Carding is known to have a critical influence on yarn quality
and
CHAPTER 1
INTRODUCTION Carding is known to have a critical influence on
yarn quality and performance in ring frame. The two proverbs of the
experts holds true today. "The Carding is the heart of spinning
mill" and "Well carded is half Spun."
Technologically the card has the task of CLg and seperation of
immature fibres and neps along with removal of other impurities and
of producing a uniform sliver with minimum uH deviation yard.
The carding quality could be judged by
1) Transfer Efficiency %
2) Nep Removal Efficiency.
3) Fibre Arrangement In Sliver.
So here we have studied some of the aspects of carding mainly
associated with the transfer of fibre between Cylinder and
Doffer.
"Transfer Efficiency is defined as the percentage of fibre
transferred to doffer from cylinder per revolution of
cylinder."
The Transfer Efficiency of card is important from the point of
view of determining the level of loading of the cylinder. A poor
Transfer Efficiency results in excessive loading of fibres on
cylinder, which restricts the further scope of card for improving
the quality and increasing the production level. But the higher
Transfer Efficiency need not be taken as a measure of good
carding.
The cylinder load consists of two parts viz-basic load and
working load. The basic load represents the fibres, which get
absorbed into the cylinder foundation over a period of time. And
the working load represents fibre load on surface from which fibre
get transferred to the doffer. In the metallic cards fibres on the
surface constitute the cylinder load.
A high cylinder load is naturally determined to good carding.
Since it enter fares with fibre separation and individualisation in
cylinder flat region.
Transfer Efficiency of card is very sensitive to some of the
settings in card. Transfer Efficiency or Transfer Ratio is going to
change not only from machine to machine but also due to some
machine parameters, like speed, settings, card clothing etc. when
ordinary card clothing is used the Transfer Efficiency is about 5%.
Now a day with metallic wires being introduced, the Transfer
Efficiency is enhanced upto 25%. This is because the loading and
unloading characteristics of the card varies with the flexible wire
and metallic wire.
CHAPTER 2
LITERATURE REVIEW
1. Cylinder Load And Transfer Efficiency
Chattoppadhyay (l) shows that during the course of carding, a
layer of fibre accumulates on cylinder. Part of it continuously
passes on to the doffer whilst it is replenished by fresh fibres
from feed. The quantity of fibre that remains on cylinder at the
steady state operation level is termed as cylinder load. This has a
considerable influence on carding efficiency and productivity.
1.1 Transfer Efficiency:
The nature and direction of cylinder and doffer wire points and
their relative surface speeds are such that only a fraction of the
fibres on the cylinder are get transferred to the doffer during
each rev of cylinder. This fraction when expressed as percentage of
cylinder load is termed as transfer efficiency. It can be
calculated as per cut and weight method.
1.2 Cylinder Load Built Up :
As only some fibres get transferred from cylinder to doffer
during each revolution of cylinder the cylinder load will built up
initially when an empty card is first started and attains a steady
state after a few minutes of working, at this stage, the rates at
which fibres are fed to the cylinder and transferred to the doffer
are equal. The steady state of cylinder load will depends upon
other things like cylinder speed, card production rate and transfer
efficiency.
1.3 Carding Quality:
A high cylinder load is naturally determined to good carding
since it interferes with fibre separation and individualisation in
cylinder flat region. Low transfer efficiency is also undesirable,
as it not only leads to building up of higher cylinder load but
also over working of fibres since poor transfer efficiency results
in the fibres being taken round the cyl more no. of times than
necessary and it causes nep generation.
1.4 Behaviour Of A Card During Transient State :
When a carding machine is started with feed engaged, one can
notice that the sliver that comes out initially is very thin. The
linear density of the sliver gradually builds up and reaches the
steady state value. Similarly when the feed to the card is stopped
suddenly the linear density of the sliver gradually reduces till it
becomes zero. The behaviour of the card during these two transient
stages is very important and gives an interesting insight about the
carding process.
1.5 Simpson's Analysis :
Simpson(2) shows that it has been pointed out that the doffer
collecting fraction i.e. the proportion of fibre transferred to
doffer depends upon the following ratio of wire angles
i.e.
