card zones.pptx in yarn manufacturing section

yarn

1. The operating zones of the card Generally there are five functional zone of carding: Feeding Zone Liker-in Zone Carding Zone Doffing zone Sliver formation Zone Coiling zone 1

2. Material feed requirement: Among other requirements, the product is expected to be; Very even and as far as possible free of faults . Irregularities in the sliver can be traced through into the yarn, i.e. They diminish yarn quality. If the feedstock is not in an adequate condition, a fault-free sliver cannot be obtained. Feeding Zone 2

3. To obtain even feeding , the batts in the individual feed chutes of all cards must be: Equally thick, Evenly distributed over the whole width of the chute and of equal density and High degree of openness. There are two types of feeding to the card: Lap feed (conventional): material feed in the form of scutcher lap. Chute feed mechanism: it is modern types of feeding system and the flocks are transported pneumatically. 3

4. Advantages of lap feed system: Linear density of the lap is very good and easier to maintain (uniformity). Installation is very flexible. Autolevellers are not required, hence investment cost and maintenance cost is less. Lap feed system: 4

5. Disadvantages of lap feed system: Transportation of lap needs more manual or labour efforts. Lap run out is additional source of fault and replaced by a new lap. More good fiber loss during lap change. More load on the taker-in  as laps are heavily compressed . 5

6. Chute feed system: Air stream helps for smooth flow of materials. Uniform weight per unit length and width maintained by a mechanism. Sensor is provided to keep some reserve material. 6

7. Advantages of chute feed system: Eliminate lap formation . Man power requirement in doffing laps, weighing, transportation to card, feeding at card is eliminated . Fibers are fed in loose form , so trash removed easily in carding action . Crushing of foreign matter and difficulty of removing is reduced . 7

8. Disadvantages of chute feed system: Blow room should run the same number of hours as the cards do, Card production must be assure continuous feed to draw frame, When stoppage of blow room for maintenance and other problem, Linear density of the web to the card is not as good as lap, Installation is not flexible. Flock feeding is the only solution for high production cards, Autolevellers required, so investment and maintenance cost is more. 8

9. Two basic tuft feed concepts: One-piece chute without an opening system; Two-piece chute with an opening system. Fig: Tuft feed with a two-piece chute Fig: Tuft feed with a one-piece chute 9

10. A column of material of a height that is somewhat variable over time is pushed toward the feed rollers. This form of chute is: Simple, Uncomplicated, Economical and needs little maintenance, But does not comply with the requirements of a high-performance card . Tuft feed with a one-piece chute One-piece chute: 10

11. It is more complex and expensive , but delivers a more even batt with better opened material. The upper half of the chute is a reserve chamber that serves to receive the material from the blow room and to separate the material from the air. In the lower portion , after an opening stage at the opening roller the quantity of material is held constant. This material is lightly compressed by compressed air or by vibrating plates in a continuous and even manner to form an even batt. Two-piece chute: 11

12. The fiber tufts are separated from the transport air in the upper section of the card chute ( 1, 2 ) A feed roller with a feed trough ( 4 ) and a needled cylinder (3) produces small tufts and thus a large tuft surface. The integrated mote knife immediately eliminates the exposed trash particles . 12

13. 4. The released tufts are blown into the lower section (5) of the shaft by means of an additional controlled air current and condensed there into a homogeneous batt. 5. The perforated rear wall at this point permits additional dedusting of the tufts. 13

14. A well designed feed device is expected to perform the following tasks: Clamp the batt securely over its full width; Be able to hold the material back against the action of the licker-in; Present the batt to the licker-in in such a manner that opening can be carried out gently. Feed device to the licker-in : 14

15. The conventional feed assembly comprises a stationary feed table with a feed plate (1) and a feed roller (2) pressed against the plate. The feed plate is formed as a special extension of the feed table and is adapted to the curvature of the cylinder. Conventional feeding system: 15

16. a: nose, b : guide surface length Shape of feed plate The guide surface length (b) and nose (a) of the feed plate play important roles in opening . A sharp nose holds the fiber strongly helps intensive, but less gentle opening. The length of guide surface has influence on waste %. A short guide surface leads to more waste removal by mote knife. 16

17. Long surface results in low waste (also, low separation of trash ). The length is dependent on fiber length Feed roller diameter is usually 80-100 mm. Some machines do have feed rollers without teeth , but with flutes . a: nose, b : guide surface length Shape of feed plate 17

18. New developments of feeding device: In the conventional feed , the batt has a tendency to move in the direction of the feed roller , and Therefore, a sharp bend in the direction of rotation of licker-in needed. This does not contribute to the gentleness of opening. A new system provided in some modern cards, The feed cylinder is located below the spring loaded plate. 1: feed plate 2: feed roller 3: licker-in 18

