Carding - Textile Triangle

1. Fundamentals of Carding

Carding may be defined as the reduction of the entangled mass of fibres to a filmy web by working between two closely spaced, relatively moving surfaces clothed with sharp wire points.The carding is the heart of the spinning mill and well carded is half spun demonstrate the immense significance of carding for the final result of the spinning operation. The importance of carding is still greater where new spinning systems are concerned.

2. Objects of Carding

1)Opening to individual fibres– The blow room only opens with material to flocks whereas the card opens it to the stage of individual fibres. This enables the elimination of impurities & good performance of the other operation.
2)Elimination of impurities and dust– Elimination of foreign material occurs mainly in the region of the taker in (Licker in). In addition to free dust, which can be directly sucked away as in the B/R, the card also removes a large proportion of the micro-particles. The card is good dust removing M/C.
3)Removing of neps– The card reduces the no. of neps from the B/R.Actually, neps are not eliminated at the card, they are mostly opened out. An improvement in disentangling of neps is obtained by: closer spacing between the clothing, sharper clothing, Optimal speeds of the licker-in; low doffer speeds lower throughput.
4)Elimination of short fibres– Short fibres can be only be eliminated if they are passed into the clothing. Elimination of short fibres in the card must be viewed in proportion, actually very small, less than 1% short fibres.
5)Fibre blending– The card is the only m/c to process individual fibres. In the formation of the web & with repeated rotation of the fibres on the main cylinder, intimate fibre with fibre mixing is achieved.
6)Fibre orientation– It is often attributed to the effect of parallelizing. The card can be given the task of creating partial longitudinal orientation of the fibres.
7)Sliver formation– To deposit the fibre material,to transport it & process it further, an appropriate product must be formed.So, carding is called the heart of spinning.

3. Carding Action (Point to Point Action)

If two closed surfaces have opposite wire direction & their speed direction or relative motion is also opposite,then the action between two surfaces is known as carding action.

It is occurred between flat & cylinder
Here wire direction is opposite
Speed direction is opposite.
If the two surfaces move in the same direction at different speed.
There always should be point against point direction result of carding action.

Result of carding action:

Maximum individualization of fibres is achieved in this region by apposite spikes.
Neps,short fibres,dirt & dust are removed
The difference of surface speed cylinder & flat is more

So,carding action is maximum occured.

4. Stripping action (Point to back action)

When two surfaces have same wire direction & their speed direction or relative motion is also same then action between two surfaces is called stripping action.

It is occurred between Licker-in & cylinder
Same wire direction
Same speed direction
There always should be against back action.

Result of stripping-Trash,neps are transferred from cylinder to Taker -in & offer to stripper by stripping action.

5. Doffing Action

When two close surfaces wire points are inclined in opposite direction & their speed direction is same,then action between two surfaces is called doffing action.

Doffing action is occurred between cylinder and doffer
Wire direction is opposite but speed direction is same.
It is special type of carding
Sliver formation is done by this action.

6. Combing Action

These actions take place between feed roller & Licker -in , here pin direction is same.

7. Revolving Flat Carding Machine

The various parts of carding m/c are shown in figure.The direction of revolving is indicated by the arrow sign.The lap is placed upon a slowly revolving lap roller & the sheet of cotton passes over the smooth surface of the feed plate & on between the curve portion of this plate & feed plate.

The slow revolution of this roller brings the cotton in to the contact with saw teeth of quickly revolving Licker-in. There are two mote knives under the licker-in which remove the dust from the cotton. There are several metal grid bars under the Licker-in by which the dust & impurities are gathered in licker-in under casing. The cotton receives a very effective cleaning at this point & the loosened fibres are carried round to the cylinder from licker-in. There is flexible or metallic card clothing in the surface of cylinder. The surface speed of cylinder is double to licker-in. The flocks themselves are carried along with the main cylinder and carry them forwards to the flats which surrounding almost one third of the cylinder & covered also with similar teeth. Their movement is extremely slow and in the same direction as the cylinder.Due to cylinders high speed and flats smooth speed, there is action of point against point that means carding occurred. As a result fibre becomes straight and parallel to each other.After carding operation has been completed,the carded cotton is now transferred from cylinder to doffer.After carding the fibres do not forms a transportable intermediate product.Here an additional cylinder(doffer) is required for this purpose .The offer combines the fibre in to a web because of its substantially lower peripheral speed relative to the main cylinder.Here also doffing action is doneThe stripping roller draws the web from the doffer.Then its passed through the template & calender roller.Here sliver becomes compressed to some extent,and then coiler deposits it in cans.Under the cylinder a cylinder undercasing is placed.The working rollers cylinder & flats are provided with clothing which becomes worn during fibre processing & these parts must be reground at regular intervals.

