Sample warping This warping process, which was developed for sampling purposes, gives full proof of its performances during this production phase of new items. This particular process is composed of several warping operations which wind up a limited thread length and place on the warping width several bands of different colours to get the colour variants of the fabric. This kind of warps can be obtained also by section warping, which however involves a considerable loss of time owing to frequent cone changes and definitely higher investments in raw materials. In practice a cone per colour is sufficient to obtain any required warping sequence. The machine is composed of a small creel where the cones of the warping sequence are placed, by a thread guide which winds up a pre- set number of meters (selectable with a pattern or a control device) taken from the cone according to the thread sequence in progress. The latest solution with revolving creel permits to wind up to 12 threads at a time at a winding speed of max. 1200 meters/minute. Once the winding operation is concluded, the threads are beamed on a weaver’s beam which follows the usual production cycle. The machine manufacturers proposed initially two solutions for this kind of warpers: the first solution envisaged a vertical development of the winding blanket, whereas according to the latest solution the threads are pre-wound on a drum before being wound on the weaver’s beam. The warp length in this last model varies from 7 to 420 meters; some weavers consider this length as normal for their productions and therefore use this system side by side with the traditional sectional warping machine. It is evident that the correct use of this machine permits to feed the weaving machine in a very short time while minimizing the use of materials and labour, especially if an automatic drawing-in equipment is available upstreamWarping Calculations

Machine Efficiency E = (R * 100)/R+S

R = Uninterrupted running Time for 1000 meters (sec) = (1000 * 60)/Machine speed in mtr/min

S = total of time, in seconds for which the machine is stopped for a production of 1000 meters.

   = R + (B * N * T1)/400+ T2/L + T3/(L*C )+ T4

B = End breaks / 400 ends / 1000 meters           N = Number of ends.

L = Set Length in 1000 meters                            C = Beams per creel.

Timing of activities in Seconds are

T1 = To mend a break           T2 = To change a beam

T3 = To change a Creel         T4 = Miscellaneous Time loss / 1000 mtrs.

Production in meters. per 8 hrs.(K) = 480 x mtrs / min x E / 100 Kgs.

Production in Kgs. Per 8 hrs. = (K x N) / (1693 x English Count)

Warping Tension = 0.03 to 0.05 x Single Thread Strength

Textile Warping

It is a commonly known fact that fabrics are constructed through two major techniques- weaving and knitting apart from other minor techniques. In these processes, two distinct sets of yarns called the warp and the weft are interlaced with each other to form a fabric.

'Warp' is the set of yarns that are laid out first on a loom or frame and 'Weft' is the yarn that is woven under and over the warp yarns that are already stretched onto the loom. Thus warp is the continuous row of yarns and the wefts are the yarns that are woven in from

side to side. If we go by these definitions, it is clear that textile warping is the processing of creating the base yarn that runs top to bottom on woven cloth.

Beginning of Warp Knitting Warp knitting is an important and an ever growing industry. When compared to weaving,

this industry can be considered as newer. Nobody knows about who invented weaving and hand knitting but it is known that mechanical knitting, in form of socks producing machine, was invented by Reverend William Lee in 1589. Crane of Nottingham applied warp yarn guides to the knitting frame invented by Lee in around 1775 which initiated warp knitting.

Paget, in 1861 and Willium Cotton, in 1864, made certain improvements in the looms. The compound needle was invented by Mattew Townsend in 1849, which contributed in making

the textile knitting machine simpler and faster.

Warp Knitting MachinesThere are two basic types of warp knitting machines . They are- Tricot knitting

machine and Raschel knitting machine. Earlier, the Tricot machines were equipped with bearded needles and Raschel machines were equipped with the compound

needles. However, the modern versions of both these types of machines are equipped with compound needles. The distinction between these two machines is,

therefore, made by the type of sinkers in them and the roles these sinkers play in loop formation. The sinkers in a Tricot machine control the fabric throughout the knitting cycle. However, in the Raschel machines, sinkers are only used to ensure that the fabric stays

down when the needles rise. The type of knitting machine influence the product construction specifications and, therefore, is an important factor in the whole process.

Yarn Preparation Yarn preparation in warp knitting combines methods used in weaving and knitting. In some

cases, the ends of yarn can be fed directly off cones into the knitting machine but the number of cones needed restricts this working method. The large floor space required for a

creel is justified only when it is technologically essential- for example, with Jacquard and curtain machines. In all the other cases, the yarn ends are fed off warp beams. Yarn

preparation can be reduced to a simple winding of yarn ends on to the warp beams in a knitting machine since artificial yarn is mainly used along with moderate tensions applied to the knitting yarn. As such, smooth operation can be ensured without sizing the yarn.

The quality of warp beam is crucial for determining the quality of the knitted fabric. Variations in yarn thickness, tension, twist and other factors too might result in a defective

fabric. In most of the cases, warping mistakes are not easy rather impossible to correct

during the knitting process.

