Characteristics of Cotton | Cotton Characteristics

Cotton Staple LengthIf the length of fiber is longer, it can be spun into finer counts of yarn which can fetch higher prices. It also gives stronger yarn.

Cotton Strength Stronger fibers give stronger Yarns. Further, processing speeds can be higher so that higher productivity can be achieved with less end-breakages.

Fiber Fineness Finer Fibers produce finer count of yarn and it also helps to produce stronger yarns.

Cotton Fiber Maturity Mature fibers give better evenness of yarn. There will be less end - breakages . Better dye absorbency is additional benefit.

Uniformity Ratio If the ratio is higher. Yarn is more even and there is reduced end-breakages.

Cotton Fiber Elongation A better value of elongation will help to reduce end-breakages in spinning and hence higher productivity with low wastage of raw material.

Non-Lint Content Low percentage of Trash will reduce the process waste in Blow Room and cards. There will be less chances of yarn defects.

Sugar Content Higher Sugar Content will .create stickiness of fiber and create processing problem of licking in the machines.

Cotton Moisture Content If Moisture Content is more than standard value of 8.5%, there will be more invisable loss. If moisture is less than 8.5%, then there will be tendency for brittleness of fiber resulting in frequent yarn breakages.

Cotton Feel If the feel of the Cotton is smooth, it will be produce more smooth yarn which has potential for weaving better fabric.

Cotton Grade Cotton having better grade in classing will produce less process waste and yarn will have better appearance.

Grey ValueIf the reading of calorimeter is higher it means it can reflect light better and Yam will give better appearance.

Yellowness When value of yellowness is more, the grade becomes lower and lower grades produce weaker & inferior yarns.

Cotton Neppiness Neppiness may be due to entanglement of fibers in ginning process or immature fibers. Entangled fibers can be sorted out by careful processing But, Neps due to immature fiber will stay on in the end product and cause the level of Yarn defects to go higher.

Cotton parameters It is better if quality parameters are established for different varieties so that buying decisions are easy for buyers Following standards have been found to be appropriate for Strict Middling Grade Cotton of staple 1.3/32".

• Staple Length ( 2.5% Spun Length) - Minimum 1.08" or 27.4 mm

• Micronaire : Minimum 3.8, Maximum-4.6.Variation within bulk sample should not be more than 0.1

• Colour : Readingd not less than 75 not more than 10

• Nep Content: Less than 150 per gram

• Strength : More than 30 grams/tex

• Length Uniformity Ratio: Not less than 85%

• Elongation : More than 8%

• Short Fiber Content: Less than 5%

• Seed Count Fragments : Less than 15 per grams

Cotton and Yarn Quality Co-Relation | Cotton Yarn Properties | Cotton QualityThe Cotton Yarn Properties which can be directly Attributed to Cotton Quality are

Cotton Yarn Count Higher Count of Yarn can be produced by longer, finer and stronger fibers.

Coefficient of Variation of Count Higher Fiber Uniformity and lower level of short fiber percentage will be beneficial to keep C.V.(Coefficient of Variation) at lowest.

Cotton Yarn Tensile Strength This is directly related to fiber strength. Longer Length of fiber will help to produce stronger yarns.

C.V. of Strength This is directly related to CV of fiber strength.

Cotton Yarn Elongation Yarn elongation will be beneficial for weaving efficiently. Fiber with better elongation have positive co-relation with Yarn elongation.

C.V. Of Yarn Elongation C.V. of Yarn Elongation can be low when C.V. of fiber elongation is also low.

Cotton Yarn Hairiness It is due to faster processing speeds and high level of very short fibers

Cotton Yarn Brightness Yarn will have brighter appearance if cotton grade is higher.

Yarn Testing | Coefficient of VariationYarn occupies the intermediate position in the manufacture of fabric from raw material. Yarn

results are therefore essential, both for estimating the quality of raw material and for controlling the quality of fabric produced. The important characteristics of yarn being tested are:

• Yarn Twist

• Linear Density

• Yarn Strength

• Yarn Elongation

• Yarn Evenness

• Yarn Hairiness

Yarn Twist Twist is defined as the spiral disposition of the components of yarn, which is generally expressed as the number of turns per unit length of yarn, e.g turns per inch, turns per meter, etc.

• Twist is essential to keep the component fibers together in a yarn.

• The strength, dyeing, finishing properties, the feel of the finished product etc. are all dependent on the twist in the yarn.

• With increase in twist, the yarn strength increases first , reaches a maximum and then decreases.

• Depending on the end use, two or more single yarns are twisted together to form "plied yarns" or "folded yarns" and a number of plied yarns twisted together to form "cabled yarn".

• Among the plied yarns, the most commonly used are the doubled yarns, wherein two single yarns of identical twist are twisted together in a direction opposite to that of the single yarns.

• Thus for cabled and plied yarns, the direction of twist and the number of turns per unit length of the resultant yarn as well as of each component have to be determined for a detailed analysis. Direction of twist is expressed as "S"-Twist or "Z"-Twist.

• Direction depends upon the direction of rotation of the twisting element.

• Twist take up is defined as, The decrease in length of yarn on twisting, expressed as a percentage of the length of yarn before twisting.

Coefficient of Variation of TwistIn handling large quantities of data statistically, the coefficient of variation (C.V.%) is commonly used to define variability and is thus well-suited to the problem of expressing yarn evenness. Coefficient of Variation is currently probably the most widely accepted way of quantifying irregularity. It is given by coefficient variation (C.V.%) = (standard deviation/average) x 100

The coefficient of variation for twist per metre shall be not more than 7% when tested.

Linear Density or Count of YarnThe fineness of the yarn is usually expressed in terms of its linear density or count. There are a number of systems and units for expressing yarn fineness. But they are classified as follows

Direct System

• English Count (Ne)

• Metric Count (Nm)

• French Count (Nf)

Indirect System

• Tex

• Denier

English Count (Ne)No of 840 yards yarn weighing in One pound

Metric Count (Nm)No of one kilometer yarn weighing in One Kilogram

French Count (Nf)No of one kilometer yarn weighing in 0.5 kilogram

TexWeight in grams of 1000 meter(1 kilometer) yarn

DenierWeight in grams of 9000 meter(9 kilometer) yarn

• For the determination of the count of yarn, it is necessary to determine the weight of a known length of the yarn. For taking out known lengths of yarns, a wrap-reel is used. The length of yarn reeled off depends upon the count system used.

• Another factor which determines the length of yarn taken for testing is the type of balance used. Some balances like quadrant balance, Beesley's blanace have been specially designed to indicate the yarn count directly from tests on specified short lengths of yarn and are very useful for determining the counts of yarn removed from the fabrics. The minimum accuracy of balance required is 0.001mg

• One of the most important requirements for a spinner is to maintain the average count and count variation within control. The term count variation is generally used to express variation in the weight of a lea and this is expressed as C.V.%. This is affected by the number of samples and the length being considered for count checking. While assessing count variation, it is very important to test adequate number of leas. After reeling the appropriate length of yarn, the yarn is conditioned in the standard atmosphere for testing before it's weight is determined.

• The minimum number of sample required per count is 20 and per machine is 2.

Yarn Strength and ElongationYarn Breaking strength, Yarn elongation, Yarn elastic modulus, resistance abrasion etc are some important factors which will represent the performance of the yarn during actual use or further processing. Yarn Strength testing is broadly classified into two methods single end strength testing skein strength or Lea strength

Yarn Strength - Tensile Strength of Single Strands of Yarn

• During routine testing, both the breaking load and extension of yarn at break are usually recorded for assessing the yarn quality. Most of the instruments record the load-elongation diagram also.

• Various parameters such as initial elastic modulus, the yield point, the tenacity or elongation at any stress or strain, breaking load, breaking extension etc can be obtained from the load-extension diagram

• Two types of strengths can be determined for a yarn

Yarn Strength - Tensile StrengthLoad is applied gradually

Yarn Strength - Ballistic StrengthApplying load under rapid impact conditions

• Tensile strength tests are the most common tests and these are carried out using either a single strand or a skein containing a definite number of strands as the test specimen.

• An important factor which affects the test results is the length of the specimen actually used for carrying out the test. The strength of a test specimen is limited by that of the weakest link in it.If the test specimen is longer, it is likely to contain more weak spots, than a shorter test specimen. Hence the test results will be different for different test lengths due to the weak spots.

• The amount of moisture in the yarn also influences the test results. Cotton yarn when fully wet show higher strength than when dry, while opposite is the case with viscose rayon yarns. Hence, to eliminate the effect of variation due to moisture content of the yarn, all yarn strengrth tests are carried out, after conditioning in a room where the standard atmospheric condition is maintained.

• The rate of loading as determined by the "time-to-break", which is the time interval between the commencement of the application of the load and the rupture of the yarn, is an important factor , which determines the strength value recorded by using any instrument. The same specimen will show a lower strength when the time-to-break is high, or higher when the time-to-break is low.

• The instruments used for determining the tensile strengh are classified into three groups, based on the principle of working.

CRT - Constant Rate of Traverse

CRE - Constant Rate of Extension

CRL - Constant Rate of Loading

• In the instruments of CRE type, the application of load is made in such a way that the rate of elongation of the specimen is kep constant. In the instruments of the CRL type,the application of load is made in such a way that the rate of loading is constant througout the duration of the test. This type of instruments are usually preferred for accurate scientific work. In the CRE and

CRL types of instruments, it is easy to adjust the "time-to-break" while this adjustment is not easy in the CRT types of instruments.

• The uster Tensorapid applies the CRE principle of tensile testing. Constant Rate of Extension describes the simple fact that the moving clamp is displaced at a constant velocity. As a result, the specimen between the staionary and the moving clamp is extended by a constant distance per unit of time and the force required to do so is measured. Apart fron single values, this instrument also calculates mean value coefficient of variation and the 95% confidence range of maximum force, tenacity,elongation and work done

• The total coefficient of variation describes the overall variability of a tested lot, i.e the within-sample variation plus the between-sample variation. If 20 individual single-end tensile test are performed on each of ten bobbins or packages in a sample lot, the total coefficient of variation is calculated from the pooled data of the total number of tests that were carried out.

• In tensorapid, the breaking tenacity is calculated from the peak force which occurs anywhere between the beginning of the test and the final rupture of the specimen. The peak force or maximum force is not identical with the force measured at the very moment of rupture. The breaking elongation is calculated from the clamp displacement at the point of peak force. The elongation at peak force is no identical with the elongation at the very moment of rupture(elongation at rupture).

• The work to break is defined as the area below the stress/strain curve drawn to the point of peak force and the corresponding elongation at peak force. The work at the point of peak force is not identical with the work at the very moment of rupture.

• To compare tensorapid test results with other results,

a) A measurement must be performed according the CRE princple

b) Testing speed must be exactly 5 m/min

c) The gauge length or the length of the specimen should be 500 mm

d) The pretension should be 0.5 cN/tex

• There are two fundamental criteria which affect the compatibility between different measurements of tensile yarn properties.

a) Testing conditions, i.e the testing principle(CRE,CRL),Testing speed, gauge length, and pre-tensioning.

b) The second criteria,which also affects the magnitude of the differences, relates to the specific stress/strain characteristic of the yarn itself, which is determined by the fibrous materials, the blend ratio, and the yarn construction.

Yarn Strength - Yarn Skein Strength or Yarn Lea Strength The skein breaking strength was the most widely used measure of yarn quality in the cotton textile industry. The measurement of yarn quality by this method has certain drawbacks. Firstly, in most of the subsequent processing, such as winding, warping or weaving, yarn is used as single strand and not in the form of a skein except occasionally when sizing ,bleaching, mercerising or dyheing treatments are

carrried out on hanks. Secondly, in the method used for testing skein strength, the rupture of a single strand at a weak place affects the result for the whole skein. Further, this method of test does not give an indication of the extensibility and elastic properties of a yarn, the characters which play and important role during the weaving operations. However, since a large size sample is used in a skein test as against that in a single strand test, the sampling error is less. The skein used for strength test can be used for determination of the linar density of the yarn as well.

• In addition to the factors influencing the yarn strength, the size of the skein(lea) will affect to a large extent the strength recorded. The usual practice is to use a lea(120 yards) of yarn prepared by winding 80 turns on a wrap-reel having a perimeter of 1.5 yards(54 inches), so that during a test, there are 160 strands of 27 in.(") length. There are different systems in use. But the actual breaking strength recorded on the machine would depend on the type of skein used as both the number of strands and test length may differ. The instruments most commonly used for this test is CRT type, where the bottom hook moves at 12 inches per min.

• After findingout skein strength, broken skeins are also weighed to determine the linear density. The most common skein used is the lea and the results of lea strength tests are expressed as C.S.P., which is the product of the linear density(count)of the yarn in the English system (Ne) and the lea breking strength expressed in lbs. In view of the fact that C.S.P. is much less dependent on yarn count than on strength, especially when count diffferences are small, C.S.P. is the mostg widely used measure of yarn qauality.

Yarn HairinessYarn hairiness is a complex concept, which generally cannot be completely defined by a single figure. The effect of yarn hairiness on the textile operations following spinning, especially weaving and knitting, and its influence on the characteristics of the product obtained and on some fabric faults has led to the introduction of measurement of hairiness.

Facts About Yarn Hairiness

• Hairiness occurs because some fibre ends protrude from the yarn body, some looped fibres arch out from the yarn core and some wild fibres in the yarn.

• Torsion rigidity of the fibres is the most important single property affecting yarn hairiness. Other factors are flexural rigidity, fibre length and fibre fineness.

• Mixing different length cottons-No substantial gain in hairiness. Although the hairiness of a yarn could be reduced to some extent by the addition of a longer and finer cotton to the blend. The extent of reduction is not proportional to the percentage of the longer and finer component. This is probably due to the preferential migration of the coarser and shorter component, which has longer protruding ends, from the yarn body. The addition of wastes to the mixing increases the yarn hairiness; the effect of adding comber waste is greater than that of adding soft waste.

• Blending-not a solution to hairiness. The blended yarns are rather more hairy than expected from the hairiness of the components; a result similar to that found in cotton blends. This may be due to the preferential migration of the shorter cotton fibers; a count of the number of protruding ends of both types of fiber shows that there is more cotton fiber ends than expected, although the difference is not very great.

• The number of protruding ends is independent of twist, whereas the number of loops decreases

when the yarn twist increases because of a greater degreee of binding between hte fibres owing to twist. The number of wild fibres decreases only very slightly with twist because of their position on the yarn periphery.