R = ( Sin (2 + Cos (2)/( Sin (1 + Cos (1)
(1 = inclination angle of cylinder wire point.
(2 = inclination angle of doffer wire point.
This ratio reaches its maximum value 1.414 when (1 =90 and
(2=45.
However, since a cylinder wire point angle of 90 would not given
a good carding action. Hence angle of 88 for cylinder and 45 for
doffer are suggested.
1.6 Parameters Affecting Cylinder Load And Transfer Efficiency
:
1.6.1 Doffer Speed:
Krylov's [3] shows keeping production rate constant, if doffer
speed is enhanced with a proportionate reduction in sliver hank the
load on cylinder decreases and Transfer Efficiency increases.
It means at the same production rate a combination of faster
doffer and lighter sliver improves carding.
1.6.2 Cylinder Speed:
Krylov's [3] experimental data shows an increase in cylinder
speed reduces load on cylinder. Baturin plotted values of transfer
coefficient (K) as a function of ratio of production rate to
cylinder surface speed (P/Vc). it may be observed from data that
transfer efficiency (K) gets affected to a substantial extent bd
reduction in ratio P/Vc. By enhancing cylinder speed, the load
cylinder reduces.
Bhaduri [4] has shown that with an increase in cylinder speed
the load on cylinder reduces with a concomitant increase in
transfer coefficient.
1.6.3 Sliver Linear Density:
Simpson and Fiori [5] the influence of liver linear density can
be studied by following two different methods.
1. Change in linear density at a constant cylinder speed and
production rate (i.e. varying constant cylinder doffer surface
speed ratio).
2. Change in linear density at a constant production rate and
varying cylinder speed (i.e. constant cylinder doffer surface speed
ratio).
In the first case, in order to keep the production rate
constant, the doffer speed needs to be adjusted according to sliver
linear density. This however changes cylinder doffer surface speed
ratio since cylinder speed remains unaltered.
In the Second Case, to keep the cylinder doffer surface speed
ratio constant, the cylinder speed is also changed in proportion to
change in doffer speed.
From above discussion it can be concluded that heavier sliver
increases loading and decreases transfer efficiency.
Simpson and Fiori [5] had also observed the load to be more for
heavier sliver (80 gr/yd) than the lighter (50 gr/yd) one
irrespective of production rate. Transfer efficiency was always
higher for lighter sliver
1.6.4 Cylinder Doffer Surface Speed Ratio:
Bhaduri [4] shows that this ratio can be changed by tow ways
i.e. by changing
1. Doffer speed keeping cylinder speed constant
2. Cylinder speed keeping doffer speed constant.
However, method (1) will also need to change the sliver linear
density, in order to keep the production rate constant. A study
conducted by Bhaduri [4] shows that the influence of this ratio
depends upon methodology adopted for its change. When the ratio is
increased by decreasing doffer speed, cylinder load increases and
transfer efficiency decreases. However if it increased by
increasing cylinder speed, loading decreases and transfer
efficiency increases.
1.6.5 Production Rate:
Through increase in doffer speed
Bhaduri [4] shows that an increase in production rate through
doffer speed results in increase in loading and as well as transfer
efficiency. It means even though transfer efficiency increases, it
does not increase proportionate to increase in production rate,
resulting cylinder load to increase. Simpson and Fiori [5] have
also reported cylinder load to increase with production rate which
was varied in the range of 15-50 lb/h. Transfer efficiency
increased with production rate only in the case of higher
micronaire (5.5) cotton. For others it shows a tendency to
decrease.
Through increase in sliver linear density
Change in production rate (from 6.1 lb/hr to 18.1 lb/hr) through
(gr/yd) increases loading and decreases Transfer Efficiency [5] as
shown.
1.6.6 Cylinder Doffer Setting:
Chattopadhyay [1] have shown using fluorescent tracer fibres
that Transfer Efficiency increases with closer setting Nerukar and
Murthy [6] also had made a similar observation. Bhaduri [4] also
has reported loading to decrease and transfer coefficient to
increase with closer setting since it increases the zone of
interaction between cylinder and doffer.
