Weft Preparation for Shuttleless Weaving

Weft insertion rate is high and unwinding is intermittent on shuttleless weaving machines. Hence it is necessary to have a hard wound package. It is essential to have anti patterning device to prevent slough-off on the fabrics. For spun yar ns, parallel wound package with core diameter of package of 95 mm and a traverse of 90 mm give a good performance. Smaller core diameter of package increases the unwinding tension and enhances the possibility of high weft breakage. Weft accumulators are to be used on high speed weaving machines when the weft insertion rate is above 1000 m/min.

The 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.

Sizing for Shuttleless Weaving

The process of sizing greatly influences the performance of the shuttleless weaving machine. The concept of single end sizing is more ideal for yarn prepared for all shuttleless weaving machines particularly wider width machines with a large number of ends. Single end sizing facilitates proper encapsulation of size on the yarn and reduces hairiness particularly of blended yarns resulting in a ver y clear shed formation which is a must for shuttleless weaving. Double size beams are recommended to avoid over crowding. An optimum number of ends in the size box is given by optimum ends = 0.5 x (width of nip of size box) / dia. of yarn.

Warping requirements for Shuttleless Weaving

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 :

A) Frictional drum should be kept in a polished state.

B) Brake should be very efficient.

C) Aluminium cast flanges should be used to get faulteless selvedges.

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

E) For wider width looms, wider war ping machines are preferred.

Winding requirements for Shuttleless Weaving

All medium and fine counts and all blended yarns with polyester components should be wound on automatic winding machines like Autoconer, Murata, etc. In choosing optimum clearing settings, indiscrimate removal of thick places is not desirable since removal of each fault is replaced by another fault namely a knot. Knots act as sharp instruments on the adjacent threads, besides being responsible for peak tensions generated during weaving. Tail ends of knots come in the way of clear shed formation and can be a cause of multiple breaks. Hence, each thick place is to be assessed with respect to its length, and only objectionable faults may be removed. This is possible only with electronic yarn clearer in conjuction with Uster Classimat which classifies yar n faults into twenty one categories (reference length & C.S.) The size of the tail ends of knots should be small. The knotter is to be selected based upon the yarn number. A spliced yarn gives good results. It would be desirable that a splicer is provided instead of a knotter on the winding machine to give good results and to get rid of all the disadvantages of knots. A large no. of automatic winding machines are equipped with knot / splice tester which ensures 90-95% prefect joints.

Warp and Weft Preparation for Shuttleless Weaving

It is absolutely necessary that machine stoppage rate per 10,000 war p ends and 1,00,000 picks should be considerably reduced for successful installation of shuttleless looms. Because of much smaller shed size,reed sweep and abrasion time, the war preparation standards acceptable for automatic looms will lead to less warp breakages if the same yarn is used on high speed looms. Yarn imperfections which would pass into the cloth on an automatic loom fail to do so on a machine like projectile loom because of the following reasons:

• The reed is less flexible.

• The characteristics of beat-up are considered to be more detrimental than those with conventional sley.

• When the movement of adjacent shed is impeded due to some projection hanging in the form of wild yarn, fluff, scissoring action of the knots, etc, hindrance in the path of the yar n will be chopped off to cause a multiple break.

• Number of abrasion cycles is more because of high speed.

Yarn Quality Requirements for Shuttleless Weaving

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 war p. Weft tension on Sulzer Ruti projectile weaving machine, is equally high, where tucked-in selvedge is for med. Consistency of single end strength, C.V. of count and elongation is essential. 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 war p 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.

Shuttleless Weaving

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.

The quality of yarn used on shuttleless looms is the prime criteria considered for quality weaving. 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.

Introduction

For the successful installation of shuttleless looms, it becomes inevitable to go for quality yarn and optimization of the preparatory operations prior to weaving. A better quality yarn leads to a quality war p and sized beam which consequentially gives and efficient weaving operation both qualitatively and quantitatively.

Loom Attachments

To achieve minimum defects in fabrics, with increase in loom efficiency and to meet the requirements of export quality fabric, the following additional motions may be installed in ordinary power looms.

• Electronic Weft Feelers

• Electro Mechanical Weft Fork

• Electronic Warp Stop Motion

• Sudden Brake Motion

• Positive Let off Motion

These devices will increase the productivity, reduce fabric defects due to double picks, weft cracks, starting marks, broken picks, uneven pick density, etc.

