cotton spinning lecture notes for students (07 mart 2011)

COTTON

SPINNING

CHAPTER I

COTTON

4 parts: cuticle; primary wall; secondary wall of concentric cellulose layers; lumen

Fibrillar structure

Collapsed and twisted longitudinal appearance

Fibres of different degrees of maturity

• Cotton is a soft fibre that grows around the

seeds of the cotton plant (Gossypium spp.),

a shrub native to the Indian subcontinent and

the tropical and subtropical regions of Africa

and the Americas. The fibre is most often

spun into thread and used to make a soft,

breathable textile, which is the most widely

used natural-fibre cloth in clothing today. The

English name derives from the Arabic word

al qutun, meaning "cotton fibre". (The

Spanish word algodón has the same

etymology.) Africa and South America are

large providers of cotton.

• Cotton fibre, once it has been processed to

remove seeds and traces of wax, protein,

etc., consists of nearly pure cellulose, a

natural polymer. Cotton production is very

efficient, in the sense that ten percent or

less of the weight is lost in subsequent

processing to convert the raw cotton bolls

(seed cases) into pure fibre. The cellulose is

arranged in a way that gives cotton fibres a

high degree of strength, durability, and

absorbency.

• Each fibre is made up of twenty to thirty

layers of cellulose coiled in a neat series of

natural springs. When the cotton boll is

opened, the fibres dry into flat, twisted,

ribbon-like shapes and become kinked

together and interlocked. This interlocked

form is ideal for spinning into a fine yarn.

USES

• Cotton is used to make a number of textile products. These include terrycloth, used to make highly absorbent bath towels and robes; denim, used to make blue jeans; chambray, popularly used in the manufacture of blue work shirts (from which we get the term "blue-collar"); and corduroy, seersucker, and cotton twill. Socks, underwear, and most T-shirts are made from cotton. Bed sheets are often made from cotton. Cotton is also used to make yarn used in crochet and knitting. Fabric can also be made from recycled or recovered cotton that would otherwise be thrown away during the spinning, weaving or cutting process. While many fabrics are made completely of cotton, some materials blend cotton with other fibers, including rayon and synthetic fibers such as polyester.

• In addition to the textile industry, cotton is used in fishnets, coffee filters, tents and in bookbinding. The first Chinese paper was made of cotton fiber, as is the modern US dollar bill and federal stationery. Fire hoses were once made of cotton.

• The cottonseed which remains after the cotton is ginned is used to produce cottonseed oil, which after refining can be consumed by humans like any other vegetable oil. The cottonseed meal that is left is generally fed to livestock. In the past, cotton seeds were used as an abortifacient, that is, a folk remedy to provoke abortion

• Cotton linters are fine, silky fibres which adhere to the seeds of the cotton plant after ginning. These curly fibers are typically less than 1/8in, 3mm long. The term may also apply to the longer textile fibre staple lint as well as the short fuzzy fibres from some upland species. Linters are traditionally used in the manufacture of paper and as a raw material in the manufacture of cellulose.

• Shiny cotton is a processed version of the fibre that can be made into cloth resembling satin for shirts and suits. However, its hydrophobic property of not easily taking up water makes it unfit for the purpose of bath and dish towels (although examples of these made from shiny cotton are seen.)

CHAPTER II

~FIBRE

PROPERTIES~

2.1. FIBRE FINENESS

2.2. FIBRE LENGTH

2.3. FIBRE MATURITY

2.4. FIBRE STRENGTH

2.5. ELONGATION

2.6. FIBRE STIFFNESS

2.7. FIBRE CLEANNESS

2.8. COLOUR

2.1. FIBRE FINENESS

• The number of fibres present in yarn

cross-section in a given thickness

represents fineness. In order to be able to

spin there should be at least 30 fibres in

yarn cross-section.

Fineness influences:

• Spinning limit

• Yarn strength

• Yarn evenness

• Yarn fullness

• Drape of the fabric product

• Luster

• Handle

• Productivity

• Cotton fineness is expressed in micronaire

value (mg/inch). It represents the average

value of the total fibre fineness. Number of

fibres in the cross-section and the different

properties of fibres can be seen by this

value.

dtex = µ x 0,394

• Fineness by airflow is affected by the maturity

as well. So, maturity must be known before.

