Yarn Sizing: Important Warp Preparatory Process

Last Updated on 18/07/2022

Yarn Sizing: Important Warp Preparatory Process

Mr. Aqif Yunus Kavathekar1
Mr. Irfan Shafik Mujawar
D.K.T.E Textile & Engineering Institute, Ichalkaranji, India.
Email: aqif8484@gmail.com1


The object of sizing that is binding the fibers and coating the yarn so as to increase the strength and abrasion resistance and making it smooth and uniform, can be achieved by different mechanical techniques of dipping the yarn in size paste and drying. The technique used for yarn sizing depends upon the scale on which the warp yarn is required for weaving. When it is required on small scale only, hank sizing process is followed. In India this technique mostly followed by the hand loom weavers in India. Ball warp yarn sizing also same time called as chain warp sizing is a slight advanced method used when sized warp on slightly larger scale is required. This method is not seen much in our country but was particularly used in Europe when spinning mill sold there yarn in the form of sized warp ready for weaving. However most commonly employed technique of yarn sizing all over the world is slasher sizing or tape sizing.
warp yarn sizing
Fig: Warp yarn sizing (Image courtesy: CCI TECH INC)

Warp Preparatory Processes:
The processes required for warp are called as warp preparatory process. Warping, Sizing, Drawing are the preparation for warp.

Necessity of sizing:
Interlacement of warp and weft are carried out by means of a machine called as loom. Various motions are provided on the loom to carry out the interlacement since the motions used on the loom are numerous they are divided into three groups that is primary, secondary and auxiliary motions this motions imposes various stresses and strains on the warp yarn and tends to the break the yarn. Whenever an end broken loom is to be stopped. This reduces the efficiency and productions of the machines, increase the work load on the weavers and produces the cloth of sab standard qualities. Hence in order to judge the weavability of warp, commonly accepted criteria is the warp breakage rate, such types of breaks are generally due to the various stresses that are imposed on warp during the process of weaving the primary objects of all the process is to reduce the warp end break that will weave a quality fabric with maximum loom efficiency.

Various stresses acting on warp during weaving –

  • Stretching of the warp yarn due to the opposite acting forces.
  • Dynamic stresses having maximum values, followed by minimum 1 in quick succession due to shedding operation about 200 times a minute when the loom runs at that speed
  • Chafing of abrasive forces acting on warp sheet lying on the race bard of a slay during the quick passage of the wooden surfaced shuttle from the one shuttle box to another during picking.
  • Momentary impact forces acting on warp sheet during beat up of the weft pick to the fell of the cloth
  • Abrasion rubbing of yarn with lease rod, drop wire, heald eyes, friction with reed wire, and I case of dense wire, set the friction between adjacent warp ends, during the moment of warp yarns from the beam to the fell of the cloth.

Object of sizing:
Object of warp yarn sizing is to increase the weavability of warp yarn by,

  • Increase in abrasion resistance
  • Making the yarn smooth and uniform
  • Increase the fiber lay
  • Increase the tensile strength of the yarn.

Different fibers, different sizes:
The resistance of the yarns to various stresses and strain mentions above is not the same for all the fibers, on the other hand different fibers act differently toward these stresses. For examples silk and continuous filament manmade fibers have strong cohesion due to continuity of this filaments and have good elastics behavior towards cyclic extension. Therefore this yarns are to be protected mainly against abrasion rather than against cyclic extension. Wool fibers has high extensibility but low tenacity, while flax and jute have high tensile strength but low elongation at break and only limited resistance to cyclic extension. Thus it is not only the strength but the toughness of yarns is more important than the strength or elongation alone.