19. 1: feed plate 2: feed roller 3: licker-in The feed batt runs downwards without any diversion , and It helps gentle opening in licker-in. In conventional system, feed plate to licker-in setting is adjusted, Whereas, in the new system, setting point is b/a. "a" and "b“. 19

20. The licker-in zone The Taker-in: Taker-in is a cast iron roller with a diameter usually around 250 mm . A saw tooth clothing is applied to it. Beneath the taker-in, there is an enclosure of grid elements or carding segments . In high performance cards, its rotation speeds is in the range of 800 - 2000 rpm for cotton but for synthetic fibers around 600 rpm. Taker-in 20

21. The major functions of licker-in are: Open material into very small flocks To clean fibres by separating trash particles Deliver material to the main cylinder In modern carding machines, almost 50-70% of material is transferred into cylinder by licker-in in the form of very small flocks, and The rest 30-50% as individual fibers. Very intensive opening is performed by the licker-in. Opening: 21

22. The draft between feed roller and licker-in is more than 1000. But, higher fiber damage, possibly more loss as short fibers get eliminated and stress on the fiber also increases . The degree of cleaning , opening and fiber damage depend on: Thickness of batt Density of batt (which depends on pre opening) Degree of orientation of feed fibers Material throughput speed Speed and clothing of the licker-in Type of feed and settings 22

23. Waste elimination is very intensive and takes place under the licker-in by means of special devices. The standard cleaning assembly consisted of 1 - 2 mote knives and a grid, one half of which was made of slotted sheet and another half of perforated sheet . In this arrangement, elimination of foreign matter took place exclusively by scraping off on the mote knives. The grid sheets tend to serve as devices for guiding and holding back fibers , i.e. they prevent additional fiber losses that could arise from ejection. Elimination of waste: 23

24. High-performance cards require alternative assemblies in order to be able to deal with the high material throughput. The tufts are first guided over a mote knife (2), then over a carding plate (3), then again over a mote knife and again over a carding plate , before they finally pass to the main cylinder . The carding plates are fitted with special clothing. 24

25. An increase in production at the card means quite simply that more fibers must be passed through the machine. In order to obtain the same carding effect (i.e. the same number of points per fiber), the number of points per unit of time must also be increased . This can be achieved by: More points per unit area (finer clothing); Higher roller and cylinder speeds; More carding surface or carding positions; Finer opening of the fibers before feeding to the cylinder Need for auxiliary carding devices: 25

26. Little  can now be done to  increase  the  number of points . Coarse fibers and a high throughput demand coarser clothing . Fine fibers and a lower throughput permit the use of finer clothing . Much has already been achieved by increasing speeds , but further increases will prove steadily more difficult. Due to the severe deterioration of fibres , insertion of additional carding surface or additional carding positions and/or installing more licker-in have been put in to practice; in two possibilities: Increase in the number of lickers-in; Fitting of additional carding plates 26

27. If carding elements or additional lickers-in are not used, it mostly delivers the whole tufts to the main cylinder . These are compact and relatively poorly distributed across the licker-in. If they pass into the space between the cylinder and the flats in this form, fiber-to-fiber separation becomes very difficult and imposes considerable loading on the clothing. The whole carding operation suffers. 27

28. Therefore spreading of individual fibres evenly over the whole surface of the cylinder can be obtained only by increasing the number of lickers-in and the inclusion of carding elements, Since they ensure further opening, thinning out and primarily spreading out and improved distribution of the fibers over the total surface area. Due to such high speeds, trashes are eliminated due to centrifugal force. Speeds are progressively increased, Multiple Lickers-in 28

29. Carding Zone Is an area between flat and main cylinder Function of carding zone : Opening of tufts into individual fibers; Elimination of remaining impurities; Elimination of some of the short fibers; Untangling neps (possibly their elimination); Dust removal; High degree of longitudinal orientation of the fibers. Flats Main cylinder 29

30. Carding Cylinder The cylinder is usually manufactured from cast iron , but is now sometimes made of steel. Most cylinders have a diameter of 1280 - 1300 mm and rotate at speeds between 250 - 500 rpm . Rieter C 50 card has diameter of 814 mm , and speed up to 900 rpm It is essential that the speed can be changed ; i.e. Exactly adapted to the requirements according to the raw material, spinning process etc., because the cylinder speed has some influence on yarn quality . The setting tolerance must be maintained within extremely tight limits – the narrowest setting distance (between the cylinder and the doffer) is only about 0.1 mm . 30

31. The cylinder is generally supported in roller bearings . Beneath the cylinder, either there is a grid with traverse slots or a closed sheet. This is designed to remove impurities and maintain constant air-flow conditions . Above the licker-in and also above the doffer, there are protective casing . One of these protective sheets near the flats (known as front plate ) is specially formed as a knife blade . 31