Card Setting

1. Introduction

2. Licker-In

Specification–

Diameter-9 inch
Speed-800 to 1500 rpm
Wire point direction-Anticlockwise
Circumference speed-50 km per hour
Draft -1000
At 1000 rpm,600000 beating points
Surface speed 1000 inch per min

Objects–

To unwind the lap continuous feed with uncontrolled stretching
To eliminate the impurities
To transfer the fibres as evenly as possible
To perform the primary cleaning & opening of cotton fibre
50% opening of entire carding machine is achieved here

3. Cylinder

Specification–

Diameter-50 inch
Speed-250 to 600 rpm
Wire point direction-Anti clock wise
Surface speed-2000 inch per min

Objects– 1) Back plate

To hold the fibres
To prevent the development of undesirable air current

2) Top feather edge sheet

It controls the weight and thickness of flat strips

3) Cylinder stripping zone

This door is used to strip the wire point of cylinder

4) Bottom sheet

To hold the fibre
To prevent the development of undesirable air current

5) Cylinder undercasing

Remove dust
To maintain constant air flow

4. Flat

Specification

No. of flats-100 to 120
Wire point direction-Clockwise
Surface speed-2 to 7 inch/min

Object–

To open the flocks to individual fibres
Eliminate of remaining impurities
To eliminate some short fibres
To remove dust
To detangle neps
High degree of longitudinal orientation of fibres

5. Doffer

Objects–

Transferring of fibres from the main cylinder on to the doffer
Stripping the fibre web from the doffer
Gathering the fibre web in to a twistless strand(sliver)
Condensing or calendering the sliiver
Depositing the sliver in to the sliver can

The doffing operation– The cylinder is followed by a roller called as doffer.The diameter of doffer is 24 to 27 inch and it rotates at a speed of 20 to 60 rpm.The surface speed of the cylinder is about 20 to 25 times more than the surface of the doffer.On average a fibre rotates 3 to 5 times around the cylinder before it is transferred to the doffer.The spacing between the cylinder and doffer clothing is reduced to only 3/1000 inch as compared to a standard stripping gauge of 7/1000 inch.

6. Card Setting

In the card setting distance between subsequent part is called card setting.Setting of different parts are of very fine gauge,which are expressed in terms of 1/1000 inch i.e. in Thio.Factors which are considered for optimum card setting–

Type of feed material(Cotton,synthetic etc)
Staple length of the material
Fibre fineness
The amount of trash to be removed
The hank of lap feed
The expected waste percentage
Type of card clothing
Hank of delivered sliver
Production rate
Mechanical condition of machine

1. Major setting points of carding with their effect

Lap guide to feed roller:
Settings::3/4 inch-1 inch
Effects:It controls the selvedge of web.Higher distance makes bad selvedge.
2)Feed roller to licker-in:
Setting::9-12 thio
Effect:For higher staple,heavy lap,setting will be wider.Excessive impurities in lap,setting will be closer
3)Mote knife to licker-in:
Setting::

Bottom-12 to 15 Thio (Closer setting for heavy dust)
Top-10 Thio (Wider setting for less impurities)

Effects:The setting would be sufficiently close to remove heavy impurities on the licker-in surface.If the sitting is too wide the mote knives operate inefficiently.
4)Licker-in to cylinder:
Setting:7 Thio
Effect:The object of this setting is to transfer the fibres to the cylinder & enable the licker-in to present clean teeth to the lap fringe.
5)Back plate to cylinder:
Setting:

Bottom-12 Thio
Top-10 Thio

Effect:It influences the air current .Wider setting,high air current,which makes cloudy web
6)Flat to cylinder:
Setting:10 Thio
Effect:Normal and heavy production ensure this setting.For light sliver close setting,tends to produce cleaner web where and exclusive wide settings result in insufficient removal of neps & a poor appearance in web.
7)Doffer to cylinder:
Setting:5 Thio
Effect:The object of this setting is to take all good cotton from cylinder to doffer.A wider setting may be many fibres go round the cylinder unecessarily more times & weaken by the time they are transferred to doffer & a cloudy web will result.These closer settings will damage each other & leading hook may result.
8)Licker-in to Licker-in undercasing:
Setting: 5/16 inch
Effect:If the setting is too wide,a loss of fibre may occur.Close setting increases the fibre extraction with the waste.
9)Cylinder to cylinder undercasing:
Setting:

Back-12 Thio
Middle-32 Thio
Front-64 Thio

Effect:These settings influence air currents & production of fly& too wide setting causes loss of good fibre.All settings are done by leaf gauge.

