RINGS And TRAVELLERS

n most cases, the limit to productivity of the ring spinning machine is defined by the traveller in interdependence with the ring, and yarn. It is very important for the technologist to understand  this and act on them to optimize the yarn production. The following factors should be considered

• materials of the ring traveller
• surface charecteristics
• the forms of both elements( ring and traveller)
• wear resistance
• smoothness of running
• running-in conditions
• fibre lubrication
  
  TRAVELLER:
  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 behind by the spindle.
  
  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. Heat produced when by the  ringtraveller  is around 300 degree celcius. This has to be dissipated in milliseconds by traveller into the air.
  Parts of a traveller:
      
    
  
  Height of bow:  It should be as low as possible for stable running of traveller. It should also have sufficient yarn pasage.
  Yarn passage: According to count spun the traveller profile to be selected with required yarn passage.
  Toe gap : This will vary according to traveller number and flange width of the ring
  Wire section: It plays an important role for yarn quality, life of traveller.
  Ring contact area: This area should be more, uniform, smooth and continuous for best performance.
  Inner width: This varies according to traveller profile and ring flange.
  
  SALIENT FEATURES OF A TRAVELLER:
  
• Generate less heat
• dissipate heat fastly
• have sufficient elasticity for easy insertion and to retain its original shape after insertion
• friction between ring and traveller should be minimal
• it should have excellent wear resistance for longer life
• hardness of the traveller should be less than the ring

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 aveller
• to the traveller mass
• toto the square of hte 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.
• 
  
• In order to maintain the same friction or spinning tension with different coefficients of friction, different traveller weights must be used. The coefficient of friction is determined by the fiber lubrication and is subject to fluctuation. Dry cotton means higher coefficient of friction. For manmade fibres depending upon the manufacturer, lower to medium coefficient of friction.

The coefficient of friction with fiber lubrication can vary from 0.03 and 0.15.
R = Co ficeint of friction  x N
where
R - traveller friction in mN
N = Normal force >= (Fc x ML x V xV)/(R)
Fc - centrifugal force
ML - mass of the traveller in mg
V - traveller speed in m/s
R - radius of the ring (inside)

• 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 the 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.

Introduction to Open End Spinning

• In conventional spinning ,the fibre supply is reduced to the required mass per unit length by drafting & then consolidated into a yarn by the application of twist.
• 2.There is no opportunity for the internal stresses created in the fibres during drafting to relax.
• 3.In open end spinning, the fibre supply is reduced, as far as possible , to individual fibres, which are then carried forward on an air-stream as free fibres.
• 4. This permits internal stresses to be relaxed & gives rise to the term “free fibre spinning”.
• 5.These fibres are then progressively attached to the tail or “open end” of already formed rotating yarn.
• 6.This enables twist to be imparted by rotation of the yarn end.
• 7.Thus the continuously formed yarn has only to be withdrawn & taken up on a cross-wound package.

 

METALLIC CARD CLOTHING

INTRODUCTION:

As Carding machine design improved in 1950's and 60's, it became apparent that card clothing was a limiting factor

Much time and effort was spent in the development of metallic card clothing.
There are two rules of 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 responsibilitgy of the 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

CYLINDER WIRE: The main parameters of CYLINDER Card clothing
Tooth depth
Carding angle
Rib width
Wire height
Tooth pitch
Tooth point dimensions
Shallowness of tooth depth reduces fibre loading and holds the fibre on the cylinder in the ideal position
under the carding action of the tops. The space a fibre needs within the cylinder wire depends upon
its Micronaire/denier value and staple length. ould have to be reduced.
The recent cylinder wires have a profile called "NO SPACE FOR LOADING PROFILE"(NSL). With this
new profile, the tooth depth is shallower than the standard one and the overall wire height is reudced
to 2mm , which eliminates the free blade in the wire. This free blade is responsible for fibre loading.
Once the fibre lodges betweent the free blade of two adjacent teeth it is difficult to remove it.Inorder
to eliminate the free blade, the wire is made with a larger rib width

FRONT ANGLE:

Front angle not only affects the carding action but controls the lift of the fibre under the action
of centrifugal force. The higher the cylinder speed , the lower the angle for a given fibre. Different fibresM
have different co-efficients of friction values which also determine the front angle of the wire.
If the front angle is more, then it is insufficient to overcome the centrifugal lift of the fibre
created by cylinder speed. Therefore the fibre control is lost, this will result in increasing flat waste
and more neps in the sliver.
If the front angle is less, then it will hold the fibres and create excessive recyling within the carding
machine with resulting overcarding and therefore increased fibre damage and nep generation.
Lack of parallelisation, fibre damage, nep generation, more flat waste etc. etc., are all consequences
of the wrong choice of front angle.

TOOTH PITCH:
Each fibre has a linear density determined by its diameter to length ratio. Fine fibres and long fibres
necessitates more control during the carding process. This control is obtained by selecting the
tooth pitch which gives the correct contact ratio of the number of teeth to fibre length.
Exceptionally short fibres too require more control, in this case , it is not because of the stiffness but
because it is more difficult to parallelise the fibres with an open tooth pitch giving a low contact ratio.

RIB THICKNESS:

The rib thickness of the cylinder wire controls the carding "front" and thus the carding power.
Generally the finer the fibre, the finer the rib width. The number of points across the carding machine is
determined by the carding machine's design, production rate and the fibre dimensions. General trend is towards finer rib thicknesses, especially for high and very low production machines.

Rib thickness should be selected properly, if there are too many wire points across the machine for a
given cylinder speed, production rate and fibre fineness, "BLOCKAGE" takes place with disastrous results from the point of view of carding quality. In such cases, either the cylinder speed has to be increased or most likely the production rate has to be reduced to improve the sliver quality

POINT POPULATION:
The population of a wire is the product of the rib thickness and tooth pitch per unit area. The general rule
higher populations for higher production rates, but it is not true always. It depends upon other factors
like production rate, fineness, frictional properties etc.