• The proportion of fiber ends that protrude from the yarn surface, counted microscopically has been found to be about 31% of the actual number of ends present in the yarn.

• If the length of the protruding fibre ends as well as that of the loops is considered, the mean value of the hairiness increases as the cross-sectional area increases and decreases with the length of the loops. The hairiness is affected by the yarn twist, since an increase in twist tends to shorten the fibre ends

• Wild fibres are those for which hte head alone is taken by the twist while the tail is still gripped by the front drafting rollers.

• Fibre length influences hairiness in the sense that a greater length corresponds to less hairiness.

• Cotton yarns are known to be less hairy than yarns spun from man-made fibres. The possible reason for this is the prifile of the two fibres.Because of taper, only one end, the heavier root part of the cotton fibre, tends to come out as a protruding end in a cotton yarn. With man-made fibres, both ends have an equal probability of showing up as protruding ends.

• Combed yarn will have low yarn hairiness, because of the extraction of shorter fibres by the comber.

Different Methods Used to Measure Hairiness

Uster Hairiness IndexThis is the common method followed in India. The hairiness index H corresponds to the total length of protruding fibres within the measurement field of 1cm length of the yarn.

Zweigle Hairiness IndexThis zweigle hairiness measurement (S3) gives the number of protruding fibres more than 3 mm in length in a measurement length of one meter of the yarn. From the above you can infer that Uster hairiness index give the total length of hairs whereas zweigle hairiness testers give the absolute number of fibres. Though the later measurement is more accurate, most of the Indian spinners are still following Uster hairiness index only.The factors effecting hairiness can be sub divided into 3 major components.

a) The fibre properties

b) Yarn parameters

c) Process parameters

a) The Fiber PropertiesFibre length, Uniformity ratio, Micronaire and short fibre content are the properties exerting high influence on hairiness. Among the above the length and short fibre content exerting major influence.

For a particular count, higher length of fibre leads to lesser hairiness and high short fibre content leads to high hairiness.

b) Yarn ParameterHairiness is dependent on the number of fibres present in the cross section of the yarn. Hence coarser yanrs have more hairiness compared to finer yarns.

The yarn twist is another major factor and higher twists lead to less hairiness up to a certain extent. This is the main reason while hosiery yarns normally have high hairiness compared to warp yarns.

However in a mill condition, the fibre parameters and yarn parameters cannot be adjusted. Hence the next topic, process parameters, assumes very high significance, as this is the only available option at the mill level to reduce the hairiness.

c) Process ParameterThe preparatory machines do not have a big influence on hairiness. The Speed frame, Ring frame and the Cone winder are the only machines to be attended for reduction in hairiness.

Textile Carding | Carding | Carding Fiber | Spinning Carding | Carding Machines

The Purpose Of Carding:

• To open the flocks into individual fibres

• Cleaning or elimination of impurities

• Reduction of neps

• Elimination of dust

• Elimination of short fibres

• Fibre blending

• Fibre orientation or alignment

• Sliver formation

Spinning CardsThere are two types of feeding to the cards

• Feeding material in the form of scutcher lap

• Flock feed system (flocks are transported pneumatically)

Carding Lap Feeding in Carding Machines

• Linear density of the lap is very good and it is easier to maintain(uniformity)

• The whole installation is very flexible

• Deviations in card output will be nil, as laps can be rejected

• Autolevellers are not required, hence investment cost and maintenace cost is less

• Transportation of lap needs more manual efforts( more labour)

• Lap run out is an additional source of fault, as it should be replaced by a new lap

• More good fibre loss during lap change

• More load on the taker-in, as laps are heavily compressed

Fiber Carding Flock Feeding in Carding Machines

• High performance in carding due to high degree of openness of feed web

• Labour requirement is less due to no lap transportaion and lap change in cards

• Flock feeding is the only solution for high prouduction cards

• Linear density of the web fed to the card is not as good as lap

• Installation is not felxible

• Autoleveller is a must, hence investment cost and maintenance cost is more

There are two rules of fiber carding

• The fibre must enter the carding machine, be efficiently carded and taken from it in as little time as possible

• The fibre must be under control from entry to exit

Control of fibres in a carding machine is the responsibility of the card clothing

Card Clothing

Following are the Five Types of Clothings used in a Carding Machine

Cylinder wire

Doffer wire

Flat tops

Licker-in wire

Stationary flats

Process Parameters in Carding | Carding Process | Best Carding Settings for Synthetic Fiber

Carding is the most important process in spinning. It contributes a lot to the yarn quality.

The following Carding process parameters and specfications are to be selected properly to produce a good quality yarn with a lower manufacturing cost. Carding Settings

• cylinder wire(wire angle, height, thickness and population),

• flat tops specification, licker-in wire specification,

• doffer wire specification,

• feed weight,

• draft between feed roller and

• doffer cylinder,

• grinding doffer, grinding flat tops, grinding cylinder,

• falt tops, doffer wire life, Licker-in wire life,

• Cylinder speed. flat speed, Licker-in speed,

• setting between cylinder and flat tops,

• setting between licker-in and feed plate, setting between licker-in and undercasing elements like , mote knife,combing segement etc..

• setting between cylinder and doffer, setting between cylinder and back stationary flats, setting between cylinder and front stationary flats, setting between cylinder and cylinder undercasing.

Cylinder Wire and Cylinder Speed Cylinder wire selection is very important. it depends upon cylinder speed ,the raw material to be processed and the production rate. The following characteristics of cylinder wire should be considered.

• Wire angle

• Tooth depth

• Wire population

• Rib thickness

• Tooth profile

• Tooth pitch

• Tooth point

• Overall wire height

• Wire front angle depends on mainly cylinder speed and coefficient of friction of raw material.

Higher the cylinder speed, lower the angle for a given fibre. The cylinder speed in turn depends upon the production rate.

• Higher production means more working space for the fibre is required. It is the wire that keeps the fibre under its influence during carding operation.Therefore the space within the wire should also be more for higher production. Higher cylinder speed also increase the space for the fibre. Therefore higher cylinder speed is required for higher production.

• In the case of high production carding machines, the cylinder surface is very much higher, therefore even with higher number of fibres fed to the cylinder, the cylinder renews the carding surface at a faster rate.

• Higher the cylinder speed, higher the centrifugal force created by the cylinder, this tries to eject the fibres from the cylinder, along with the trash.It is the cylinder wire's front angle which overcomes the effect of this force. Low front angle With too low cylinder speed and with high frictional force, will result in bad quality, because the fibre transfer from cylinder to doffer will be less. Hence recyling of fibres will take place, which result in more neps and entanglements.

• The new profile with less free blade avoids loading of the cylinder with fibre and/or trash. This helps in keeping the fibres at the tip of the tooth. The movement of the fibres towards the tip of the tooth, coupled with centrifugal action demands an acute front angle to hold the fibre in place during carding.

• Lack of stiffness associated with fine and/or long fibres necessitates more control during the carding process.This control is obtained by selecting the tooth pitch, which gives the correct ratio of the number of teeth to the fibre length. Tooth pitch reduction is therefore required for exceptionally short fibres and those lack stiffness.

• Number of points across the carding machine is decided by the rib width. It is selected based on the production rate and fibre dimensions. Finer the fibre, finer the rib width. The trend is to finer rib width for higher production.

• The population of a wire is the product of the rib thickness and tooth pitch. The general rule is higher populations for higher production rates, but it depends upon the application.

• Sharp tooth points penetrate the fibre more easily and help to intensify the carding action. Cut-to-point wires are sharp and they have no land at all. The effective working depth of a cylinder wire tooth for cotton is approximately 0.2mm and for synthetic materials approx.0.4mm. Manmade fibres require more space in their cylinder wire than does cotton.More tooth depth allows the fibre to recyle, resulting in damaged fibres and neps. If tooth depth is insufficient, there will be loss of fibre contro. This will result in even greater nep generaion.

Doffer, Licker-in and Flat Tops:

• The basic funtion of doffer is to strip the fibres from Cylinder.

• The doffer wire's front angle plays a very important role in releasing the fibre from the cylinder. For most carding applications the optimum angle is 60 degrees.

• Increased population over 400 ppsi does not give any advantage in the production of quality yarn. For smaller doffers, 5 mm doffer wire height helps in tranferring the fibres from cylinder to doffer.

• If the fibre holding capacity of the doffer wire is less due to fibre friction or due to very high doffer speed, it is better to use a doffer wire with striations. For high production carding it is

always better to use doffer wire with striations.

• Licker-in plays a major role in opening the fibre tufts. In general 85 degrees is used both for synthetic and medium and long cottons. For coarse and dirty cottons 80 degrees can be used.

• Strength, hardness and sharpness are very important for Lickerin wire. Licker-in wires should neverbe ground. Thinner blades penetrate the fibres more efficiently and increase the wire life.

• Higher number of rows per inch gives better results. Now upto 12 rows per inch is being used. This is always better compared to 8 rows per inch.

• If the wire pitch is not sufficient, it can be compensated by increasing the licker-in speed. Higher licker-in speeds for fine and long cottons will rupture the fibres. Licker-in speed depends upon the fibre type and the production rate.

• It is better to use a flat top with more than one population. The general combination is 280/450. This is suitable for both cotton and synthetics. The rigidity of the fillets is different for cotton and synthetic. If cotton flat tops are used for synthetic processing, the load on the cylinder will be more, more heat will be produced and hence the probability of cylinder loading due to electrostatic charge will be high.

• Instead of using Rigid type flat tops, it is better to use semi-rigid type flat tops while processing synthetic fibres.

Settings:

• The setting between cylinder and doffer is the closest setting in the card. This setting mainly depends upon the cylinder speed ,hank of the delivered sliver and the type of wire. Cylinder speed upto 360, the setting should be 0.1mm. For cylinder speeds more than 450 , the setting ranges from 0.125 to 0.15.

• If the setting between cylinder and doffer is very close, the wires will get polished and this will affect the fibre transfer. If the setting is too wide, the fibres will not be transferred to doffer from the cylinder, hence cylinder will get loaded. While processing synthetic fibres cylinder loading will badly affect the yarn quality. Moreover, it is difficult to improve the wire condition if the loading is severe. The only solution would be to change the wire. Therefore enough care should be taken while processing synthetic fibres.

• The most critical setting in a carding machine is between cylinder and flat tops. While processing cotton, it can be as close as 0.175 mm provided the mechanical accuracy of flat tops is good. Since most of the cards are with stationary flats at the licker-in side, the setting from the back to front for flats can be 0.25,0.2.0.2,0.2,0.2mm.

• Closer the setting between cylinder and flats, better the yarn quality. Neps are directly affected by this setting. Of course, very close setting increase the flat waste. For processing cotton the setting can be 0.25,0.2,0.2,0.2,0.2mm. For synthetic fibres it can be 0.3,0.25,0.25,0.25,0.25mm

• Most of the cards are with 6 to 11 stationary flats at the licker-in side. This setting can start with 0.4 mm and end with 0.25mm.

• The wire points can start with 140 ppsi and end with 320 ppsi. The work done by the first few stationary flats is very high, therefore the wear of these flats is also high. It would be better if the first 50% of the flats are changed after 100000 kgs of production and the rest after 150000 kgs of production.

• These stationary flats open the material so that, the setting between cylinder and flats can be as close as possible.

• The setting between feed plate and Licker-in depends upon the type of feed plate. Conventional feed plate setting is decided mainly by the feed weight and to some extent by the fibre length and type. With the latest feed plate and feed roller arrangements, the setting is decided mainly by the fibre length and to some extent by the feed weight.

• Normally the setting between the feed plate and Licker-in is around 0.45 to 0.7mm, depending upon the feed weight and fibre type.

• The setting between Licker-in and the first mote knife is around 0.35 to 0.5 mm. This helps to remove the heavier trash particles and dust. Closer the setting , higher the waste%ge. The setting between Licker-in and combing segments is around 0.45 to 0.6. This helps to open the material.

• Some cards have two mote knifes in the Licker-in undercasing. The setting is around 0.4 to 0.5mm. This helps to remove the smaller trash and dust particles.

• The setting between the cylinder and stationary flats at Doffer side, helps to transfer the fibres to doffer by stripping the fibres to the top of the cylinder wire. This setting can be as close as 0.15mm. The number of wire points on stationary flats also play a major role . It is normally around 300 to 400. For a high production application it can be as high as 600.

• For cotton processing, the stationary flats are fixed with a knife attachement. The setting should be as close as possible,i.e.around 0.15mm. This helps to remove the trash particles of very small size

• The setting between cylinder and cylinder undercasing should be as per the manufacturer's recommendation. The design of undercasing is different for different manufacturers. This setting is very important , as wrong settings will affect the fibre transfer and can also create air turbulance.

Cylinder Speeds:

• Higher cylinder speed helps fibre transfer. Higher the production, higher should be the cylinder speed.

• Higher cylinder speed improves carding action, thereby imperfections are reduced.

• Higher flat speed, improves yanr quality and at the same time increases the flat waste

• Higher Licker-in speed for coarse fibres and diry cotton helps to remove the trash and improves , the yarn quality.For fine and long cottons , higher speed results in fibre ruputre, therefore, flat waste and comber noil will be more.

• With the same flat speed, higher the carding production , lower the flat waste and vice-versa.

• Very high tension drafts will affect carding U%. It is better to keep the draft between feed roller to doffer around 75 to 95. The results are found better with these drafts.

Wire Maintenance:

• For a modern cylinder wire of 2mm height, grinding with the normal grinding stone is not recommended. It is better to use TSG grinder from GRAF. It is better to grind the wire every

2nd or 3rd month, so that the sharpness of the wire is always maintained.

• TSG grinder does not grind the wire, therefore if the wire is worn out very badly the quality improvement using this grinding machine will be nil. Frequent grindings are recommended. If TSG grinder is not availbale, it is better not to grind 2mm wires.

• The number of traverse should increase depending upon the life of the wire. The number of traverse for successive grindings should be like this 3,5,10,17 etc. Anyway the best method is to confirm with the microscope. If the grinding is not sufficient, the number of traverse should be increased.

• Doffer is still working with a concept of Land formation. A normal grinding machine will be good for doffer grinding. All the wire points should be touched by the grinding stone. A slow and gradual grinding with the grind-out concept will give the best results. Harsh grindings will result in burr formation on the land. This will increase the number of hooks in the fibre, thereby the effective length of the fibre from this card will be reduced.