Tension imposed by sizing machine:
Mechanism of weaving imposes various stresses on the yarn. In addition the process of slasher sizing itself introduces certain stresses which vary along the path of the yarn. Through the warp yarn sizing machine and same time magnitude of such stresses are so high. This stresses varies in different part of sizing machine and they change the condition of the yarn also. Such stresses are developed during the passage of the warp passes between the creel and nip of sizing and squeezing roller then again during drying, during separation of the warp at the head stock and lastly during winding of the sized warp on to the weavers beam. These are the termed as various tension zones of the yarn sizing machine

The size ingredients:
1) Adhesives: Is the main ingredients of size paste. It performs two functions binding of fiber and coating over the yarn surface. Binding of the fiber increases tensile strength of the yarn there by breakages due to the tensions and shocks are minimized. Coating over the yarn surface makes the yarns smooth and uniform. Also less the protruding fibers along the yarn surface. This minimizes breakages due to abrasion.

Adhesives are generally polymeric substances having cohesion between fibers and also other molecules of itself. This is called binding property and film forming property. Mostly various starches are used as adhesives.

According to origin starches are divided in to three groups – Natural, modified and synthetic. 

A) Natural starches –Natural starches are derived from natural raw material that is vegetable origin various grains – maize, wheat, rice, tkp, etc are the natural starches.

B) Modified starches – Natural starches have main draw backs that they required very long boiling to prepare size paste, they give very thick and viscous paste and low penetration. To overcome this modified starches have been developed. This starches are produced from natural starches by modifying their chemical structure by chemical means for example – CMC, Amylopectin, Amylose, dextrin.

C) Synthetic starches – Are entirely man-made they are made form simple chemical by means of chemical synthesis. Synthetic starches are mainly used for sizing of man-made fiber and there bends for example- polyvinyl, alcohol, polyacrylic acid, polymethacrylics, polystre.

2) Gum: Same natural gum, modified gums, and synthetic once can also be used as adhesives. Gums gives very thin viscosity but they give good penetration and binding property. For example- Gum arebic.

3) Softener: After adhesive, softener is the next important ingredient of the size paste. Most of the adhesives after drying produces film which is rigid and inflexible. This makes the yarn rigid and inflexible. Therefore during shedding such film tends to break. To correct this rigidity softener is used. Softener is generally oil or fats or a substance made either of these. A softener is a long chain compound having flexible molecules in its structure. A softener breaks continuity of adhesive film and makes it flexible, so that yarn can break and elongate. In addition to softening the adhesive film, softener also makes the size film hence the yarn surface is smooth. Due to smoothness causes less friction when it rubs against adjacent threads or loom parts this is called as lubricating effect and plays an important role in minimizing the warp breaks due to friction as a well as minimizing the weaving out and dropping off of the adhesive film during weaving. A softener usually possesses both this properties that is softening and smoothing.

Mutton tallow was once more common softener used for yarn sizing but now a day’s it’s used in textile has been banned. Oils like coconut oil, TRO, soap, vegetable tallow, poly ethylene emulsion are used as softener in sizing.

4) Antiseptic: Mostly natural starches are used as adhesives for yarn sizing. Since these are also food materials they give rise to growth of microorganisms particularly in warm and humid atmospheres. These microorganisms then cause bad smell and colored stains to be formed on warp threads. In long run they may attack the fibers of the warp threads itself and threads may get tendered. To prevent this a substance will required which will prevent the growth of the microorganisms on the adhesives film. Such a substance is called as antiseptics are necessary when natural starches are used in yarn sizing. Example- Zink chloride, copper sulfate, Zink sulfate etc.

5) Weighting agent: In previous days the cloth was sold in grey state, after calendaring and on weight basis. In order to increase fullness, hand, and weight of the fabric ingredient called as weighting agent added to the size paste. So that cloth was made more attractive and its sale value is increased. Weighting agents are the names given to these compounds. Weighting agents are usually cheap salts, barium sulfate etc. are used as weighting agents.

6) Brightening agent: These are used to increase whiteness of the grey fabric and increase its sale value when cloth is sold in grey state.

