Spinning preparatory process

Date: 14-12-2007
SPINNING PREPARATORY PROCESSES
“The processes that are performed in a textile spinning mill on the raw material before the manufacturing of yarn are called spinning preparatory processes.”

Major Objectives of Spinning Preparatory Processes
1) Cleaning: to prepare the raw material such that it has less proportion of impurites
2) Mixing: to prepare the marerial such that it has uniform properties throughout the material
3) Blending: to mix the two or more different type of fibers

Types of Impurities
In cotton and other natural fibers, there are two types of impurities;
Natural impurities (oils, protien, etc.)
Added impurities (dust, hair, rags, etc.)
(Added impurities become a part of fibers due to the carelessness of pickers.)

As cotton of different areas is different in characteristics because of the difference in the climate. This difference in climate and the variation in the use of fertilizers, seed, etc. creat variations in cotton parameters. The cotton parameters are;
i) Staple length
ii) Micronair
iii) Fineness
iv) Presly strength
v) Trash percentage
vi) Color grade
vii) Short fibers
viii) Maturity ratio
ix) Uniformity ratio

Cotton varies from area to area, region to region, zone to zone, country to country and lot to lot; due to this variation we have to well mix the cotton before the preparation of lap (for the card feeding).

Objective of Mixing
ü The basic objective of mixing is to reduce variations in parameters of cotton of different areas
ü To create homogeneity throughout the material

If there is not good mixing, we could not get yarn of uniform quality.

Date: 18-12-2007
Q: How to get good mixing?
Ans: If we want to prepare good mixing, then we should mix more number of lots of different areas (or of different properties). If we mix more number of lots then there will be more homogeneity in properties of the out put material throughout the year.

Q: What is an issuing plane?
Ans: Consider a spinning mill consumes 140 bales daily; the bales are issued from the godown to the blow room. The issuing plane is that how much bales should be issued from different lots such that there will be a homogeneous mixing of cotton at blow room.

Q: What are the criteria that how much bales are to be picked from different lots in godown?
Ans: The criteria depend upon the following factors:
i) Fineness
ii) Cotton grade
iii) Color grade
iv) Cotton growing area/zone
These factors decide that how much bales are to be taken from different lots.

Q: How will you decide about the cotton grade?
Ans: The grades are decided at the time of arrival of cotton. The grades are given to cotton as; A, B, C, +B, etc. The grade standards are not universal and vary from organization to organization. When cotton is arrived, samples are taken, tests are done in the laboratory and a grading chart is constructed. A sample grading chart is shown;
Mic
Points
Grade
4.4 – 4.9
+90 (90 & above)
A
4.91 – 5.1
+82 (82-89)
+B
5.11 – 5.4
+72 (72-81)
B
5.41 – 5.6
+60 (60-71)
C

Staple Length
Points
Grade
1.09 – 1.1
+85 (85 & above)
A
1.08 – 1.089
+80 (80-84)
+B
1.07 – 1.079
+70 (70-79)
B
1.06 – 1.069
+60 (60-69)
C
Suppose 4000 bales are received, A à 1100, B à 700
+B à 1900, C à 300
At the time of issue planning, the grade +B will have greater proportion than others and vice versa.
Date: 01-01-2008
Q: Which cotton parameter is the most important at the time of issue planning?
Ans: The importance of cotton parameters depends upon the end product, e.g. if we want to prepare hosiery yarn, the mixing plane/ issue plane should be on the basis of fineness of cotton but other factors (color, zone, grade) are also considered.
Issuing of cotton or cotton mixing plane is the same thing.
Good mixing will result in good quality and good production.

Ø If micronair is 5.0; à (thick, coarse)
Ø If micronair is 4.5; à (thin, fine)

Question: If we have cotton of different micronair, then what should be the method of issue planning?