TOOTH POINT:
The tooth point is important from a fibre penetration point of view. It also affects the maintenance and consistency of performance. Most of the recent cylinder wires have the smallest land or cut-to-point.
Sharp points penetrate the fibre more easily and thus reduce friction, which in turn reduces wear on the
wire and extends wire life.

BLADE THICKNESS:
Blade thickness affects the fibre penetration. The blade thickness is limited by practical considerations,but the finer the blade the better the penetration of fibres. Wires with thin blade thickness penetrate the more easily and thus reduce friction, which in turn reduces wear on the wire and extends wire life.


BACK ANGLE:
A lower back angle reduces fibre loading, but a higher value of back angle assists fibre penetration. Between the two extremes is an angle which facilitates both the reduction in loading and assists fibre penetration and at the same time gives the tooth sufficient strength to do the job for which it was designed.

Fibre Dynamics in the Revolving-Flats Card

A Critical Review
Over the last 30 years numerous developments have taken place with the cotton card. The production rate has risen by a factor of 5  with the main rotating components running at significantly higher speeds.
 Triple taker-in rollers and modified feed systems are in use, additional carding segments are fitted for more effective fibre opening, and improved wire clothing profiles have been developed for a better carding action. Advances in electronics have provided much improved monitoring and process control. Most of these developments have resulted in enhanced cleaning of cotton fibres, reduced neppiness of the card web and better sliver uniformity.
Despite the various improvements made to the card a commonly held view is that more is known about the cleaning processes on the card than about the carding process itself .   For instance, modern cards can achieve an overall cleaning efficiency of 95%. It is well established that the cleaning efficiency of modern taker-in systems is a round 30%, that the cylinder/flats action with the latest wire clothing profiles gives 90% cleaning efficiency and that effective cleaning is associated with lower neps in the card web .
However, even though the nep content and the sliver Uster CV% are used as quality measures of carding performance they are not satisfactory indicators for anticipating yarn quality. This is because some fibre arrangements in the sliver may lead to nep formation and imperfections during up-stream drafting processes .
In addition to the removal of trash and neps, important aspects of the carding process in relation to yarn quality and spinning performance are the degree of fibre individualisation, the fibre extent and the fibre hook configurations in the sliver. With regard to these factors, increased production rate can reduce carding quality . It is therefore of importance that a better understanding is established of the effect that carding actions have on such quality parameters, particularly at high production rates.
The most widely accepted view of how fibres are distributed within the card under steady-state conditions is illustrated in Figure 1 . Reported studies into the fundamentals of the carding process have largely been concerned with how the principal working components of the card affect this distribution of fibre mass and interact with the mass to achieve:trash and nep removal from cottons; the disentangling of the fibre mass into individual fibres, with minimal fibre breakage; and the alignment of the fibres to give a sliver suitable for drafting in down stream processes.
These actions occur at the interface of the card components within the three zones indicated in Figure 1. This paper therefore gives a critical review of published research on the:
· mechanisms by which the fibre mass is broken down into individual fibres,
· mechanisms of fibre transfer between the component parts of the card
· effect of the saw-tooth wire geometry on these actions

Figure 1: Distribution of Fibre Mass during Short-Staple Carding

Q1: fibre mass transferred from cylinder to doffer
K : transfer coefficient
Q2: recycling layer
QL: fibre mass transferred from taker-in to cylinder
Qf : flat strips
Qo : operational layer
(where Q is mass per unit time)

Zone 1: Fibre-Opening
Separation and Cleaning of the Input Fibre Mass:
The taker-in has effectively a combing action , which results in the breakdown of the tufts, consituting the fed fibre mass, into single fibres and smaller size tufts (tuflets), and in the liberation of trash particles ejected from the mass flow by the mote knives positioned below the taker-in. To effectively breakdown the fibre mass feed into tuftlets with minimal fibre breakage, the taker-in wire has to be coarse, with a low number of points per unit area (4.2 to 6.2 pcm-2) and not too acute an angle of rake. The objective is to obtain gentle opening of the fibre mass feed and easy transfer of the tuftlets to the cylinder. Angles of  80o – 85o are used for short and medium length cottons to give effective opening and cleaning. For longer cottons and synthetics, a 90o or negative rake may be needed to facilitate gentler opening and satisfactory fibre transfer to prevent lapping of the taker-in .
Fibres, usually very short fibres, which are not adequately held by the teeth or present in the interspaces of the clothing are ejected causing fibre loss. However, it is the mote knives that govern the amount of fibre to trash (i.e. lint) in the extracted waste. Experimenting with the settings of two mote knives below the taker-in, Hodgson  found that the absence of the knives greatly increased the lint content with little increase in trash. With the knives present, the best setting was that which gave the least waste since increasing the amount of waste did not improve cleaning. Artzt  found that irrespective of teeth density and tooth angle  the waste increased with taker-in speed but the increase was attributed to higher lint content.
It is reasonable to assume that the smaller the tuftlet size and the greater the mass ratio of individual fibres to tuftlets the better the cleaning effect of the taker-in. Supanekar and Nerurkar   suggest that the takerin breaks down the fibre feed into tuftlets of various sizes and mass, conforming to a normal frequency distribution.  In the case of cotton, some tuftlets may consist of only fibres whilst others will contain seed or trash particles embedded among the fibres, these tuftlets constituting the heavier end of the distribution curve. Thus, the mean of the distribution would depend on the trash content of the material, as well as on the production rate, the taker-in speed and the wire clothing specification. However, the authors did not report any data to support their ideas.
Little detailed information has yet been published on the mass variation of tuftlets or on the relative proportion of discrete fibres to tuftlets resulting from the combing action of the taker-in. Nittsu  using photographic techniques studied the effect of process variables on tuftlet size. It was found that the total number of tuftlets decreases the closer the feed plate setting, the lower the feed rate, the smaller the steeper rake of the saw-tooth clothing and the higher the licker-in speed. Since th licker-in opens the batt into both tuftlets and individual fibres , a decrease in the total number of tuftlets suggests an increase in the mass of individual fibres. Liefeld  calculated estimates of the opened fibre mass at various stages through the blowroom and gives a value of 50mg for tuftlets on the taker-in. Mills  claims that the calculated optimum number of fibre per tooth is one, and that this should be maintained at increased production rates by increasing the taker-in speed. There is, however, the question of fibre damage at high taker-in speeds.

