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 β2 + Cos β2)/( Sin β1 + Cos β1) β1
=
inclination angle of cylinder wire point.
β2
=
inclination angle of doffer wire point. This ratio reaches its maximum value 1.414 when β1 =90° and β2=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 hampered
for want of an
carding
have
been
considerable
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 Where,
(1)
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 π Rd nd / nc where
(2)
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 π Rdnd / 840 × 36 Ne nc (g)
(3)
Hence
K = (453.6 2π Rdnd /840 × 36 NencQo)100
(4)
or
Qo = (453.6 2π Rdnd / 840 × 36 Ne nc K) 100
(5)
If P is production rate, (g/min), then P = 453.6 2π Rdnd / 840 × 36 Ne (g) Hence K can also be expressed as
(6)
Or
K= (P / ncQo)100
(7)
K= (2π 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.
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
ii) LC300:
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
-
88-360
-
is apposite to the sense of
Speed -
mm/min
Travel Direction
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
=
S.S. of Doffer in cm/min/cylinder Speed in rpm
=
8576.55 / 450
=
19.05 cm
Lengths deliver per Revolution of cylinder
n
=
176 = 9.23 19.05
log q =
−1 = −0.108 n
n
∴
Length calculated from graph (Cylinder Load) Lengths deliver per revolution of cylinder
=
= log-1 - 0.108
q
= 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. Name No. of Card 1 2
LC -300 M
Doffer
680
Cylinde r 450
39
27
Surface Cylinder Transfer Load efficien speed cy (%) Ratio of cylinder to Doffer 21.88 3.000 21.16
706
450
39
27
21.08
Diameter (mm) Cylinde r 1290
Doffer
1290
Speed
Production
(Kg/hr)
5.365
15.16
Hank
0.11 0.11
3
ARZ OLI DK740
1290
700
450
39
27
21.26
5.650
19.61
Table 5.2 Wire Specifications On Cards Machine MARZOLI LC- 300 DK-740
Cylinder Wire Point 865 30 865 30 860 55
Doffer Wire Point 395 25 395 25 416 40
Tables 5.3 Sliver Produced On Wire Sr. No. 1 2 3
Machine
Production (Kg) 169600 158522
LC - 300 DK-740 MARZOLI Tables 5.4 Testing Parameter Of Cards Sliver
Machine MARZOLI LC-300 TRUMAK DK-740
Uster (%) 5.02 3.84 4.39
Nep Content/gm 120 40 98.6
C.V. (M) 3.90 3.03 3.02
Tables 5.5 Calculated Reading of Transfer Efficiency And Cylinder Load
0.11
Machine MARZOLI
Transfer Efficiency 15 18.32 13.56 22.05 21.21 20.23 19.87 19.36 19.60
LC 300 TRUMAK DK-740
Average Transfer Efficiency 15.63 21.16 19.61
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 Observed reading
-
LC - 300
Machine Parameters Cyl. Speed
=
450 rpm
Doffer speed =
39 rpm
Doffer φ
70 cm
=
S.S. of doffer =
8576.55 cm/mm
Length delivered /rev. of cyl. =
=
S.S. of doffer in cm/min cyl. speed in rpm 8576.55 450
= 19.05 η=
length calculated from graph 176 = = 9.23 length delivers / rev. of cyl. 19.05
log q =
−1 = −0.108 n
∴Now T.E. = p = (1-q) × 100 = (1-0.77) × 100 = 22.01