Method-I:
The available cotton is of 5 different mic (i.e. 5.4, 5.3, 5.2, 5.1 & 5.0)
Plane for January 2008
Date
Mic
1-1-08
5.4
2-1-08
5.4
3-1-08
5.4
4-1-08
5.3
5-1-08
5.3
6-1-08
5.3
7-1-08
5.2
.
.

10-1-08
5.2
.
.

20-1-08
5.1
.
.

31-1-08
5.0
In this method at the time of issuing, coarse fibers are issued and consumed first and the fine fibers. It is because that the treatment of coarse fibers is harsh and that of fine fibers is soft (harsh means more speeds and close settings of machine and vice versa is known as loose settings).
With the above plane, the yarn made in early days of the month will be better than the last days of the month.

Drawbacks
This system/method has some drawbacks.
i) If a customer has bought 5,000 bags for fabric manufacturing at 02-01-2008 while you were using 5.4mic. In 20 days he consumed 4,990 bags. To continue the same variety he needs more bags of the same quality but at 26-01-2008 you are using 5.0mic. Now the remaining 10 bags of the customer are useless.
ii) At 03-01-2008 you are using the roving of 5.4mic. for yarn making. Due to some reason 4 roving could not continue for 12 day. After 12 days there were roving of 5.2mic. Now those 4 roving of 5.4mic will create problems with roving of 5.2mic.


Method-II:
The available cotton is of 15 different mic (i.e. 5.4 – 4.0)
Suppose the consumption of spinning mill is 60 bales daily. Then the issue planning to get homogeneous cotton will be;
First day of a month
Mic
Lot No.
No. of bales
5.4
7
4
5.3
11
4
5.2
9
4
5.1
32
4
5.0
71
4
4.9
98
4
4.8
9
4
4.7
6
4
4.6
15
4
4.5
17
4
4.4
61
4
4.3
77
4
4.2
91
4
4.1
57
4
4.0
42
4
Total

60

This plane is followed throughout the year. In this method, the production remains uniform through out the year. 4.65 is the average mic which is maintained throughout the year.
In ideal condition all lots have equal number of bales. Each lot has 100 bales.

Q: What is the proper way of sampling the raw material for testing in the lab?
Ans: If a lot has 100 bales, then take four samples such that the first sample comes from first 25 bales, second sample comes from the next 25 bales and so on.
1 – 25
1st sample
26 – 50
2nd sample
51 – 75
3rd sample
76 – 100
4th sample

Q: How theoretical value of Average mic varies with the practical value/actual value?
Ans: There are many reasons of this variation, but the most important are;
i) Negligence at the time of issue (you said to bring 10 bales from lot No. 12 but the worker brought from lot No. 32 or you said to bring 12 bales but the worker brought 5 bales, etc.)
ii) Negligence at the time of sampling and testing


Assignment No. 1:
For a spinning mill prepare an issuing plane. The available cotton is;
Mic
Total No.
of Bales
5.0
4000
4.9
3000
4.8
4500
4.7
2500
4.6
6000
4.5
5000
4.4
3000
4.3
3500
4.2
2500
4.1
6500

è Each mic has lots 25 – 65 inclusive.

Solution:




Date: 04-01-2008
Q: Why opening and cleaning is required?
Ans: After ginning we receive cotton with impurities (like broken seed, leaves, husk and dust), so it is basic requirement of spinning that before preparation of yarn the raw material should be well cleaned. As we know that the ginning industry is away from the spinning industry and also ginned cotton is in loose form, thus not manageable for the whole year. That is why cotton is pressed into bales and lots are formed each of almost 17,000 kg containing 100 bales.
When we convert this bulky material in bales, the cotton is well pressed so in spinning mills opening is required because without opening extraction of impurities is not possible. Actually the main objective of opening is to prepare the cotton for removal of impurities, so in blow room which is the first department of a spinning mill these objectives are achieved. We can say that the cleaning is the result of opening. When the cotton is well opened and we pass it through cleaning beaters and condensers, the impurities are extracted.