They should be evaluated together. Micronaire

value of cotton fibres are classified as followed:

Micronaire value Fineness

Up to 3.1µ very fine

3.1 - 3.9 fine

4 - 4.9 medium

5 - 5.9 slightly coarse

Above 6 coarse

• As the number of fibres in the yarn cross

section increases, strength and irregularity

improve. By looking at the µ value, we have

the idea about spinnability of the fibre. Before

processing the fibres, the fineness must be

known.

•Spinning limit for the carded cotton rotor yarn relative to the degree of maturity of the cotton

2.2. FIBRE LENGTH

• After fibre fineness, length is the most important property of a fibre. In general, a longer average fibre length is to be preferred because it confers a number of advantages. Firstly, longer fibres are easier to process. Secondly, more even yarns can be produced from them because there are less fibre ends in a given length of yarn. Thirdly, a higher strength yarn can be produced from them for the same level of twist. Alternatively a yarn of the same strength can be produced but with a lower level pf twist, thus giving a softer yarn.

Cotton staple diagram

Mean Length • In the case of natural fibres the definition of

mean length isn’t as straightforward as it might at first seen. This is because natural fibres besides varying in length also vary in diameter at the same time. If the fibres all had the same cross-section then there would be no difficulty in calculating the mean fibre length. However, if the fibres have different diameters then the thicker fibres will have a greater mass so that there is a case for taking mass into count when calculating mean length.

• There are in fact three possible ways of

deriving the mean length:

1. Mean length based on number of fibres

(unbiased mean length)

2. Mean length based on fibre cross-section

(cross-section biased mean length)

3. Mean length based on fibre mass ( mass-

biased mean length)

Fibrograph

• Fibrograph is an automated method of

measuring the fibre length of cotton

sample. It uses an optical method of

measuring the density along the length of

a tuft or parallel fibres.

• The first part of the measuring process is the preparation of a suitable sample. This can be done either by hand or with a fibrosampler. The fibrosampler has a rotating brush which withdraws cotton fibres from a perforated drum and deposits them on a comb. The outcome is that the fibres are placed n the comb in such a way that they are caught at random points along their length to form a beard. The beard is scanned photoelectrically by the fibrograph from the base to the tip. The intensity of light that passes through the beard at a given position is used as a measure of the number of fibres that extend to hat distance from the comb. The sample density is then plotted against the distance from the comb.

• Fibrograph values are used to prepare the recipe

and ratch settings. For instance:

Recipe 40% Bergama cotton and 60%

Menemen cotton mixture)

• This method makes the assumption that a fibre is

caught on the comb in proportion to its length as

compared with the total length of all fibres in the

sample and that the point where it is caught is at

random along its length. The span lengths are

given percentages of fibres are usually measured;

the 2.5% span length is considered to correlate

with the classer’s staple length.

• Uniformity index is another parameter used

for evaluating the cotton fibre fineness. From

50% span length and the 2.5% span length a

uniformity index can be calculated.

• U.I. = (50% S.L / 2,5% S.L) x 100

Uniformity index Span length

%2, 5 spun length is used instead of effective length.

(%66, 7 shows average length) Effective length

Shows us short fibres

• Cotton fibres having a uniformity index less than 40% can not be used in yarn production. Because in that case the differences between long and short fibres in the batch will be so high this will affect the spinnability.

• If short fibre content is high, the loss of fibre in the production will be higher; waste in the production will be higher. Accordingly, the cost of yarn production will be higher.

• In ideal drafting, when fibres are released by trailing end, the next one should catch the leading end simultaneously. If they don’t, they start collecting. There’ll be deposition. These groups create irregularity in the yarn.

Movement direction

Trailing end Leading end

• Fibre length is essential since longer fibres

can produce finer yarns. So, spinning limit is

related to length.

Ring Spinning Length is at 1st

place.

Open-end Spinning Length can go to

2nd place but fineness is 1st.

• Yarn strength is dependent on length. Better

doublings will be done with longer fibres.

Handling

• Nowadays, the touch of the material is important. Customer demands are increasing. Finer yarns are produced if longer cotton fibres are used.

• Fineness Bending Rigidity

Stiffness

• Reflectance of light from the surface of fibres will be affected by fineness.

Hairiness

• Pilling is related to hairiness. Hairiness has to be decreased. If breakages increase, should decrease the production. Less production is better than having spotted yarn. End breaks are related to length.

• When there are equal lengths of fibres, that give more volume to yarn. In manmade fibres, the aim is to produce a diagram similar to cotton. In most cases, stretch-breaking method is used in production of manmade fibres. They are broken between two cylinders. Fibre length diagram is more like cotton.