1.6.7 Effect Of Cylinder And Doffer Diameters:
Chattopadhyay [1] shows that the diameter of Cylinder and Doffer
affect two important parameters namely
1. Entrapment Power
2. Length of interacting zone.
The coefficient determining the ration of entrapment powers of
the card clothing of cylinder and doffer in relation to the angle
of inclination of front flank (K2) gets affected by the diameters
of cylinder and doffer. The higher is the coefficient the less will
be the fibre load.
If the diameter of doffer is reduced by half, the zone of
interaction is reduced by 0.7 and the coefficient of entrapment by
1.18. Hence reduction in size may increase cylinder load.
1.6.8 Wire Parameters:
Wire Point Density
Simpson [2] analysis reveals that a higher wire point density on
doffer will reduce cylinder load. A comparison of data indicate
that though cylinder load reduces with enhancement of wire point
density on doffer but the effect is less critical than wire
angle.
The influence of all the variable discussed so far has been
given in a tabulated form.
2. Mechanism Of Transfer Of Fibres In Card
The production rate of the card is considered to have a critical
influence of processing at subsequent machines a well as on yarn
quality and it is only recently that attempts to increase the
production rate of the machine without deterioration of quality
have met with some success. Developments in carding have been
considerable hampered for want of an adequate measure of carding
quality, that would give appropriate weightage to the different
actions of carding and bear a significant relationship with yam
quality and processing performance. The operation of carding can be
broadly classified into the following aspects:
1. Cleaning capacity of the card
2. Degree of fibre to fibre separation
3. Level of nep generation in card
4. Time required to get the fibres carded
5. Time during which fibre remains on the card after carding
action is over
6. Means by which only the carded fibres are taken cut while the
uncarded portion of fibre is allowed to remain in the card till the
carding is complete for that portion.
Insufficient fibre-to-fibre separation, blunt card wire which
causes rolling of fibre and improper machine settings. A low level
of neps may not always assure satisfactory degree of fibre to fibre
to fibre separation. Hence, degree of fibre-to-fibre separation has
to be considered as another aspect of carding.
Poor level of fibre-to-fibre separation produces cloudy web and
further affects the even drafting of card sliver at the subsequent
processes even upto ring frame. But a present there is no tool to
measure the degree of fibre separation achieved in carding.
The time required to get the fibres carded, and the time for
which fibres remains on the card after carding action is over
decide the potentiality of the card for high production rates
without deterioration of the quality. With increase of this time
element, loading of cotton fibres on cylinder increases, resulting
either in deterioration of carding quality or limiting any increase
in the card production rate further. Put, here also, actual time
required for carding and the time for which the fibres remain in
the card after carding cannot be measured separately.
When the production rate of carding has to be increased, three
factors should be considered:
1. Card should be able to clean the cotton at the highest
speed;
2. It should separate fibres from other in the time available;
and
3. Fibres should get transferred from cylinder to doffer
immediately after carding (fibre-to-fibre separation) is complete
and there is no undue build up of load on the cylinder.
The studies revealed that a fibre rarely gets transferred from
cylinder to doffer at the first revolution, but, in fact, goes
around the cylinder a number of times before getting transferred to
the doffer. This technique of tracing the path of an individual
fibre has given valuable information about the transfer efficiency
of a card but it has the limitation that it involves measurements
to be made on a large number of fibres to get adequately reliable
information.
Trials were conducted at BTRA pilot plant both on metallic card
and flexible clothed card at different production rates, with the
objects mentioned above, and information obtained is presented here
in this note.
The transfer efficiency of card is important from the point of
view of determining of level of reading of the cylinder. Poor
transfer efficiency results in excessive loading of fibres on
cylinder, which restricts the scope of the card for improving
quality and increasing the production level.
A greater proportion of the fibres fed goes into the foundation
of the clothing and this action continues, though more gradually,
until the foundation gets fully saturated with fibres. This
quantity of fibres is termed as termed as 'basic load'. There is
build-up of layers of fibres on the surface of the cylinder, which
arises from the very low rate of transfer of fibres between
cylinder and doffer. This is termed as 'working load'. There is no
dear line of demarcation between working load and the basic load in
the
flexible clothed card and the figures for transfer efficiency
obtained should be used for comparing experiments made under
similar conditions.