BLOW ROOM
Objectives of Blow Room
i) Opening
ii) Cleaning
iii) Mixing
iv) Blending
v) Regularization
vi) Lap formation

Actions of Blow Room
1) Opposing spike action
2) Air current action
3) Beating action
4) Regulating action

1) Opposing Spike Action
In this action the cotton is passed through a machine in which spikes of evener lattice (inclined lattice) oppose the spikes of evener roller, so with the result of this opposing spikes the tuft size reduces and the material become open. In this action inclined lattice and evener roller are revolving in opposite direction and with particular speed (i.e. 60 m/min & 250 rpm respectively).
If we increase the speed of evener lattice then the out put material will have more tuft size and vice versa, so with trails best speed can be traced. If we increase evener roller speed then there will more opening because this roller is providing a resistance to the material flow. How ever when you are doing any adjustment of the machine, effect of adjustment should be checked and observed on the followings;
i) Fiber growth
ii) Waste percentage of the machine
iii) Cleaning efficiency of machine
iv) Tuft size

The degree of opening can be increased by closing the settings of evener lattice to the evener roller. However with the result of more close settings, there is a risk of fiber damaging and fire. This setting must be as close as possible for safety and good fiber growth.

To achieve good results spike’s sharpness should be maintained and mixing of spikes must be avoided. However, there is no hard and fast rule for the settings and speed of the evener roller. A comparison of closer and wider settings is given below;
More close settings
i) More cleaning efficiency of the machine
ii) More recirculation of the material which will result more neps
iii) More chances of fire
iv) Less production
v) Less fiber growth

Wider settings
i) More production
ii) Bigger tuft size
iii) Less neps generation

Date: 09-01-2008
2) Air Current Action
To achieve basic objectives of blow room, second action is the air current action. Actually the objective of blow room is to open the cotton at different stages gradually, so the movement of cotton from one machine to another and even within the machine is usually by means of air current action. These air currents not only shift the cotton from one machine to another but also it assists to separate the trash, short fibers and dust form the lint. As with air current we can achieve opening and cleaning so it is included in the list of blow room actions.

The movement of air current must be under controlled conditions, so many fans are used in the blow room as per requirement of the machine and capacity of air current. The actual air current settings are done as per demand.
How ever some basic and essential conditions for air current are as follows;
i) Fan
ii) Air tight trunking
iii) Predetermined places for entry of air
iv) Means of air separation from cotton
v) Suitable exit for air
Machine to machine the cotton travels through a pipe and traveling speed depends upon the speed of suction fan. If speed of the fan is more, there will more speed of cotton in the pipe. If with the same speed of fan we increase the diameter of the pipe, the speed of cotton in the pipe will reduce.
When ever cotton or other fibrous material is carried from one place to the other, then there must be a system/method of separation of air from the cotton. For this purpose cage method is very effective and in this method, other than air, short fibers, trash and dust are also separated by small holes in the cage.

Cage is a revolving perforated cylinder on which cotton passes and air is sucked by a suction fan. In this way we can achieve our objectives of blow room by air current action, so if we want maximum extraction of impurities during the air separation then cage speed should be more. When the speed of cage is more, then cotton sheet on the cage will be thinner and there are more chances of removal of maximum impurities. Similarly if suction of air is more, then there will be more extraction of impurities, short fibers and dust, etc.
Date: 11-01-2008
3) Beating Action
Beating action is very important and effective because with the help of this action heavy impurities are extracted. Beaters are of different types and can be divided into three groups;
i) Those striking the cotton when it is held by spikes
ii) Those striking the cotton when it is held by air current
iii) Those striking the cotton when it is held by a pair of feed roller



i) Beating of Cotton Held By Spikes
If there is a beater striking the cotton when it is held by spikes then it will in the first category of beating action. Example of this is bale breaker, step cleaner and axiflow.

ii) Beating of Cotton Held By Air Current
The Creighton opener is a good example of second category because here cotton is held by air current. Air and cotton enter in the bottom chamber of the beater and go out after opening.