• Flat tops grinding is very important. Every time a flat top is ground, yarn quality is improved. It is better to use a grinding machine with the emery fillet. Frequent flat tops grinding will result in less neps and the yarn quality will be consistent.

• Some mills increase the life of the flat tops compared to cylinder wire. But it is better to change flat tops and cylinder wire together for better and consistent yarn quality.

• It is a good practice to check the individual card quality before changing the wire.

• Licker-in wire should be changed for every 150000 kgs. Earlier changes will further improve the yarn quality.

• Stationary flats should be changed for every 150000 kgs. But it is a good practice to change the first 3 or 6 stationary flats at Licker-in side for every 100000 kgs. This helps to maximise the carding effect between cylinder and doffer which is critical for better yarn quality.

Others:

• Lower the feed variation, better the carding quality. Even if the card is with an autoleveller, feed variations should be kept as low as possible (plus or minus 10%). With the latest chute feed systems, it is easy to control the feed variation with in 5%. Lower the feed variation, lower the draft deviation, therefore yarn quality will be consistent.

• If the card is with autoleveller, the nominal draft should be selected properly. Improper selection will affect sliver C.V% and yarn quality.

• Improper feed roller loading and the setting between feed roller and feed plate will affect the quality, especially C.V% and neps.

• Before mounting , the eccentricity of cylinder and doffer should be checked. Eccentric cylinder and doffer will affect the U% and will affect C.V.% also.

• Defective bearings , gears and timing belts will affect U%.

• Uneven distribution of tension drafts will affect U%.

• Selvedge of feeding bat should be good. It should not be folded and double. This will increase the neps and sometimes it may result in cylinder loading. Lap fed to the carding machine should be narrower than the nominal width of the machine.

• For processing cotton, minimum 800 pascal suction pressure should be maintained at trash master (at knife)for effective removal of trash and dust particles.

• If Cylinder undercasing nose at doffer side is too long for the type of fibre being carded web disappearing problem will arise. If the nose is set too close to the cylinder, web disappearing problem will arise. Damaged and dull doffer wire also will result in web disappearing problem.

• Worn or damaged scraper blades will lead to web sticking to crush rollers. Insufficient pressure between scraper blade and crush roller will also result in web sticking. If the calender roller pressure is too high web sticking will also be high.

Cotton Combing | Combing | Cotton Comb | Combing Cotton

Cotton Combing is the process which is used to upgrade the raw material.

Combing influences the following yarn quality

• Yarn evenness

• Strength

• Cleanness

• Smoothness

• Visual appearance

In addition to the above, combed cotton needs less twist than a carded yarn

Task of the Cotton Comber To produce an improvement in yarn quality, the comber must perform the following operation.

• Elimination of short fibres

• Elimination of remaining impurities

• Elimination of neps

• The basic operation of the comber is to improve the mean length or staple length by removing the short fibres.

• Since fineness of short fibres(noil) is low, the overall micronaire of the sliver after combing is high.

• Because of combing, fibre parallelization increases. But the high degree of parallelisation might reduce inter-fibre adhesion in the sliver to such an extent that the fibres slide apart while pulled out of the can. This may lead to sliver breaks or false draft.

Combing Process

• Feeding, lap is fed by feed roller

• Feed lap gripped by the nipper

• Gripped lap is combed by circular comb

• Detaching roller grips the combed lap and moves forward

• While the detaching roller delivers the material, top comb comes into action to further clean the lap

• While going back,nipper opens and receives a new bit of lap

The rawmaterial delivered by the carding machine can not be fed directly to the comber. Lap preparation is a must .

A good lap fed to the comber should have

• Highest degree of evenness so that lap is gripped uniformly by the nipper

• A good parallel disposition of fibres so that long fibres will not be lost in the noil

• Trailing hooks from carding should be fed as leading hooks to reduce long fibre loss in the noil

• Degree of parallelisation of lap fed to the combers should be optimum. If fibres are over parallelised lap licking will be a major problem. Because of fibre to fibre adhesion, mutual separation of layers within the sheet is very poor.Moreover the retaining power of the sheet can be strongly reduced that it is no longer able to hold back the neps as it usually does. Some of these neps also pass thro the top comb. Neppiness of the web is increased.

• Retaining power of the fibres results in self cleaning of the lap during combing operation. A thick sheet always exerts a greater retaining power than a thin one.To certain extent, the bite of the nipper is more effective with a higher sheet volume.On the negative side , a thick sheet always applies a strong load to the comb and this can lead to uncontrolled combing.A compromise should be struck between quality and productivity.

• If the sheet is more even across the width, clamping effect at the bite of the nipper will be better. Evenness of the lap is therefore of considerable significance. The most effective method of obtaining a high degree of evenness of the sheet is through more number of doublings in the web form. (as it is done in Ribbon Lap)

• Fibres must be presented to the comber so that leading hooks predominate in the feedstock. This influences not only the opening out of the hooks themselves, but also the cleanliness of the web.If the sheet is fed to the comber in the wrong direction, the number of neps rises markedly.

• Both quantity and form of fibre hooks depend mainly upon the stiffness of the fibres. This rises to the second or third power with fine fibres. Fine and long fibres will always exhibit more and longer hooks than short and coarse fibres. Accordingly, the role of fibre hooks in the spinning process becomes more significant as fibres become finer

• There are two types of feeds in Comber

Forward feed (concurrent feed):Feed of the sheet into the nippers occurs while the nippers move towards the detaching roller

Backward feed (counter-feed) : Feed of the sheet occurs during return of the nippers

• Higher Noil % always improves the imperfections in the final yarn. But the strength and other qality parameters improve upto certain noil %, further increase in noil results in quality

detrioration.

• The Feed Length has a direct influence on production rate, noil %, and the quality of combing. High feed length increases the production rate but cause deterioration in quality. Higher the quality requirement, feed length should be lower. To some extent , the feed length may be decided by the length of the fibre also. Detaching length is the distance between the bite of hte nippers and the nip of the detaching rollers. This distance direectly affects the noil %. More the detaching distance, higher the elimination of noil.

• Needles of the comber top comb have a flattened cross section and are used with a point density in the range of 22 to 32 needles per centimeter. More the needles, more the noil%.

• The Depth of Penetration of top comb also affects the Noil %. If the comb depth is increased by 0.5mm, approximately 2% increase in noil will occur. When the depth is increased , the main improvement in quality is seen in Neps.Over deep penetration of top comb disturbs fibre movement during piecing which will deteriorate the quality.

• Since the web from detaching roller is intermittent because of the intermittent functions like feeding, combing and detaching, to have a continuous web from the comber,fibre fringes are laid on the top of each other in the same way as roofting tiles. This process is called Piecing. This is a distinct source of fault in the operation of Rectinlinear Combing. The sliver produced in this way exhibits a periodic variation.

• As large a lap as possible with adapted lap weight which is as high and as uniform as possible must be positioned in front of the comber. The better the comber lap is prepared, the heavier the lap weight can be set on the comber and the less the resultant noil waste with the same degree of cleanliness of the yarn.

• The higher degree of combing out are used in order to permit final spinning of ultra-fine yarns or to increase the strength of a yarn. Reducing the lint content improves the medium staple. However, not all cottons meet these requirements. Low degree of combing out , on the other hand, frequently serve to improve purity. When the card sliver is pulled through the needle bars, these separate off foreign bodies, large neps and torn fibres. Light combing out has also been introduced to a greater extent owing to the impairments in cotton purity influenced by mechanical harvesting. Even when combing with minimum noil percentages, there is a noticeable improvement in fibre parallelsim in the sliver. Even the smoothness and shine of the yarn are improved. It must thus be anticipated that this method will become more and more popular in the future.

Production of Comber

Production of the comber is dependent upon the following N- Nips per min S- feed in mm/nip G- lap weight in g/m K- Noil percentage A- tension draft between lap and feed roller(from 1.05 to 1.1) E- efficiency

Production = (E * N * S * G * (100-K) * 60 * 8) / (1000 * 1000 * A *100)

Process Parameters in Combing | Combing Process | Combing Yarn

What is CombingCombing is a process which is meant for upgrading the cotton raw material so that the following yarn properties will improve compared to the normal carded yarn. U% of yarn tenacity gms/tex trash in the yarn(or kitties in the yarn) Lustre and visual appearance

Parameters of Combing Following parameters are very critical as far as the yarn quality of combed yarn is concerned

• Noil percentage(waste percentage)

• Type of feed

• Feed length

• Feed wight in grams per meter

• Piecing length

• Top comb penetration depth

• The distance between unicomb to nipper

• Unicomb specification

• Number of needles in top comb

• The cleaning of unicomb

• Variation in nipper grip

• Variation in noil percentage

• Type of lap preparation

• Total draft between carding and comber i.e total draft employed in lap preparation

• Drafting roller settings in comber

• Drafting roller settings in lap prepartion machines

• No of doublings in lap preparation

• Short fibre content

• Fibre micronaire

• The type and the amount of trash in the card sliver

Waste Percentage The noil percentage from a comber depends upon the following

• Short fibre content

• Detaching distance

• Feed length

• Top comb penetration

The distance between unicomb to top comb

• The basic idea of removing the waste is to remove the short fibres i.e to improve 50% span length or mean length.

• The two impartant basic parameters to be considered in deciding the waste percentage are,

1.Yarn quality requirement and

2.Short fibre content in the raw material

• Combing efficiency is calculated based on the improvement in 50% span length, expressed as a percentage over 50% span length of the lap fed to the comber multplied with waste percentage. i.e. ((S-L)/(L*W))*100

where S- 50% span length of comber sliver L- 50% span length of comber lap W- waste percentage

• Higher the noil %ge , lower will be the combing efficiency.

• It is better to remove waste more from top comb penetration than increasing the waste percentage by increasing the detaching distance. When the detaching distance is more the control during detaching will be less.

• It is better to work with backward feed than forward feed for the same waste percentage.Nep removal will be better, loss of long fibres in the waste during detaching will be less.

• With backward feed, top comb penetrates into the fibre fringe which is already combed by the unicomb, therefore combing action done by top comb will be better and there will not be longer fibres in the waste

• Waste percentage depends upon the feed length and type of feed. In backward feed, higher the feed length, higher the waste percentage. In forward feed, higher the feed length, lower the waste percentage.

• With backward feed, the detaching distance will be less for the same waste percentage compared to forward feed. Therefore fibre control during detaching and during top comb action will be better

• Higher the noil, higher the yarn strength. But this is true upto certain level of waste. Further increase may not increase the yarn strength. Very high %ge of noil will reduce the yarn strength and will increase the breakage rate in ring frames.

Top Comb and Unicomb

• The number of needles in Top comb depends on the Fibre micronaire , the lap weight and fibre parallelisation in the lap. If the fibre Micronaire is less than 3.6, number of needles per cenitmeter in top comb can be 30.In general for fibres above 3.8 Micronaire, 26 needles per centimeter is used.

• Top comb plays a major role in removing the waste. Around 40 to 60% of noil is removed by top comb. But top comb will get damaged very fast. Top comb damage will result in slubs in the sliver. Even 4 ro 5 needle damages will result in bad webs. Top comb maintenance is very very important to produce good qyality yarn.

• Different types of unicombs are used in different combers. The circumference of unicombs , the number of wire points and its variation in the unicomb are different. It is not true that 110 degree unicomb will produce good quality yarn compared to 90 degree unicomb.

• In most of the cases, 75 degree unicomb has given better results compared to 90 degree unicomb in E7/4 combers, for different types of cottons.

• Rieter has standardised 90 degree unicomb for its E-62 combers. 110 degree unicomb can not be used in this comber

• Unicomb action will be effective as long as nipper and unicomb moves in opposite direction.If unicomb and nipper move in the same direction, unicomb can not do its work properly. Moreover the finer needles will not be utilised properly. That may be the reason why 90 degrees unicomb do not produce a good qyality yarn compared to 75 degrees unicomb.

• The setting between unicomb and nipper should be same. When nipper is loaded with the the feed roller, the setting may be around .4 to .5 for E7/4 combers and .5 to .7 for E-62 combers. This setting can be corrected by fixing spacers between unicomb and unicomb body. Some unicomb manufacturers supply the spacers along with the unicombs.

Lap Preparation:

• There are different types of lap preparation. The best combination is drawframe and unilap combination. Lap piecing will be less in this combination compared to sliver lap and ribbon lap combination. Every lap piecing is a major fault compared to sliver piecing. If number of lap piecings are less, top comb damages will also be less.

• The total draft for sliver lap and ribbon lap combination should be around 9 .

• If Micronaire is less than 3.8, the lap licking tendency will be more. For such fibres, the total draft between card and comber should be kept as low as possible, i.e around 8.5.

• For drawframe and unicomb preparation the total draft can be from 9.5 to 11, depending upon the fibre and lap weight

• Fibre parallelisaion in a lap should be reasonably good, to avoid long fibres in the noil. With the modern cards, the fibre parallelisation is improved because of the stationary flats.

• The self cleaning effect of the lap sheet arises from the retaining power of the fibres relative to the impurities. This depends on the lap weight. If lap weight is more, the unicomb efficiceny may not be good. But the nipper grip will be good for heavier lap weight. Therefore an optimum lap weight should be decided, It depends on

Fibre micronaire(the number of fibres present to the nipper)

Nipper type

• For E7/4 comber, lap weight of 52 to 60 gms per meter can be selected to produce a fairly good quality yarn. In case of E-62 comber(latest from RIETER), it can range from 65 to 75 grams per meter to produce a fairly good yarn.

• Lesser the number of piecings in comber , better the quality. Every piecing in comber is a defect. Therefore, it is better to increase the lap weight as high as possible. For modern lap preparation it is around 20 to 23 kgs/lap and for older lap preparation, it is around 12 to 13 kgs per lap.

Others

• Piecing is a distinct source of fault in comber operation. It is a periodic variation. The amplitude of this fault should be as low as possible. The following affect this fault - detaching roller timing - arranging this fault before entering tthe draft zone, so that this faults cancel each other.

• Detaching roller timing depends upon the index setting and feed length. This setting should be selected in such a that with the minimum length of overlapping comber works without any problem.

• Drafting setting should be done according to the recommendation. Trials can be taken with different setting to optimise the same.(both in lap preparation and in comber)

• Lower the feed length, lower the production. But better the yarn quality.