Determine the draft between taker in and cylinder, Cylinder and doffer and draft between feed roller and doffer-
The process of reducing weight per unit length is called drafting.

Mechanical Draft=Surface speed of delivery roller(Faster)/Surface speed of feed roller(Slower)

Where surface speed = Circumference*RPM
= π d*RPMRPM
= Dia of driver*RPM of driver / Dia of driven

Actual draft = Delivered count/Feed count And

Actual draft = Mechanical draft*100/(100-waste%)

Card Clothing

1. Introduction

In carding machine,different parts (i.e.Licker-in, cylinder,Doffer & flats) are covered with different types of wire which are known as card clothing.To cover the surface of licker-in, cylinder,doffer & flats of carding machine with the help of a number of unlimited fine,closely spaced & specially bented wire is called as card clothing.The wire points are inserted on the machine surface by means of a base material or foundation.Base material may be of textile fabric or may be of some other material which is very hard and stiff.

2. Types of Clothing

Card clothing is divided in to three groups:-

Flexible clothing
Semi-rigid clothing
Metallic clothing

1. Flexible Card Clothing

These have hooks of round or oval wire set in to elastic,multiply cloth backing.Each hook is bent to a U-Shape & is formed with a knee that flexes under bending load & return to its original position when the load is removed.Flexible clothing is used in cylinder,flats & doffer. In short staple spinning mills this clothing now found only in the stripping roller.

Advantages:

Higher point density ,so better carding action.
Fibre damage is less due to flexible wire point
Only the damaged part of the clothing is needed to be prepared
Exerts desirable force on cotton causing good carding
Less expensive
Finer yarn count can be prepared

Disadvantages:

Requires textile fabric or rubber as foundation material
The wires can be loosened
Production less due to stripping
Neps regular grinding
Wire & foundation material may get damaged
Fibre becomes loose for grinding action
Any carding action can not be chosen.

2. Semi-Rigid Clothing

Here flat or round wires with sharp points are set in backing which are less elastic than those of the flexible clothing.These backing are multiple ply structures,with more plies than the backing of flexible clothing,comprising both cloth & plastic layer.Flat wires are not formed with a knee but round wires may have one.The wires can not bend & are so deeply set in layers of cloth & possible foamed material that they are practically immovable.The wire does not need sharpening.When subjected to bending loads,they are therefore much less capable of yielding than flexible clothing.They also found only in the flats for wood and long staple fibre.

Advantage:

No need of frequent sharpening
No need of stripping as well as there is no knee & no dirt & dust is stored.

3. Metallic Clothing

These are continuous ,self supporting flat wire structure in which teeth is cut at the smallest spacing by process resembling a punching operation .They do not need any base material or foundation.The wire has no knee.Metal surface of m/c acts as metallic foundation.If the teeth are relatively largely used for example as in licker-in.Then the clothing is referred to as saw tooth clothing.Now a days the licker-in,main cylinder & doffer are without exception clothed with metallic clothing.The application of metallic card clothing on to spinning carding machine has no limits & is used in the production of low,medium and high quality yarns.

Advantage:

Does not require separate foundation material.The metal surface of the m/c works as foundation material
As teeth and foundation material are both metallic ,there no possibility of the fibre loose.
Can choose any carding angle
Saved 3% good fibre

Disadvantage:

Carding action is not better due to less point density
Fibre damage is mere as the wire points are metallic
Difficult to repair in the mill when a portion of it is worn out
Not suitable to prepare finer count

3. Card Stripping

During carding operation, fibres and impurities become embedded in the teeth & wires of the several carding organs which reduce carding carding power as well as effectiveness of the carding m/c subsequently yarn quality.The process of removing adhering fibres & impurities is known as stripping or card stripping.When the direction of two moving surface wire are bent to the same direction & they are moving to the opposite direction or in the same direction at different speed,then stripping takes place there,In a word ,stripping is the point to point action of the wire.

Objects:

To clean all the fillets of the carding organs
For getting higher qualities of sliver,it is necessary to clean the carding organs regularly
For high qualities cotton,it is necessary to clean doffer cylinder trice in a day

Types of stripping:

Hand stripping
Roller striping
Continuous roller striping
Vaccum stripping

4. Grinding

Grinding is the operation by which good working condition of the wire points of all organs in the carding m/c is maintained i.e. the process of sharpening the wire points of different organs of carding.