CHAPTER 3
METHOD TO CALCULATE TRANSFER EFFICIENCY
To calculate Transfer Efficiency we have to find cylinder load
of the carding machine, which we have to find Transfer Efficiency.
There are two methods to find out cylinder load and Transfer
Efficiency
i) Krylov's Method
ii)Cut Weight Method
I) Krylov's Method
a) Determination Of Cylinder Load
A card should be started and allowed to run till it attains
steady state operation condition i.e. the sliver of nominal linear
density starts coming out. The movement of flat should be stopped
followed by simultaneous stopping of feed roller and doffer by
disengaging appropriate gears. The cylinder is allowed to run
continuously. The doffer is restarted keeping drive to feed and
flat inoperative. The doffer will at first deliver a web (in the
form of a sliver), which was already on its lower half. It is then
followed by fibres stored on cylinder.
A clear cut dividing line exists between the fibres, which were
already on the lower half of doffer when it was stopped and the
fibres transferred from cylinder later on, in the form of a thick
deposition.
The sliver is detached across the thick portion and the weight
of the sliver portion delivered later is taken. The quantity of
these fibres is the cylinder load.
b) Transfer Efficiency
It is defined as the percentage of fibre transferred to doffer
from cylinder per revolution of cylinder. Mathematically
K = (q/Q0) ( 100
(1)
Where, K = Transfer Efficiency
q = Amount of Fibre transferred to doffer per revolution of
cylinder.
Q0 = Load on cylinder i.e. quantity of fibre on cylinder at
steady state.
During one revolution of cylinder the length of sliver (L)
delivered by doffer is,
L = 2 ( Rd nd / nc
(2)
where Rd = doffer diameter (inch)
nd = speed of doffer (r.p.m.)
nc = speed of cylinder (r.p.m.)
If Ne is the sliver count (English), then the weight of sliver
(q) delivered per revolution of cylinder becomes.
q = 453.6 2 ( Rdnd / 840 ( 36 Ne nc (g)
(3)
Hence K = (453.6 2( Rdnd /840 ( 36 NencQo)100
(4)
or Qo = (453.6 2( Rdnd / 840 ( 36 Ne nc K) 100
(5)
If P is production rate, (g/min), then
P = 453.6 2( Rdnd / 840 ( 36 Ne (g)
(6)
Hence K can also be expressed as
K= (P / ncQo)100
(7)
Or K= (2( Rc P / VcQo)100
(8)
The transfer efficiency can be easily calculated from either
equation (4) or (8), after experimentally determining the magnitude
of cylinder load Qo.
II) Cut Weight Method:
Allow the card to run for 15-20 min. so that cylinder load could
be built up to maximum level. The flats are to be disengaged by
removing the belt from the pulley, in the running condition of
machine stop the feed of the machine.
As the feed is stopped, but the card is running the sliver from
the delivery end continuously goes on decreasing in the weight per
unit length and at last all the cylinder load is removed from
cylinder surface collect this sliver cut into small pieces of 10cm
length and sequentially go on weighing it and record it.
Plot the graph of weight of cut sliver against the number of
readings. After plotting the graph you will get a point on the
graph from whore the weight per unit length of the sliver decreased
suddenly the point from where the weight drop suddenly is nothing
but the cylinder load in gms (Q).
Precaution
While taking reading card should run minimum 20 minutes other
wise you will get improper cylinder load.
Next thing is that the sliver should not mishandle. It is
observed that any variation could lead to false reading.
CHAPTER 4
EXPERIMENTAL DETAILS
Material:
For calculating Transfer Efficiency we select few models of
modern generation cards from Navmaharashtra Co-Op Spinning Mills
and Indira Mahila Co-Op Spinning Mills of different companies as
follows:
i) Marzoli
ii) Trumac DK740
For calculating Transfer Efficiency we have followed Cut Weight
Method
as discussed earlier.
