Yarn quality requirement for shuttle less weaving

                                

INTRODUCTION

Modern weaving machines stand out as an expensive class compared to conventional machines in terms of capital investment. This basic difference requires certain prerequisites to be considered while planning to venture into modern weaving machines. This paper is intended to throw light on the essential requirements to be met by the preparatory operations involved in shuttleless weaving. The quality of yarn used on shuttleless looms is the prime criteria considered for quality weaving. Parameters related to the quality warp and weft has been discussed. The machine parameters to be controlled for an optimised preparatory operation have been dealt with respect to winding, war ping and sizing operations. Guidelines for machine stoppages corresponding to warp and weft breakages in weaving are considered as important in deciding the efficiency of a shuttless weaving shed.

Limitations of Shuttle Looms

Despite the relatively high speed and efficiencies in loom with conventional
picking, productivity of these machines will continue to be limited as long as their
fundamental constructions involved the use of shuttle propulsion. Vincent has shown that the power required for picking is proportional to the cube of the loom speed. If the loom speed isincreased from 200 to 300 picks per minute, the power requirement would increase by a factor of (3/2)3 i.e. 3.4 times approximately. This results in following disadvantages

1. Greater strain imposed on the picking mechanism, thus rendering it liable to frequent failure.

2. Greater amount of noise and vibration.

3. Because of superior energy in shuttle, greater strain is again imposed on the Checking mechanism.                                                                                                                                     

4. The movement of shuttle will be more difficult to control and there will be a Greater possibility of its ejection from the loom.

The dynamic problems created by the picking and checking mechanism and the
inherent process of pirn winding for shuttle looms had encouraged the loom
makers to develop alternative means of weft insertion in which heavy shuttle is not
refer these looms as shuttleless looms. The various shuttleless looms that have been
developed over a period of about 50 years can be classified into various groups.

·         Projectile Looms

·         Rapier Looms

·         Air Jet Looms

·         Multiphase Looms

Yarn quality requirements

Tension on the warp on a high speed shuttleless weaving machine is higher than that on conventional loom. On some Repier looms, interference by rapiers, at the initial points of entry and terminal point of shed exit, can cause bending of the top yarn sheet around the rapier head producing excessive warp strain on the selvedge region of warp. Weft tension on Sulzer Ruti projectile weaving machine is equally high, where tucked-in selvedge is formed. Consistency of single end strength, C.V. of count and elongation isessential. Quality of yarn should be at least within 25% Uster which means the quality is among the best 25% of the mills in the world. Normally shuttleless weaving machine works three to four times faster and if the quality of warp remains the same, warp breaks will increase three to four times resulting in low production. Yarn should be more even and the following parameters of yarn are to be critically reviewed; C. V. of count, single thread strength, C. V. of single thread strength, imperfections per 1,000 meters such as thick places, thin places, and neps. Hairy yarn will not be suitable in air jet weaving as it will misdirect the weft insertion.

1. Warping

At warping, the goal should be to avoid missing ends. Number of thread breakages should not exceed seven per 10 million meters. This can be achieved by ensuring a top quality yarn package and by following the warping process parameters mentioned below:

·         Precise creel alignment

·         Reliable stop motion on creel and on warping drum, so that broken ends are traceable for knotting.

·         Minimum wobbling of warping beams.

·         Uniform selvedge with good flanges.

·         Yarns should by preferably warped on spindle driven machines to avoid thermal damage due to abrasion. Warping machines such as Benninger or Hacoba are preferable.

With drum driven warpers such as the BC Warper, the following precautionary measures are to be taken:

·         Frictional drum should be kept in a polished state.

·         Brake should be very efficient.

·         Aluminium cast flanges should be used to get faulteless selvedges.

·         Breakages rate should not exceed 0.3~0.5 breaks per 1000 m / 500 ends.

·         For wider width looms, wider warping machines are preferred.

Ends breaks during warping

Weaving unit	Count (Ne)	Warping speed(m\min)
1	30s	400
2	40s	600
3	40s	350
4	50s	600
5	50s	1000
6	60s	800
7	60s	900
8	60s	600
9	80s	600
10	80s	900

Quaility levels of yarns during high speed warping

Yarn quality	40s	50s	60s
Rkm	18.98	19.11	19.05
Cv of Rkm	7.99	7.33	10.26
Breaking elongation	4.97	5.63	4.91
Hairiness	5.16	4.8	4.51
Normal imperfections\km	142	128	169

International norms for end breaks during high speed warping

Count(Ne)	End breaks per million meter of yarn
30s to 40s	0.65
50s to 60s	0.80
80s to 100s	1.0

2. Sizing

During sizing, in view of the stretch the yarn undergoes at various zones, some loss in yarn elongation is inevitable.however, these needs to be maintained at its lowest possible level to ensure better working in loom shed.this is particularly important for Indian yarns where the breaking elongation is comparatively lower.