The advantage derived like minimum defects, increase in production, improved quality and increase in efficiency will enable the manufacturer to recover the amount invested in a very short period. Moreover the loom allotted to a weaver can also be increased depending on the variety woven.

So the improve quality, production, efficiency and to face competition when textiles will be available from other countries also, the manufacturers have to expeditiously modernize and tune up the operational efficiency of their existing loom.

A Loom Developed by SITRA

The modern shuttleless looms not only produce faster, but also the cloth produced by these looms possess much better quality as compared to conventional looms. The main problem faced by the decentralized weaver is that imported shuttleless looms are very expensive. In order to overcome this disadvantage to a decentralized sectoer SITRA has developed a low cost rapier shuttleless loom with a likely price tag of around Rs. 3.5 lakhs. The major advantages of this loom as compared to ordinary loom are:

• The speed of the machine can be increased by 25%.

• When the four colour weft is used, the speed increase will be more than 40% compared to drop box loom.

• Weaving defects in fabric will be considerably reduced.

• Since rapier machine feed weft yarn from cone, the process of pirn winding is eliminated.

• 10 to 15% increase in efficiency is possible when compared to ordinary power looms.

• Higher work assignment is possible.

• Because of low cost, power loom units can afford to install this machine

Weft Package Handling

Complete automatic weft package handling, loading the package frame and package changing can be incorporated on Sulzer Ruti projectile weaving machines and Tsudakoma Airjet weaving machines. These include automation equipment for detecting the broken picks with drawing it from the open shed, correcting the cloth fell position and restarting the machine. The entire cycle is completed in about 12 seconds.

Jacquard Shedding Mechanism

Staubli's Unival 100 electronic jacquard shedding mechanism offers a new concept. The shed formation is achieved by controlling each individual warp end with a stepping motor. The harness cord / warp end selection is performed electronically and hence fabric design is achieved in the same way as any electronic jacquard system. The design of the Unival 100 permits the elimination of hook and the gantry.

Electronic Jacquard Head

Grosse has introduced its patented UniShed positive electronic jacquard head. The shed formation in the UniShed is achieved by leaf spring. Each leaf spring is connected to a heddle that controls one warp end. The leaf springs which are controlled by actuators control the bottom shed as well as the top shed (positive shed type). The dimensions of the jacquard head and the individual control of each heddle (warp end) allow the heddles to be set vertically. These settings permit the elimination of harness cords, hooks, magnets, pulleys, pull down springs and more significantly, the gantry. The jacquard head is mounted directly on the side frame of the weaving machine, thus allowing quick style changes.

Tuck-in-Devices

Some of the important development are new tuck in motions based on pneumatic. The principle of pneumatic trucking in is the use of air to hold the filling end and then forcing the filling end to be tucked in, in the next shed, by air. In airjet weaving the automatic weft repairer which repairs the weft break and starts the machine automatically is made simple by using mechano pneumatic device. It is a positive factor in higher weaver allocation and increased efficiency. Dornier exhibited their pneumatic tucker on two airjet weaving machines (LTN F8/J and LWV2/E). Tsudokama demonstrated their ZNT needleless tuck-in on two airjet weaving machine. Somet showed its patented tucking motion on a clipper airjet machine. Elimination of tuck in needle by pneumatic tuck in motion enables the loom run much faster as compared to mechanical devices.

Electronic Control Mechanism

The use of central microprocessor control system and automatic functional with bidirection communication and diagnostic features are the common features of most of these latest weaving machines. Sulzer Ruti P7100 with central microprocessor control, electronically controls progressive weft break, automatic weft feed backup which switches over to a feeder head with intact weft intact weft thread in the event of weft break, at the same time informing the weaver an optical automatic weft break repair and package handling system.

In repair machines electronic control weft tensioner reduces the yarn tension specially during insertion. The opening and closing time can be selected according to the material usually at yarn pick up. Automatic package switching device prevents the machine from being stopped in the event of a weft break between the package and the weft feeder. The microprocessor switches over immediately to a reduced number of packages in the circle, so that the machine continues to run.