Unbleached cotton cloth is cream’s yellow in appearance and looks duller. When blue coloring matter is added to size mixture it appears whiter. Since blue color is complementary color to cream’s yellow ness, it suppresses yellowness and cloth appears more whiter so that its appearance is enhanced. Ultramarine blue and blue soluble dyes are used as bluing agents.

Brightening agents are also used for same purpose. Brightening agents are also absorb sunlight and reflects ultraviolet light so that cloth appears more whiter and brighter. Ranipalare the fluroscent or optical brightening agents used f or this purpose.

7) Deliquescent: After sizing yarns are dried. In previous days there was a tendency of over drying so that it contains less than its normal moisture makes the warp threads weak, less flexible and brittle. Leads to more warp breakages. If it is not possible for the warp to regain the normal moisture, makes the warp threads weak less flexible and brittle leads to more yarn breaks. If it is not possible for the yarn to regain the normal moisture during weaving operation. Therefore to helps the warp to regain its moisture, hygroscopic substances are added to the size paste. These are called as deliquescent. They also help’s to increase the weight of warp. Example- magnesium chloride, glycerol.

8) Antistatic agents: Synthetic fibers are hydrophobic, give rise to the formation of static electricity on them when they undergo some rubbing action. Static generation is troublesome in many respects. It attracts dirt and dust particles and spoils the cloth, causes fibers and yarns to repel one another and may give rise to spark formation. Antistatic agents are added to the size mixture to overcome this problem. Example- glycerol, polyethelene glycol, lissapol NX, soaps

9) Wetting agents: These are also required for Synthetic warps. Since these are hydrophobic they are difficult to be wetted by aqueous solution of adhesives.it helps synthetic warp to be wetted easily by size paste.

10) Antifoaming agents: When antistatic and wetting agents are used there is too much formation of foam. This sometimes carried over to the drying cylinders. To suppress or smother the foam, antifoaming agents which are some oils like pine oil are added.

Preparation of size paste formulation:
Before starting the yarn sizing process it is necessary to prepare the size paste before preparing the size paste it is necessary to select various ingredient, there % in the size paste which is selected based upon type of warp and type of loom and quantity of size paste required. In sizing two factors are important concentration and viscosity of size past and % size add on required for warp. After this actual preparation of size paste take place.

Gelatinization process:
Mostly natural starches used as an adhesive which is the main and essential ingredient of the size its proper and uniform distribution in the past is very important starches are white or nearly white powder in the form of granules and are insoluble in cold water. To make its stable colloidal solution starch has to be gelatinized. In gelatinizing starch powder is mixed with water to form a smooth paste or slurry and heated by means of steam. As the slurry gets heated starch granules gets swollen due to absorption of water. A point is riche when the swelling of the granules reach maximum and the granules occupy the whole volume of water this is the formation of the size paste. This is called as gelatnisation in the size paste. The minimum temperature at which is take place called as gelatnising temperature. Different starches shows different gelatnising temperature example- potato starch 80Dc to 82Dc, rise 80Dc to 83Dc.

Common size ingredients:
There is tendency to add two many ingredients to make the paste. Previously no of size ingredients used where up to 15 or even more. Many of dent added whit more blind faith than reasons. Even today it is not vary uncommon to see a dozen different materials added to the size paste. It is easily to see that there Is hardly only reason to added more than 3 to 6 ingredient for most purposes.

There is tendency in sizers to added to Many ingredient in too large quantities and over size the warp. To avoid blame of under sizing in an experiment carried out by BTRA sizing composition used by a mill an consisting 7 ingredients with a total concentration of 50% was modified to content only ingredients with total concentration of only 7.6%. The warp breakages where found to be reduced by 35% and the efficiency of the loom was increased by 4.5 %. In the experimental formulation CMC was used hence cost of sizing in the two cases remained almost same.