iii)
Beating of Cotton Held By Rollers
This is very important and effective method to open and clean the cotton. In this method the cotton mass is held by a pair of rollers and at that moment beater strike the cotton. The distance between the striking point and griping point should be more than the length of the fibers otherwise fiber will damage. Grid bars under the beater is provided and waste is extracted through the bars.
When there will be more gaps between the bars, there will be more waste percentage. However one must be sure that good fibers should not be in the waste because only extraction of impurities and short fibers is required. By increasing the speed of beaters, there will be more cleaning efficiency. However fiber growth should also be checked to control the fiber damage.


Assignment No. 2:
Show the diagrams of half beating point and full beating point; at least three diagrams are required.

Date: 11-01-2008
4) Regulatory Action
After achieving main objectives of blow room, the material is converted into sheet form to feed the card. As material is shifted form machine to machine with the help of air currents, so there is a lot of weight variation in the material. Hence before its conversion into sheet, the material is regularized by a mechanism known as piano motion.
At scutcher, after hoper feeder, material comes on lattice and pass through pedals and a pedal roller. During the passage of material under the pedal roller, the pedal will be depressed. The amount of depression varies according to the thickness of the material going through.

With the result of depressing the pedals, the levers at the end will be depressed and ultimately the speed of cone drum will be changed by shifting of the belt/strap. This change of speed depends upon the amount of variation that is thick and thin portion of the material.
If half of the pedals are depressed due to thick portion of the material and the other half are going upward then due to thin portion, there will be no change in the speed of cone drum and ultimately in speed of feed roller.
Thus if there is weight variation in the material, it is controlled by this system, i.e. by changing the speed of feed roller through cone drum.
Lap variation is measured by weighing and by calculating C.V percentage.
J Say the standard weight of a lap is 20 kg and + 200 grams is the tolerance limit.
J To measure the variation, C.V %age is required. To calculate C.V %age, take the lap, cut it into pieces, find the weight of each pieces, find the average weight and the calculate C.V %age using the following relation.
C.V %age = (S.D/mean) x 100

S.D = ∑ (x – x’)2
n - 1

Assignment No. 3:
Calculate the C.V %age of a lap which have average weight 450 g/yard and 45 pieces each of length one yard.
Solution:


Mean = 452.13
∑ (x-x’) = 96
S.D = ∑ (x-x’)2
n-1
S.D = 96
45-1
S.D = 96
44
S.D = 2.18
S.D = 1.48

C.V % = (S.D/mean) x 100
C.V % = (1.48/452.13) x 100
C.V % = 0.0033 x 100
C.V % = 0.33 %

Date: 20-02-2008 + 22-02-2008
Major Objectives of Blow Room:
Major objectives of blow room are:
1) Opening
2) Cleaning
3) Mixing
4) Blending
5) Formation of lap sheet

CARDING
“The conversion of tufty material into single fiber stage (filmy web) by passing it between the two wiry surfaces is called carding.”

Objectives of Carding
Main objectives of carding are:
1) Opening of flocks into single fiber stage (fiber to fiber opening)
2) Extraction of remaining heavy impurities (like motes, leaves, etc.)
3) Extraction of light weight impurities (like dust, dirt, trash, etc.)
4) Extraction of short fibers (to some extant)
5) Extraction of neps (to some extant, 100% extraction is not possible)
6) Orientation of fibers and sliver formation

Q: In raw cotton a lot of heavy and light weight impurities like motes, leaves, dust, etc. are present and these impurities are removed at blow room, why carding is required?