Figure 2: Frequency distribution of tuftlet mass
N: Taker-in speed (rpm), P: Production rate (kg/hr)
Honold and Brown   found no fibre damage occurred at speeds of up to 600 r/min. Krylov  reports the absence of fibre breakage at speeds up to 1,380 r/min, and Artzt’s  work shows taker-in speeds to have a negligible effect on fibre shortening and subsequently on yarn strength. In all cases cotton fibres of 26.5- 30.2 mm (2.5% span length) and 3.8 – 4.9 micronaire were processed. The level of fibre breakage, however, would seem to depend on production rate and the batt fringe setting to the licker-in. High production rates achieved by increased sliver counts and a close setting of the batt fringe result in significant fibre breakage.No fundamental studies have been reported on the forces involved in the fibre-wire interaction of revolvingflat card components. However, Li and etal  report a simulated study of fibre-withdrawal forces for wool in high-speed roller- clearer cards. Although impact forces could cause damage , it was found that card component speeds had no significant effect on the withdrawal-force, and that fibre configuration and entanglement were the important factors.
The importance of producing small size tuftlets is evident form the various components fitted in the fibreopening zone on modern short-staple cards. Saw-tooth wire covered plates, termed combing segments, fitted below the taker-in or built into the taker-in screen are claimed to give improved trash removal. Reportedly , the stationary flats fitted between the taker-in and the revolving flats provide extra opening of the tuftlets transferred to the cylinder from the taker-in.
They also act as a barrier to large, hard, trash particles such as seed coats, protecting the wire of the revolving flats from damage, particularly at high cylinder speeds. This enables finer wire to be used for the revolving flats and thereby improves the cleaning effect of the interaction between cylinder and revolving flats. The chances are also reduced of longer length fibres becoming deeply embedded in the revolving flats to become part of the flat strips. These attachments are widely accepted by the industry as beneficial, particularly at high production speed. However, there is no published systematic study of their effectiveness in reducing tuft size, and the effect of stationary flats on the recycling layer, Q2, is unknown. The little information that is available attempts to illustrate the effectiveness of these components on yarn quality, but there is no evidence of analytical rigour in the way the data were obtained.

CARDING

INTRODUCTION
"Card is the heart of the spinning mill" and "Well carded is half spun" are two proverbs of the experts.
These proverbs inform the immense significance of carding in the spinning process.High production in carding to economise the process leads to reduction in yarn quality.Higher the production, the more sensitive becomes the carding operation and the greater danger of a negative influence on quality.The technological changes that has taken place in the process of carding is remarkable. Latest machines achieve the production rate of 60 - 100 kgs / hr, which used to be 5 - 10 kgs / hr, upto 1970.

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

TECHNOLOGICAL POINTS IN CARDING
There are two types of feeding to the cards
1. feeding material in the form of scutcher lap
2. flock feed system (flocks are transported pneumatically)

lap feeding
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

flock feeding
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
Rieter has devloped a "unidirectional feed system" where the two feed devices(feed roller and feed plate
are oppositely arranged when compared with the conventional system. i.e. the cylinder is located below and the plate is pressed against the cylinder by spring force. Owing to the direction of feed roller, the fibre batt runs downwards without diversion directly into the teeth of the taker-in(licker-in) which results in gentle fibre treatment. This helps to reduce faults in the yarn.

The purpose of the taker-in is to pluck finely opened flocks out of the feed batt, to lead them over the
dirt eliminating parts like mote knives, combing segment and waste plates, and then to deliver the fibres to the main cylinder. In high production cards the rotational speed ranges from 700-1400

MIXING

MIXING (COTTON)

Cotton is a hygroscopic material , hence it easily adopts to the atmospheric airconditions. Air temperature inside the mxing and blowroom area should be more than 25 degree centigrade and the relative humidity(RH%) should be around 45 to 60 %, because high moisture in the fibre leads to poor cleaning and dryness in the  fibre leads to fibre damages which ultimately reduces the spinnability of cotton.
Cotton is a natural fibre. The following properties vary very much between bales (between fibres) fibre micronaire fibre length fibre strength fibre color fibre maturity   Out of these , fibre micronaire, color, maturity and the origin of growth results in dye absorption variation.
There fore it is a good practice to check the maturity , color and micronaire of all the bales and to
maintain the following to avoid dye pick up variation and barre in the finished fabric.

• Micronaire range of the cotton bales   used should be same for all the mixings of a lot
• Micronaire average of the cotton bales used should be same for all the mixings of a lot
• Range of color of cotton bales used should be same for all the mixings of a lot
• Average of color of cotton bales used should be same for all the mixings of a lot
• Range of matutrity coefficient of cotton bales used should be same for all mixings of a lot
• Average of maturity coefficient of cotton bales used should be same for all mixings of a lot Please note, In practice people do not consider maturity coefficient since Micronaire variation and
  maturity variation are related to each other for a particular cotton.
  

It the cotton received is from different ginners, it is better to maintain the percentage of cotton from different ginners throught the lot, even though the type of cotton is same.
It is not advisable to mix the yarn made of out of two different shipments  of same cotton. For example , the first shipment of west african cotton is in january and the second shipment is in march, it is not advisable to mix the yarn made out of these two different shipments.  If there is no shadevariation after dyeing, then it can be mixed.
According to me, stack mixing is the best way of doing the mixing compared to using
automatic bale openers which picks up the material from 40 to 70 bales depending on the length of
the machine and bale size, provided  stack mixing is done perfectly. Improper stack mixing will lead to BARRE or SHADE VARIATION  problem.  Stack mixing with Bale opener takes care of short term blending and two mixers in series takes care of long term blending.
why?