For sizing of cotton warp yarn starch is steel the main adhesive ingredient. It is relatively chef and commonly available. Among the starches maize starch is more preferred due to its good adhesively and high viscosity. The stiffness of the film liability of the mildew formation and its relative difficulty in its removal wet processing are its drawback it is usually combining with other starches like tapioca there addition increase the solid concentration without increasing the viscosity of the size paste this increase penetration the uniformity the size film and allows higher speeds of operation at yarn sizing. Many time only thin boiling starches are used alone without any starch when they are used together the best ratio in which they should be used is set to be 1:3 as starch to thin boiling starch

Gum possess superior binding property and low viscosity. Therefor they should be used for sizing coarse yarn in small quantities like about 2% gum Arabic is ideal one

Softeners are mostly fats. But the point is that fat reduce the strength of the size film. Therefor they must be limited to the barest minimum quantity required. Quantity equivalent to 5 to 7.5% on the maize starch 5% on the wait of the thin boiling starch, CMC does not required any softener then antiseptics it is prfrable to add 0.5 to 1.5% of a good antistatic like sodium pentachlorophreate on the wait of the natural adhesive. They should be added towards the end of the boiling period. CMC & PVA do not required antiseptics.

There are low special requirement regarding the quality of water to be used for making the size paste. It should only be clear color less, natural free from excessive proportion of inorganic salts and microorganism acidic water affects the viscosity of paste. IF the water is alkaline foaming will be caused. To high proportion of salts wither hardness salts or otherwise will affects the stability of fat dispersion’s the microorganisms will cause the degradation of size or will make the antiseptics in active.

Preparation of size paste:
To prepare the size paste volume and concentration of size paste size ingredients and there % is decided. In the kettle water is taken which is less than final volume is taken first adhesives are added with constant stirring taking care that lump formation is prevented and a smooth paste called slurry is form. The stirring in the cold condition is carried out for 15 to 45 min, and then heating is started. When the paste is hot enough softener, gum paste etc are added and heating is continued to the boiling point. The boiling is continue to 45 min to 1 hour depending on the amount of starch and other ingredients present. In case of thin boiling starches boiling period can be reduced to 1 hr. If the all ingredients are water soluble even shorter period will be enough. In mills softeners and antiseptic agents are added only about 15 min before the heating is stopped.

Sequence of addition of size ingredients:
The usual practice is to mix as many ingredients as possible in the cold water while stirring. Adhesives which are partly or completely soluble in cold water and also those which are likely to form cloths (lumps) in water are steeped in to cold water so that they come in contact with the cold water in there finely divided condition. Starches may be added in the same way to the cold water. In case of starch and china clay, it should be preferable to mix them with cold water in a separate mixing and slurry is then added to the mixing pan containing the other ingredients added in the cold condition. Those ingredients which partly or wholly dissolve in cold water and form a thick paste like CMC, thin boiling starches, PV alcohol PH, gum derivatives etc. Which do not required long steeping are added in the dry condition only through a sieve to cold water in cooking vessel while stirring.

Gum can directly added to cold water only if they are in a finely divided power form. If they are in the lump form they should be steeped in water for several hours to swell them, then boiled to make the solution before adding to size cooking beck. Gum tragacarth requires 3 day of steeping period and them boiling before adding to mixing pam if the gum is available in the form of plates.

Softener is added preferably when the temperature of the mixture is above the melting point of softener but below the gelatinizing temperature of starch in between 50Dc to 60 Dc. The assumption here is that, if the insoluble ingredients are in a finely divided condition during gelatinizing process. Then after gelatinizing starch can keep them in stable. Suspension preventing them from separating but during boiling or sizing.

Some properties of starch paste:
Congealing property of the starch paste if after making the size paste is kept aside, without heating and without stirring, its starts cooling and its viscosity goes on increasing with time. A thick skin is formed on its surface and the paste its smoothness is loss and formation of lumps take place. It losses its flowing property and become self adhesive. In the language of the colloidal since this is called gel formation. We called as congealing property of starch. Some starch are quick congealing like maize starch while some others are slow congealing like potato starch.