Ans: In blow room cotton is opened into tufts and then it is cleaned. The tuft size is gradually reduced in blow room. This cotton in tuft form is not completely cleaned. Carding is required for;
i) Fiber to fiber opening of cotton is done at carding
ii) All remaining impurities are removed at carding which are remained in cotton after blow room processes
iii) In blow room neps are generated, at carding neps are removed (100% removal of neps in not possible)
iv) Short fibers are removed at carding

Q: Which type of impurities is extracted at carding, light weight or heavy impurities?
Ans: At carding each and every type of impurities are extracted that are remained in cotton after blow room processes. (Both light weight and heavy impurities)





Q: Define short fibers and also tell that what is the source of short fibers?
Ans: “The fibers of cotton which are much smaller than the average staple length of cotton are called as short fibers.”
The source of short fibers is:
i) Poor picking
ii) Poor ginning
iii) Poor/sever opening (high speeds in blow room or close setting of B/R machines)

Q: What is fly?
Ans: The short fibers thrown off the material during cleaning of fibrous material at card machine is known as fly.

Q: What is nep? How neps are produced?
Ans: “A nep is a small knot (entanglement) of entangled fibers.” Neps are small masses even smaller than the head of a common pin, round in shape and white in colour. Neps are also called as nips or nits.
The neps are generated in blow room;
i) Due to more recirculation of material
ii) If moisture in the material is more, then more neps are generated
iii) If machine to machine distance is more, then there will be more transit (transformation) of the material due to which neps (entanglements) are generated. (More travelling of material results in more neps in blow room.)
i) Neps are generated in B/R and are removed at carding
ii) 100% extraction of neps is not possible at carding
iii) The fault caused by the presence of neps cannot be recovered

Q: Why extraction of short fibers is necessary?
Ans: The extraction of short fibers is necessary because short fibers;
i) Produce more variation in yarn
ii) Reduce the strength of yarn
iii) Create more hairiness

Q: If we want to extract heavy impurities and these are extracted at taker-in region, then what should be the conditions?
Ans: The following conditions are required;
i) Settings must be as close as possible
ii) Maximum speed differential
iii) Wire points should be sharp


Q: How carding objectives can be achieved?
Ans: The carding objectives can be achieved by following the carding principles by doing these principles as good as possible. The carding principles are;
i) Point to back action
ii) Point to point action
iii) Back to back action

Principles of Carding w.r.t Regions of the Card Machine
1) Taker-in region (Point to Back Pin Relationship)
2) Carding region (Point to Point Pin Relationship)
3) Brushing region (Back to Back Pin Relationship)

1) Taker-in Region (Point to Back Pin Relationship)
In this region first principle of carding takes place, which is point to back action. Points of one wiry surface come into contact with the back of other wiry surface. With the result of this principle, material is transferred from one surface to the other. Due to this transferring of material this principle is also known as stripping action.

For better stripping or transference the setting between these two wiry surfaces should be as close as possible. The most important point in stripping action is that the surface on which material is to be transferred must be having high speed than the surface from which material is being transferred.

The example of this principle on cotton card is between taker-in and cylinder and second example is between doffer and doffing comb. Example at woolen card is between worker and stripper roller and second example is between taker-in and swift.
Date: 29-02-2008
Motes and other heavy impurities are extracted at taker-in region. At taker-in region cotton is well opened and heavy impurities are extracted. Light impurities like neps, micro dust, etc. are not extracted at taker-in region. Thus the material is transferred to carding region.

In carding region there is a cylinder and flats, the material pass through these two wiry surfaces. The cylinder is revolving with high speed while the flats are moving very slowly.

2) Carding Region (Point to Point Pin Relationship)
In carding region, carding principle (point to point pin relationship) is applied. This is the most important principle to achieve the card objectives. Due to this principle opening of the flocks and mixing of the fibers takes place. So after carding, material is converted into single fiber stage and these fibers are well mixed. Hence with the result of this principle, impurities held in the fibers are removed. In blow room material tuft size is reduced and converted into flocks. So, we extracted almost 60% impurities in blow room and with the result of conversion on flocks in single fiber stage, remaining impurities are extracted at carding. In carding principle points of the wire of one surface come in contact with the wire points of second surface.