• When the lengths are similar to each other, it is easier to retch settings.

Influences of Fibre Length

• Spinning limit

• Yarn strength

• Yarn evenness

• Yarn fullness

• Drape of the fabric product

• Luster of product

• Handle of product

• Productivity

2.3. FIBRE MATURITY

• Fineness is explained by the secondary wall of fibre, how it’s grown. If there is 50 – 80 of fibre in cross - section, it is mature. Immature fibres are:

1. Less fibre strength less yarn strength.

2. During production, main problem is nepiness of the yarn, (the fibres are in knotted state.) If maturity is lower, neps formation will be higher. Neps is formed and eliminated in carding machines. Neps cause problems in production and yarn properties.

3. High proportion of short fibres. In order to clean fibres, fore is exerted. If they are immature, the fore will affect them more. Short fibres will increase. (Less strength)

4. Dye uptake: Shade of the colour will be affected, if there are dead fibres, or maturity degree of them is different, they will take dye differently. There’ll be shading.

If cotton yarns are mixed in different times (from last yarn etc.), the yarns will be made of different fibres, there’ll be differences between fibres. They are all mature but their maturity degrees are different. Stripes will be seen in the fabric. Once this problem occurs, it can not be solved.

• During knitting stripes occurred. Yarn may

be redyed but;

a . it’s a cost

b . a darker dye must be used, every dying

process will cause loses on fibres

c . some properties will be changed, quality goes

down, and we obtain 2nd quality with higher cost.

5. Processing difficulties. If maturity is low, there’ll be

problems in carding. Web control is difficult. The

uniformity of web will be affected. Carding will be

difficult.

• Dead fibres cause:

* Nepiness

* Loss of yarn strength

* Varying dye ability

* High proportion of short fibres

* Processing difficulties

• Cotton maturity “R” can be calculated

from:

2.4. FIBRE STRENGTH

• The strength of fibre to be processed should be at least 6cN/tex.

• If fibre is broken, its length decreases and this affects its properties. By using fibre, which has double strength, doesn't mean a yarn, which has double strength. For instance, there is a fibre of 8 cN/tex. When it is doubled, it will be 16cN/tex. Yarn strength doesn't double, because, fibre strength is reflected to yarn strength directly. It is 35-40% reflected.

• When a piece of yarn is taken and it breaks, it is observed that just some fibres at breaking point are broken not all of them, most fibres are separated.

• Friction coefficient, surface characteristics are important factors on fibre strength.

• Strength of Polyester= 40-50cN/tex

Cotton = 15-40cN/tex

Wool <Cotton

• In order to contribute yarn strength polyester is used. For example, if cotton is mixed with polyester, yarn strength increases.

• Cotton strength, Pressley Index (Bundle strength) is used. But it can’t be used for manmade fibres since the correlation between single fibre strength and bundle strength is very low.

PI = breaking load / weight

=Lbs/mg

93 < excellent

87 – 92 very strong

81 – 86 strong

75 – 80 medium

70 – 74 fair

< 70 weak

2.5. ELONGATION

• Elongation is the increase in length of the

specimen from its starting length

expressed in units of length. The distance

that a material will extend under a given

force is proportional to its original length;

therefore elongation is usually quoted as

strain or percentage extension. The

elongation at the maximum force is the

figure most often quoted.

• Elastomer fibres will cause problems as overlapping around cylinders but fibres should be extensive. If load is applied, fibre resists it but with no damage it turns to back position, without any breakages. This property is important for process, endues and elongation.

• Elastic region = turn back to its original position

• Plastic region = some residual extensions occur

• Young modulus = the slope of the curve gives information about elongation.

• Elongation of cotton is 6 –10%.

2.6. FIBRE STIFFNESS

• Fibre stiffness has an important role on rolling$ revolving and twisting.

• It affects handle and softness. Soft fabrics can’t be produced from harsher yarn (if chemicals aren’t used).

Stiffness= fibre length/diameter

(If it’s round fibre)

• Stiffness: Fibre yarn fabric

• If diameter is increased, flexural rigidity increases. For example, if diameter is doubled, flexural rigidity increases more than double.

Finer fibres stiffness

• In microfibres (with fineness less than 1 denier), although they are softer, they can have neps problems during the production.

• It is impossible to bound fibres into the yarn if the fibres are too stiff. However, if they aren’t stiff enough, they don't return to original shape after a force is applied, don't have longitudinal resistance and in most cases this leads to formation of neps.