Electronically controlled warp let off and cloth take up units ensure high degree of fabric regularity and prevent all kinds of start and stop marks. Electronic monitoring control system have simplified the communication with the machine and facilitate its easy handling by any one concerned with the operation of the machine e.g. weaver, technical, maintenance, personnel, etc.

In airjet weaving machine electronic let-off maintains consistent warp tension from full beam to empty beam. Electronic cloth take up generates a pick density resolution of 0.1 picks/cm and holds it constant, under all operating conditions.

In terry plus airjet terry weaving machine of Gunne Web Machinen Fabric GMBH & Co. The microprocessor monitors the entire insertion cycle and keeps all the different elements perfectly synchronized.

Minimum Down Time of Looms

Many of the weaving machine manufacturers offer quick style change (QSC) system. The basic idea of these developments is to prepare module outside the weave room and keep them ready for a switch over with empty module in the weaving machine. Dornier demonstrated quick style changes from a fine worsted fabric to a pure cashmere fabrics in less than 30 minutes. Similarly, almost all major weaving machine makers offer their own version of QSC. Dornier offers Fast Dobby Change (FDC) which allows a mill exchange a dobby shedding for a cam drive when a basic style is being woven and higher shedding machine speeds are possible. The exchange times is not more than 1.5 hours per occurrence.

Production Rates of various Looms

The Production rates of the various types of looms are presented for comparison in Table

Loom type Available width in cms Speed in rpm Weft insertion rates(ppm)

Projectile

Sulzer Ruti P7100             190-540                 320                      1100-1200

Sulzer Ruti P7200             190-540                 430                      1500

STB Russia                      180-330                 300                     750

Rigid Rapier

SACM                              150                       550                      1110

Dornier                            150-400                460                      1000

Gunne                             230                       330                      1200

Flexible Rapier

Somet                             165-410                 550                      1300

Vamatex                          160-380                510                      1300

Sulzer Ruti                       110-280                 325                      1200

Nuovo Pignone                 220-420                 440                      1000

Water Jet

Metor SPA                       230                         1000                    1600

Nisson                            150-210                   1000                    2000

Tsudakoma                    150-210                   1000                     2000

Air Jet

Sulzer Ruti                     upto 300                  750                       1600

Picanol Omni                  190-380                  800                       1800

Picanol Delta                  190                         1110                     2000

Toyoda                          150-330                  850                       2000                          

Tsudakoma                   152-340                   1000                     2200

Lakshmi Ruti                  190                         500                       1200

Dornier                          430                         600                       2520

Linear Multiphase

Elitex                            about 190               1100-1600               2000-3000

Drum type Multiphase

Sulzer M8300                 190                        3230                       6088

 

Out of these single phase looms, Air jet loom is having maximum speed and maximum weft insertion rate. Because of the very high quality of yarn required, the yarn must be of very high standard, otherwise the loom stoppages due to warp breaks and weft breaks will be high. The efficiency achieved will be in the order of 93 to 95%.
Other looms like projectile and repair will give an efficiency of about 90 to 95%. The cover of the fabric in air jet will not be as good as projectile and rapier looms. Efficiency in multiphase loom is in the order of 90 to 95% These are the speeds obtained by the weavers at commercial level. The main reason for targeting higher productivity is to reduce the cost of production, especially labour cost. The increase in speed is being achieved the improvement in all major functional parts of the modern looms Today the market particularly demands wide variety as much as possible at the lowest possible cost. These machines provide the feature such as :

• The possibility of weaving more difficult products in terms of yarn employed and also in combinations

• Application potential in all weaving sectors.

Sulzer Ruti 6300 rapier loom will weave not only fashion, fabrics with us many as 8 weft colours but also furnishing fabrics, simple print base fabrics and denims as efficiently as light to heavy weight industrial fabrics.
The terry plus airjet terry weaving machines of Gunne not only permit greater pile height and heavier fabrics, it also offers greater flexibility in operation with the ability to change the fabric width and pile height. On the machine the drawing width can be changed using the same reed, simply by shifting the weft stop motion and the weft cutter. The pile height is programmable within the same fabric. Special fabric constructions with different pile heights on front and back are also possible. For Sulzer P7300 projectile looms a variety of back rest roller and cloth take up systems are available to suit the density and the type of fabric woven.