• But in some application ,lower feed length with forward feed(concurrent feed) has resulted in inferior quality.But in general lower feed will improve the yarn quality. It is always better to take a trial and confirm this. Feed length to some extent depends on the fibre staple length also.

• With backward feed, the unicomb penetrates thro the fibre fringe more often than in the case of forward feed. Therefore the quality of the combing operation is increased in the case of backward feed.

• In combing operation, the hank of the sliver will not affect the comber production. Therefore, if old type of combers are used, where the drafting is not good, lower drafts can be preferred in comber and the draft can be increased in a good drawframe like RSB-951 OR RSB-D-30 if it is used as a finisher.

Drawing Frame | Draw Frame Machine | Drawing Frame

Tasks of Drawframe | What is Draw Frame | Draw Frame Process1) Through doubling the slivers are made even

2) Doubling results in homogenization(blending)

3) Through draft fibres get parallelised

4) Hooks created in the card are straightened

5) Through the suction ,intensive dust removal is achieved

6) Autoleveller maintains absolute sliver fineness

• Quality of the drawframe sliver determines the yarn quality.

• Drawing is the final process of quality improvement in the spinning mill

• Drafting is the process of elongating a strand of fibres, with the intention of orienting the fibres in the direction of the strand and reducing its linear density.In a roller drafting system, the strand is passed throgh a series of sets of rollers, each successive set rotating at a surface velocity greater than that of the previous set.

• During drafting, the fibres must be moved relative to each other as uniformly as possible by overcoming the the cohesive friction. Uniformity implies in this context that all fibres are controllably rearranged with a shift relative to each other equal to the degree of draft.

• In drawframe, the rollers are so rotated that their peripheral speed in the throughflow direction increases from roller pair to roller pair, then the drawing part of the fibres, i.e.the draft, takes place. Draft is defined as the ratio of the delivered length to the feed length or the ratio of the corresponding peripheral speeds.

• Drawing apart of the fibres is effected by fibres being carried along with the roller surfaces. For this to occur, the fibres must move with the peripheral speed of hte rollers. This transfer of the roller speed to the fibres represents one of the problems of drafting operation. The transfer can be effected only by friction, but the fibre strand is fairly thick and only its outer layers have contact with the rollers, and furthermore various, non-constant forces act on the fibres.

• Roller drafting adds irregularities in the strand.Lamb states that,though an irregularity causing mechanism does exist in drafting, drafting also actually reduced the strand irregularities by breaking down the fibre groups. Drafting is accompanied by doubling on the drawframe, this offsets the added irregularity.

• Two passages of drawing with eight ends creeled each time would produce a single sliver consisting of 64 ribbons of fibre in close contact with each other.In the ultimate product, each ribbon may be only a few fibres thick, and thus the materials of the input slivers are dispersed by the drawing process. The term doubling is also used to describe this aspect of drawing

Drafting Arrangement is the heart of the Draw frame. The Drafting Arrangement should be

• Simple

• Stable design with smooth running of rollers

• Able to run at higher speeds and produce high quality product

• Flexible i.e suitable to process different materials , fibre lenths and sliver hanks

• Able to have good fibre control easy to adjust

Roller Drafting causes irregularities in the drafted strand since there is incomplete control of the motion of each individual fibre or fibre group.

The Uniformity of the Drafted Strand in Draw frame or Drawing frame is determined by

• Draft ratio

• Roller settings

• Material characteristics

• Pressure exerted by the top roller

• Hardness of top roller

• Fluting of the bottom rollers

• Distribution of draft between the various drafting stages

Drafting is Affected by the following Rawmaterial Factors in Draw frame• Number of fibres in the cross section

• Fibre fineness

• Degree of parellelisation of the fibres

• Compactness of the fibre strand

Fibre cohesion which depends on surface structure, crimp, lubrication, compression of the strand, fibre length, twist in the fibre, distribution of fibre length

• 3-over-3 roller drafting arrangements with pressure bar is widely used in the modern drawframes Bigger front rollers are stable and operated at lower speeds of revolution, this necessitated pressure bar arrangement for better control of fibres. Some drawframes are with 4-over-3 drafting arrangement, but strictly speaking it behaves like a 3-over-3 drafting system except for the fact that fourth roller helps to guide the sliver directly into the delivery trumpet.

Drafting Wave in Draw frameFloating fibres are subject to two sets of forces acting in opposite directions. The more number of fibres which are moving slowly because of the contact with the back rollers restrain the floating fibres from accelerating. The long fibres in contact with the front rollers tend to accelerate the floating fibres to the higher speed. As the floating fibres move away from the back roller, the restraining force by back roller held fibres reduces, and the front roller influence increases.

At some balance point, a fibre accelerates suddenly from low to high speed. This balance point is compounded by the laws of friction, static friction being higher than dynamic friction.When one floating fibre accelerates, the neighbouring short fibres suddenly feel one more element tending to

accelerate them and one fewer trying to restrain them. Thus there may be an avalanche effect which results in drafting wave.

Process Parameters in Drawing | Drawing Process | Drafting SystemDrawframe is a very critical machine in the spinning process. It's influence on quality, especially on evenness is very big.If drawframe is not set properly, it will also result in drop in yarn strength and yarn elongation at break.The faults in the sliver that come out of drawframe can not be corrected . It will pass into the yarn.

Drafting SystemThe Factors that affect the Yarn Quality are

• The total draft

• No of draw frame passages

• Break draft

• No of doublings

• Grams/meter of sliver fed to the drawframe

• Fibre length

• Fibre fineness

• Delivery speed

• Type of drafting

• Type of autoleveller

• Autoleveller settings

The Total Draft Depends upon • Material processed

• Short fibre content

• Fibre length

Following are some Facts Derived from Trials • Wider back roller setting will result in lower yarn strength

• Wider back roller setting will affect yarn evenness

• Wider back roller setting will increase imperfections

• Higher back top roller loading will reduce yarn strength

• Higher back top roller loading will reduce end breakage rate

• Wider front roller setting will improve yarn strength

• Higher draft in drawframe will reduce sliver uniformity, but will imrprove fibre parallelisation. Somtimes the improvement in fibre parallelisation will overcome the detrimental effects of sliver irregularity.

• Most of the improvement in fiber parallelization and reduction in hooks takes place at first drawframe passage than at second passage

• Better fibre parallelisation generally results in more uniform yarns and a lower end breakage rate in spinning.

• Higher the weight of sliver fed to drawframe, lower the yarn strength, yarn evenness, and it leads to higher imperfections in the yarn and more end breakages in ring spinning

• Irregularities arise owing to the instability of the acceleration point over time. The aprons and rollers are used in the drafting zone to keep the fibre at the back roller velocity until the leading end is firmly gripped by the front roller, but individual fibre control is not achieved.

• Drafting wave is caused primarily not by mechanical defects as such but by the uncontrolled fibre movement of a periodic type resulting from the defects. As the fibre-accelerating point moves towards the front rollers, the draft increases( and vice versa), so that a periodic variation in linear density inevitably results.

• With variable fibre-length distribution(with more short fibre content), the drafting irregularity will be high.

• More the number of doublings , lower the irregularity caused due to random variations. Doublings does not normally eliminate periodic faults.But it reduces the effects of random pulses. Doubling does not have any effect on Index of Irregularity also, since both the irregularities are reduced by square root of the number of doublings.

• Fibre hooks influences the effective fibre length or fibre extent. This will affect the drafting performance. For carded material normally a draft 7.5 in both breaker and finisher drawframe is recommended. Seven of a draft can be tried in breaker, since it is a carded material.

• For combed material, if single passage is used, it is better to employ draft of 7.5 to 8

• If combers with four doublings are used, it is better to use two drawframe passages after combing. This will reduce long thick places in the yarn.

• In case of two drawframe passage, first drawframe passage will reduce the periodic variation due to piecing. Therefore the life of servomotor and servo amplifier will be more , if two drawframe passage is used. Quality of sliver will also be good, because of less and stable feed variation.

• For synthetic fibres (44 mm to 51 mm), 8 of a total draft can be employed both in breaker and finisher passage.

• The number of doublings depends upon the feeding hank and the total draft employed. Most of the modern drawframes are capable of drafting the material without any problem, even if the sliver fed is around 36 to 40 grams per meter

• Especially for synthetic fibres with very high drafting resistance, it is better to feed less than 38 grams per meter to the drawframe.

• Break draft setting for 3/3, or 4/3, drafting system is as follows

For cotton- longest fibre +(8 to 12 mm)

For synthetic fibre- fibre length + (20 to 30% of fibre length)

• Break draft for cotton processing is normally 1.16 to 1.26. For synthetics it is around 1.42 to 1.6

• To meet the present quality requirements , finisher drawframe should be an autoleveller drawframe

• Since the drawframe delivery speed is very high the top roller shore hardness should be around 80 degrees.

• It is advisable to buff the rubber cots once in 30 days(minimum) to maintain consistent yarn quality.

• Coiler size should be selected depending upon the material processed. For synthetic fibres, bigger coiler tubes are used. This will help to avoid coiler choking and kinks in the slivers due to coiling in the can.

• Speed of the coiler will also affect the coiling. Speed of the coiler should be selected properly. In drawframes like RSB D-30(RIETER) , any coiler speed can be selected through the variator type pully. Since, the option is open, there is also more probability for making mistakes. One should take enough care to set the coiler speed properly.

• Whenever coiler speed is adjusted, the diameter of the coil is also changed. Hence it is necessary to check the gap between the sliver and can. If it is more than 5 mm, then turn table position (can driving unit) should be altered so that the gap between coil outer and can inner is around 5 mm.

• Pressure bar depth plays a major role in case of carded mixing and OE mixings. If it is open, U% will be affected very badly.It should always be combined with front roller setting. If the pressure bar depth is high,Creel height should be fixed as low as possible (esepcially for combed material).

• Top roller condition should be checked properly. While processing 100% polyester fibres, fibre scum should be removed by a wet cloth from the top roller atleast once in a shift.

• Sliver funnel size should be selected properly. Very wide funnel will affect the U%. But very small funnel will end up in more sliver breaks at the front.

• If the department humidity variation is very big, then corresponding correction to be made for checking the wrapping of sliver ( sliver weight). Otherwise, there will be unwanted changes in the drawframe which will affect the count C.V.% of yarn.

• Most of the Autoleveller drawframes are working on the principle of OPEN LOOP control system. Sliver monitor should be set properly. Whenever there is a problem in sliver weight, this will stop the machine. Sometimes sliver monitor may malfunction. If it is found malfunctioning , it should be calibrated immediately.

AutoLevelling:

• Most of the modern autolevllers are open loop autolevellers. This system is effective on short, medium and to some extent long tem variations.

• Mechanical draft should be selected properly in autoleveller drawframes. To decide about the

mechanical draft, drawframe should be run with autoleveller switched off.If the sliver weight is correct, then the mechanical draft selected is correct. Otherwise, the gears should be changed so that the sliver is weight is as per the requirement without autolevller.

• Intensity of levelling and timing of correction are two important parameters in autolevellers.

• Intensity of levelling indicates the amount of correction. i.e If 12% variation is fed to the drawframe the draft should vary 12% , so that the sliver weight is constant

• Timing of correction indicates that if a thick place is sensed at scanning roller, the correction should take place exactly when this thick place reaches the correction point(levelling point)

• Higher the feed variation, higher the correction length. e.g. if feed variation is 1 %, and if the correction length is 8 mm, if feed variation is 5% the correction length will be between 10 to 40 mm depending upon the speed and type of the autoleveller.

• Higher the speed, higher the correction length

• Whenever the back roller setting, guide rails setting, delivery speed,break draft etc are changed, the timing of correction should also be changed.

• U% of sliver will be high, if timing of correction is set wrongly

• If intensity of levelling selected is wrong , then 1 meter C.V % of sliver will be high.

• Most of the modern autolevellers can correct 25% feed variation. It is a general practice to feed 12% varition both in plus and minus side to check A%. This is called as Sliver test. The A% should not be more than 0.75%. A% is calculated as follows

If no of sliver fed to drawframe is N, Check the output sliver weight with "N", "N+1", "N-1" slivers. then

A% = ((gms/mt(N-1) - gms/mt(N))/ gms/mt(N) ) x 100

A% = ((gms/mt(N+1) - gms/mt(N))/ gms/mt(N)) x 100

Roving | Textile Roving | Roving Frame1) Attenuation- drafting the sliver into roving

2) Twisting the drafted strand

3) Winding the twisted roving on a bobbin

• Fibre to fibre cohesion is less for combed slivers. Rollers in the creel can easily create false drafts. Care must be taken to ensure that the slivers are passed to the drafting arrangement without disturbance. Therefore, a perfect drive to the creel rollers is very important.

• The drafting arrangement drafts the material with a draft between 5 and 15.The delivered strand is too thin to hold itself together at the exit of the front bottom roller

• Bobbin and flyer are driven separately, so that winding of the twisted strand is carried out by running the bobbin at a higher peripheral speed than the flyer.

• The bobbin rail is moving up and down continuously, so that the coils must be wound closely and parallel to one another to ensure that as much as material is wound on the bobbin.

• Since the diameter of the packages increases with each layer, the length of the roving per coil also will increase. Therefore the speed of movement of bobbin rail must be reduced by a small amount after each completed layer

• Length delivered by the front roller is always constant. Owing to the increase in the diameter of the package for every up and down movement, the peripheral speed of package should keep on changing , to maintain the same difference in peripheral speeds between pakcage and flyer.

Types of Drafting

1) 3/3 Drafting System

2) 4/4 Drafting SystemIn general 3/3 drafting system is used, but for higher draft applications 4/4 drafting system is used.

• The draft often has limits not only at the upper limit (15 to 20), but also at lower limit. It is around 5 for cotton and 6 for synthetic fibres. If drafts below these lower limits are attempted, then the fibre masses to be moved are too large, the drafting resistance becomes too high and the drafting operation is difficult to control. It is advisable to keep the break draft(predarft) as low as possible, because lower breakdraft always improves roving evenness.

• In general two condensers are used in the drafting arrangement. The purpose of this condensers is to bring the fibre strands together. It is difficult to control, Spread fibre masses in the drafting zone and they cause unevenness. In addion, a widely spread strand leaving the drafting arrangement leads to high fly levels and to high hairiness in the roving. The size of condensers should be selected according to the volume of the fibre sliver.

• Flyer inserts twist. Each flyer rotaion creates one turn in the roving. Twist per unit length of roving depends upon the delivery rate.