2.7. FIBRE CLEANNESS

Examples of trash fragments and neps founded in baled cotton (Courtesy of Trützschler

GmbH & Co. KG.)

• Because of the reason that cotton has natural wax, which makes production easier, it doesn't have to be washed. But it has some impurities as;

– Mineral materials (husk, seed, stem, leaf)

– Vegetable materials (earth, sand, ore dust, coil dust)

– Metal fragments

– Cloth fragments

– Packing materials

• Trash content:

1.2 > very clean

1 – 2 % clean

2 – 4 % medium

4 – 7% dirty

7% < very dirty

Trash extraction in the whole

spinning process (Standard

values with modern machinery)

(Cleanness of Turkish cotton is

around 4 %.)

• The foreign materials can cause problems during production as;

– Metal parts can cause fire or damage card clothings

– Cloth fragments and packing material can lead to foreign fibres in yarn

– Vegetable material causes drafting disturbances, yarn breakages, filling up card clothings, contaminated yarn

Neps/Dust

• Neps are small entanglements and knots

of fibres. In case of neps problems

maturity should be checked, because

there is a relationship with maturity index

and neps. Neps are also depending on the

fibre fineness because fine fibres have

less stiff.

• Dust is very important in spinning. It can cause

many problems as:

– Collection of dust can be seen on machine, this

decreases quality

– Human health is affected

– Dust creates stress in human

– Some people may have allergy to dust

– It can cause lung illnesses

– Environmental problems will occur

– Machines will start to run faulty.

– Endbreaks will increase

– Yarn irregularity will increase

• Dust makes a thin cover on machine. This

causes yarn breakages, but more important

is yarn production has less quality. To

avoid dust collection is impossible, so the

best is to eliminate dust during preparatory

stages and to use air conditioning system

efficiently, that is why preparatory stages

are essential in spinning.

COTTON SPINNING

Ring Spinning Open-end Spinning

Carded Combed

BASIC OPERATIONS USED IN

NATURAL FIBRE SPINNING

1. Opening Blowroom machines

Card

OE spinning machines

2. Cleaning Cleaning machines

Card

Comber

Draw frame

Rotor spinning machines

3. Blending Blowroom machines

Card

Drawframe

4. Aligning Card

Comber

Drawframe

Roving frame

Final spinning

machine

5. Uniting Card

Comber

OE spinning machine

6. Equalising Card

Draw frame

OE spinning machine

7. Attenuating Card

Draw frame

Roving frame

Final spinning machine

8. Imparting strength Final spinning machine

9. Winding Roving frame

Final spinning machine

CHAPTER III

~BLOWROOM~

3.1. OPENING & CLEANING

3.2. MIXING & BLENDING

3.3. OPERATION ZONES

3.4. MACHINERY

3.1. OPENING AND CLEANING

• When fibres are opened they are cleaned at the same time. Opening – cleaning action takes fibres cleaner but it makes fibres damaged also.

• In blowroom, there is 5 – 10% production cost. This not a high proportion but it is important in cotton.

Cleaning loss of good fibre

• If the short fibre content increases 10%,

the blowroom needs one machine more. In

blowroom there is an opening – cleaning –

mixing line. So, the number of machines is

depending on the cleaning. Number of the

machines isn’t fixed; it is changed

according to the material that is used.

Opening points: fibres can be opened in nip

points or in grip position.

An opening point

Material isn’t free

Material is sent free.

• Number of the opening points is between

2 and 5 in blowroom. If staple manmade

fibres are used, they are just put in

blowroom in order to be separated and

prepared for the next step. They just need

cleaning action. However, if it is cotton,

which is dirty, it needs more cleaning, like

5 opening points.

• Opening points are chosen due to type of fibre and content of impurities. Blowroom eliminates ~50% of impurities in cotton. Increasing the waste elimination doesn’t mean exactly the separation of impurities since also the good fibres will be eliminated. After a certain level, if the opening points are increased, cleanness of fibres will not change but they will be damaged. Waste content coming out of machinery is important, it should be checked by cleaning efficiency:

CE = (AT-AF)*100/AT

where AT = total waste and AF = good fibres eliminated

• In blowroom, cotton is tuft or flocks and the separation it is done more in the first machinery.

• Whereas formerly cleaning effect of a machine could be only estimated , today it can be established fairly exactly, reproducibly and so as to enable comparisons. For this purpose the cleaning index is defined as:

CT = (DF-DD)*100/DF %

where DF = the dirt content of the feed material

DD = the dirt content of the delivered material and

T= total

Opening of cotton bales (Courtesy of Marzoli.)