Methods of Warping The yarn manufacturers, these days, can supply prepared warps but most of the knitting

firms prefer to prepare their own warping equipment and warp beams independently. Mostly, they select the standard types of yarns and warp effect yarns in the plant. There are two basic methods of warping that can be used to prepare the warps for the knitting

machines- Indirect Warping and Direct Warping

Indirect Warping: The yarns from the yarn packages are wound onto an intermediate cylinder (mill) in many parallel groups with a specified density, and then they are back

wound onto the warp beam.

Direct Warping: The ends of the yarn are wrapped in one operation, from the yarn packages onto the warp beam.

However, there are certain requirements that have to be kept in mind while using both the methods, information about which has been given in the table below.

Requirements for Direct and Indirect Warping

Requirement Yarn ends density Direct Warping

Yarn ends per section R R

Number of revolutions R R

Warp length R R

Number of sections NA R

Yarn ends per section NA o

R - Required; O - Optional; NA - Not Applicable

Warping Defects There are certain major warping defects on beam warpers as given below.

Lapped Ends :The broken end of yarn is not tied to the end on the warp beam and overlaps the

adjoining yarn. The beam is not properly braked and the signal hook fails to operate.

Bulges : Yarn ends are drawn from the middle and the broken end is not correctly pieced up to the adjoining yarn.

Broken ends on the beam : It occurs due to reasons mentioned in the above point. A group of ends is broken and tied as a bunch or worked-in with overlapping.

Yarn cut at the butts of the warp beam/ slackness of extreme yarns : It occurs when the reed is improperly set with respect to the warp beam flanges or there is a

deformation of the warp beam flange.

Excessive or insufficient number of yarn ends : The number of yarn ends of the beam becomes excessive or insufficient due to the incorrect number of bobbins in

warping.

Conical winding on the beam : It occurs due to incorrect load applied by the pressure roller.

Slacks & irregular yarn tension :It happens due to any on of these reasons- improper threading of the yarn into the tension devices, ejection of yarn from under the disc of the yarn tensioning device,

or yarn tension devices of poor quality.

Frequent yarn breakages at the beam edges : It results due to burrs and nicks on the surface of the warp beam flanges.

Improper length of warping :It is due to malfunction of the counter, and the brakes of the measuring device & warp beams.

Coarse Knots : It is due to manual tying-up.

Loose yarn winding :It happens when the pressure roller is lightly pressed against the warp roller.

Fluff, oily ends and yarn of different density : It is due to the careless work of the operater, creeler and oiler.

Bulgy winding on the warp beam :It is due to Irregular laying of yarn ends in the reed, missing a dent and placing two

ends in the adjoining yarn

WARPINGIt is practically not possible to place hundreds or thousands of cones before a loom for the sake of providing warp to the fabric, so warping is used. Warping is basically the process of winding a part of the total ends of warp in full width on to a beam.

What Warping Should Do? To form from a predetermined single end packages, such as cones or

cheeses, a continuous sheet of yarn of specified length and width.

The individual ends of the sheet should be spaced uniformly across its full width.

All the ends in the sheet should be wound at almost uniform tension.

The density of wound yarn beam should be uniform across the width and from start to end of winding the sheet.

What Warping Should Not Do? Attempts should not be made to remove the yarn faults during the process of

warping; the yarn breaks during warping should be as minimum as possible.

Density of the beam should be controlled not by increasing yarn tension but by adjusting the pressure roll on the beam in case of spindle driven beam.

The yarns should not get damaged during warping --- this can happen if the drum surface is not smooth and/or the parts in the yarn path have cut marks.

The yarn sheet or the beam should not have faults, such as missing ends, cross ends, slack ends, fluff or wild yarn, high variation in tension between ends, damaged flanges etc. that will cause end break or defects at subsequent processes.

TYPE OF WARPING

Beam Warping

Yarn is directly wound from cone onto the beam.

This process is suitable for single color weaving

The end product is called warp beam and must sent to the sizing department for further process .

Types of Beam Warping MachineThe warping machines are classified according to the 'package drive'; there are two basic types of the warping machines:

1. Direct driven or the spindle driven, in which yarn winding speed on to the beam increases as the diameter of the beam increases. Beam size is therefore limited due to the increase in yarn winding tension.

2. Surface driven; in which beam gets its motion while in contact with a drum, revolving at fixed r.p.m. In this case yarn winding speed remains constant through out the build of the beam.

Section Warping

Yarn is wound firstly wound onto a drum and then wound onto the beam

This process can be used for both single or multicolour weaving .

The end product is called Weavers beam and can be directly installed onto the weaving loom

Ball Warping

Ball warping is an intermediate process for storing yarn for transport , dyeing or reserve .