Types:

Flexible wire
Metallic wire

Objects:

To increase sharpness of wire points
To keep equal height of wire
To get regular carding action & uniform sliver

5. Heal & Toe arrangement

The top half of the cylinder is surrounded by a series of flats.The flats are also covered with wire teeth,the point of which oppose & are set close to the wire on the cylinder.The setting between flats & cylinder is arranged that there is a wider setting at the back or trailing edge on which the cotton first reaches for being carded & closer setting at the leading edge where the cotton leaves the flat.This arrangement is generally termed as Heal & Toe arrangement.

Important:The object of this type of arrangement is to effect a gradual opening & carding of the fibres at each flat. Carding faults:Faults which apparently effects the sliver quality are-

1) Sliver variation-The main cause of sliver variation are

Irregular feed
Uneven feed
Damaged or eccentric feed roller
Bend side shaft

2)Cloudy web–

Overloading of wires
Damaged taker-in wires
Excessive production
Feed plate set too far from licker-in
Licker-in undercasing set too far from licker-in
Wide setting between cylinder and flat

3)High nep count–

Incorrect setting
Dull or damages flats
Excessive cylinder loading
Too high a relative humidity

4)Higher cylinder loading–

Doffer set too far from cylinder
Dirty cylinder wire
Local damage on cylinder wire

5)Loss in yarn strength–

Crush roller pressure too high
Excessive licker-in speed
In correct type of licker-in wire
Insufficient flat strip.

6. Cleaning efficiency of carding

C.E.%=(Trash in lap-Trash in sliver)*100/Trash in lap

7. Nep Removal efficiency

N.R.E%=(Neps/gm of feed material-Neps/gm of delivered material)*100/Neps per gm of feed material

8. Carding power

Carding power = Rotary speed of cylinder/Surface speed of flats
or = Beating points per unit time/Fibres fed in unit time

Periodic Mass Variation in Card Sliver

The numerical values such as U% or CV% are not influenced by the periodic variations. A spectrogram is used to measure the periodic or nearly periodic mass variations in a sliver, roving and yarn by analyzing the frequencies at which faults occur electronically.

C.V.%=1.25U%The irregularity U% is proportional to the intensity of the mass variations around the mean value. The U% is independent of the evaluating time or tested material length with homogeneously distributed mass variation. The larger deviations from the mean value are much more intensively taken into consideration in the calculation of the coefficient of variation C.V. %. C.V. % has received more recognition in the modern statistics than the irregularity value U%. The coefficient of variation C.V.% can be determined extremely accurately by electronic means.CV%= ϭ/µ*100 ,ϭ=S.D ,µ=Mean valueU%=Ʃ(X-µ)/n*100

The spectrogram (or spectrograph) is a graphical representation specifically designed for identification and analysis of the periodic faults. It is a representation of the mass variations in the frequency domain. In other words, a spectrogram shows how many times a mass variation repeats itself in a tested length of yarn.The wavelength of a spectrogram directly indicates the distance over which the periodic fault repeats. Frequency and wavelength are related as follows

Frequencty( ʄ)=Speed(v)/Wavelength(ʎ )

In a spectrogram, the X-axis represents the wavelengths and Y-axis represents the amplitude of the faults .A spectrogram starts at 1.1 cm if the testing speed is 25 to 200 m/min. It starts at 2.0cm if the testing speed is 400 m/min and it starts at 4 cm if the speed is 800 m/min. For spun material the maximum wavelength range is 1.28 km.The spectrogram consists of shaded and non-shaded areas. If a periodic fault passes through the measuring head for a minimum of 25 times, then it is considered as significant which is displayed by shaded area. When a fault repeats for about 6 to 25 times within the tests length of the material, then it is considered as unessential which is displayed by non-shaded area. Faults which occur less than 6 times will not appear in the spectrogram.Wavelength range covered by an evenness tester depends on the test speed and the evaluation time. With staple fiber yarns it covers a wavelength range 2 cm to 1280m and with filament yarns a range of 2 cm to 2560m.

Peaks:A chimney type fault, consisting of one or more ‘peaks’ or ‘chimneys’, is normally due to a mechanical fault such as eccentric roller/gear, improper meshing, missing gear teeth, missing teeth in the timing belts, damaged bearings, etc.If the height of the peak (P) above the basic spectrogram at any wavelength equals or oversteps by 50% of the height of the basic spectrum at that wavelength i.e. P≥B/2, then it can be considered to be sufficiently serious fault.Drafting waves are responsible for periodic faults. Drafting waves caused by factors such as improper draft zone settings, improper top roller pressure, too many short fibers in the material, etc. These produce chimney type fault/spectrogram.Mechanical fault such as eccentric roller/gear, oval shape roller, improper meshing, missing gear teeth, missing teeth in the timing belts, damaged bearings, defective apron, etc. are responsible for periodic faults. These mechanical faults produce chimney type fault/spectrogram.