Efficiency of the carding region depends upon the following:
i) Better contact of the two wiry surfaces
ii) Maximum speed differential
iii) Close settings (as close as possible)



i) In carding principle points of the wire of one surface come in contact with the wire points of second surface. The better is this contact the better will be the carding action.
ii) Speed of the two wiry surfaces must have maximum speed differential, that is one surface is very slow in speed and other surface must be fast to maximum. The larger is the speed differential, the better will be the carding.
iii) The setting between the two wiry surfaces must be as close as possible. With the result of close settings the material will be well opened and thus well cleaned.

The example of carding action on woolen worsted card is between swift and workers.

Q: What impurities are extracted at carding region?
Ans: At carding region light weight impurities like neps, short fibers, micro dust, etc. are extracted.

Q: Why light weight impurities are not extracted at take-in region?
Ans: At taker-in region the tuft size of cotton material is reduced to flocks but material is not opened into single fiber stage. Thus at taker-in region light weight impurities like neps, short fibers, micro dust, etc. can not be removed because to remove these light weigt impurities, the material must be in single fiber stage.

3) Raising or Brushing Region (Back to Back Pin Relationship)
In this principle back of the wire pints of one wiry surface come in contact with the back of wire points of the second wiry surface. With the result of this principle material is raised from bottom of the points to the top of the points. To collect and wrap the raised fibers subsequently, roller is facilitated. To achieve good results or maximum raising following conditions should be fulfilled:
i) Back to back pin relationship
ii) Closeness or deep setting
iii) Maximum speed differential

The better these three conditions, the better will be raising or brushing. On cotton card normally brushing is done on revolving flats. On woolen card this principle is applied between swift and fancy roller.








MID-Term Examination
Held at Saturday 08-03-2008
Date: 23-04-2008
DRAWING
In carded sliver fibers are in different configurations and there is a lot of variation in fiber parameters. More over carded sliver has more variation, unevenness and fiber hooks. So, the machine used for parallelization, straightening, leveling, mixing and blending is called as drawing machine.
Major objectives of drawing machine are:
i) Parallelization
ii) Straightening
iii) Leveling
iv) Mixing
v) Blending

Drawing Actions
For above objectives, following drawing actions are done;
1) Doubling
2) Drafting

1) Doubling
“The process of combination of two or more slivers for purpose of mixing, blending and reduction of weight variation is called as doubling.” Normally at drawing we apply 6, 8 or 10 doubling. However, 8 doubling are more common in the industry. Slivers obtained from carding machine have more weight variation as well as variation in the fiber parameters. More number of doubling means less variation and vice versa.

Q: On what factors the No. of doubling depends?
Ans: It depends upon the following factors;
i) Grains/yard of Fed Sliver
ii) Drafting Zone Working Area
iii) Drafting Range
iv) Blending Ratio

i) Grains/yard of Fed Sliver
As slivers are passed from the specific area of drafting zone and if sliver grains/yard are more, then the capacity of drafting zone will reduce. So with the increase in carded sliver grains/yard behind the certain limit, No. of doubling will decrease. If slivers are overlapping then doubling will be effected, so No. of doubling should be adjusted by considering the card sliver weight (grains/yard).


ii) Drafting Zone Working Area
At those drawings where the working area is more, we can apply more No. of doubling. For example, at the drawing having 140 mm working area; less No. of doubling can be applied and more No. of doubling can be applied at the drawing having 180 mm working area.

iii) Drafting Range
The No. of doubling also depends upon the available drafting range. Because with the result of doubling, sliver weight is too much increased, and the required weight of drawing sliver for simplex machine is less. So if sufficient draft can not be applied then we reduce the No. of doubling.

iv) Blending Ratio
If we double the slivers of different type of fibers in a particular ratio, then it is technically called as blending. So doubling also depends upon the required blending ratio. The blending ratio is changed by increasing or decreasing the No. of doubling.
Date: 23-04-2008
2) Drafting (Main Objective = Reduction of weight/yard)
As a result of doubling, we achieve heavier material which is not required for the subsequent process. So, a stretching force is applied to reduce the weight which is known as drafting. By applying this force most of the fibers are straightened and parallelized.