In the weaving units covered in the study, the loss in elongation during sizing varies between as low as 0.3% to as high as 1.6%.

To minimise loss in yarn elongation during sizing, the total stretch during sizing need to be maintained at lower than 1.0%. Optimum yarn tension levels during sizing in different zones with a view to avoid exessive stretch are given.  

Optimum yarn tension during sizing

Loss in yarn elongation and lappers during sizing

	% of single yarn strength
Zone	Creel	Between finishing squeeze roll to the first drying cylinder	Head stock
Yarn tension	2%	5%	10%

Lappers during sizing vary between 0.2 per 1000 ends per 1000m and 1 per 1000 ends per 1000m in the sizing units studied, under good working conditions, incidence of lappers during sizing needs to be maintained below 0.2per 1000ends per 1000 m.in general, when the sizing lappers are more, the corresponding yarn has higher loss in elongation.results of a study conducted in this connection for 60s and 80s yarns are given.

Count(Ne)	Lappers during sizing (per 1000ends\1000m)	Loss in yarn elongation during sizing (absolute values)(%)
60s	0.1	0.27
60s	0.33	0.60
80s	0.28	0.50

The hairiness reduction during sizing varies between 25 and 80% in different sizing units.in sizing units where the hairiness reduction is of ahigher order,they generally employ hihger proportion of PVA as the film former in the size mix.earlier PVA was generally used for pet and p\c blends.now even for 100% cotton yarns PVA as a sizing ingradiant is being increasingly used particularly for yarns meant for shuttle less looms,where weft insertion rate is of a higher order.the PVAcoating is strong,abrasion resistant and can easily be desized in hot water.its strength is greater than standard starch and it is also more flexible.

The size recipes used in 4 sizing units with different level of hairiness reduction during sizing are provided

Sizing unit	Count of warp(Ne)	Type of loom	% reduction in yarn hairiness after sizing	Sizing ingradiants of the size mix	% size pick up
1	50s	Projectile	70.10	PVA       23% Starch  69% Lubricants8%	15
2	50s	Air jet	70.34	PVA       23% Starch   69% Lubricants8%	18
3	60s	Projectile	52.08	PVA      6% Starch    87% Lubricants7%	15
4	60s	Air jet	44.49	PVA       12% Starch    82% Lubricants 6%	18

     In units 1 and 2 where hairiness reduction is of the order of 70% the size recipe has PVA at 23%.on the other hand in units 3and 4 where hairiness reduction is around 50% the size recipe has relatively lower concentration of PVA at 6 to 12%.

Among the weaving units surveyed, some have achieved breakage rate close to the gudeline balues recommended in this.major quality attributes of warp yarns used in those uints are given. 

Uster statistics rating of quality levels of warp yarns

Quality parameters	Air jet		Projectile			Rapier
	50s	60s	50s	60s	80s	40s	60s
Rkm	Between 25-50%	75%	50%	Between 75-95%	Between 75-95%	Between 5-25%	Between 75-95%
CV of Rkm (%)	5%	Between 75-95%	Between 25-50%	75%	Between 75-95%	Between 25-50%	Between 25-50%
Breaking elongation (%)	Between 25-50%	95%	75%	75%	95%	75%	95%
Hairiness index	50%	50%	Between 5-25%	75%	75%	Between 5-25%	25%
Normal imperfections
Thinplaces\km (-50%)	Between 5-25%	Between 5-25%	5%	Between 25-50%	Between 5-25%	5%	50%
Thick places\km(+50%)	Between 5-25%	Between 5-25%	Between 5-25%	Between 5-25%	25%	5%	50%
Neps\km(+200)	Between 5-25%	Between 5-25%	Between 5-25%	Between 5-25%	Between 25-50%	Between 25-50%	Between 5-25%
Total imperfections	Between 5-25%	Between 5-25%	Between 5-25%	Between 5-25%	25%	25%	25%

Suggested values of yarn quality

Yarn quality	40S	60s	80s
Rkm(G\tex)	18	20	20
CV of Rkm (%)	8.5	9	10
Br.elongation (%)	5.25	5	4.75
Normal imperfections\km	125	150	300
Hairiness index	5	4.2	3.6
Classimat faults\Lakh m	1 or below
Long thin faults(H1+I1)	10	15	22

Case study 1

Count 60s, projectle loom, satin

Yarn qulity		Weaving performance
Rkm value	18(19)	Warp breaks\10000 ends \Lakh m of weft insertion;4 Guide line value;3
Imperfections\km	300(150)
Classmat faults;long thin	31(15)

The values given in the parenthesis refer to suggested values of yarn quality requirments for projectile loom

Case study 2

Count 80s, projectile loom, satin

Yarn qulity		Weaving performance
Rkm value	16(20)	Warp breaks\10000 ends \Lakh m of weft insertion;7.7 Guide line value;1.5
CV of Rkm	13.5(10)
Classmat faults;long thin	95(15)

The values given in the parenthesis refer to suggested values of yarn quality requirments for projectile loom.