It does not produce a beam .

The usual form is a cross wound cheese in which multiple ends are wound at the same time in a ribbon which contains perhaps 50 or a 100 ends.

Description of the Warping Machine

Warping machine consists of:

(i) Head stock or winding head. In itself it consists of the following:

a. Main driving gear which may be a fractional cone - clutch arrangement or it may be direct motor driven.

b. Adjustable reed to regulate the width of warp.

c. Yarn length measuring device.

d. Adjustable back reed for even distribution of warp threads.

e. Arrangement to detect thread breakage.

(ii) CreelIt is an arrangement where packages are placed on pegs. Single threads are taken from the packages passed through a tensioner, a guide and then on the front winding head. Function is to place all the threads in a sheet form so that whenever a thread breaks it can be easily traced out. The number of packages in a creel must be decided on the economic merit of any given situation with warper's bobbin its capacity is from 400 --600 packages; while with cones and cheeses the range is wider, i.e., 600 -- 1000 packages. In deciding about creel size, weight of yarn on supply packages, floor space available and number of beams required must all be considered.

Creel Types

There are four main types of creels

Truck Creel

Magazine creel

Reversible Creel

Duplicate Creel

Truck Creel

The yarn packages are placed on a moving stand know as truck in a preparation area .

A number of trucks are required per creel .

At the end of the run the yarn of is broken between the package and the guide . The truck are then wheeled out from the centre of the creel to be replaced by the pre-loaded trucks .

It is then necessary to tie up the yarn from each end to the correspond end in the creel .

There are a great many variants of the truck creel system but the principle is to use 'trucks', or mobile

package carrier units, each consisting of a number of columns and tiers on either side so that when

inserted on the axis of the creel frame it becomes a part of the creel. The side members carrying the

tension units in positions corresponding to the packages on the mobile unit when correctly installed in

the frame, can be moved outwards to provide working space between the tension device and the

expended packages prior to running them out. The trucks have varying numbers of columns and tiers,

generally in the range 6x9 per side, depending on the package size to be used and the corresponding creel

gauge, which generally varies from 200 to 300mm.

The trucks are creeled-up away from the warper, frequently at the winding machine to avoid double handling, provided sufficient trucks are made available. This is not a low cost solution as many reserve trucks arc essential and these are not inexpensive units. If double handling is accepted the trucks can be reduced to one set in the creel and one complete reserve set, but this sacrifices some of the flexibility of the system. A truck creel with the trucks being loaded to the running position. Some of the more highly developed truck creels have a chain loading device, which pulls the trucks into the creel, correctly locates them sequentially, and with draws them from the back of the creel when a replacement is indicated. This type of creel is frequently used for very large creel package applications, which make trucks difficult to maneuver. Two arrangements are possible. The creel can be loaded from outside with inside draw-off or vice versa. The former arrangement is preferable as it not only provides a straighter thread-path but also is easier to load. They both can be arrange automatically.

Magazine creel

Each package position is duplicated with one package in the running position and the other in the reserve position tied nose to tail.

The package holders swivel to enable the empty cones to be removed and new cones tied to in nose to tail to the running package whilst the machine is in operation

Drawback – it is normally a very long creel which greatly increased m/c stoppage time per break.

It is desired to avoid the knots in the body of the warp and thus preferable to rewind the yarn left on cones owing to the uneven yarn count from one cone to another.

OR

This creel allows the tail of yarn from the package that is supplying yarn, to be tied to the leading end of the yarn , of the new package .

Both packages are mounted on the spindles, which are aligned with the same guide, and the transfer of the feed from one package to the other is automatic.

Although the space required for the creel is greatly increased

The system is ideal for mass production.

Reversible Creel

· This creel allows the position of the old packages and the new ones to be reversed at he end of a run .

· The vertical racks of packages are arranged in sections which can be turned inside out .

· Or they are placed on a chain which carried the new packages from the creel’s inside position to

· the outside , from where the yarn is fed tot the headstock .

The creel sides are arranged in a V-form , which leaves plenty of room for re-creeling in the inside position while the machine is

running .

The two wings of an acute angled creel are each served by an endless chain, which moves the columns of yarn package holders, and

tension units round an endless track, transferring the expended packages from the running position outside the creel wings to the

creeling position inside the creel and the creeled packages into the running position. Creel changes inside cycle can be completed using

such a system in less than; 15 minutes. A ‘creel’ is being transferred from the creeling position to the running position. The pegs shown

as empty will normally carry cone residues from the running position to the creeling position where they are replaced by full packages

for the next creel. There is considerable storage space within the creel for storage of creel trolleys.

Duplicate Creel

· There are 2 creels per headstock and at the end of each run they are moved sideways so that a full creel is quickly positioned

behind the headstock .

· It is possible that one of the reverse creel positions could be behind the running position of

· the creel . However it is more usual for the headstock to move sideways as this requires less

· space .

