelets in the thread tensioners and package creel are to be replaced by fine ceramic, so as to prevent the damage to the threads due to abrasion.


h) The closing of warp shed should be late, ie, 10 - 250 for ground threads, and between 3250 - 3400 for the selvedge zone.

i) The whip roll and the warp detectors should be adjusted as horizontally as possible, so that the top and the bottom shed are tensioned as equally as possible.

j) Stoppage due to broken warp threads should take place about 3350 to 3400. If the normal setting of 3500 - 00 is selected, there will be a great risk of starting marks.

Rapier weaving machines

These machines can satisfactorily weave sheeting, flannels, drills, muslins, print cloths, etc and it can be extended to the weaving of carpets from continuous filament yarns. Textured filaments made from Taslan, untwisted filament and intermingled cotton and polyester covered core yarns and elastomeric yarns can be effectively woven on these machines. Heavy denier multifilament yarns can also be successfully used. PET with crepe twist or reinforced Lurex are both woven as weft without problems. Industrial fabrics, tyrecords, tents, screens, sail cloth tarpaulin, and glass fabric can also be woven

Air-jet weaving machine

These machines have proved to be ideal for spun yarns. Recently it has been possible to weave a wider range of fabrics in spun as well as filament yarns and with up to six colours in weft or yarn counts. However, the yarn quality restricts the machine speed. Modern spinning mills are able to give better quality yarns. Modern warp preparation is crucial for today’s weaving machines.

Water-jet weaving machine

This system has proved very useful in the case of synthetic filament yarns, which are hydrophobic. It is advantageous as compared with shuttle looms for bulk production of fabrics made of polyamides and other hydrophobic fibres. This machine is confined to only hydrophobic synthetic filament yarns. This is due to the problems associated with sizing, wet strength of hydrohphillic yarns and also the requirement of a perfectly clear warp shed.

Thus the machine is restricted to filamental warp yarns that do not require sizing and also do not lose strength on wetting. Normally weaves such crepe, matt, and twill are used, with yarn counts ranging between 10 - 120 denier. The warp/weft thread sett or density ranges between 25/25 and 360/240 per square inch and the maximum achievable areal density of the fabric is about 6oz/sq yd. Since the construction of the weaving machine, specially, the sley, is light, heavier varieties of fabrics cannot be woven. There is a possibility to increase the weft set to 300 picks/inch. However, the maximum dents/inch in reed is only 76. If reeds of higher densities are used, there is problem of water clogging, which can create difficulties in shedding. The twist in warp yarns is minimum, about 7.5 tpi, as the yarn is unsized. Fabrics such as lingerie, ladies dresses, shirting, tent canvas and industrial fabrics can be successfully woven on these machines.

 

The overall quality of the fabric is below the expected level, which is mainly due to the problems concerned with the water jet weft insertion. These machines have the advantages of high speed and low noise. Also they are well suited for weaving of super fine continuous filament yarns. The effectiveness of the weft propulsion is mainly dependent on the wettability of the weft. The drag on hydrophobic filament yarn is much lesser than that on cotton yarns.

Generation of static charges is prevented due to the presence of water. It is crucial that the weft yarns do not contact the warp yarns during their insertion into the shed, as otherwise this could lead to fabric defects due to entanglement. Effectiveness of weft insertion requires the fluid jet to remain in contact with the weft and to move into the shed more quickly than the yarn. A major problem with hydraulic picking is the presence of partial of full double picks across the width of the fabric, which can arise due to a number of reasons.

Weaving with multifilament yarns

Multifilament yarns are used in the manufacture of apparels so as to get an excellent hand, drape, appearance, wrinkle resistance and easy care properties. The yarn are either used as single, or plied together with or without twist. The yarns are denoted as denier/number of constituent filaments/twist. Generally higher the number of filaments of equal denier, more fuller is the fabric. The yarns can be woven successfully on any of the following types of machines (Table 2) but certain modifications on looms are required for satisfactory weaving. It is desirable to weave the filament warp beams on better and sophisticated looms.

Table 2. Suitability of weaving machines for filamental yarns

___________________________________________________________________

Type of weaving machine                        Products

___________________________________________________________________

1. Projectile/rapier                               a) Fancy multicolour fabrics coarser than

                                                                30dtex, both flat and texturised

                                                           b) High twisted fabrics

2. Air jet                                              Fabric with single colour weft for mass production

3. High speed automatic shuttle            a) Fancy monocolour fabrics

looms, conventional automatic              b) High twist fabrics

looms

4. Non-automatic looms                       All type of synthetic fabrics

______________________________________________________________________

Machine alterations

Some of the suggested modifications on the weaving machine are as follows:

a) Chrome plated iron or highly polished wooden back rollers should be used.

Extended backrest should be preferred.

b) The number of heald shafts and the number of rows of drop pins should not have a common factor. Thus, for a plain weave on four shafts, three or five rows of drop pins should be used according to the number of ends in the warp. This procedure ensures that the ends from any given heald shaft are distributed over all rows of pins.

Sizes of drop wires

Suitable dimensions of drop wires are to be used (Table 3). Heald frames made of metal and having flat heald wires (with rectangular eyes) are recommended. The rectangular eyes of the heald wires have large area of contact, which reduces the pressure on length of yarn during shedding.

Shuttles made of laminated wood and having consistent size and weight are to be used. The eye of the shuttle should be padded and have ceramic pins. Low and uniform yarn tension are necessary for weft yarn during weaving. This can be achieved by using shuttle lined with fur or nylon loop strip. The distance between the pirn tip to the eye should be 12 - 30 mm.