Turns per metre = (flyer rpm)/(delivery speed (m/min))

Higher levels of roving twist, therefore, always represent production losses in Roving frame and possible draft problems in the ring spinning machine. But very low twist levels will cause false drafts and roving breaks in the roving frame.

• Centrifugal tension is created at the bobbin surface as the layers are being wound and is created by the rotation of the package. Each coil of roving can be considered as a high-speed rotating hool of roving on which centrifugal tension increases with increasing diameter of the package. centrifugal tension in the roving is proportional to the square of the winding surface velocity.In this context, ccentrifugal force acts in such a manner as to lift the top roving strand from the surface of the package so that the radial forces within the strand that hold the fibres together are reduced and the roving can be stressed to the point of rupture. Breaks of this type may occur at the winding-on Point of the presser or in strands that have just been wound on the top surface of the package. This phenomenon is known as "bobbin-bursting". This phenomenon will be prominent if the twist per inch is less or the spindle speed is extremely high when the bobbin is big.

• Apart from inserting twist, the flyer has to lead the very sensitive strand from the flyer top to the package without introducing false drafts. Latest flyers have a very smooth guide tube set into one flyer leg and the other flyer leg serves to balance the flyer. The strand is completely protected against air flows and the roving is no longer pressed with considerable force against the metal of the leg, as it is in the previous designs. Frictional resistance is considerably reduced, so that the strand can be pulled through with much less force.

• False twisters are used on the flyers to add false twist when the roving is being twisted between the front roller and the flyer.Because of this additional twist, the roving is strongly twisted and this reduces the breakage rate. Spinning triangle is also reduced which will reduce the fibre fly and lap formation on the front bottom roller.

• Because of the false twister, the roving becomes compact which helps to increase the length wound on the bobbin. This compactness helps to increase the flyer speed also.

• Roving strength is a major factor in determining winding limitations. It must be high enough for the fibres to hold together in a cohesive strand and low enough for satisfactory drafting at the spinning machine.

The Factors Affecting Roving Strength are as follows:1) The length, fineness, and parallelisation of fibres

2) The amount of twist and compactness of the roving

3) The uniformity of twist and linear density.

Builder Motion:

This device has to perform the following tasks 1) To shift the belt according to the bobbin diameter increase

2) To reverse the bobbin rail direction at top and bottom

3) To shorten the lift after each layer to form tapered ends

• Shifting of the belt is under the control of the ratchet wheel. The ratchet wheel is permitted to rotate by a half tooth. The bobbin diameter increases more or less rapidly depending upon roving hank. The belt must be shifted through corresponding steps. The amount of shifting, which depends upon the thickness of the roving, is modified by replacement of the ratchet wheel or by other gears.If a ratchet wheel with fewer teeth is inserted, then the belt is shifted through larger steps, i.e. it moves more rapidly, and vice versa.

• To form a package, the layer must be laid next to its neighbours. For that the lay-on point must continually be moved. The shift of the winding point is effected by moving the bobbin rail. This raising and lowering is done by rails.Since the package diamter is steadily increasing, the lift speed must be reduced by a small amount after each completed layer.

• During winding of a package, the ratchet is rotated at every change-over.Reversal of the bobbin layer occurs little earlier for every reversal.This gives a conitnuous reduction in the lift of the rail . Thus bobbins are built with taper

Process Parameters in Speed Frame | Speed Frame Machine

The following Parameters are very important in Speed frame. They are

• Feed hank

• Delivery hank

• Roving tension

• Break draft

• Drafting system

• Bottom roller setting

• Top roller setting

• Condensers and spacers

• Twist in the roving

• Bobbin content

• Flyer speed

• Creel and creel draft

• Drawframe sliverand can

• Bobbin height

• Breakage rate

• Piecings

Drafting System

• Since modern Ringframes are capable of handling higher drafts in ringframe without quality detrioration It is better to have coarser hanks in the speed frame. This helps to increase the production in speed frame. Investment cost will also be less,because the number of speed frames required will be less and the cost per mchine is also high.

• With 4 over 4 drafting system, the toal draft can be upto 13, whereas in the case of 3 over 3 drafting system , the draft can not be more than 11.

• The Roving thickness and Roving hairiness(yarn hairiness) will be less with 4 over 4 drafting system compared to 3 over 3 drafting system.

• In 4 over 4 drafting system, since the fully drafted material is just condensed in the front zone, if the stikiness in case of cotton or static in case of synthetic is high, then the lapping tendency will be very high on second top roller or second bottom roller. But in case of front roller, since the twist is penetrating upto the nip, lapping on the front bottom or top roller will be less.

• As long as stickiness, honey dew in cotton and static in synthetic fibres is less, 4 over 4 drafting system with front zone as condensing zone, will give better results upto even 51 mm fibre.Of course the humidity conditions should be good.

4 over 4 Drafting System can be Described as follows Bottom roller diameter is 28.5 mm

Top roller diameter is 28 mm

Break draft is between 4th roller and 3rd roller

Main draft is between 3rd roller and 2nd roller

Bottom apron is run by a 3 rd roller

Between front roller and 2nd roller is a condesning zone

Front zone setting 35 mm( even for 51 mm fibre)

Main draft zone setting is 48 mm

Back zone setting depends on break draft, but it is normally 5o mm for cotton and T/c and 55 mm for Synthetic fibres(44 to 51mm)

• 3 over 3 drafting system is good for fibres longer than 51 mm. 30 or 32 mm bottom roller diameters will be used with this system.

• Feed hank depends upon the total draft in speed frame. The drafts mentioned in the above table can be consdiered as a guide line.

• While processing 51 mm synthetic fibres, if the delivery hank is coarser,and the delivery speed is very high, the break draft and the back zone setting to be widened. Break draft and break draft setting does not depend only on T.M and fibre properties, it depends on the total production also. If the total production is very high, with low break draft and closer setting, roving breaks

due to undrafted strand will increase.

• Therefore, for very high production rate , higher break draft and wider break draft setting is required. This will result in very high "H" and "I" classimat faults(long thin faults). Therefore the breakage rate in spinning will increase

• Break draft setting and break draft should be nominal. Abnormal break drafts and wider break draft settings indicate that there is a major problem in the process.

• Some times draw frame coiling is a very big problem with synthetic fibres . If kinks are formed in the sliver, the kink has to be removed before entering the draft zone

Kinks in the Drawframe Sliver depends upon 1) Drawframe delivery speed

2) Delivery can diameter

3) Coiler type

• Higher the delivery speed, more the chances for kinks to be formed in the sliver. Lower the can diameter more the kinks. If a coiler which is meant for cotton is used, the kinks in the sliver will increase in case of synthetic fibres.

• While processing synthetic fibres if kinks are more, it would be better if the creel is stopped. Sometimes it would be recommeded to use a rod between top arm and the first creel roll, so that the sliver takes a 90 degree bend before entering the top arm. This will help to remove the the kinks in the sliver. Otherwise, slubs in the roving will be more and the breakage rate in speed frame due to undrafted strand in the drafting zone will be more.

Roving Tension

• The roving tension depends on the delivery rate and the difference between peripheral speeds of flyer and the bobbin.

• If the delivery length and the peripheral speed difference are same, then the tension is ideal.If delivered length is more than the difference in peripheral speed , then the roving tension will be loose. If the delivered length by the front bottom roller is less than the difference in pheripheral speeds of flyer and the bobbin, the roving tension will be tight.

Roving Tension can be of three types 1) Roving tension at the starting. It depends upon the Bare bobbin diamter and the Cone drum belt position

2) Roving tension during build-up. It depends upon the Ratchet wheel and lifter wheel. The difference between peripheral speeds of flyer and bobbin should be same and it should be slightly more than the length delivered by the front roller.

3) Roving tension during up and down movement of the bobbin rail should be same. It depends upon

the half tooth movement of the ratchet. If it is not exactly half tooth, then the tension will be different during up and down movement of the bobbin rail

• With modern machines, cone drum is removed. Bobbin speed, bobbin rail speed and flyer speed is determined by the computer depending upon the tension settings.In some machines, it can be programmed and the tension sensor helps to control a bit.In some makes, the tension setting totally depends upon the sensing by sensors. The sensing accuracy depends upon the twist cap type, twist cape fixing, oil on top of twist cap etc. If only one roving tension is different due to various other reasons, then the entire machine tension will be altered. This is very dangerous. Enough care should be taken to avoid this problem.

• If lifter wheel is changed, then tension during build up will also change, the ratchet has to be selected accordingly. For a particular roving hank, ratchet wheel depends on Lifter wheel also.

• If the tension is low but unfiorm through out the bobbin, then the bobbin will be soft. Bobbin content will also be less. Chances of roving damages will be high.

• If the roving tension is more, then the stretch on the roving will be more, thin places will be more. But it is better to increase the TPI little bit and increase the roving tension so that the bobbin content is more, roving damages are less, and creel stretch in the ring frame will also be less, because of higher TPI in the roving.

Others

• It is better to adopt group creeling in speed frame. Because every piecing of sliver will result in a thin and thick place. Therefore it is preferable to change 30 upto 60 cans together and remove the sliver piecing from the roving.

• Care should be taken so that no sliver piecing and roving piecing enters the ringframe and results in yarn. This yarn always results in thin and thick places from .6 to 2 meters length. This will not be cut by the yarn clearers if the difference in size is less.

• Roving Breaks in speed frame should not be more 1 to 2 per 100 spindle hours.If it is more than that, the reasons should be analysed and corrective action should be taken immediately.

• Spacers should be as small as possible, to improve yarn quality. If slubs and roving breaks due to undrafted is more, it would be better to use a bigger spacer(distance clip) instead of increasing the break draft and break draft zone setting to an abnormal level.

• It is better to use good quality apron and rubber cots , since the quantity produced by one apron and top roller is very high compared to ringframe. If the apron breaks and top roller damages are under control, It is always better to use the best apron and rubber cots available in the market. One should not think about cost saving in this machine. Cost saving for apron and cots can be considered for ringframes.

• Buffing should be done once in 3 months and the top roller shore hardness is around 80 to 85 degrees. After buffing, it is better to treat with acid or some special liquids which are being supplied to reduce lapping

• Bottom and top clearers should rotate and should touch the top and bottom roller properly.

• While processing cotton combed material, flyer speed is very critical. When the bobbin diamter is big, because of the centrifugal tension, surfact cuts will increase. i.e. roving breaks may occur at presser or in strand that have just been wound on the top surface of the package. To avoid this

problem, it is better to use inverter drive system, to reduce the flyer speed, when the bobbin diameter is big. Otherwise the overall speed should be less for the entire doff, this will reduce the production of speedframe. Sometimes, higher Twist will also reduce the surface cuts.

Ring Spinning / Ring Spinning Frame / Ring FrameWhat is Ring SpinningThe Ring Spinning will continue to be the most widely used form of spinning machine in the near future, because it exhibits significant advantages in comparison with the new spinning processes.

Following are the Advantages of Ring Spinning Frame

• It is universaly applicable, i.e.any material can be spun to any required count

• It delivers a material with optimum charactersticss, especially with regard to structure and strength.

• It is simple and easy to master the know-how is well established and accessible for everyone

Ring Spinning Process / Ring Spinning Technology

• To draft the roving until the reqired fineness is achieved

• To impart strength to the fiber, by inserting twist

• To wind up the twisted strand (yarn) in a form suitable for storage, transportaion and further processing.

Process Parameters in Ring FrameRing frame Technology is a simple and old technology, but the production and quality requirements at the present scenario puts in a lot of pressure on the Technologist to select the optimum process parameters and machine parameters, so that a good quality yarn can be produced at a lower manufacturing cost.

Following are the Points to be Considered in a Ring Frame

• Draft distribution and settings

• Ring and travellers

• spindle speed

• Twist

• Lift of the machine

• Creel type

• Feed material

• Length of the machine

• Type of drive

Raw material chracteristic plays a major role in selecting the above said process parameters in Ring Frame

Technical information and guidelines are given below based on the learnings from personal experience and discussions with Technologists. This could be used as a guideline and can be implemented based on the trials taken at site. Some of this information can be disproved in some other applications, because many of the parameters are affected by so many variables. A same machine or rawmaterial cannot perform in the same way in two different factories. This is because of the fact that no two factories can be identical.

DraftingThe break draft should depend upon the following,

• Fibre type

• Fibre length

• Roving T.M

• Main draft

MAIN DRAFT ZONE Mostly for cotton fibres, short cradles are used in the top arm. Front zone setting is around 42.5 mm to 44 mm depending upon the type of drafting system. The distance between the front top roller and top apron should be around 0.5to 0.7mm when correct size top roller is used. This is normally taken care of by the machinery manufcturer. If a technician changes this setting, this will surely result in more imperfections, especially with karded count the impact will be more. Therefore when processing cotton fibres, care should be taken that the front zone setting should be according to the machinery

RING AND TRAVELLER

• Ring diameter, flange width and ring profile depends upon the fibre, twist per inch, lift of the machine,maximum spindle speed, winding capacity etc.

• Operating speed of the traveller has a maximum limit, because the heat generated between ring and traveller should be dissipated by the low mass of the traveller with in a short time available.

• If the cotton combed yarn is for knitting, traveller speed will not be a limiting factor. Since yarn TPI is less, the yarn strand is not strong enough. Therefore the limiting factor will be yarn tension. Following points to be considered

1) For 12s to 24s , 42mm ring with 180 mm lift can be used

2) For 24s to 36s, 40 mm ring with 180 lift can be used

3) For 36s to 60s , 38 mm ring with 170 mm lift can be used

4) For 70s to 120s, 36 mmring with 160 mm lift can be used.

5) If winding is a problem, it is better to go for reduced production with bigger ring dia.

6) Anti-wedge ring profile is better, because of better heat dissipation

7) Elliptical traveller should be used, to avoid start-up breaks in hosiery counts

8) Special type of travller clearer can be used to avoid accumulation of fibre on the traveller as traveller with waste does not perform well during start-up.

• For polyester/cotton blends and cotton weaving counts yarn strength is not a problem. The limiting factor will be a traveller speed. For a ring diameter of 40 mm, spindle speed upto 19500 should not be a problem. Rings like Titan(from Braecker), NCN(bergosesia) etc, will be able to meet the requirements.