• Tuft sizes can be as low as 10 grams and it is the best way of opening the material(nep creation will be less, care has to be taken to reduce recyling in the inclined lattice)
• contaminations can be removed before mixing is made
• The raw material  gets   acclamatised to the required temp and R.H.%, since it is allowed to stay in the room for more than 24 hours and the fibre is opened , the fibre gets conditioned well. Disadvantages:
  
• more labour is required
• more space is required
• mixing may not be 100% homogeneous( can be overcome by installing double mixers)
  If automatic bale opening machine is used the bales should be arranged as follows
  let us assume that there are five different micronaires and five different colors in the mixing,
  50 bales are used in the mxing. 5 to 10 groups should be made by grouping the bales in a mixing so that each group will have average micronaire and average color as that of the overall mixing. The
  position of a bale for micronaire and color should be fixed for the group and it should repeat in the
  same order for all the groups
  It is always advisable to use a mixing with very low Micronaire range.Preferably .6 to 1.0 . Because
  
• It is easy to optimise the process parameters in blow room and cards
• drafting faults will be less
• dyed cloth appearance will be better because of uniform dye pickup etc
  It is advisable to use single cotton in a mixing , provided the length, strength micronaire ,
  maturity coefficient and trash content of the cotton will be suitable for producing the required counts.  Automatic bale opener is a must if more than two cottons are used in the mixing, to avoid BARRE or SHADE VARIATION problem.
  It is better to avoid  using the following cottons
  
• cottons with inseparable trash (very small size), even though the trash % is less
• sticky cotton (with honey dew or sugar)
• cotton with low maturity co-efficient
• Micronaire range of the cotton bales   used should be same for all the mixings of a lot
• Micronaire average of the cotton bales used should be same for all the mixings of a lot
• Range of color of cotton bales used should be same for all the mixings of a lot
• Average of color of cotton bales used should be same for all the mixings of a lot
• Range of matutrity coefficient of cotton bales used should be same for all mixings of a lot
• Average of maturity coefficient of cotton bales used should be same for all mixings of a lot Please note, In practice people do not consider maturity coefficient since Micronaire variation and
  maturity variation are related to each other for a particular cotton.
  

It the cotton received is from different ginners, it is better to maintain the percentage of cotton from different ginners throught the lot, even though the type of cotton is same.
It is not advisable to mix the yarn made of out of two different shipments  of same cotton. For example , the first shipment of west african cotton is in january and the second shipment is in march, it is not advisable to mix the yarn made out of these two different shipments.  If there is no shadevariation after dyeing, then it can be mixed.
According to me, stack mixing is the best way of doing the mixing compared to using
automatic bale openers which picks up the material from 40 to 70 bales depending on the length of
the machine and bale size, provided  stack mixing is done perfectly. Improper stack mixing will lead to BARRE or SHADE VARIATION  problem.  Stack mixing with Bale opener takes care of short term blending and two mixers in series takes care of long term blending.
why?

• Tuft sizes can be as low as 10 grams and it is the best way of opening the material(nep creation will be less, care has to be taken to reduce recyling in the inclined lattice)
• contaminations can be removed before mixing is made
• The raw material  gets   acclamatised to the required temp and R.H.%, since it is allowed to stay in the room for more than 24 hours and the fibre is opened , the fibre gets conditioned well. Disadvantages:
  
• more labour is required
• more space is required
• mixing may not be 100% homogeneous( can be overcome by installing double mixers)
  If automatic bale opening machine is used the bales should be arranged as follows
  let us assume that there are five different micronaires and five different colors in the mixing,
  50 bales are used in the mxing. 5 to 10 groups should be made by grouping the bales in a mixing so that each group will have average micronaire and average color as that of the overall mixing. The
  position of a bale for micronaire and color should be fixed for the group and it should repeat in the
  same order for all the groups
  It is always advisable to use a mixing with very low Micronaire range.Preferably .6 to 1.0 . Because
  
• It is easy to optimise the process parameters in blow room and cards
• drafting faults will be less
• dyed cloth appearance will be better because of uniform dye pickup etc
  It is advisable to use single cotton in a mixing , provided the length, strength micronaire ,
  maturity coefficient and trash content of the cotton will be suitable for producing the required counts.  Automatic bale opener is a must if more than two cottons are used in the mixing, to avoid BARRE or SHADE VARIATION problem.
  It is better to avoid  using the following cottons
  
• cottons with inseparable trash (very small size), even though the trash % is less
• sticky cotton (with honey dew or sugar) cotton with low maturity co-efficient
• Stickiness of cotton consists of two major causes. Honeydew from Whiteflies and aphids and high level of natural plant sugars. The problems with the randomly distributed honey dew contamination often results in   costly proudction interruptions and requires immediate action often as severe as discontinuing the use of contaminated cottons.An effective way to control cotton   stickiness in processing is to blend sticky and non-sticky cotton.  Sticky cotton percentage should be less than 25%.

POWER FACTOR

RESISITVE LOADS:

Resistive loads include devices such as heating elements and incandescent lighting. In a purely resistive circuit, current and voltage rise and fall at the same time. They are said to be "in   phase."

TRUE POWER:

All the power drawn by a resistive circuit is converted to usefulwork. This is also known as true power in a resistive circuit. Truepower is measured in watts (W), kilowatts (kW), or megawatts(MW). In a DC circuit or in a purely resistive AC circuit, truepower can easily be determined by measuring voltage and current. True power in a resistive circuit is equal to system voltage (E) times current (I).

INDUCTIVE LOADS:

Inductive loads include motors, transformers, and solenoids. In a purely inductive circuit, current lags behind voltage by 90°.Current and voltage are said to be "out of phase." Inductive circuits, however, have some amount of resistance. Depending on the amount of resistance and inductance, AC current will lag somewhere between a purely resistive circuit (0°) and a purely inductive circuit (90°). In a circuit where resistance and inductance are equal values, for example, current lags voltageby 45°.