Sizes of heald wires

The dimensions of flat heald wires are given in Table 4.

Table 3. Dimensions of flat healds

______________________________________________________________

Warp count       Cross section of         Size of eyes  Maximum    heald wire per cm

                               Heald                                         Simplex           Duplex

Dtex                    mm x mm                 mm x mm

_______________________________________________________________

Up to 150              1.0 x 0.25               5.0 x 1.0          16                    24

150 to 300             2.0 x 3.0                 5.5 x 1.2          12                    20

_______________________________________________________________

a) Reed made of metal with 60% air space and 10 cm depth is preferable

b) Box front should be smooth and preferably lined with fur

c) Sley should be covered with corduroy fabrics, or velvet to reduce the damage that may take place due to frictional contact between the moving shuttles and the sley race board.

d) Warp tension should be enough just to get a clear shed

e) Photoelectric weft stop motion should be used

f) Tipless shuttles should be used for high-speed looms

g) For filament weaving, it is important that the cloth take-up roller should hold the cloth firmly without slippage, but without causing any abrasion of the filaments. Emery roll should be covered with rubber fillet.

h) The direct take-up motion where the cloth is wound on the take-up roller directly is ideal as it ensures better control and avoids slippage of fabrics.

i) Circular disc or sun temples are ideal. Roller temples with rubber sleeves can be used. Ring temples with 2 or 3 rings are also used.

j) Part of the hammers coming in contact with the yarn should be lined with fur to prevent damage to filament.

Processing factors

The following recommendations are made for weaving of texturised as well as flat continuous filament yarns:

a) Back rest should be levelled with the breast beam or front rest and drop wire stand is aligned to give an even shedding.

b) Tension in the top and bottom levels of shed should be equalised as far as possible. Low warp tension, enough to get a clear shed opening, is preferable.

c) Weft tension should be set to minimum level enough, to prevent weft snarl or loopy selvedge (approximately 0.10 - 0.15 gpd). The difference in tension between the full and the empty pirn should not exceed 15g.

d) Late shedding by 150 or more for filament warp and normal for spun warps with filament weft-flat or texturised is recommended.

e) Selvedge should be about 15 mm wide for dress material and 20 mm wide for suiting.

Weaving of monofilament fabrics

Monofilaments are normally used both as warp and weft. However, in special applications, such as parachutes, conveyor belt linings, ski-anoraks, etc monofilaments are used in combination with multifilament yarns. There is no restriction in the warp yarn with regard to the thread density (sett) and yarn linear density. However, in the case of weft yarn the yarn linear density and cloth width are to be considered, since other conditions prevail for the monofilaments (10 - 1000 dtex) as, for coarse monofilament wires (D 1 - 0.85 mm) in weft insertion, which are influenced by the stiffness of the monofilament itself. Depending on the final use polyester, polyamide, polypropylene, carbon fibres or PVC monofilaments or wires are used. Some of the applications of monofilament fabrics are bolting cloth, geo-textiles, filter fabrics, etc.

Conclusion

Weaving with synthetic filament yarns has now become possible on all types of shuttleless weaving machines with suitable modifications. It has become possible to weave wider denier range of yarns. Rapier weaving machines can effectively weave industrial fabrics, tyrecords, tents, screens, sailcloth tarpaulin, and glass fabrics. In the case of air-jet weaving machines, it has been possible to weave a wider range of fabrics in spun as well as filament yarns and with up to six colours in weft or yarn counts. However, the yarn quality restricts the machine speed. Modern spinning mills are able to give better quality yarns. Modern warp preparation is crucial for today’s weaving machines. Multifilament yarns of varying denier can also be woven on projectile, rapier and air-jet weaving machines with certain modifications.

Note: For detailed version of this article please refer the print version of The Indian Textile Journal May 2008 issue.

N Gokarneshan.

Department of Textile Technology,

Kumaraguru College of Technology,

Coimbatore 641 006.

Email: advaitcbe@rediffmail.com.

published May , 2008
back to Features   |   back to Spinning & Weaving
ViewpointFeaturesFeatures
MMF Front Looks Up
Glad tidings have come from India's man-made fibre (MMF) export front, after seven consecutive quarters of decline in its growth. MMF textile exports for the 9-month period, April 2013 to December 2013 touched US $4.2 billion against US $3.8 billion. One of
Cotton yarn: Quality depends on mixing strategy
A systematic mixing plan by maintaining the lowest possible variation in cotton quality parameters ensures trouble-free yarn production with consistent yarn quality, affirms Sunil Kumar Sharma. In a
Airbag: Life saving textiles
The airbag fabric may be coated to increase the strength of the fabric so that the fabric is reinforced, and by increasing the strength of the fabric, breakage of the airbag can be minimised, assert R Senthil Kumar and S Sundaresan
full viewpoint... more... more...
Table of Contents Most Recent Issues Write to Editor
Subscribe to ITJ | Write to the Editor | Rate Card | ITJ Ads | Tell A Friend | About Us | Contact Us  | Login | Register  | Home
Associated Portals:  | www.ipfonline.com | www.automotiveproductsfinder.com
IPFonline Limited, 2nd Floor, Shafika Building, 17/7 Kodambakkam High Road, Nungambakkam, Chennai - 600 034.
Tel: +91 44 42991234 (30 Lines). Fax: +91 44 42108441. Email: admin@ipfonline.com