When a starch paste is congealed, it is very difficult to use in yarn sizing. This is because solidify, and lost its flowing property once paste has congealed no amount of heating and stirring again well bring it to the smooth flowing condition as before if this happens in the pipeline, the pipeline gets choked one. Quick congealing starches show variations In viscosity with temperature. Than slow congealing one. Slow congealing starches remain smooth flowing for longer time. Therefor in sizing department size paste is kept continuously stirred at hot temperature to prevent congealing.

Keeping property of starch paste :
If starch paste after preparation is kept at room temperature. It viscosity Increase depending upon weather the starch is low congealing or quick congealing. If it is kept still further on long enough the paste slowly thinner. If starch is losing its adhesively. Still later its starts giving bad smell, bubbles of gas well be seen to be coming out of it. It shows acidic test with litmus paper. Finely it becomes watery foul smelling liquid and ultimately useless. This is termed as keeping property of starch. Some starches shows good keeping property. Some shows poor keeping property potato starch having poor keeping property.

Concentrations of size paste:
The concentration of size paste indicates the total wets of various ingredients use the per unit volume of the size paste and is expressed as % for example if size concentration is 10% it means that there are 10kg of total size ingredients in 100 liter of size paste. It is given by formula

Concentration of size paste = wt. of oven dry size material / wt. of the paste *100

Size cooking equipment’s:
Perhaps most neglected job in the warp yarn sizing process is the size preparation. Though at present, many synthetic sizes are available in liquid form, so that they are only to be stored in water the processes of starch paste has not been eliminated. In many mill although care full attention is given to warp sizing on sizing machine very little supervision is provided at size preparation state. If it is left to a jobber or senior worker who is played less than front sizes or back seizer with the result that, many times mixing jobber is not fully aware of the importance of sequence of adding the ingredients the temperature to be maintain the duration of the cooking the size paste etc.

The size cooking equipment is generally placed in the same room as the sizing machine, so that size paste flows to size box of the sizing machine due to gravitational flow. Sometimes there is a gallery suspended from the ceiling to accommodate the cooking equipment or sometimes the cooking equipment are relegated to a corner of the sizing room where it is not possible for the supervisory staff of the sizing department to keep strict vigilance during the preparation of the size mixture however a good weaving technician will always pay a close attention to get the size prepared with almost desired conditions so as to avoid worrying afterword’s when a properly prepared size is not made available for the sizing.

Size cooking kettles and storing becks:

The beck: the beck is the simplest and the oldest cooking vessel and previously it was made from wood. a beck is a cubical shaped vessel with about 1.25 meters sides. Sometimes there is a twin beck with a common side. One is used for cooking and other is for storage purpose. The beck is provided with a stirrer or an agitator driven by the bevel wheels on a shaft or a separate motor Through reduction gear.

Sometimes instead of square boxes circular kettles made up of cast iron shell lined inside with copper sheet are used for cooking .now a days cylindrical vessels made from thick steel sheet are more popular. Advantage of cylindrical shells is that the stirrer when rotating can reach all the parts of the beck.

Factors affecting viscosity of the paste:

  • Concentration of the paste- Higher the concentration of a paste more will be viscosity. However it should be remember that if a viscosity against concentration graph is plotted it is not a straight line.
  • Type of starch- Different starches gives different viscosity for same concentration. Some starches gives higher viscosity than others. Among natural starches maize and potato starch gives more viscosity while sago and tapioca shows lower viscosity. Wheat starch gives medium viscosity.
  • The temperature of the paste- Viscosity is a temperature dependent phenomenon. At higher temperature viscosity is less and at lower temperature viscosity increases.
  • Effect of stirring- Very vigorous mechanical stirring lowers the viscosity of the paste.
  • History of the paste- The viscosity of the paste is not affected by concentration, temperature and stirring but by whole set of circumstances leading up to the measurement of viscosity. Like how the paste was prepared, how the temperature was required, how it was stirred before and during cooking, how long it was kept after cooling and up to the test etc. All this factors constitutes the history of test and for the paste to be compared, must be kept constant.