• For spindle speeds more than 20000 rpm, ORBIT rings or SU-RINGS should be used. As the area of contact is more with this rings, with higher speeds and pressure, the heat produced can be dissipated without any problem. Normal ring and traveller profile will not be able to run at speeds higher than 20000 to produce a good quality yarn.

• ORBIT rings will be of great help, to work 100% polyester at higher spindle speeds. Because, of the tension, the heat produced between ring and traveller is extremely high. But one should understand, that ,the yarn strength of polyester is very high. Here the limiting factor is only the heat dissipation. Therefore ORBIT RINGS with high area of contact will be able to run well at higher spindle speeds when processing 100% polyester.

• While running 100% cotton, the fibre dust in cotton, acts like a lubricant. All the cottons do not form same amount of lubricating film. If there is no fibre lubrication, traveller wears out very fast. Because of this worn out or burn out travellers, microwelding occurs on the ring surface,< which results in damaged ring surface, hence imperfections and hairiness increases in the yarn.

• Lubrication is good with west african cottons. It may not be true with all the cottons from West africa. In general there is a feeling, cottons from Russia, or from very dry places, lubrication is very bad. If the fibre lubrication is very bad, it is better to use lighter travellers and change the travellers as early as possible.

• Traveller life depends upon the type of raw material, humidity conditions, ringframe speeds, the yarn count, etc. If the climate is dry , fibre lubrication will be less while processing cotton.

• Traveller life is very less when Viscose rayon is processed especially semi dull fibre, because of low lubrication. Traveller life is better for optical bright fibres.

• Traveller life is better for Poly/cotton blends, because of better lubricatiion between ring and traveller.

• Because of the centrifugal force excerted by the traveller on the yarn, the particles from the fibre fall on the ring where the traveller is in contact. These particles act like a lubricating film between ring and traveller.

Rubber Cots and Apron

• For processing combed cotton, soft cots (60 to 65 degree shorehardness) will result in lower U%, thin and thick places

• There are different types of cores (inner fixing part of a rubber cot)available from different manaufacturers. Aluminimum core,PVC core,etc. It is always better to use softer cots with

aluminium core.

• When softer cots are used, buffing frequency should be reduced to 45 to 90 days depending upon the quality of the rubber cots, if the mill is aiming at very high consistent quality in cotton counts.

• If the lapping tendency is very high when processing synthetic fibres for non critical end uses, It is better to use 90 degree shore harness cots, to avoid cots damages. This will improve the working and the yarn quality compared to working with 83 degree shore hardness.

• If rubber cots damages are more due to lapping, frequent buffings as high as once in 30 days will be of great help to improve the working and quality. Of course,one should try to work the ringframe without lapping.

The basic reasons for lapping in the case of processing synthetic fibre is• End breaks

• Pneumafil suction

• Rubber cots type

• Fibre fineness

• Oil content(electrostatic charges)

• Department temprature and humidity

Almost all the lappings orginate after an end break. If a mill has an abnormally high lapping problem the first thing to do is to control the end breaks,

• After doffing

• During speed change

• During the maximum speed by optimising the process paramters.

• It is obvious that fine fibres will have a stronger tendency to follow the profile of the roller. Therefore lapping tendency will be more.

• If the fibre is fine, the number of fibres in the cross section will be more, therefore lapping frequency will be more.

• If the pressure applied on the roller is more, then lapping tendancy will be more. Hence fine and longer fibres will have more tendency for lapping because of high top roller pressure required to overcome the drafting resistance.

• If the pneumafil suction is less, the lapping tendency will be more both on top and bottom roller. But the pneumafil suction depends on the fan diamater, fan type, fan speed, duct design, length of the machine, profile of the suction tube etc. If any one of the above can be modified and the suction can be improved, it is better to do that to reduce the lapping.

• The closer the setting between the suction nozzle and the bottom roller, the higher the suction efficiency and lower the lapping propensity

• Higher roving twist will reduce the lapping tendency to some extent. Therefore it is better to have a slightly higher roving twist, provided there is no problem in ringframe drafting, when the

lapping tendency is more

• With Softer rubber cots lapping tendency will be more due to more surface contact.

• The most minute pores, pinholes in the rubber cots or impurities in the cots can cause lapping. Therefore the quality of buffing and the cots treatment after buffing is very important. Acid treatment is good for synthetic fibres and Berkolising is good for cotton.

• Electrostatic charges are troublesome especially where relatively large amount of fibre are being processed in a loose state e.g drawframe, card etc.Lapping tendency on the top roll increases with increasing relative humidity. The frequently held opinion is that processing performace remains stable at a steady absolute relative humidity, i.e. at a constant moisture content per Kg of dry air.

TWIST:The strength of a thread twisted from staple fibres increases with increasing twist, upto certain level. Once it reaches the maximum strength, further increase in twist results in reduction in yarn strength

• Coarser and shorter fibres require more Twist per unit length than finer and longer fibres

• Twist multiplier is a unit which helps to decide the twist per unit length for different counts from the same raw material.This is nothing but the angle of inclination of the helical disposition of the fibre in the yarn. This is normally expressed as TWIST PER INCH = TWIST MULTIPLIER * SQRT(Ne)

• If the two yarns are to have the same strength, then the inclination angles must be the same

• For 40s combed knitting application, if the average micronaire of cotton is 3.8 and the 2.5% span length is around 29 mm, Twist multiplier of 3.4 to 3.5 is enough . If the average micronaire is around 4.3, it should be around 3.6 to have better working in Ring frame.

• cotton combed knitting T.M. = 3.4 to 3.6

• cotton combed weaving T.M. = 3.7 to 3.8

• cotton carded knitting T.M. = 3.8 to 4.0

• cotton carded weaving T.M. = 3.9 to 4.2

The above details are for cottons of 2.5% span length of 27 to 30 mm and the average Micronaire of 3.7 to 4.4. For finer and longer staple, the T.M. will be lower than tha above.

• In general for processing poly/viscose , the T.M. is as follows

• 51 mm, 1.4 denier fibre : T.M. = 2.7 to 2.9 for knitting application

• 51 mm, 1.4 denier fibre : T.M. = 2.9 to 3.1 for weaving application

• 44 mm, 1.2 denier fibre : T.M. = 2.9 to 3.0 for knitting application

• 44 mm, 1.4 denier fibre : T.M. = 3.0 to 3.1 for knitting application

• 38 mm, 1.2 denier fibre : T.M. = 3.1 to 3.3 for knitting application

OthersThe following ROVING parameters will affect the ring frame process parameters

1) Roving T.M.

2) Bobbin weight

3) Bobbin height

• Higher the roving T.M., wider the back bottom roller setting or higher the break draft in ring frame

• For combed material the creel height should be as low as possible in ringframe

• Very long creel heights in ringframe, lower roving T.M. and heavier roving package will result in many long thin places in the yarn.(especially in combed hosiery counts)

• In general 16 x 6 " bobbins are used. This helps to increase the spare rovings per machine with higher creel running time. Therefore one should aim at increasing the bobbin weight as well as increasing the number of spare rovings in the ring frame.

• Normally 6 row creels are used in modern ring frames. Six row creels will accomodate more spare rovings compared to 5 row creels.(around 150 rovings for 1000 spindle machine.) Creel height should be as low as possible for cotton combed counts.Spare rovings will improve the operators efficiency.

• Shorter machines are always better compared to longer machines. But the cost per spindle will go up. For cotton , polyester/cotton blends, poly/viscose(upto 44mm length), number of spindles upto 1200, should not be a problem. But maintenance is more critical compared to shorter machines.

• For synthetic fibres with very high drafting resistance, it is better to use shorter machines, because the load on break draft gears and on second bottom rollers will be extremely high. If long machines are used and the maintenance is not good for such application, the bearing damages, gear damages, bottom roller damages etc. will increase. This will result in coarse counts, higher count C.V., long thin and thick places.

• Four spindle drive is always better compared to Tangential belt drive. Because small variation in machining accuracy of bolster , spindle beam etc will affect the spindle speeds, thereby the twist per inch. Waste accumulation between contact rollers, bent contact rollers, damaged contact rollers, oil spilling from any one spindle etc. will affect the spindle speeds and thereby TPI. The spindle speed variation between spindles in a 5 year old ringframe will be verh high incase of tangential belt ? drive compared to 4 spindle drive.

• Noise level and energy consumption will be low in 4 spindle drive compared to Tangential belt drive

• Compared to Contact rollers, Jockey pully damages are nil. I have worked with 20 year old ring frames with Jocky pulleys,but the variations in spindle speed between spindles is very less compared to a 5 year old ringframe with Tangential belt drive. I have made this comment based on my personal experience.

• When processing coarse counts at higher speeds, the air current below the machine is a big problem with 4 spindle drive . This is due to the more running parts like tinrollers and jockey pullys. This will lead to more fluff in the yarn, if humidification system is not good enough to suck the floating ,fluff.

• If spindle speeds is high for cotton counts, every end breaks will result in more fluff in the

department due to the free end of the yarn getting cut by the traveller when the distance between traveller and the bobbin with the yarn is less. Higher the delay in attending the end break , higher the fly liberation.If the number of openings of return air system for a ringframe is less and the exhaust air volume is not sufficient enough, then fly liberation from an end break will increase the endbreaks and thereby will lead to multiple breaks. End break due to a fly entering the traveller will get struck with the traveller and will result in heavier traveller weight and that particular spindle will continue to work bad.

• Multiple breaks are very dangerous, as it will result in big variation in yarn hairiness and the ringframe working will be very badly affected due to heavier travellers because of the fluff in the traveller.

• Dry atmosphere in ringframe department will result in more yarn hairiness, more fly liberation and more end breaks

• It is a good practice to change spindle tapes once in 24 months.Worn out spindle tapes will result in tpi variations which is determinetal to yarn quality

Com-4 Concept | Compact Cotton Yarn | Elite YarnsWith the Comfor Spin technology a new yarn with perfect yarn structure - the COM4 yarn - has been established in the market. With the help of a microscope the structure of the yarns can easily be compared. The conventional ring yarn shows to be far less perfect than commonly assumed. The long, protruding fibres cause a number of problems in downstream processing. COM4 yarn shows a very compact structure with highly parallel fibres and much less disturbing hairiness.

The air current created by the vacuum generated in the perforated drum condenses the fibres after the main draft. The fibres are fully controlled all the way from the nipping line after the drafting zone to the spinning triangle.

An additional nip roller prevents the twist from being propagated into the condensing zone. The compacting efficiency in the condensing zone is enhanced by a specially designed and patented air guide element.

Optimal interaction of the compacting ele-ments ensures complete condensation of all fibres. This results in the typical COM4 ® yarn characteristics. Optimal interaction of the compacting ele-ments ensures complete condensation of all fibres. This results in the typical COM4 ® yarn characteristics.

The ComforSpin ® technology allows aero-dynamic parallelization and condensation of the fibres after the main draft. The spinning triangle is thus reduced to a minimum. The heart of ComforSpin machine is the compacting zone, consisting of the following elements:

• Perforated drum

• Suction insert

• Air guide element

The directly driven perforated drum is hard to wear and resistant to fibre clinging. Inside each drum there is an exchangeable stationary suction insert with a specially shaped slot. It is connected to the machine's suction system.

Elite YarnsAfter the fibres leave the drafting system they are condensed by an air-permeable lattice apron,which slides over an inclined suction slot.The fibres follow the outer edge of this suction slot and at the same time they perform a lateral rolling motion.

Above the front bottom roller of the drafting system,the fibre band influenced by high draft is spreading.In the area of the suction slot,which is covered by the lattice apron,the fibre band is condensed.Commencing from the semi-dotted clamping line of the EliTe Q Top Roller,twist is being inserted.There is no spinning triangle.

The twist imparted by the spindle cannot flow up to the clamping line.The outer fibres spread out and are thus more highly tensioned than those on the inside. The right side of the picture does not show a spinning triangle.The yarn twist flows right up to the clamping line.The yarn is round and smooth.Since the spinning triangle is very very small, the end breaks will be very less and therefore the fly liberation will also be less.

Condensing of the fiber bundle,which follows the drafting process,can already be seen as a significant development of the ring spinning technology.Condensed ring yarn is more than a speciality.In view of its manifold advantages.

It is of technological importance that the suction level relevant for the condensing operation is exactly the same for all spinning positions. To fulfil this criteria,individual motors combined with suction units for 6 spinning positions,have been arranged accordingly.This provides short air-flow distances with identical negative pressures at all spinning points .

During yarn formation all fibres are perfectly condensed and gathered parallel to each other in the compacting zone. Consequently all fibres are twisted in and contributing to the superior fibre utilisation rate compared to conventional ring yarn. The result is exceptionally low hairiness combined with higher yarn tenacity and elongation. These are the unique characteristics of these yarns

Advantages of Compact Cotton Yarn

• Higher fibre utilisation

• Higher tenacity with same twist factor

• Same tenacity with reduced twist factor for higher production

• Lowest hairiness (highest reduction in hairs longer than 3 mm)

• Fewer weak points

• Better imperfections (IPI) values

• Higher abrasion resistance

• Greater brilliance of colour

• Intensive dye penetration

• No singeing before printing

• Due to better utilization of fibre substance it is possible to reduce yarn twist of these

Yarns,particularly of knitting yarns,by up to 20%,maintaining the yarn strength of conventional ring yarns.This increases yarn production. The ends-down rate in spinning these Yarns is reduced by 30 to 60%,which improves machine efficiency.

• Applying the same winding speed as with conventional ring yarns,there are less raised points in these Yarns and the increase in yarn imperfections is reduced because they have a better resistance to shifting. Higher winding speeds are therefore possible with compact yarns Yarns .

• In accordance with up to 20%twist reduction in spinning compact yarns ,the twisting turns can be reduced for certain types of yarn.As a result,production of twisting frame is increased and twisting costs are reduced.

• Owing to the lower hairiness and higher tenacity of compact Yarns,the ends-down rate in beaming is reduced by up to 30%.Higher beamer efficiency,higher produc tion and fewer personnel for repair of ends-down in beaming are the consequence

• Compact Warp yarns help to save up to 50%of sizing agent,while the running behaviour of weaving machi-nes is the same or even better. Cost can be saved in sizing and desizing processes.

• Owing to the better work capacity of compact Yarns ,ends down can decreased by up to 50% in the warp and by up to 30%in the weft. Efficiency is consequently increased by 2 to 3%, production is increased and weaving costs are reduced. In practice,the average ends-down rate is reduced by 33% per 100,000 weft insertions of compact Yarns on rapier weaving machines and by 45% on air-jet weaving machines. Instead of a weft insertion of 500 -600 m/min with conventional ring yarn,700-800 m/min is possible with compact Yarns on air-jet weaving machines.