As we have discussed in literature review there are number of
parameters affecting Transfer Efficiency. So to study machine wise
and effect of wire point density we have to keep other parameter
constant These parameters are,
i) Production Rate
ii) Cylinder Speed
iii) Doffer speed
iv) Sliver Linear Density (Hank)
Machine Parameter:
i) Marzoli C40:
Working Width - 1016mm (40")
Flats - Total Present - 104
Working
- 40
Feed roller
- 84mm
Cylinder
- 50 inch
Cans
- 24"-40"
Total draft with chute feeding- 90-25
Carding Cylinder Speed- 300-600
Taker in Speed
- 655 - 1500
Doffer Speed
- 16-65
Flat Speed
- 64-179 mm/min.
ii) LC300:
Flats - Total Present
- 112+stn
Working
- 43
Cans
- 24"-45"
Total draft with chute feeding - 80-190
Carding Cylinder Speed- 300-600
Carding Cylinder Dia
- 1280mm
Taker in Speed
- 655-1500
Doffer Speed
- Maximum 53
Doffer Dia
- 680 mm
Flat Speed
- 82 - 430 mm/min
iii) Trumac -DK-740: Inner Frame Width
-1055mm
Feed Roller Dia
-100mm
Licher in Dia
-250mm
Rotational Speed with Cotton -350,400,450
Man Made Fibres
-280,350
Doffer Dia.
-27.56"
Flats Total
-80
Working
-30
Speed - mm/min
-88-360
Travel Direction
-is apposite to the sense of
cylinder rotation
Application Of Method:
Allow the card to run for 15 - 20 min so that cylinder load
could be built up to maximum level. The flats are to be disengaged
by removing the belt from the pulley, in the running condition of
the machine, stop the feed of the machine.
The feed is stopped, but they are running, the sliver density of
from the delivery end goes on decreasing and then the flow stops.
Then the total cylinder load is removed from the cylinder surface.
Collect this sliver cut into small pieces of 10 cm length and
sequentially it is weighed and readings are noted.
The graph is plotted of weight of cut sliver against the no of
readings. After plotting the graph, we get a point on the graph
from where the weight/unit length of the sliver decreased suddenly
the point from where the weight drops suddenly is nothing but the
cylinder load in ml gms (Q)
For understanding purpose we have discussed one example.
e. g. LC300
1. 0.013 2. 0.020 3. 0.031 4. 0.050 5. 0.062 6. 0.073 7. 0.074
8. 0.088 9. 0.089 10. 0.089 11. 0.093 12. 0.102 13. 0.096 14. 0.102
15. 0.108 16. 0.118 17. 0.136 18. 0.140 19. 0.137 20. 0.146 21.
0.151 22. 0.162 23. 0.146 24. 0.152
25. 0.146 26. 0.160 27. 0.177 28. 0.184 29. 0.191
By putting this value on graph Semilog paper we get value of
cylinder =176. (Graph No. 3)
Calculation of Transfer Efficiency
Machine Parameter
Cylinder Speed
=450 rpm
Doffer Speed
=39 rpm
Doffer Dia.
=70 rpm
S. S. of Doffer
=8576.55 cm/min
Lengths deliver per
Revolution of cylinder = S.S. of Doffer in cm/min/cylinder Speed
in rpm
=8576.55 / 450
=19.05 cm
n=
n=
log q =
(q = log-1 - 0.108
= 0.7793
Now Transfer efficiency.
P = (1 - q) x 100
= ( 1- 0.77) x 100
= 22 - 01
Like this we take three readings on each card for transfer
efficiency.
Testing
Quality of silver produced on card is very important in regard
of the yarn quality. A too higher Transfer efficiency can cause
deterioration in quality of silver. So we are going to decide which
card can give the optimum Transfer Efficiency with best quality of
silver. So for this reason we have carried out testing of silver
for following.
Parameters
1. Evenness (U%)
2. Neps / gm
1. Evenness (U/o):
If Transfer Efficiency is higher, then the fibres are
transferred from cylinder to doffer a little earlier than required,
so it may have an effect on opening of fibres. This causes
variation in sliver density. So we have to test the U% of
sliver.
2. Neps:
If the Transfer Efficiency is lower, then the fibres remain on
the cylinder surface for a long time therefore rolling and rubbing
action of fibres occur. This may cause increase in generation of
neps. So we have to check neps content in c/d sliver.
CHAPTER 5
RESULT AND DISCUSSION
Table No. 1 gives us results about the Transfer Efficiency And
Cylinder
Load, which are obtained from different machines.