• Opening machinery should

– extract the material evenly from each bale

– open the material gently

– open up the smallest flocks

– form flock of equal size

– process as much as bales in a single charge

– easy to use

– blend material right at the start

– put together of a fibre blend from several

components

Dust Removing

• The dust is removed mostly by air suction.

Air suction or pipes are also used to carry

the material from one machine to other.

Heavy particle separator

(Courtesy of Trützschler

GmbH Co & KG.)

General Factors Influencing Opening

and Cleaning • type and speed of opening device

• degree of penetration

• type of feed

• spacing of the feed from the opening device

• type of grip

• area of the gird surface

• grid settings

• air flow through the grid

• condition of pre-opening

• thickness of feed web

• material throughout

• position of the machine in the line

Condenser drum for removal of dust particles Heavy particle separator (Courtesy of Trützschler GmbH Co & KG

3.2. MIXING AND BLENDING

• In blowroom, both natural and synthetic fibres can be mixed. Normally, different bales are mixed. It is essential to use more bales to get almost same proportion at the end. Blending the waste is an essential step for spinning. If the proportion of the waste level is high, problems as changing the character of the bulk will occur. The level should be controlled and kept at low level.

• At most 5% in carded ring spinning, 2.5%

in combed ring spinning, the waste can be

mixed to material in blowroom. In rotor

spinning, this percentage can be at most

20%, and the highest count can be made

is Ne35-40. The reason in rotor spinning,

waste can be used more is that the system

is less sensitive to the length of the fibre.

3.3. OPERATION ZONES

1. Opening

2. Coarse cleaning

3. Blending

4. Fine cleaning

5. Intensive cleaning or opening

6. Card feeding

3.4. MACHINERY

1. Bale openers: Today automatic bale openers

are used. Normally, 60 bales can be fed

together in blowroom. The fibres that are fed

should be same amount in each time. This is

important to gain a homogeneous mixture.

2. Cleaning machines

3. Mixing machines

4. Dust removal equipment or machines

5. Recycling machines

Automatic bale opener:

Diagram of automatic bale opener (Courtesy of Rieter Machine Works Ltd.)

1. control unit

2. fibre bales

3. working head with tooth discs

4. swivel tower

5. air duct for material transport

Operation of tooth discs (Courtesy of Trützschler GmbH.)

• Two sides of lay down (Courtesy of Trützschler GmbH.)

• The tunnel on the top moves forward and backward. It can rotate 180˚, so it can place the bales on both side of machinery. Placement of bales may be different. It depends on the length of the tunnel. This length is the limit for number of bales. At every cycle of the tunnel, the pipe of the tunnel should be adjusted. When the bales are placed, not all of them are at the same height. At the first cycle they are adjusted to same level. The amount of material, collected from bales will be constant. Sometimes foreign fibres and cover of the bales mix inside the material. These don’t cause problem in process but may cause problems in dying.

• The production rate is high. Depending on tunnel width, it may be up to 1300kg/h. But in general an effective one has 750-800 kg/h.

Ex: 800kg/h x 24 = 20 tons a day

20 x 300(work day) = 600 tons per year

• In such a production, one bale opener is enough. (But it may be risky if breaks down.) Number of the bale opener determines how much production will be made. Automatic bale opener also determines the production of the company because stopping the machine also is a cost.

Figure 2:

• in this type of machine, fibres are manually placed in the lattice. It brings material to the second lattice. It helps to mix the fibres inside the bale (the fibres are converted inside). The fibres come to number 9 in the figure, some fibres pass to other side, some fall back so the mixture is made inside. This type of machine is not used anymore too much for natural fibres; in general, it is used for man-made fibres.

Axi-flow:

Twin beater with projections

(Courtesy of Trützschler

GmbH.)

• Here, there is free fibre opening point, two

opening cylinders. Fibres are fed parallel to

the cylinder axis. As cylinders rotate, fibres

are caught and their direction is changed.

And there is suction at the end. Opening

efficiency is obtained by changing the

direction of fibres.

• This method cleans efficiently and gives

less damage to fibres.

• Under cylinders, there are grid bars to separate particles. Centrifugal force helps them to go away. The shape of the grid bars is triangular. The difference between grid bars can be changed in the axial direction. By changing this distance the count of waste that is separated can be changed which means cleaning efficiency can be changed.