It should be remembered that, while referring to the thickness of paste, not only adhesive should be kept in mind but all the ingredients in the size paste should be considered. The consistency of size paste is more correct term than viscosity.

Measurement of viscosity:
In laboratory various instrument like Redwood viscometer, strummer, Brookfield viscometer, torsion type viscometer are used and viscosity is measure in terms of it’s unit that is pause for practical purpose cop method is used. A thick metal cup has a hole at the bottom. It is dipped in the paste to fill the cup with the paste. Then if it is lifted vertically and time taken by paste to run down through the hole is noted. Time required to flow through the cup is taken as measure of viscosity. This time is directly proportional to the viscosity of the paste. Higher the viscosity of the paste more is the time and vice versa.

Viscosity of the size paste:
Size paste used for sizing must be thick enough or viscous. Viscosity is the measure of the thickness of size paste. From physic, viscosity is defined as properly to oppose flow in liquids. Viscous paste forms a thick coating over the yarn surface. This coating lays the protruding fibers along the body of yarn, also makes the yarn smooth and uniformly coated which reduces frictional effect size paste becomes viscous due to adhesives which are polymeric substances having high polymeric substances having high molecular weight . They also contains Polar groups which forms bond between the fibers and between themselves. Hence size film sticks the fibers together by penetrating in to yarn structure. But these two properties penetration and coating are opposite to each other. As viscosity increases penetration decreases therefore binding of fibers will be better binder but will not cover the yarn surface with a thick enough layer because during application thin adhesive paste will be easily squeezed out.

It has been found that for staple fiber yarns, covering of yarn is more important than binding of fibers. While in case of yarns of continues filament, binding of filament is more important hence thin sizing paste with high adhesively is required. In case of cotton, if thin paste of high penetrating and binding property is used all the space within the yarn will be filled by the adhesive. The yarns becomes to very stiff and unworkable. On the other hand if size paste is too viscous there will not be any penetration but only covering of size paste. Such yarn also will break easily during sizing. Therefore it is preferable that 100% penetration and complete binding is avoided and some empty spaces are left which will serve as cushions for preserving the flexibility.

Pressure cooking: 
Preparation of the size paste in conventional size Becks requires very long time. If requires about 2 hours of stirring and boiling. Consistency of size paste is also not uniform. In order to reduce the time required for size preparation, now a days, pressure cookers are extensively used in the sizing department apart from reducing time it also reduces steam consumption since size is cooked at higher pressure. Hence cost of size preparation is less.

A common pressure cooker is a cylindrical steam jacketed vessel about 1.25m outer diameter and 1.25 to 1.5m in height. The cooker is provided with a stirrer that can rotate at 40 to 60 rpm. On certain cookers there is a provision for two speeds a slow one 15 to 20 rpm and the other normal 40 to 60 rpm. A pressure gauge, safety valve, lid, steam outlet valve outlet for ready mix size paste. The highest temperature can be set and is controlled thermostatically.

Circulating system:
An elaborate system of piping is necessary in the size preparation section. The fluids to be transported are

  1. The size paste is required to be transported from the cooking vessel to the storage beck and from both of these to size box of the sizing machine.
  2. Water to the size cooking and storing vessels as well as to size carrying pipe.
  3. Stem to the size cooking and storing vessels, size carrying pipes and also to the size box of the sizing machine.
  4. Sometimes solutions and suspension are made separately and then they are added to the cooking kettle to avoid proper mixing and lump formation. Instead of adding dry powders direction. Example. PVA, CMC, china clay, gums, gelatin etc.

When the size paste is prepared with conventional Becks long boiling and stirring of starch slurry is necessary. Bursting of starch granules is not uniform. Therefore viscosity of paste is not uniform and is much affected by changes un temperature as well as keeping. Size film of such paste is not uniform and we get uneven size application.