As we sun that the Transfer Efficiency is mainly affected by the
entrapment power of clothing. Which will be the function of
1. Wire point density and its inclination and height and life of
wire point.
2. Dia Meter of roller and
3. Rotational Speed of wire covering surface (i.e. Doffer
arch)
Table No. 2 gives us 'the wire point specification, which is
used on that machine on which we calculate the Transfer Efficiency.
Here we have found that the difference between density, angle,
which leads to variation in Transfer Efficiency. The ratio of
entrapment power of cylinder and doffer and the ratio of their
loadings becomes equal to the ratio of tooth count of the
respective card clothing. Density varies from 865 to 860 of
cylinder and 395 to 416 of doffer. Angle also varies from 30 to 55
of cylinder and 25 to 40 of doffer. The cylinder, load is reduced
with large Cylinder and small doffer tooth angles.
Depth of tooth has a strong influence on carding intensity and
Transfer Efficiency in case of cylinder clothing, lesser the height
facilitates transfer of Fibres to doffer since fibre mainly. Stays
on the surface of the wire point. Initially the height of wire
point is same. But the wire point are being used for long time and
for No. of Kg. of production. Since from that time to uptill now
how many times grinding has done that will lead in reducing the
wire height. The life of wire point that is how much production
(Kg.) they passed out that will be shown in Table No. 5.4
Table No. 5.5 shows us about quality of sliver. Quality of
sliver is differ from machine to machine so we have carry out the
Uster evenness (U%) and nep level in the sliver and find out the
quality of sliver. Here we find out that the LC-300 produce good
quality of sliver as compare to U% and Nep
level in sliver.
Table 5.1
Important Parameters and Transfer Efficiency
Sr. No.Name of CardDiameter (mm)
SpeedProduction (Kg/hr)Surface speed Ratio of cylinder to
DofferCylinder LoadTransfer efficiency (%)Hank
CylinderDofferCylinderDoffer
1LC -3001290680450392721.883.00021.160.11
2MARZOLI1290706450392721.085.36515.160.11
3DK-7401290700450392721.265.65019.610.11
Table 5.2
Wire Specifications On Cards
MachineCylinder Wire PointDoffer Wire Point
MARZOLI8653039525
LC- 3008653039525
DK-7408605541640
Tables 5.3
Sliver Produced On Wire
Sr. No.MachineProduction (Kg)
1LC 300169600
2DK-740158522
3MARZOLI
Tables 5.4
Testing Parameter Of Cards Sliver
Machine Uster (%)Nep Content/gmC.V. (M)
MARZOLI5.021203.90
LC-3003.84403.03
TRUMAK DK-7404.3998.63.02
Tables 5.5
Calculated Reading of Transfer Efficiency And Cylinder Load
Machine Transfer Efficiency Average Transfer Efficiency
MARZOLI1515.63
18.32
13.56
LC 30022.0521.16
21.21
20.23
TRUMAK DK-74019.8719.61
19.36
19.60
CHAPTER 6
Summary And Conclusion
From the result it is dear that Transfer Efficiency of LC 300 is
high than DK 740 and MARZOLII with respect to sliver quality that
is U% and nep level at 27 kg/hr production.
The Transfer Efficiency on modern cards is improved because of
use high density wire point, angle of inclination, height of wire
point, increase in life of wire point, diameter, of roller and
rotational speed of wire covered surface i.e. doffer arc are
consider to be increase entrapment power of both cylinder and
doffer. Because Transfer Efficiency depend upon entrapment power of
clothing:
Calculations
Transfer efficiency -LC - 300
Observed reading
Machine Parameters
Cyl. Speed =450 rpm
Doffer speed =39 rpm
Doffer (=70 cm
S.S. of doffer=8576.55 cm/mm
Length delivered /rev. of cyl. =
=
= 19.05
log q =
(Now T.E. = p = (1-q) ( 100
= (1-0.77) ( 100
= 22.01
_1109234121.unknown
_1109774209.unknown
_1109784499.unknown
_1109836161.unknown
_1109774329.unknown
_1109234170.unknown
_1109234040.unknown