• Due to reduced Yarn hairiness,singeing can sometimes be dispensed with,or it can be carried out at a higher cloth advance speed.As a result,production costs are considerably reduced.

• Fibres upto 7% can be saved because singing can be avoided

• Dyeing and Printing Improved structure of compact Yarns and their reduced twist favours the absorption of colour pigments and chemical finishing agents.Saving of dyestuff is possible.

• Owing to the improved yarn strength, compact Yarns are well suited for non-iron treatment of woven fabrics. In the course of such treatment,the strength of fabrics made from conventional ring yarns can decrease by up to 25%,with frequent problems in the manufacture of clothes. compcat Yarns make up for this loss in strength.

• Knitting:Compact Yarns with their increased yarn strength and reduced formation of fluff permit to achieve higher machine efficiency and therefore production on knitting machines at a reduced ends-down rate,less interruptions and less fabric faults. Production costs therefore decrease. The enormously low hairiness of compact Yarns often permits to dispense with usual waxing. Considerable cost saving is achieved because of this.

• In knitting fibre abrasion reduced by 40% due to low hairiness. Fewer defects/ yarn breaks and better quality. Less contamination on all machines by foreign fibres . Less wear of needles, guide elements and sinkers due to less dust in the compact Yarn . Low hairiness has positive impact on loop structure . L Low pilling values get more and more important . In many cases single compact Yarns substitute conventional ply yarns. Waxing can be reduced or completely dispensed with .

• Compact Yarns are much more suitable for warp knitting than conventional ring yarns,because of their higher work capacity and lower hairiness. They are predestined to bear the high load due to numerous deflecting points with high friction in the warp knitting machine.

• Due to better embedding of fibres (including short ones)in compact Yarn,approx.6%fewer combing noils are possible

• Cheaper carded qualities instead of combed qualities can be spun with the Compact Spinning system.

• In many cases single EliTe ® Yarns can substitute conventional ply yarns

• New qualities can be developed, opening up a new creative scope for products

Spinning Parameters | Spinning Quality

The Following Parameters are very important in Spinning

Drafting Drafting arrangement is the most important part of the machine. It influences mainly evenness and strength. The following points are therefore very important 1) Drafting type

2) Design of drafting system

3) Drafting settings

4) Selection of drafting elements like cots, aprong, traveller etc

5) Choice of appropriate draft

6) Service and maintenance

• Drafting arrangement influence the economics of the machine - directly by affecting the end break rate and indirectly by the maximum draft possible.

• If higher drafts can be used with a drafting arrangement, then coarser roving can be used as a feeding material. This results in higher production rate at the roving frame and thus reducing the number roving machines required, space, personnel and so on.

• In fact increase in draft affects the yarn quality beyond certain limit. Within the limit some studies show that increase in draft improves yarn quality. The following draft limits have been established for practical operation:

Carded cotton- upto 35

Carded blends - upto 40

Combed cotton and blends(medium counts) - upto 40

Combed cotton and blends(fine counts) - upto 45

Synthetic fibres - upto 50

• The break draft must be adapted to the total draft in each case since the main draft should not exceed 25 to 30. It should be noted that higher the break draft, more critical is the break draft setting

• The front top roller is set slightly forward by a distance of 2 to 4mm relative to the front bottom roller, while the middle top roller is arranged a short distance of 2mm behind the middle bottom roller

• Overhang of the front top roller gives smooth running of the top rollers and shortens the spinning triangle. This has a correspondigly favourable influence on the end break rate

• Rubber cots with hardness less than 60 degrees shore are normally unsuitable because they can not recover from the deformation caused by the pressure on the top roller while running.

• Soft rubbercots for toprollers have a greater area of contact, enclose the fibre strand more completely and therefore provide better guidance for the fibres.However softer cots wear out significantly faster and tend to form more laps.

• Normally harder rubbercots are used for back top rollers, because the roving which enters the back roller is compact , little twisted and it does not require any additional guidance for better fibre control

• In the front top roller, only few fibres remain in the strand and these exhibit a tendency to slide apart. Additional fibre guidance is therefore necessary.Therefore rubbercots with hardness levels of the order 80 degrees to 85 degrees shore are mostly used at the back roller and 63 degrees and 65 degrees at the front roller.

• If coarse yarns and synthetic yarns are being spun, harder rubbercots are used at the front roller because of increased wear and in the case of synthetic yarns to reduce lapups.

Three kinds of Top Roller Weighting(loading) are presently in use1) Spring loading

2) Pneumatic loading

3) Magnetic weighting

• With pneumatic loading system, the total pressure applied to all top rolers is obtained by simple adjustment of the pressure in the hose using pressure reducing valve. Moreover the rubbercots will not get deformed if the machine is stopped for a longer duration, because the pressure on top rollers can be released to the minimum level.

• The fibre strand in the main drafting field consists of only a few remaining fibres. There is hardly any friction field and fibre guidance provided by the rollers alone is inadequate. Special fibre guiding devices are therefore needed to carry out a satisfactory drafting operation. Double apron drafting arrangements with longer bottom aprons is the most widely used guding system in all the modern ringframes.

• In doube apron drafting system two revolving aprons driven by the middle rollers form a fibre

guiding assembly. In order to be able to guide the fibres, the upper apron must be pressed with controlled force against the lower apron. For this purpose, a controlled spacing (exit opening), precisely adapted to the fibre volume is needed between the two aprons at the delivery. This spacing is set by "spacer" or "distance clips". Long bottom aprons have the advantage in comparison wiht short ones, that they can be easily replaced in the event of damage and there is less danger of choking with fluff.

• Spindles and their drive have a great influence on power consumption and noise level in the machine The running characteristics of a spindle, especially imbalance and eccentricity relative to the ring flange, also affect yarn quality and of course the number of end breakage. Almost all yarn parameters are affected by poorly running spindles. Hence it should be ensured that the centering of the spindles relative to the rings is as accurate as possible. Since the ring and spindle form independent units and are able to shift relative to each other in operation, these two parts must be re-centered from time to time. Previously, this was done by shifting the spindle relative to the ring, but now it is usually carried out by adjusting the ring.

• In comparison with Tangential belt drive, the 4-spindle drive has the advantages of lower noise level and energy consumption, and tapes are easier to replace.

• Lappet guide performs the same sequence of movements as the ringrail, but with a shorter stroke, this movement of the guide ensures that differences in the balloon height caused by changes in the ring rail positions do not become too large. This helps to control the yarn tension variation with in control, so that ends down rate and yarn charactersitics are under control.

• Spindles used today are relatively long. The spacing between the ring and the thread guide is correspondigly long, thus giving a high balloon. This has two negative influence

1) A high balloon results in large bobbin diameter leading to space problems

2) Larger the balloon diameter , higher the air drag on the yarn.This inturn causes increased deformation of the balloon curve out of hte plane intersecting the spindle axis.This deformation can lead to balloon stability, there is increase danger of collapse

Both these disadvantages result in higher yarn tension, thereby higher endbreaks.In order to avoid this, balloon control rings are used. It divides the balloon into two smaller sub-balloons. Inspite of its large overall height, the double-balloon created in this way is thoroughly stable even at relatively low yarn tension.

• Balloon control rings therefore help to run the mahcine with long spindles(longer lift) and at high spindle speed, but with lower yarn tension. Since the yarn rubs against the control ring, it may cause roughening of the yarn.

• Most ends down arise from breaks in the spinning triangle, because very high forces are exerted on a strand consisting of fibres which have not yet been fully bound together in the spinning triangle.

Ring and Traveller CombinationThe following factors should be considered

• Materials of the ring traveller

• Surface charecteristics

• The forms of both elements

• Wear resistance

• Smoothness of running

• Running-in conditions

• Fibre lubrication

For the rings two dimensions are of primariy importance

1) Internal diameter

2) Flange width

• Antiwedge rings exhibit an enlarged flange inner side and is markedly flattened on it upper surface. This type of profile permitted to use travellers with a lower centre of gravity and precisely adapted bow(elliptical travellers), which in turn helped to run the machine with higher spindle speeds. Antiwedge rings and elliptical travellers belong together and can be used in combination.

• Low crown profle has the following advantage. Low crown ring has a flattened surface top and this gives space for the passage of the yarn so that the curvature of the traveller can also be reduced and the centre of gravity is lowered.In comparison with antiwedge ring, the low crown ring has the advantage that the space provided for passage of the yarn is somewhat larger and that all current traveller shapes can be applied, with the exception of the elliptical traveller. The low crown ring is the most widely used ring form now.

• The ring should be tough and hard on its exterior. The running surface must have high and even hardeness in the range 800-850 vikcers. The traveller hardness should be lower (650-700 vickers), so that wear occurs mainly on the traveller, which is cheaper and easier to replace. Surface smoothness should be high, but not too high, because lubricating film can not build up if it too smooth.

A Good Ring in Operation should have the following features: • Best quality raw material

• Good, but not too high, surface smoothness

• An even surface

• Exact roundness

• Good, even surface hardness, higher than that of the traveller

• Should have been run in as per ring manufacturers requirement

• Long operating life

• Correct relationship between ring and bobbin tube diameters

• Perfectly horizontal position

• It should be exactly centered relative to the spindle

• In reality, the traveller moves on a lubricating film which builds up itself and which consists

primarily of cellulose and wax. This material arises from material abraded from the fibres.If fibre particles are caught between the ring and traveller, then at high traveller speeds and with correspondingly high centrifugal forces, the particles are partially ground to a paste of small, colourless, transparent and extremely thin platelets. The platelets are continually being replaced during working. The traveller smoothes these out to form a continuous running surface.The position, form and structure of lubricating film depends on

1) Yarn fineness

2) Yarn structure

3) Fibre raw material

4) Traveller mass

5) Traveller speed

6) Height of traveller bow

Modern ring and traveller combination with good fibre lubrication enable traveller speeds upto 40m/sec

• Traveller imparts twist to the yarn. Traveller and spindle together help to wind the yarn on the bobbin. Length wound up on the bobbin corresponds to the difference in peripheral speeds of the spindle and traveller. The difference in speed should correspond to length delivered at the front rollers. Since traveller does not have a drive on its own but is dragged along behing by the spidle.

• High contact pressure (upto 35 N/square mm)is generated between the ring and the traveller during winding, mainly due to centrifugal force. This pressure leads to generation of heat. Low mass of the traveller does not permit dissipation of the generated heat in the short time available. As a result the operating speed of the traveller is limited.

• When the spindle speed is increased, the friction work between ring and traveller (hence the build up) increases as the 3rd power of the spindle rpm. Consequently if the spindle speed is too high, the traveller sustains thermal damage and fails. This speed restriction is felt particularly when spinning cotton yarns of relatively high strength

• If the traveller speed is raised beyond normal levels , the thermal stress limit of the traveller is exceeded, a drastic change in the wear behaviour of the ring and traveller ensues. Owing to the strongly increased adhesion forces between ring and traveller, welding takes place between the two. These seizures inflict massive damage not only to the traveller but to the ring as well.Due to this unstable behaviour of the ring and traveller system the wear is atleast an order of magnitude higher than during the stable phase. The traveller temperature reaches 400 to 500 degrees celcius and the danger of the traveller annealing and failing is very great.

The Spinning Tension is Proportional • To the friction coefficient between ring and traveller

• To the traveller mass

• To the square of the traveler speed

and inversely proportional

• To the ring diameter

• and the angle between the connecting line from the traveller-spindle axis to the piece of yarn between the traveller and cop.

• The yarn strength is affected only little by the spinning tension. On the other hand the elongation diminishes with increasing tension, for every tensile load of hte fibres lessens the residual elongation in the fibres and hence in the yarn. Increasing tension leads also to poorer Uster regularity and IPI values.

• If the spinning tension is more, the spinning triangle becomes smaller . As the spinning triangle gets smaller, there is less hairiness.

Shape Of The TravellerThe traveller must be shaped to match exactly with the ring in the contact zone, so that a single contact surface, with the maximum surface area is created between ring and traveller. The bow of the traveller should be as flat as possible, in order to keep the centre of gravity low and thereby improve smoothness of running. However the flat bow must still leave adequate space for passage of the yarn. If the yarn clearance opening is too small, rubbing of the yarn on the ring leads to roughening of the yarn, a high level of fibre loss as fly, deterioration of yarn quality and formation of melt spots in spinning of synthetic fibre yarns.

Wire Profile Of The Traveller: Wire profile influences both the behaviour of the traveller and certain yarn characteristics, They are

• Contact surface of the ring

• Smooth running

• Thermal transfer

• Yarn clearance opening

• Roughening effect

• Hairiness

Material Of The TravellerThe traveller should

1) Generate as little heat as possible

2) Quickly distribute the generated heat from the area where it develops over the whole volume of the traveller

3) Transfer this heat rapidly to the ring and the air

4) Be elastic, so that the traveller will not break as it is pushed on to the ring

5) Exhibit high wear resistance

6) Be less hard than the ring, because the traveller must wear out in use in preference to the ring

• In view of the above said requirements, traveller manufacturers have made efforts to improve the running properties by surface treatment. "Braecker" has developed a new process in which certain finishing components diffuse into the traveller surface and are fixed in place there. The resulting layer reduces temperature rise and increases wear resistance.

• Traveller mass determines the magnitude of frictional forces between the traveller and the ring, and these in turn determine the winding and balloon tension. Mass of the traveller depends upon

1) Yarn count

2) Yarn strength

3) Spindle speed

4) Material being spun

• If traveller weight is too low, the bobbin becomes too soft and the cop content will be low. If it is unduly high, yarn tension will go up and will result in end breaks. If a choice is available between two traveller weights, then the heavier is normally selected, since it will give greater cop weight, smoother running of the traveller and better transfer of heat out of traveller.

• When the yarn runs through the traveller, some fibres are liberated. Most of these fibres float away as dust in to the atmosphere, but some remain caught on the traveller and they can accumulate and form a tuft. This will increase the mass of traveller and will result in end break because of higher yarn tension. To avoid this accumulation , traveller clearers are fixed close to the ring, so that the accumulation is prevented. They should be set as close as possible to the traveller, but without affecting its movement. Exact setting is very important.