CAPACITIVE LOADS:

Capacitive loads include power factor correction capacitors and filtering capacitors. In a purely capacitive circuit, current leads voltage by 90°. Capacitive circuits, however, have some amount of resistance. Depending on the amount of resistance and capacitance, AC current will lead voltage somewhere between a purely resistive circuit (0°) and a purely capacitive circuit (90°).In a circuit where resistance and capacitance are equal values,for example, current leads voltage by 45°.

REACTIVE LOADS:

Circuits with inductive or capacitive components are said to be reactive. Most distribution systems have various resistive and reactive circuits. The amount of resistance and reactance varies,depending on the connected loads.


REACTANCE:
Just as resistance is opposition to current flow in a resistive circuit, reactance is opposition to current flow in a reactive circuit. It should be noted, however, that where frequency has no effect on resistance, it does effect reactance. An increase in applied frequency will cause a corresponding increase in inductive reactance and a decrease in capacitive reactance.
For resistance
R = E/I, Where R = resistance in Ohms, E = voltage and I = current
For inductive Reactance
XL = 2 x 3.14 x f x L , where XL is inductive reactance in ohms, f = applied freq and L = inductance in henrys
For Capacitive reactance
XC = 1 / (2 x 3.14 x f x C) where XC =capacitive reactance, f = applied freq and C = capacitance in farads

ENERGY IN REACTIVE CIRUCUITS:

Energy in a reactive circuit does not produce work. This energy is used to charge a capacitor or produce a magnetic field around the coil of an inductor. Current in an AC circuit rises to peak values (positive and negative) and diminishes to zero many times a second. During the time, current is rising to a peakvalue, energy is stored in an inductor in the form of a magnetic field or as an electrical charge in the plates of a capacitor. This energy is returned to the system when the magnetic field collapses or when the capacitor is discharged.
REACTIVE POWER
Power in an AC circuit is made up of three parts; true power,reactive power, and apparent power. We have already discussed true power. Reactive power is measured in volt-amps reactive(VAR). Reactive power represents the energy alternately stored and returned to the system by capacitors and/or inductors.Although reactive power does not produce useful work, it still needs to be generated and distributed to provide sufficient true power to enable electrical processes to run.
APPARENT POWER:
Not all power in an AC circuit is reactive. We know that reactive power does not produce work; however, when a motor rotates work is produced. Inductive loads, such as motors, have some amount of resistance. Apparent power represents a load which includes reactive power (inductance) and true power(resistance). Apparent power is the vector sum of true power,which represents a purely resistive load, and reactive power,which represents a purely reactive load. A vector diagram can be used to show this relationship. The unit of measurement for apparent power is volt amps (VA). Larger values can be stated inkilovolt amps (kVA) or megavolt amps (MVA).

DETERMINATION OF THE TECHNOLOGICAL VALUE OF COTTON FIBRE:

A COMPARATIVE STUDY OF THE TRADITIONAL AND MULTIPLE-CRITERIA DECISION-MAKING APPROACHES

Introduction

Determining the technological value of cotton fibre is an interesting field of textile research. The quality of final yarn is largely influenced (up to 80%) by the characteristics of raw cotton [1]. However, the level to which various fibre properties influence yarn quality is diverse, and also changes depending on the yarn manufacturing technology. Besides, a cotton may have conflicting standards in terms of different quality criteria. Therefore, the ranking or grading of cotton fibres in terms of different quality criteria will certainly not be the same. This will make the situation more complex, and applying multiple-criteria decision-making (MCDM) methods can probably deliver a plausible solution. The solution must produce an index of technological value or overall quality of cotton fibre, and the index should incorporate all the important fibre parameters. The weights of the fibre parameters should be commensurate with their importance on the final yarn quality.

Traditionally, three fibre parameters have been used to determine the quality value of cotton fibre. These are grade, fibre length and fibre fineness. The development of fibre testing instruments such as the High Volume Instrument (HVI) and the Advanced Fibre Information System (AFIS) has revolutionised the concept of fibre testing. With the HVI it is pragmatically possible to determine most of the quality characteristics of a cotton bale within two minutes. Based on the HVI results, composite indexes such as the fibre quality index (FQI) and spinning consistency index (SCI) can be used to determine the technological value of cotton; this can play a pivotal role in an engineered fibre selection programme [2-3].

In this paper, a new method of determining the technological value of cotton using a multiplicative analytic hierarchy process (multiplicative AHP) of the MCDM method is postulated. The technological value of cotton was also determined by the three traditional methods, namely the fibre quality index (FQI), the spinning consistency index (SCI) and the premium-discount index (PDI). The ranking of

cotton fibres produced by these four methods was compared with the ranking of final yarn tenacity, and a rank correlation analysis was carried out.

Overview of MCDM and AHP

Multiple Criteria Decision Making is a well-known branch of Operations Research (OR), which deals with decision problems involving a number of decision criteria and a finite number of alternatives. Various MCDM techniques, such as the weighted sum model (WSM), the weighted product model (WPM), the analytic hierarchy process (AHP), the revised AHP, the technique for order preference by similarity to an ideal solution (TOPSIS), and elimination and choice translating reality (ELECTRE), can be used in engineering decision-making problems, depending upon the complexity of the situation [4- 8] The Analytic Hierarchy Process (AHP), introduced by Saaty [9-12], is one of the most frequently discussed methods of MCDM. Although some researchers [13-16] have raised concerns over the theoretical basis of AHP, it has proven to be an extremely useful decision-making method. The reason for AHP’s popularity lies in the fact that it can handle the objective as well as subjective factors, and the criteria weights and alternative scores are elicited through the formation of a pair-wise comparison matrix, which is the heart of the AHP.