Normal Diagram:The Normal Diagram represents a graphical plot of the basic mass variations of the textile material over its length. The reference length for the mass values is the basic measured length of 1cm.The diagram provides additional information on the mass variations which cannot be obtained with other forms of representation – either numerical or graphical. The following are some of the information which can be usefully applied for process control.With the help of diagrams of different cut lengths, the following information can be obtained:

Checking of the functioning of auto leveler fitted draw frames.

Checking of count variation (with cut length 100m).

Setting of the sensitivity of the count channel in the latest generation Yarn Clearers.

Thin, Thick, and Neps measured in Electronic capacitance testers.

Thin places : -50% that is the mass per unit length (cross section) at the thin place is 50% or less of yarns mean value (> 4 mm length)
Thick places : + 50% if the counter is actuated, the mass per unit length (cross section) at the thick place is 150% or more of yarns mean value (> 4 mm length)
Neps : +200% the thick place based on 1 mm length, is 300% of the yarn mean value or more.

Limiting irregularity::The limiting irregularity is also expressed as a CV value,denoted as CV_lim here.

Limiting irregularity of an ideal yarn without fibre variability(Synthetic staple):

CV_lim(%)=100/√n

Limiting irregularity of an ideal yarn without fibre variability(Cotton fibre):

CV_lim(%) =106/√n

For wool fibre , CV_lim=112/√n
CV_lim(Blend)=√(CV_{1 lim}*T₁)²+(CV_{2 lim}*T₂)²+………..+(CV_{n lim}*T_n)²/T_b(Count of blend)

Index of irregularity::
I=CV_eff/CV_lim,Where, I=Index of irregularity
CV_eff=Effective (Actual irregularity)
CV_lim=Limiting irregularity

Card Autoleveller

1. Introduction

In the spinning mill, the card is the effective start of the process, since the first intermediate product, the sliver, is produced here. A relatively high degree of evenness is required in this product. For various reasons, the card cannot always operate absolutely evenly, for example, owing to uneven material feed. Spinning mills are therefore forced to use auto leveling equipment under highly varying circumstances. Different principles for auto leveling can be selected depending upon the quality requirements and the operating conditions in the individual mill.

Irregularity actually can be compensated-

in the material supply system;
at the feed;
at the delivery

2. Classification of Card Autoleveller

1. Short Term Auto Leveling

Short-term leveling systems, regulating lengths of product from 10 – 12 cm (rarely used in carding).If this is used, it calls for a drafting arrangement before coiling.In the open-loop control system illustrated in figure, a measuring point (2) is provided upstream from this drafting arrangement to sense the volume of the incoming sliver and transmit corresponding pulse signals to an electronic control unit. The control signal generated by this unit is passed to a regulating device that can be of various design, and which adapts the speed of the delivery drafting rollers to the measured sliver volume. If the measuring point is located downstream from the drafting arrangement, or if the delivery roller pair itself provides the measuring point, then the system is operating on the closed-loop control principle. If the open-loop principle is used in a short-term auto leveler, short lengths can certainly be made even, but it is not always possible to hold the average sliver count constant. On the other hand, closed-loop control is not suited for regulating short-wave variation because of the dead time inherent in the system. Finally, the drive to the delivery can present problems, since in this system the delivery speed must be continually varied, and in very small ranges. There are two possible applications for assemblies of this type, namely in processing comber noil and where card sliver is fed directly to the rotor spinning machine.

2. Medium Term Auto Leveling

Medium-term leveling systems, for lengths above about 3 m.In former Zellweger equipment a medium-term auto leveler was provided as an addition to the long-term auto leveler. An optical measuring device () detects relative variations in the cross-section of the fiber layer on the main cylinder over the whole width of the cylinder. The measuring device is built into the protective cover above the doffer. The device measures reflection of infrared light from the fibers.After comparison with the set value, a difference signal is generated and passed to an electronic regulating unit. This operates via a regulating drive to adjust the in feed speed of the card so that the depth of the fiber layer on the main cylinder is held constant.

3. Long term Auto Leveling

Long term leveling for lengths above about 20 m (maintaining count). In addition, regulating can be performed by open-loop or closed-loop control systems .This is the most commonly used principle of card auto leveling and serves to keep the sliver count constant. Measuring is performed by a sensor in the delivery (at the delivery roller). The pulses derived in this way are processed electronically so that the speed of the in feed roller can be adapted to the delivered sliver weight via mechanical or electronic regulating devices.Long-term auto leveling is an integral part of modern cards, and in any case used in production of carded yarns and in the rotor spinning mill.