• Specific shape of the cop is achieved by placing the layers of yarn in a conical arrangement. In the winding of a layer, the ring rail is moved slowly but with increasing speed in the upward direction and quickly but with decreasing speed downwards. This gives a ratio between the length of yarn in the main (up) and cross(down) windings about 2:1.

• The total length of a complete layer (main and cross windings together) should not be greater than 5m (preferably 4 m) to facilitate unwinding. The traverse stroke of the ring rail is ideal when it is about 15 to 18% greater than the ring diameter

End break suction system has a variety of functions : 1.It removes fibres delivered by the drafting arrangement after an end break and thus prevents mulitple end breaks on neighbouring spindles.

2.It enables better environmental control, since a large part of the return air-flow of the aircondition system is led past the drafting system, especially the region of the spinning triangle.

3.In modern installations, approx. 40 to 50 % of the return air-flow passes back into the duct system of the airconditioning plant via the suction tubes of pneumafil suction system.

4.A relatively high vacuum must be generated to ensure suction of waste fibres for cotton - around 800 pascals, for synthetic - around 1200 pascals

5.A significant pressure difference arises between the fan and the last spindle. This pressure difference will be greater , the longer the machine and greater the volume of air to be transported. The air flow rate is normally between 5 and 10 cubic meter/ hour.

6.Remember that the power needed to generate an air-flow of 10 cubic meter/ hour , is about 4.5 times the power needed for an air-flow of 6 cubic meter/ hour, because of the significantly higher vacuum level developed at the fan.

Spinning Geometry:

• From Roving bobbin to cop, the fibre strand passes through drafting arrangement, thread guide, balloon control rings and traveller. These parts are arranged at various angles and distances relative to each other. The distances and angles together are referred to as the spinning geometry,has a significant influence on the spinning opeartion and the resulting yarn. They are

1) Yarn tension

2) Number of end breaks

3) Yarn irregularity

4) Binding-in of the fibres

5) Yarn hairiness

6) Generation of fly etc.

Spinning TriangleTwist in a yarn is generated at the traveller and travel against the direction of yarn movement to the front roller. Twist must run back as close as possible to the nip of the rollers, but it never penetrates completely to the nip because, after leaving the rollers, the fibres first have to be diverted inwards and wrapped around each other. There is always a triangular bundle of fibres without twist at the exit of the rollers, this is called as SPINNING TRIANGLE. Most of the end breaks originate at this point. The length of the spinning triangle depends upon the spinning geometry and upon the twist level in the yarn.

• The top roller is always shifted 3 to 6 mm forward compared to bottom roller. This is called top roller overhang.This gives smoother running and smaller spinning triangle. The overhang must not be made too large, as the distance from the opening of the aprons to the roller nip line becomes too long resulting in poorer fibre control and increased yarn irregularity.

• Continuous variation of the operating conditions arises during winding of a cop.The result is that the tensile force exerted on yarn must be much higher during winding on the bare tube than during winding on the full cop, because of the difference in the angle of attack of the yarn on the traveller. When the ring rail is at the upper end of its stroke, in spinning onto the tube, the yarn tension is substantially higher than when the ring rail is at its lowermost position. This can be observed easily in the balloon on any ring spinning machine.

• The tube and ring diameters must have a minimum ratio, between approx. 1:2 and 1:2.2, in order to ensure that the yarn tension oscillations do not become too great

• Yarn tension in the balloon is the tension which finally penetrates almost to the spinning triangle and which is responsible for the greater part of the thread breaks. It is reduced to a very small degree by the deviation of the yarn at the thread guide. An equilibrium of forces must be obtained between the yarn tension and balloon tension.

The roving bobbins are taken to the ring frames where it is drafted (extended) to the extent of desired level (i.e. count). The spindle along with the ring traveller mounted on a ring imparts the requisite amount of twist into the yarn. The yarn is wound on bobbins and taken to post spinning operations.

Fiber Fineness | Yarn Count | Yarn Count ConversionMicronaire Value (Cotton) | Micronaire Definition : The unit is micrograms per inch. The average weight of one inch length of fibre, expressed in micrograms(0.000001 gram).

Denier DefinitionDenier (Man-made Fibres): Weight in grams per 9000 meters of fibre.

Micron (wool): Fineness is expressed as fibre diameter in microns(0.001mm)

Conversions:Denier = 0.354 x Micronaire value

Micronaire value = 2.824 x Denier

Yarn Count Definition | What is Yarn Count | Count of YarnCount is a number indicating the mass per unit length or length per unit mass of yarn.

Yarn Count Conversion:It is broadly classified into

1) Direct and

2) Indirect system.

Direct System : English count (Ne)English Count is Calculated as No. of hanks of 840 yds present in 1 lb of yarn.

French count (Nf)

Metric count (Nm)Metric Count is calculated as No. of hanks of 1000 meters present in 1 kg of yarn.

Worsted count

Worsted Count is Calculated as No. of hanks of 560 yds present in 1 lb of Yarn. It is basically used for Wool.

Metric System: Metric count(Nm) indicates the number of 1 kilometer(1000 meter) lengths per Kg.

Nm = length in Km / weight in kg (or)

Nm = length meter / weight in grams

Indirect System:Tex count / Tex Yarn CountTex is calculated as Weight of yarn in gm present in 1000 meter length. It is a universal system of counting the yarn.

DenierDenier is calculated as Weight of yarn in gm present in 9000 meter length. It is basically used for man made fiber.

Calculations:Grams per meter = 0.5905 / Ne

Grams per yard = 0.54 / Ne

Tex = den x .11 = 1000/Nm = Mic/25.4

Ne = Nm/1.693

DRAFT = (feed weight in g/m) / (delivery weight in g/m)

DRAFT = Tex (feed) / Tex(delivery)DRAFT = delivery roll surface speed / feed roll surface speed

No of hanks delivered by m/c = (Length delivered in m/min) / 1.605

Project Costing For Starting a Spinning Mill

Following information is Required to Work out a Costing for a New Plant

• The Average Count of the Plant

• Capacity of the plant - No of Spindles to be installed and the number of back process and winding machines required

• Investment on Machineries

• Investment on Land

• Investment on Building

• Working Capital Required

• Product lay out, the count pattern

• Selling price of individual counts

• Rawmaterial cost(including freight, duty etc)

• Packing cost per kg of yarn

• Freight per kg of yarn

• Direct labour cost

• Indirect labour cost

• Fixed power cost

• Variable power cost

• Spares consumption

• Administration costs

• Selling overheads

Working Out With The Project Cost

Step 1: Contribution to be CalculatedIn general for a spinning mill, contribution per kg ofa particular count is calculated to work out the economics for a new project as well as for a running mill.

Contribution = selling price - direct cost

Direct cost for a spinning mill includes rawmaterial price, packing cost, freight. All other costs are either fixed costs or semi variable costs. The other costs cannot be conveniently allocated to per kg of a particular count.

The basic idea of a new project or a running plant is to maximise this contribution. Because once the plant is designed, spares cost, power cost, administration cost,labour cost etc almost remain constant. There will not be significant changes in these costs for different count patterns if the plant is utilisation is same.

Step 2: To Work out the Total Investment Cost ( Machineries, Accessories, Land and Builidng, Humdification and Electrical instruments)To calculate the number of back proess and winding drums required, a detailed spin plan should be worked out with speeds and efficiencies to be achieved in each machine.

While calculating the no of machines required, m/c utilisation, m/c efficiency , waste percentage, twist multipliers, delivery speeds etc should be considered properly. These factors should be decided based on yarn quality required, end breakge rates and the capacity of machine.

Investment On MachineryMachinery No. of Machines Rate/MC Total Cost in US$

Trutzschler Blowrrom line for cotton 1 Line 4,16,640 4,16,640

Trutschler Blowrrom line for Polyester 1 Line 3,21,365 3,21,365

Trutshcler DK-903 cards 22 92,500 2,035,000

Rieter RSB-D30 draw frames (with autoleveller), 6Rieter double delivery drawframe 10

Rieter unilap 2Rieter E62 combers 10 16,48,000

How a speed frames with overhead blower 7 144530 10,11,710

Ring frames with autodoffer 23 148960 34,26,080

Winding machines ( 26 drums per mc) 23 93,200 2143600

Roving transport ( manual) 1 1,50,000 1,50,000

Argus fire system 1 50,000 50,000

Total 1,12,02,395

From the above table it is clear that, 23 ringframes with 1120 spindles are working with auto doffing and with link to autoconer. The major advantage of this automation is to reduce labour and to reduce the problems related to material handling. One has to really work out the benefits achieved because of this and the pay back for the extra investment.

Drawframe contributes a lot to the yarn quality and the ringframe and winding machine working. It is always better to go in for the best drawframes like RSB-D30 drawframes with autoleveller. It is not wise to buy a cheaper drawframe and save money.

It is always better to keep excess carding and autoleveller drawframes, so that flexibility of the project is also maintained. If the coarser counts contributes more and the market is good, overall production can be increased. If the market is for finer count, both the machines (carding and drawframes)can be run at slower speeds, which will surely contribute to yarn quality.

Speeds of speedframe , combers and ringframes do not affect the yarn quality as it is affected by card and drawframe speeds.

Blow room capacity should be utilised to the maximum, as it consumes a lot of power ,space and money.

Ringframe specification should be perfect, because the working performance and power consumption of the ringframe depends on the specifications like, lift, ring dia, no of spindles etc. Ring frame specification should be decided to get the maximum production per spindle and to reduce the power consumed per kg of yarn produced by that spindle. Because the investment cost and the power consumption for the ringframe is the highest in a spinning mill.

Investment On AccessoriesAccessories No.of Machines Rate/MC Total Cost

Carding cans 36" x 48" 120 160 19,200

comber cans 24" x 48" 350 85 29,750

Drawframe cans 20" x 48" 110 53 58,500

Identification bands 20" 400 1.2 480

Identification bands 24" 50 1.8 90

Roving and spinning bobbins 36,000

Plastic crates 400 6 2400

Trolleys 10,000

Cone trolly 400 6 2400

Fork lift 1 27,000 27,000

Hand truck 3 1000 3000

Total 2,02,220

Service and Maintenance EquipmentsService and Maintenance Equipments No.of Machines Rate/MC Total

Cots buffing machine and accessories 1 20,000 20,000

Card room accessories 1 set 60,000 60,000

Spindle oil lubricator 1 4,000 4,000

Clearer roller cleaning machine 1 3,000 3,000

Vacuum cleaner 1 15,000 15,000

Pneumatic cleaners 6 500 3000

Weighing balance 3 2000 6000

Strapping machine 2 2000 4000

Premier autosorter 1 2500 2500

Premier uster tester 1 45,000 45,000

Premier strength tester 1 45,000 45,000

Premier fiber testing 1 45,000 45,000

Premier Classidata 1 25,000 25,000

Erection charges 1,50,000

Total 4,27,500

Card service machines like Flat tops clipping machine and flats grinding machine are very important for yarn quality. One should not look for cheaper machine. It is always better to go for reputed manufacturers like GRAF, HOLLINGSWORTH etc.

Rubber cots contributes a lot to yarn quality. Bad buffing in ring frame can increase the imperfections by 15%. Poor quality of buffing in drawframe and speedframes can affect both production and quality. It is better to go for the best cots mounting machine and cots buffing machine

Humidification and Electrical EquipmentsElectrical installation including transformer, incoming and outgoing panels, bus duct,

Capacitor, etc for 3800 KVA --- ------------------------------------------------ 3,50,000

Cables --------------------------------------------------------------------------------------1,25,000

Compressor, Dryer and pipe lines ------------------------------------------------- 1,80,000

Humidifaction system ---------------------------------------------------------- 7,67,000

Chillers --------------------------------------------------------------------------------------------1,76,000

Ducting and installation for humidification system --------------------------- 1,25,000

Workshops, hydrant and other equipments ------------------1,00,000

Total---------------- 18,23,000

In indonesia, most of the units use PLN power and some of the spinning mills use Gensets. A detailed costing has to be done to compare the cost per unit to decide, Whether to use the PLN power or to go in for Gensets. while working out the costing finance cost on investment , overhauling cost, running cost, efficiency of the machine should be considered for cost caluculation in the case of Genset. In case of PLN power, the losses due to power interruption( based on the area data), finance cost on initial investment, md charges, unit charges to be considered. It is better to use 50% PLN and 50 % own generation.

Land and Builiding InvestmentsLand Cost ----------------------------------------------------------------------------------- 2,00,000

Land Developement ------------------------------------------------------------------------ 40,000

Factory Building ------------------------------------------------------------------------------ 14,05,440

Road and others ----------------------------------------------------------------------------- 40,000

Total--------------14,45,440

Step No.3 : To calculate the expenses ( labour, power, stores,working capital, insurance etc)Working capital = 3,000,000

Labor:The following table gives the details about labor requirement

Department No.of People Required

Production 140

Packing 15

Maintenance 30

Utility 17

Adminstration and personal dept 20

Total no of People required per day 222

WagesWages at 50 USD/Month including Bonus and Insurence 11,000

Other Facilities 3885

Salaries for managerial staff 10000

Other Facilities 3500

Total------------------------------- 28,485

Power : The Following Table gives the Details about the PowerTotal units(KWH) produced (consumed)per day ------------------69559

Unit cost (cost / KWH) ---------------------------------------------- 0.03

Total production in Kgs --------------------------------------------17,390

KWH/ Kg of yarn -------------------------------------------------- 4.0

Total Power Cost/Day ---------------------------------------------2087

Spares : The Following Table shows the Spares Cost, Repair , and InsuranceSpares cost at usd 8/1000 spindle shift ---------------------- 222,566

Repairs and other overheads ----------------------------------- 200,000

Insurance at 0.175% on investment and working capital ----- 31320

Total Cost --------------------------------------------------- 453886

Step No.4 : Pay Back CalculationDetails In USDInvestment

Land and building 1,444,440

Machinery, accessories & service equipments 11,832,115

Electrical and Humidification ducts 1,823,000

Total Investment 15,099,555

Working Capital 3,000,000

Grand Total 18,099,555

Recurring Expenditures Per DaySalaries and Wages 949.5

Power Cost 2087

Stores , Repairs and Insurance 1260.8

Total 4297.3

Interest Calculation (per day)

On Capital 8% 3355.5

on Working Capital 9% 750

Total Expenses Including Interest 8402.8

Total Contribution Per Day 13312

Net Profit( before depreciation & taxation) 4909.2

Pay Back Period 8.54 years