Details of AHP methodology  Step 1:

Develop the hierarchical structure of the problem. The overall objective or goal of the problem is positioned at the top of the hierarchy, and the decision alternatives are placed at the bottom. Between the top and bottom levels are found the relevant attributes of the decision problem such as criteria and sub-criteria. The number of levels in the hierarchy depends on the complexity of the problem.

Step 2:

Generate relational data for comparing the alternatives. This requires the decision maker to formulate pair-wise comparison matrices of elements at each level in the hierarchy relative to each activity at the next, higher level. In AHP, if a problem involves M alternatives and N criteria, then the decision maker has to construct N judgment matrices of alternatives of M x M order and one judgment matrix of criteria of N x N order. Finally, the decision matrix of M x N order is formed by using the relative scores of the alternatives with respect to each criterion. In AHP, the relational scale of real numbers from 1 to 9 and their reciprocals are used to assign preferences in a systematic manner. When comparing two criteria (or alternatives) with respect to an attribute in a higher level, the relational scale proposed by Saaty [9-12] is used. The scale is shown in Table 1.

Table 1. The fundamental relational scale for pair-wise comparisons

CONSTANTS AND CALCULATIONS

FIBRE FINENESS, YARN COUNTS AND CONVERSIONS:

Micronaire value(cotton) :
The unit is micrograms per inch.  The average weight of one inch length of fibre, expressed in micrograms(0.000001 gram).
Denier(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 COUNTS:
It is broadly classified into 1. DIRECT and 2.INDIRECT system.
DIRECT SYSTEM:

• English count (Ne)
  
• French count(Nf)
  
• Metric count(Nm)
  
• Worsted count
  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
  
• Denier
  

CONVERSION TABLE FOR YARN COUNTS:

	tex	Ne	den	Nm	grains/yd
tex			den/9	1000/Nm	gr.yd   x 70.86
Ne	590.54/tex		5314.9/den	Nm x .5905	8.33 / gr/yd
den	tex  x  9			9000/Nm	gr/yd  x 637.7
Nm	1000/tex		9000/den		14.1 / gr/yd
grains/yd	tex / 70.86		den / 637.7	14.1/Nm

Where, Nm - metric count, Nec - cottoncount

CONVERSION TABLE FOR WEIGHTS:

	ounce	grains	grams	kilograms	pounds
ounce		437.5 grains	28.350 grams
grains	0.03527 ounces		0.0648 grams
grams	0.03527 grains	15.432 grains		0.001 kgs
kilograms	35.274 ounces	15432 grains	1000 grams		2.2046 pounds
pounds	16.0 ounces	7000 grains	453.59 grams	0.4536 kgs

CONVERSION  TABLE FOR LINEAR MEASURES:

	yard	feet	inches	centimeter	meter
yard		3 feet	36 inches	91.44 cms	0.9144 meter
feet	0.3333 yards		12 inches	30.48 cms	0.3048 meter
inches	0.0278 yards	0.0833 feet		2.54 cms	0.254 meter
centimeter	0.0109 yards	0.0328 feet	0.3937 inches		0.01meter
meter	1.0936 yards	3.281 feet	39.37 inches	100 cms

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

CARDING:
(1). P =( L x 1.0936 x 60 x effy ) / (hank (Ne) x 36 x 840 x 2.2045)
P - production in kgs / hr
L - delivery speed in m/min
effy- efficiency
Ne - English count ( number of 840 yards in one pound)
840 - constant
2.2045- to convert from lbs to kilograms
(2).production in kgs / hr = (L  x  Ktex   x 60  x   effy)  / ( 1000)
L - delivery speed in m/min
Ktex- sliver count in Ktex (kilotex)
effy - efficiency
1000- to convert to kilograms from grams
(3). production in kgs / 8 hrs = (0.2836  x L x effy) / (Ne)
L - delivery speed in m/min
effy - efficiency
Ne - English count
(4).prodn / 8 hrs = (Hank x Nd) /( Ne x 2.2045)
Hank = no of hank (840 yards)delivered by the machine
Nd = no of deliveries
Ne = hank of the material
(4).Total draft in card = (feed weight in g/m) / (sliver weight in g/m)
DRAWFRAME:
(1.)Break draft = surface speed of 2nd roller / surface speed of back roller
(2).Main draft = surface speed of 1st roller / surface speed of 2nd( middle) roller
(3).Total draft = surface speed of delivery  roller / surface of  feed roller
(4).production in kgs / 8 hrs = (0.2836  x L x effy x Nd) / (Ne)
L - delivery speed in m/min
effy - efficiency
Ne - english count
Nd - No of delvieries
(5.).prodn in kgs / hr  =   (FRD x FRrpm x 3.14 x 60 x effy  x Nd) / (Ne x 840 x 36 x 2.2045) 
FRD - front roller dia in inches
FRrpm - front roller rpm
effy - efficiency
Ne - Sliver hank
Nd - number of deliveries

SPEEDFRAME + RINGFRAME
(1).Twist / Inch (TPI) = Spindle speed / FRS
FRS - front roller surface speed in inches/min
(2).FRS = FRrpm x 3.14 x FRD
FRS - Front roller surface speed
FRD - front roller diameter
(3).T.P.I = T.M. x sqrt(count or hank)
T.M. - Twist multiplier
sqrt - square root
(4).prodn in kgs / 8 hrs = (7.2 x SS x effy) / (TPI x Ne x 1000)
SS - spindle speed
(5).Spindle speed = m/min x TPI x 39.37
(6).hank delivered   = spindle speed  / ( tpi x 62.89)
(7).Ring traveller speed in m/sec =( spindle speed x ring dia in mm x 3.14) / (60 x 1000) 
WINDING:
(1). production in kgs / 8 hrs = (0.2836  x L x effy x Nd) / (Ne)
L - delivery speed in m/min
effy - efficiency
Ne - english count
Nd - No of delvieries
(2). P =( L x 1.0936 x 60 x effy ) / (hank (Ne) x 36 x 840 x 2.2045)
P - production in kgs / hr
L - delivery speed in m/min
effy- efficiency
Ne - English count ( number of 840 yards in one pound)
840 - constant
2.2045- to convert from lbs to kilograms

PROCESS PARAMETER IN SPINNING

Ringframe 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 ringframe.