· It is always necessary to re-thread the warp at the beaming headstock before commencing

the new run .

Automatic Creels

The Schlafhorst ‘automatic’ creel Z25 is one of the most highly currently available. It is essentially a truck

creel with automatic chain unloading and with two features to reduce creel change time. The creeler yarn

from the package simultaneously through tension device break detector and collects all the ends from

one tension column and twists them together before locating them in a holder on the threading truck. As

the truck is pushed forward it automatically threads and separates the ends according to creel tiers and-

columns.

The carriage stands at the rear of the creel during beaming, and is released when the running yam

packages are almost expended. As the carriage moves along the creel every end is cut between package

and tension device, the ‘live’ end being secured in a clamp. When the knotter carriage reaches the front

of the creel, the operative operates the chain conveyer and removes the creel trucks from the creel. The

creel trucks are designed with special pegs with clamps at their extremities so that when each cone is

loaded the end is located in the clamp. This precludes the use of closed end cone shells. The knotter

carriage has a separate knotter head for each tier on each side of the creel, so a six tier creel will have

twelve knotter heads on the knotter carriage. When the full creel trucks are correctly assembled by the

convener chain, the knotter carriage ties one column on each side simultaneously.

The creel incorporates other advanced features. These include a tension unit, which is set to minimum

tension on each end of a column at the back of the creel, and this tension is matched on every end on the

front column of the creel. All the intermediate columns are then calibrated by a scale so that all ends

have equal tension as they reach the headstock. Once the basic setting has been made, uniform

simultaneous adjustment can be made to all the ends by a single hand wheel. A traveling blower keeps

the tension units and yarn packages free from 'fly' and a dust suction unit with stripping device is located

at the base of the creel.

Effects of Poor PerformanceThe performance of the warping process is judged mainly by the end breakage rate at this process.

The operation cost of an end break in warping has been estimated to be about 700 times of that in automatic winding. An end breakage in warping, besides causing stoppage of the production from all the packages (400 - 600) put in the warping creel, reduces substantially the production efficiency of the warping machine. Besides the

steep fall in productivity, an end break in warping is also likely to deteriorate the quality of the beam preparation due to three reasons:

1. When the machine stops with the broken end passed on to the beam, there is a possibility of incorrect mending --- taking the broken end from the beam in cross with the neighboring ends, bad knot, slack end--- which can lead to the formation of lapper in sizing or a stoppage in the loom shed;

2. The shortage caused in the length of the broken end during mending leads to high loss in extensibility of that end during unwinding of the beam at sizing or rebeaming and by that increases the probability of its breakage in sizing and weaving; and

3. Potential hazard to all the ends in the sheet due to rubbing of the beam yarn with the drum which stops abruptly at the time of machine stoppages.

ProductivityThe productivity in warping is governed by the machine speed, the number of ends on the beam and the machine efficiency. The speed is mainly governed by the type of warping machine and to some extent depends upon the type of yarn and its count. The number of ends per beam depends on the creel capacity and the requirement for the set. The machine efficiency is influenced besides the machine speed, by the end breakage rate, time to mend a break, number of ends per beam, set length, length of yarn on the supply package, beam doffing time, creel change time etc.

In general terms, warping is transferring many yarns from a creel of single-end packages forming a

parallel sheet of yarns wound onto a beam or a sectional beam. The warp beam that is installed on a

weaving machine is called a weaver’s beam. A weaver’s beam can contain several thousand ends and

there are several types of warping processes that can be used depending on the purpose.

Direct Warping

In direct warping, the yarns are withdrawn from the single-end yarn packages on the creel and directly

wound on a beam. Direct warping is used in two ways:

a) Direct warping can be used to directly produce the weaver’s beam in a single operation. This is

especially suitable for strong yarns that do not require sizing such as continuous filaments and

when the number of warp ends on the warp beam is relatively small. This is also called direct

beaming.

b) Direct warping is used to make smaller intermediate beams called warper’s beams. These smaller

beams are combined later at the sizing stage to produce the weaver’s beam. This process is called

beaming. Therefore, for if the weaver’s beam contains 10,000 warp ends, hen there would be –

say – 10 warper’s beams of 1,000 ends each. If this weaver’s were to be made a one stage, the

creel would have to have 10,000 yarn packages, which is impossible to manage.

Indirect Warping :In indirect warping, a section beam is produced first. The section beam is tapered at

one end. Warp yarn is wound on the beam in sections starting with the tapered end of the beam. Each

section has multiple ends and this kind of warping is generally useful for colored yarn warping.

Another type on indirect warping is ball warping. Ball warping is mainly used in manufacturing of denim fabrics. The warp yarns are wound on a ball beam in the form of a tow for indigo dyeing. After dyeing the tow is separated and wound on a beam.