Case study 3

Count 60s, air jet loom, plain

Yarn qulity		Weaving performance
Rkm value	17.9(21)	Warp breaks\10000 ends \Lakh m of weft insertion;6 Guide line value;3
Imperfections\km	408(150)
Classmat faults;long thin	29(15)

The values given in the parenthesis refer to suggested values of yarn quality requirments for airjet loom

Shuttleless Looms

Because the shuttle can cause yarns to splinter and catch, several types of shuttleless looms have been developed. These operate at higher speeds and reduced noise levels.

Some of the common shuttleless looms include water-jet looms, air-jet looms, rapier looms, and projectile looms.

Projectile Loom (Gripper Shuttle Loom)

The multi gripper projectile weaving machine, introduced by sulzer brothers in 1953, was the first system to begin shuttleless Weaving.The Company and its successors have remained the sole suppliers of projectile weaving machinery.

Pick lengths of weft yarn are drawn from large cones by a weft accumulator.The free end is held in the jaws of a weft carrier gripper(projectile),88mm long weighing 40kg and the accumulated yarn is threaded to a sophisticated tensioning and braking system.The Projectile is lifted to the picking position and is propelled across the warp shed by a torsion bar system.At the other side of the loom,the projectile is recieved,the yarn is released and the projectile is ejected for eventual return to the picking side.The weft is cut at the picking side and is held at both sides by a selvedge grippers during beat up and shed change.During the next machine cycle,tucking needles draw the outer ends of weft yarn into fabric to form selvedges.Usually 10-12 projectiles are associated with a single-width loom.

Picking rates are typically 380-420ppm for worsted yarns and 250-300 ppm for woolen yarns.

It offers the following advantages

·         Low power consuption

·         Reduced waste of filling material due to unique clean ,tucked-in selvedges

·         Quick warp and style change

·         Mechanical and operatonal reliability and ease of use

·         Low spare parts requirement and easy maintaince

·         Long machine life

Rapier Loom

Rapier Weaving is offered by many loom manufacturers and consequently is in widespread use in the worsted and woolen industry.

In this type of weaving a flexible or rigid solid element called rapier, is used to insert the filling yarn and carries it through the shed .after reaching the destination, the rapier head returns empty to pick up the next filling yarn, which completes a cycle.a rapier performs a reciprocating motion.

Single Rapier Machines

A single,rigid rapier is used in these machines.the rigid rapier is a metal or composite bar usually with a circular cross section.the rapier enters the shed from one side and pases it across the weaving machine while retracting. Therefore a single rapier carries the yarn in one way only and half of the rapier movement is wasted.also there is no yarn transfer since there is only one rapier.the single rapiers length is equal to the width of the weaving machine; this requires relatively high mass and rigidity of the rapier head.for these reasons, single rapier machines are not popular.however since there is no yarn transfer to rapier tip rapier, they are suitable for filling yarns that are difficult control.

Double Rapier Machines

Two rapiers are used in these machines.one rapier, called the giver takes the filling yarn from the accumulator on one side of the weaving machine, brings it to the center of the machine and transfers it to the decond rapier which is called taker.the taker retracts and brings the filling yarn to the other side.similar to the single rapier machines, only half of the rapier movements is used for filling insertion.

Rapier machines are known for their reliability and performance.since 1972, the rapier weaving machine has evolved into successfull, versatile and flexible weaving machine.

A very wide range of fabrics with 20 g/m2 to heavy fabrics with around 850 gm2 rapier machines are widely used for household textiles and industrial fabrics.Designed for universal use,the rapier weaving machine can weave not only the classic wool,cotton and manmade fibers,but also the most technicaly demanding filament yarns,finest silk and fancy yarns.

Air Jet Loom

Air jet loom, as one of the shuttleless looms, transports a yarn into warps using viscosity and kinetic energy of an air jet. Performance of this picking system depends on the ability of instantaneous inhalation/exhaust, configuration of nozzle, operation characteristics of a check valve, etc.