• 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, above all
• Raw material chracteristic plays a      major role in selecting the above said process parameters
  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.
  DRAFTING:
  
  The break draft should depend upon the following,
  
• fibre type
• fibre length
• roving T.M
• main draft
  Some examples are given below,
  
  Normally 1.13 to 1.18 break draft is used for
  
• 100%cotton , Poly/cotton blend, 100% synthetic
• roving T.M. upto 1.3 for cotton and .80 for Poly/cotton blend, 0.5 to0.7 for synthetic
• ring frame back zone setting of 60mm for fibres upto 44mm and 70mm for fibres upto 51mm
• total draft in ringframe upto 35 1.24 to 1.4 break draft is used for
  
• 100%cottton, poly/cotton blend, 100%synthetic fibre
• strongly twisted roving i.e higher than the above mentioned T.M.s
• total draft from 33 to 45
• back zone setting(R.F) around 52mm for fibres upto 44mm and 60mm for fibres upto 51mm-
  If the total draft is more than 45 or the fibre length is more than 51 and the fibre is a fine
  fibre(i.e more number of fibres in the cross section)with a very high interfibre friction, break draft
  more than 1.4 is used.
  Please note that for most of the application, lower break draft with wider setting is used. With higher break
  drafts, roller setting becomes very critical. Higher the break draft, higher the chances for thin places
  i.e. H1 classimat faults.
  Higher draft with improper back zone setting will lead to thin places and hence more end breaks
  even though more twist flows into the thin yarn.
  
  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 manufacturers recommendation.
  For synthetic fibres upto 44 mm , it is better to use short cradles. Even with 42.5 mm bottom roller
  setting, 44 mm fibre works well without any problem. Because, the clamping distance will be around 52 mm or 50 mm. The imperfections and U% achieved with short cradle is better than with medium cradle(52mm setting).
  Instead of using medium cradle for processing 44mm synthetic fibre, it is always better to use
  short cradle with 1 or 2mm wider setting than the recommended to avoid bottom apron damages.
  If a mill has got a problem of bottom roller lapping, the apron damages are extremely high, it is better to use short cradle for 44 mm fibre and widen the setting by 1 or 2mm. This will minimise the complaints and improve the basic yarn quality also.
  Please note that if the bottom apron breakages are high, then the mill is working with a lot of
  bottom apron which is defective and with a lot of top roller which is defective. Both the defective
  parts produces a defective yarn, which can not rejected by older version of yarn clearers, and improperly set new type of clearers. This yarn will very badly affect the fabric appearance.
  Therefore it is always advisable to use a wider front zone setting upto 2mm , if the mill faces a problem of excessive bottom roller lappings. Please note that the defective bottom apron and top roll will not only affect the quality, but also the production, because the defective bottom apron and top roll make the  spindle a sick spindle which will be prone to end breaks. A wider front zone setting will increase the imperfection and uster, but there will not be major deviations of yarn quality.
  Nose bar height setting is very important. Depending upon the design, it is 0.7mm or .9 mm. Variation in heigh setting will affect the yarn quality and the apron movement. The distance between nose bar  and middle bottom roller should be less than apron thick ness or more than 3 mm to avoid apron buckling if there is any diturbance in apron movement.
  
  

PROCESS PARAMETERS IN SPEED FRAME

Roving machine is complicated, liable to faults, causes defects, adds to production costs and delivers
a product that is sensitive in both winding and unwinding.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 SYSTE                                                                                                                 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 prodction in speed frame.
  Investment cost will also be less,because the number of speedframes required will be less and the cost per mchine
  is also high. The following table can be a guidle line for speed frame delivery hank  
  

  MATERIAL	YARN COUNT	HANK	TOTAL DRAFT
  COTTON combed	36s to 40s	1.2	10
  Cotton combed	24s to 30s	1.0	10
  Cotton combed	14s to 24s	0.7 to 0.8	9
  Cotton karded	36s to 40s	1.3	9
  Cotton karded	24s to 36s	1.1	8
  Poly/cotton	36s to 45s	1.2	11
  Poly/cotton	24s to 36s	1.0	10
  Poly/viscose	36s to 40s	1.0	11
  Poly/viscose	24s to 36s	0.85	10
  Poly/viscose	16s to 20s	0.7	8

  The above said details are for producing a good quality yarn. This is suitable for 4 over 4 drafting
  system with front zone as a condensing zone without a draft.
  
• 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
  1. bottom roller diameter is 28.5 mm
  2. Top roller diameter is 28 mm
  3. Break draft is between 4th roller and 3rd roller
  4. Main draft is between 3rd roller and 2nd roller
  5. Bottom apron is run by a 3 rd roller
  6. between front roller and 2nd roller is a condesning zone
  7. front zone setting 35 mm( even for 51 mm fibre)
  8. Main draft zone setting is 48 mm
  9. 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
  verh 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.

PROCESS PARAMETERS IN DRAW FRAME

INTRODUCTION:
Drawframe 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.

The factors that affect the yarn quality are

• the total draft
• no of drawframe 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           
  1. material processed
  2. short fibre content
  3. fibrelength                                                                                                                                          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 fibre 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 reudce 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.
• 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
  1. For cotton, longest fibre +(8 to 12 mm)
  2. For synthetic fibre, fibre length + (20 to 30% of fibre length)

PROCESS PARAMETERS IN COMBING

Collected By: Muhammad Abid Farooq

INTRODUCTION
Combing 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   POINTS TO BE CONSIDERED
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
• 
  Let us assume that the following cotton is used/> 2.5 span lenth = 28 to 30 mm
  uniformity ratio = 50 to 53%
  FFI % = 6 to 14
  Micronaire = 3.8 to 4.2
  fibre strength = 24 to 28 gms/tex
  and the quality requirement for counts 30s to 40s, is to meet 5% uster standards in U%, imperfection,
  strength and classimate faults.
• 
  To meet this quality requirement with the above rawmaterial ,the amount of noil to be extracted
  may be around 16 to 18% if E7/4(RIETER MAKE)comber is used or 15 to 16 % if E-62(RIETER MAKE) comber
  is used. The above example is given to highlight the effect of noil removed and the quality achieved.
  This is just an approximate figure, the parameters may vary depending upon the application.
  