Distance Cleaning efficiency

• Fibres coming from axi-flow are distributed into chambers. Depending on their coming duration, they make layers inside. A sandwich mixing is made here. It helps homogeneity.

Cleanomat:

Knife edge and suction slot for fine particle removal (Courtesy of Trützschler GmbH &

Co. KG.)

Figure 7: Step cleaner:

(Courtesy of Pneumatic Conveyors Ltd.)

(Courtesy of Rolando-Beilla)

( left to right) needle beater followed by coarse,

medium, and fine saw-tooth beaters (Courtesy of

Trützschler GmbH & Co. KG.)

• It is a composed machine. Trütscher had

developed it. There are six rollers rotate in

the same direction. Material is fed by the

air. Then they caught by the first cylinder

and at last goes from the sixth cylinder.

Conventional grid bars are placed under

cylinders. These eliminate the impurities.

• Material entering the machine has the highest impurity. The content of the impurities are not the same on all cylinders. Also the adjustments of the grid bars are not the same for all cylinders. These adjustments changed according to the cylinders’ placements.

• Cleaning action takes place in the air. The fibres damage isles than axi-flow.

CHAPTER IV

~CARDING~

4.1. TASKS OF CARD

4.2. FEED OF THE MATERIAL

4.3. CARDING

4.4. CONTROL SYSTEMS IN

CARDING

MACHINES

Schematic of tandem carding system (Courtesy of Crosrol UK Ltd.)

• There is not a machine combination in carding

room. There is one type of machine. Fibres come

to carding machine in small tuft, and after this

machine sliver is obtained.

• In wool and cotton spinning carding machines are

different because of the length of fibres that are

used. But the machines haven’t been changed

for many years.

4.1. TASKS OF CARD • Opening to individual fibres: there is more chance to

clean fibres

• Elimination of impurities: esp. in the first part of the machine 80-90% of impurities are removed. 95% of them are removed at the end of this process. The trash content will be at most 3% in sliver.

• Elimination of dust : it is obtained by the contract of fibres and machine elements (fibre to fibre, fibre to machine).

• Elimination of short fibres: it is done by flats. The carding action takes place between flat and cylinder. Fibres in between are carded by the pins of flats. Short fibres are caught by the flat; longer ones stay on the cylinder. These short fibres are removed from the surface of flat when they go out of carding area. Flat waste is around 8%. It depends on the type of cotton that is used.

• Disentangling of neps: in blowroom neps are created (like in ginning) nut in carding machine neps aren’t separated but are opened. The sharpness of the cylinders is important in this point. If they are sharp, neps are opened efficiently. If the number of neps increases, wires have to be checked. If it is necessary, they can be changed or renewed. For an improvement in disentangling of neps: – closer spacing between the clothings

– sharper clothings

– optimal speed of taker-in

– low doffer speed

– low throughput

• Fibre blending: fibre blending is mainly performed in order to – give the required characteristic to the final product

– compensate for variations in the raw material

– hold down raw material cost

– achieve effects by varying colour and so on during processing

• Fibre orientating:

• Giving sliver formation: at the end of carding machine, material comes out as sliver. It is the beginning of the yarn. This is the place where the real form is given. The sliver count is generally 3-6 ktex. This enables to obtain real sliver quality that helps in yarn production.

4.2. FEED OF THE MATERIAL

1. Lap feeding

• Advantages of lap feeding are: – maintenance of constant lap thickness in easier

– whole installation is more flexible

– blend can be allocated to individual machines

• Disadvantages of lap feeding are: – greater manual effort in transport and lap change

– an additional source of faults

– more clean waste

– an additional burden on the taker-in

2. Flock feeding

a. one-piece chute without an operating system

b. two-piece chute with an operating system

* Degree of deterioration can be controlled by the adjustment of: – thickness of the butt

– degree of openness of the raw material in the feed stock

– degree of orientation of fibres in the feed stock

– aggressiveness of the clothings

– distance between device

– rotational velocity of the taker-in

– material throughput

4.3. CARDING

• Neps occurs during the opening, so the fibres are stretched when they come to carding zone. Fibres are stretched by the carding force. Carding force depends on two parameters:

a. angles of wires

b. friction coefficient between wire and fibre

• Length of the fibre Friction coefficient

Cohesion

Representation of fibre mass distribution within a revolving-flats card

• There is a continuous interaction between flat and cylinder. Real carding effect is given between first and fourth flats at the beginning of the carding zone. Half of the flats are really in contact with cylinder and make carding. Most of the neps are being opened here. Separation of neps is related to distance between cylinder and flat, and the sharpness of wires. If the number of neps is increased, wires need grinding. The first grinding may be needed after 80-150000kg. And flats should be checked after 120-150000kg.