Drafting Arrangement in Roller Drafting
There are so many roller drafting arrangements which include bottom rollers (steal fluted) and top rollers (rubber mounted). These may be 5/4, 4/3, 4/4 and 3/3 varying from machine to machine. The bottom rollers are positively driven through motor by gearing; where as top rollers are negatively driven only due to the surface contact with bottom rollers. On top rollers rubber cots are used which are changed after a certain period depending upon the speed of machine, material weight, grinding frequency and the material of cot.

To maintain the evenness of top roller surface, it is grinded. Grinding frequency should be decided by considering the sliver test results. When sliver test results start to show unevenness, then we grind the top rollers. As with grinding, diameter of the top rollers decreases, so after a certain time a minimum limit of diameter comes and beyond that limit these rollers cannot be used and rubber cots are replaced.

If roller system is 3/3 then there will be two zones of drafting, first zone is between back roller and middle rollers and it is called as back zone. Second zone is between middle roller and front roller and it is called as main zone. Draft applied in back zone is called as break draft and the draft applied in main zone is called as main draft.
SLIVER LAP MACHINE


Fig (a) Fig (b)
LAP FORMING
At combing machine material in lap form is fed in lap form. So, to prepare the lap following process is adopted. Carded sliver is passed through a drawing machine for better uniformity, straightening and parallelization of fibers. The sliver achieved form the drawing machine is fed to sliver lap machine and normally from 20-48 slivers can be doubled. More doubling results in better uniformity. Width of prepared lap is 10 –11.5 inches and lap weight is 15 –25 Kg.

At ribbon lap machine, suppose we are feeding 36 slivers, then these will be divided into two or three equal groups. Each group prepare a fleece of the material known as ribbon as shown in figure (b). These two or three ribbons are combined to prepare a uniform lap. So this machine is also called as ribbon lap machine.
Date: 02-05-2008
COMBING

Combing is a process of extraction of short fibers, small neps, micro-dust and micro-trash particles to achieve a yarn with more evenness and less impurities. The short fibers that are extracted during this process on combing machine are called as comber noel. Normally we can extract comber noel from 5% to 25% and this percentage depends upon required quality of yarn. By increasing noel percentage, evenness of yarn increases and vice versa. For combing, lap is required for feeding and for one machine 6 to 8 laps run simultaneously because there are 6 to 8 heads of the machine.
At those machines which have 6 heads, three slivers are doubled and at those which have 8 heads four slivers are doubled. These slivers are drafted as per requirement so we can say that combing machine or combing processes have the following objectives;
i) Doubling
ii) Drafting
iii) Noel rejection
iv) Sliver formation

COMBING MACHINE WORKING SYSTEM/ COMBING PRINCIPLES
The lap is taken from the ribbon lap machine or the sliver lap machine and placed on corrugated wooden or silver rollers behind the comb. Machine is divided into several sections called as heads, which may be 6 or 8 in number. Each head takes a lap and is complete within itself except the driving arrangement.

COMBING PRINCIPLES
The machine work as per following combing principles;
i) Feeding (material is coming for combing)
ii) Combing (combing action)
iii) Detaching (further transformation of material after combing)

i) Feeding
In this principle material enters in the feed rollers and come close to the cylinder. We can say that in this principle material is to get ready for combing but combing not started. Nippers will be close and fringe of fibers is presented to the cylinder pinned portion. The top comb is in top most position and detaching rollers are stationary.

ii) Combing
The cylinder moves forward. Nippers start to open and prepared flange of fibers is combed by the needles of cylinder. So short fibers, neps and micro-trash are extracted; the extracted material is called as comber noel.



iii) Detaching
The cylinder moves forward and top comb fully penetrate the material, so in this way combing action is completed and combed material is detached by detaching rollers.
































FINAL Examination
Held at Monday 19-05-2008