• 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.
• Given a chance, 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.
• Given a chance, 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.
• 
  

PROCESS PARAMETERS IN CARDING

INTRODUCTION:

Carding
                     is the most important process in spinning. It contributes a lot to the yarn quality. The
following process parameters and specfications are to be selected properly to prodce a good quality
yarn with a lower manufacturing cost. 
 
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 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 is renewing the
  carding surface at a faster rate.
  
• Higher the cylinder speed, higher the centrifugal force created by the cylinder, this tries to eject
  the fibre 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, whihc 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. Looking into the above details, the following specifications can be used as a guideline

MATERIAL	PRODN. RATE	RIB WIDTH	ANGLE(degrees)	POPULATION
Cotton low grade	low	0.6	65	700
Cotton low grade	high	0.5	55	840
Cotton Medium	low	0.6	60	800
Cotton Medium	high	0.4 to 0.5	55	840 to 950
Cotton fine	low	0.5	60	840
Cotton long	high	0.4 to 0.5	55	900 to 1100
Synth.coarse	low	0.7 to 0.5	70	550 to 650
synth.coarse	high	0.6	65	760
Synth.medium	low	0.7	65	700
synth.medium	high	0.5	65	760
Synth.fine	low	0.6	65	700
synth.fine	high	0.5	60	840

MATERIAL	PRODCUTION RATE	CYLINDER SPEED
cotton	low	360 to 400
cotton	medium	430 to 470
cotton	high	500 to 550
synthetic	low	300
synthetic	medium	380
synthetic	high	460

PROCESS PARAMETER IN BLOW ROOM

With all harvesting methods, however, the cotton seed, together with the fibers, always gets into the ginning plant where it is broken up into trash and seed-coat fragments. This means that ginned cotton is always contaminated with trash and dust particles and that an intensive cleaning is only possible in the spinning mill.
Nep content increases drastically with mechanical harvesting, ginning and subsequent cleaning process. The reduction of the trash content which is necessary for improving cotton grade and apperance unfortunately results in a higher nep content level.

The basic purpose of  Blow room is to supply
small fibre tufts
clean fibre tufts
homogeneously blended tufts if more than one variety of fibre is used to carding machine  without increasing  fibre rupture, fibre neps , broken seed particles and without removing more  good fibres.

The above is achieved by the following processes in the blowroom

• Pre opening
  
• pre cleaning
  
• mixing or blending
  
• fine opening
  
• dedusting
  
  
  CLEANING EFFICIENCY:
  Cleaning efficiency of the machine is the ratio of the trash removed  by the machine to that of  total trash fed to the machine, expressed as percentage
  Cleaning efficieny % =(( trash in feed % - trash in del %) x 100) / (trash in feed%)
  
  Following are the basic parameters  to be considered in Blowroom process.
  
• no of opening machines
  
• type of beater
  
• type of beating
  
• Beater speed
  
• setting between feed roller and beater
  
• production rate of individual machine
  
• production rate of the entire line
  
• thickness of the feed web
  
• density of the feed web
  
• fibre micronaire
  
• size of the flocks in the feed
  
• type of clothing  of the beater
  
• point density of clothing
  
• type of grid and grid settings
  
• air flow through the grid
  
• position of the machine in the sequence
  
• amount of trash in the material
  
• type of trash in the material
  
• temp and relative humidity in the blow room department
  

PREOPENING:
Effective preopening results in smaller tuft sizes, thus creating a large surface area for easy  and efficient removal of trash particles by the fine openers.
If MBO (Rieter) or  BOW ( Trutzschler) type of machine is used as a first machine

• the tuft size in the mixing should be as small as possible. Normally it should be less than 10 grams
  

• since this machine does not take care of long term blending, mixing should be done properly to maintain the homogenous blending
  

• the inclined lattice speed and the setting between inclined lattice and clearer roller decides the production of the machine
  

• the setting between inclined lattice and clearer roller decides the quality of the tuft
  

• if  the setting is too close, the tuft size will be small, but the neps in the cotton will be increased due to  repeated action of the  inclined lattice pins on cotton.
  

• the clearance should be decided  first to confirm the quality, then inclined lattice speed can be decided according to the   production required
  

• the setting of inclined lattice depends upon the fibre density, fibre micronaire and the tuft size fed. If smaller tuft is fed to the feeding conveyor, the fibre tufts will not be recycled many times, hence the neps will be less.
  

• if the machine is with beater, it is advisable to use only disc type beater. Saw tooth and Pinned beaters should not be used in this machine, becasue the fibre  damage at this stage will be very high and heavier trash particles will be broken in to small pieces.
  

• the beater  speed  should be around 500 to 800 rpm depending upon the rawmaterial. Coarser the fibre,  higher the speed
  

• the setting between feed roller to beater should be around 4 to 7 mm
  

• this machine is not meant to remove trash ,  hence the fibre loss should also be less
  

• trash removal in this machine will result in breaking the seeds, which is very difficult to remove
  
  • It is easier to remove the bigger trash than the smaller trash, therefore enough care should be taken to avoid breaking the trash particles
    
• this machine is  just to open the tufts into small sizes so that cleaning becomes easier in the next machines.
  

• the fibre tuft size from this  machine should be  preferably around 100 to 200 milligrams.
  

• If tuft size is  small, removing trash particles becomes easier , because of large surface area
  

•