Upper and lower fiber transfer zones

• In order to obtain the same carding effect

while increasing the productivity:

– more points per unit area

– higher roller and cylinder speed

– more carding surface or carding positions

• increase in the number of rollers

• fitting of additional carding

– under the taker-in

– between the taker-in and the flats

– between the flats and the doffer

• Cylinder-doffer transfer of fibres (Courtesy of WIRA)

Carding plates and multiple taker-ins (Courtesy of a. Rieter Machine Woerks, b. Trützschler

GmbH & Co. KG)

• Carding segments:

– improve dirt and dust elimination

– improve entangling of neps

– create possibility of speed and production

increase

– preserve clothings

– create a possibility of using finer clothings

– decrease fibre damage

– keeps clothings clean

Clothings

• Card clothing selection criteria:

– type and design of card

– rotational speed of cylinder

– production rate

– material throughput

– raw material type

– fibre characteristics

– overall quality requirements

– price

– service offered by the supplier

• Clothings are classified in to three

groups:

1. flexible clothings: only in the flats. The

wires are fixed into an elastic backing

2. semi-rigid clothings: flats

3. metallic clothings:

• Most important operating parameters of the

clothings are:

– point density and speed of the cylinder

– base width

– height of the clothing

– tooth pitch

– carding angle

– tooth point

4.4. CONTROL SYSTEMS IN

CARDING MACHINES

Figure K-3: Autoleveller: at the end of the blowroom, there is lap. Its count has to be checked if it is suitable to feed to carding machine but nowadays this system isn’t used. Lap is directly fed to the machine. In order to overcome lap mass variation, autolevellers are used. Autolevellers regulates material in short, long or middle term.

Trumpet + feed roller = long term

Drawbox = short term

• There are two control systems:

1. Closed loop system: material is measured

and checked at the exit because there is no

chance after.

2. Open loop system: material is checked

after measurement point.

• Closed-loop and open-loop systems

Figure K-4:

• The control is on the cylinder. There is

photocell here. It checks the reflectance.

Depending on the amount of fibre,

reflecting changes and it affects rate of

feed roller.

CHAPTER V

~COMBING~

5.1. TASKS OF COMBING

5.2. EFFECTS OF COMBING

5.3. COMBING PROCESS

5.4. PARAMETRES INFLUENCIG

COMBING

Fibre configuration in relation to

detachment

• It is selected to process the material

whether in comb or drawframe. In comb

the quality of the material is increased.

The fibres are removed that aren’t wanted

to be present in the yarn. This removal

affects the medium or fine count to be

produced. Combing machine is used for

the production of medium, medium-fine,

and fine yarns.

5.1. TASKS OF COMBING

• eliminate the pre-determined quantity of

short fibre

• eliminate the remaining impurities

• eliminate the large proportion of neps in

the fibres

• form a sliver having maximum possible

evenness

5.2. EFFECTS OF COMBING

• Yarn evenness: will be improved

• Strength: is reacted to the fibre length

• Cleanness: is increased Combing removes foreign particles, dust, and trash present in material. Trash content of sliver fed to machine is low, but they are much smaller in size. Total percentage of weight is small but they cause spots on the yarn.

• Smoothness:

• Visual appearance:

• Less twist: Combing process gives opportunity to decrease twist factor, so the production is improved by combing.

• Decrease short fibres: that cause hairiness are eliminated.

• Eliminate short fibres

• Eliminate further neps

• Clean impurities

• Hairiness: decreases

• Staple length: increases

• Raw material: decreases

• Cost: increases

• These improvements obtained with

additional expenditure on:

– machine

– personnel

– floor space

– loss of raw material

5.3. COMBING PROCESS 1. Feed cylinder feed the fibres coming from the web.

2. Upper nipper lowers down on lower nipper and nips the already fed fibres coming from web.

3. Rotary comber rotates; carry away short fibres, neps and impurities are decreased.

4. Nippers open. Detaching rollers return back and feed back a put of sliver which has already been combed.

5. The projecting fibres are placed on the previous combed sliver.

6. Detaching rollers start to move forward and they pull the fibre bundle forward being hold by feeding cylinder.

7. Top combers lower and comb the pieced bundle.

8. The brush removes the impurities, etc. away from the rotating cylinder.

• After carding the sliver has hooks. To change the direction of hooks other machines can be used. This action is called preparatory stage. There two different ways of these stages:

1. Lap/Web doubling process: 1. Card

2. Sliver lap machine

3. Ribbon lap machine

4. Comber

5. Drawframe

2. Sliver doubling process: 1. Card

2. Drawframe

3. Doubling machine

4. Comber

5. Drawframe

Sliver lap machine

• Totally, 24 slivers are fed (12 each side)

they are drafted in an arrangement and then

drafted slivers are squeezed by the

calendar cylinder. Main task is draw and

double 24 slivers and form a web.

Ribbon lap machine

• The concept is the same with sliver lap

machine but 6 slivers are fed in this one.

5.4. PARAMETRES INFLUENCING

COMBING

• raw material:

– fibre type

– fibre length

– fibre stiffness

– uniformity of fibre length

– moisture content

• material preparation:

– parallelisation of fibres: if the parallelisation is maximum to carry the sheet will be impossible and the strength will decrease. Also in this case neps and impurities can’t be hold inside during the detaching stage. So they can pass into the combed sheet. If there isn’t enough parallelisation, the actual fibre length can’t be used because fibres are seemed shorter and can’t be separated even if they are long.

– sheet thickness: thin sheet can be combed effectively but it decrease the productivity. If sheet is thick, it can’t be combed properly and neps are held in.

– sheet evenness

– orientation of hooks

CHAPTER VI

~DRAWFRAMES~

6.1. TASKS OF DRAWFAME

6.2. PROCESS IN DRAWFRAME

6.3. BLENDING IN DRAWFRAME

6.1 TASKS OF DRAWFRAME

• Equalizing

• Parallelization

• Blending

• Dust removal

6.2 PROCESS IN DRAWFRAME

• The material form is not changed in drawframes.

The sliver is fed and gotten. The evenness is

changed. The doubling is made. The sliver

evenness directly affects the yarn irregularity.

Secondly, the production speed in drawframe is

increased which may cause poor quality of sliver

as well.

• Important point here is parallelization. The hook

fibres from the cord are straightened in

drawframe.

Fibre parallelism

in the yarn

structure

• Very short fibres cause irregularities in

drafted material or yarn. They can also

cause yarn breakages, therefore they

should be eliminated. Moreover, fineness,

strength and extension of fibre are also

important parameters in drafting stage.

• Draft given at this zone is the relative speeds of cylinders.

If 5 drafts are given, that means the sliver is stretched 5

times. If there are 5 fibres at the beginning, only one of

them is gotten at the end.

+

+

+

+

ZONE

2 nip points

(5 fibres 1 fibre)

• Single-zone roller drafting

• For single drafting zone, two pairs of rollers are

used. This is why the name of this kind of

drafting called roller drafting. As seen in the

figure, drafting zone is between the nip lines of

the rollers along the horizontal axis. The

material is fed from roller A with V1 surface

speed, and goes away from roller B with V2

surface speed. By the difference between the

speeds of the pairs of rollers draft is given:

In this formula, the orientation, the shape, and the length variations between the fibres are neglected.

Representation of perfect drafting

• If fibre has a trailing hook, it touches the other fibres when it’s caught by a cylinder. So, it has a possibility to be opened by the help of other fibres.

• Maybe, leading hooks can be opened by the help of the acceleration. The probability of straightening of a fibre with the leading hook is only dependent on one fibre but, if it has a trailing hook, it’s dependent on other 4 fibres. (for 5 drafts)

• In carding machine, %50 of fibres has trailing hooks. In order to straighten both sides of the hooks, the material must be put through drawframe twice. 2 passages are applied in the spinning shed but configuration may be different.

• There’ll be some fibres still left with hooks at the exit of drawframe. So, the feed of the material to the ring-spinning machine, the direction of the fibres is important. It is tried to feed the material with trailing hooks. This is seen on the yarn properties.

Example: With a roving and trailing hooks the spinning machine is fed and a yarn is processed. If the direction of the material is changed, there will be still hooky fibres.

-Evenness

-Elongation improve by a true feed direction.

-Strength

• The machine sequences and passages are

adjusted according to that idea. (to feed

with trailing hook)

Parallelization is made by draft. It is

not done in carding but done in drawframe.

Evenness: The slivers are doubled

by 6 or 8 in drawframe.