Air-jet weaving is an advanced weaving method with high efficiency and productivity

·         In air-jet looms, the weft is introduced into the shed opening by air flow.

·         The energy resulting from air pressure is converted into kinetic energy in the nozzle.

·         The air leaving from the nozzle transfers its pulse to stationary air and slows down.

·         To this end, in order to achieve a larger rib width, a confuser is developed, which maintains air velocity in the shooting line.

·         The confuser drop wires are profiles narrowing in the direction of shoot, and they are of nearly circular cross section open at the top.

·         These drop wires are fitted one behind the other as densely as possible. Therefore, they prevent in the shooting line the dispersion of air jet generated by the nozzle.

Water Jet Loom

A water jet is more coherant than an air jet.it does not break up easily, and the propulsive zone is elongated,making it much more effective.it is effective in terms of energy requirements ,it is quite and when the jet does break up, it goes into droplets which create very little turbulence to disturb the filling.

The droplets spread in such a way as to wet much of the warp; thus a sized warp containing a water soluble adhesive can be adversely affected.because of this ,water jet weaving is usually restricted to filament yarn,but there is some hope that it might become economically feasible to weave staple yarns on these looms.

Two main reasons for the efficiency of the water-jet loom are that there are no varying lateral forces to cause the filling to contract and the moving element is more massive because it is wet.thus there is less chance of fault due to contact with the warp.

The range of jet, and thus the width of the loom, depends on the water pressure and the diameter of the jet.water is virtually incompressible and a simple jerk pump can be used to give adequate pressure with difficulty.

A firmans hose has a tremendous range but the jet is several cm in diameter;large volumes of water and considerable pumping powers have to be used .in weaving , a much more modest jet is used; in fact , it is possible to reduce the diameter of the jet to some 0.1 cm, and the amount of water used per pick is commonly less than 2c.c. even with these small jets , it is possible to weave at upto 2 meters in width with small power consuptions.it is also possible to weave at upto 1000 picks/min on narrower looms .several forms of water-jet loom have now become established.

Circular Loom

The circular weaving machine proposed by the invention is designed for the manufacture of tubular fabrics and has an annular frame with an upper ring plate and a lower ring plate Vertically moving laces are fitted to direct the warp ends and are mounted at constant intervals round at least one circular trackway . The two ring plates have bores in them for mounting and directing the laces. The lower ends of the laces have follower rollers which operate in conjunction with a cam plate.

Conclusion

It can be concluded that the yarn parameters and machinery in preparatory for the conventional shuttle looms should be thoroughly assessed and suitably modified or replaced for their performance for the efficient functioning of a shuttleless weaving shed. The above factors play a deciding role in giving quality weaving and better returns thereof.

References

1.    Shuttle Looms - Its Present Status by A. I. Thakkar. NCUTE Pilot Programme on Weaving I - Shuttle looms Page. 47. (NCUTE, New Delhi, 1999)

2.    Vincent J. J. Journal of Textile Institute, vol. JTI, 50 1959 Page 261.

3.    Weaving - A Special Feature by Dr. Arindam Basu, SITRA in Indian Textile Journal ITJ, June 2002. P. 23.

4.    Advances in weaving technology and looms, S. Rajagopalan S.S.M. College of Engineering, Komarapalayam.

5.    modular device for weft yarn presentation in shuttleless looms,by Luciano corain;Luigi corazzla;Guilio Bortoli,all of V.E.Romangna N1-36015,schio(4),Italy.

1. Importance of yarn breakages in weaving process

In the weaving industry it is always emphasized to increase production and maintain quality of woven fabric so the mill can meet the demands of both national and international quality familiar consumers and markets. Also Competitiveness is the main feature of the textile industry in future. The main issue is able to compete at international levels. It is clear from many international exhibitions that the competition will be very brutal in the coming years. Nowadays many mills are able to produce similar quality of the woven fabric. Therefore the main issue is the cost of grey cloth per meter. In order to lower the production costs per meter of woven fabric the yarn breakages are essential to be reduced at every stage of manufacturing the woven fabric. In weaving industry one of the most frequent facing problems is breakages of both warp and weft yarns which not only reduce the production rate and also deteriorate the quality of the produced fabric. These breakages on the preparatory processes and also on loom produce lots of problems and become labor intensive. Lesser the number of yarn breakages lesser will be the defects. So by reducing these breakages of both warp and weft yarns not only increase the productivity of the processes involved to the production of fabrics including warping, sizing etc maintain quality of the woven fabric can be increased but also reduces wastages of yarn, and energy ultimately the cost per meter/yard of the prepared fabric reduces.

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