The process of homogenization consists of first heating the starch slurry to a temperature. Just above the gelatinization temperature of a particular starch and then forcing the paste through a microscopic orifice with tremendous force and at a great velocity. While passing through a hole swollen granules rub against each other. Forces of shear and turbulence come into play thereby swollen starch get broken into small uniform size. The paste thus obtained has more stable viscosity and that it forms on the yarn is also more uniform.

The mixture of starch and water heated up to gelatinization temperature. Enters through an inlet from a pressure cylinder at high pressure and is forced against the backside of homogeneous valve. The very fine clearance between the valve and valve seat starts breaking the particles. Reciprocating action of the plunger type pump forces the slurry against the impact ring. The velocity is about 1600m/sec. and the pressure between 150 to 250 bar. The pressure can be controlled by hand wheel which restricts the valve gap and liquid is forced through by the pressure which is build up.

The mixture is discharged to an intermediate pressure area. Then second homogenization is carried out by second homogenising valve. Finally the homogenized paste is discharged at atmospheric pressure. All this stage again release from a very high pressure to a lower atmospheric pressure causes an explosive action within the paste which combined with the vehement dynamic impact results in further breakdown of the starch granules into more or less uniform minute particles.

The advantage of Homogenizers are that starch slurry is to be heated up to gelatinizing temperature. Only hence there is some saving in consumption of steam and saving in size ingredients. Time required for cooking the size is also less. Most important is the uniform viscosity of the size paste and hence uniform size application.

However there are severe disadvantages of Homogenizers. The saving in steam energy is very marginal. But mechanical energy required for breaking the granules is very high. Higher energy requirements for the powerful pump offset the saving energy. Also maintenance cost of pump is also higher due to frequent replacement of impact ring and other parts.

Tape or Slasher sizing:
Slasher sizing is universally followed for large scale production. In this method warp sheets of equal lengths in which warp ends are in parallel order are assembled together to form a single sheet having required no of ends. This single sheet passed through size paste and squeezed , and dried. Finally dried warp is wound on to a weavers beam. All this operations for assembling the warp sheets, sizing, drying and winding are made in a continuous manner. Also there are supplemented by the ancillary functions like separating the warp ends , measuring the length of warp, marking into cut length and winding required length on the weavers beam. All this functions are to be performed by tape or slasher sizing machine we also called as multicylinder sizing machines.

Slasher sizing process
Fig: Slasher sizing process

Multicylinder sizing machine:
For the purpose of sizing a set of warp beam is prepared in warping. There are about 6 to 10 beams each containing about 400 to 600 warp ends. This beams are placed at back side of sizing machine in a stand called as creel. The warp sheet from each beam is combine with sheet from next beam and process is continued till all sheets are converted in to single sheet. During this operations each sheet passes over and under of the beams in front of it. Then it passes over and under the guide rollers and finally enters in to the size box containing size paste.

The size paste is kept at near boiling condition by injecting steam directly through it by steam pipes. Warp sheet is dipped in to paste by means of a partially immersed immersing rollers and squeezed by passing through the nip form by size rollers and squeeze roller. There is at least one pair of this in the size box. The squeezing rollers presses the size in to the yarn structure, remove excess of paste and the at the same time drag the sheets through the paste

The yarn loaded with the wet size. Then passes through the drying arrangement. Comprising cylinders 5 to 13 cylinders are used as per the requirement usually the drying is controlled in such way that warp contains predetermined moisture contain and over drying of warp is avoided. The last cylinders is kept cool so that the warp sheet get cooled when it leaves the drying range.

Dried warp sheet is separated to as many sheets As there are no of wrappers beam on creel, passed through and expanding comb to adjust it width when after passing between the nip of drag roller and a nip roller, is finally wound on weavers beam. This front position of a yarn sizing machine after drying range is called as head stock. It consist of no of auxiliary mechanisms such as measuring and marking device, full speed arrangement, length indicator, beam pressing arrangement for weavers beam etc. Also there is a driving motion for weavers beam to accommodate the increasing circumference of the beam.

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