32. Flat strip can be regulated by adjusting the distance between the cylinder and the front plate. Flats creates a large surface area by its clothing strips. Long fibers have more contact with the clothing of main cylinder than the short fibers. Therefore the long fibers are carried along but the short fibers edges are caught by the flat strippings and leave the machine. The elimination is carried out by filling the clothing and the flats then past by a cleaning device. 32

33. Flats Flat bars are made of cast iron . But recently developed cards have aluminum bar flats. Each bar is approximately 32-35 mm wide. Bars are given ribbed form ( T shape ) in order to prevent longitudinal bending . The arrangement of wire points towards the material flow direction is narrower . So that fibers are not pushed along , but can pass underneath the wires points and have progressive opening . 33

34. Fig: Carding zone between cylinder and flats Together with the cylinder the flats form the  main carding zone .  Here, the following effects should be achieved: Opening of tufts into individual fibers; Elimination of remaining impurities; Elimination of some of the short fibers; Disentangling neps (possibly their elimination); Dust removal (3); High degree of longitudinal orientation of  the fibers. Function: 34

35. In order to fulfill all these requirements, a large continuous carding surface is needed. The surface is created by a large number of individual clothing strips secured to the bars of the flats ( 2 ) and arranged in succession. 40 to 46 such strips are commonly used to make up the carding surface in the operating position. Since elimination of waste can be carried out only by filling the clothing, the flats must be cleaned continuously 35

36. They must therefore be moved past a cleaning device ( 4 ) (hence the name 'Revolving flat cards '). The bars of the flats must be joined together to form an endless, circulating belt , for which purpose they are fixed to chains or toothed belts . In addition to the 40 - 46 flats ( 2 ) (Rieter C 60 card: 27 flats) that interact with the cylinder (1), further flats are needed for the return movement on the endless path , So that altogether 100 – 120 flats are fitted to the rotating chains. 36

37. Doffing zone The doffer The cylinder is followed by the doffer, which is designed to take the individual fibers from the cylinder and condense them to a web. The doffer is mostly made of a cast iron (or steel) drum with a diameter of about 600 - 707 mm . ( 680 mm on Rieter machines). It is fitted with metallic clothing and runs at speeds up to about 300 m/min . Doffer 37

38. Card Clothing Arrangements and Fiber Transfer Card clothing : the material used to cover the working surfaces of the card, i.e., cylinder and rolls or flats. The clothing consists of either wire teeth set in a foundation fabric or rubber, or narrow saw like metal flutes, Which are spirally arranged around the roll. Fig: Basic features of a Revolving flat card 38

39. It can be easily reasoned that carding is most effective with very small , well opened tufts , i.e., containing only a few tens of fibers on the order of a few milligrams , Wire points between two surfaces under action in a carding machine are disposed in the following two forms: The carding disposition [ point- to – point ] and The stripping or doffing  disposition [ point- to – back ]. Analysis of Disposition: 39 Cont…

40. Fig: point- to – point tooth disposition Carding disposition [point- to – point ] 40 The teeth face in  opposite directions . This is the typical arrangement  between: The   main cylinder  and the flats , and also Between the  main cylinder  and  the  doffer . To enable carding, must be  greater than or    must be in  the  opposite direction  to  v1 .  In this action, the fibers are  drawn apart, separated, and aligned.  

41. The motion of the slower surface may be in the same or opposing direction , but the sharp points would be angled to oppose those of the faster-moving surface. Thus, point-of-tooth to point-of-tooth gives the carding action . For individual fibers attached to the faster-moving surface, point-to-point tooth may also be used as a stripping action to build a web of individual fibers. 41 Cont…

42. Effectiveness depends upon: Relative direction of movement of the working surfaces Relative surface speeds Point density and angle of wires Setting (gap between the wires of two surfaces) 42 Cont…

43. Stripping or Doffing disposition [point- to – back] The teeth of both clothing surfaces face in the same direction. This is the typical arrangement  between licker-in and main cylinder . The principle is that p oint-of-tooth to back-of- tooth gives a stripping action. Here there is a deliberate   transfer of material from one clothing surface to another, but     must be greater than      (feeding clothing).   Fig: point- to – back tooth disposition 43

44. 44 The following are important influencing factors for fiber transfer : Relative direction of movement of the working surfaces Relative surface speed Point density and angle of wire Setting ( very important ) Cont…

45. Back-to- back tooth , which enables the points on the faster moving surface to lift individual fibers from the base of the points on the slower surface . This action may be used as an aid to fiber stripping for web formation. 45 Cont…

46. It appears logical to arrange the clothing's of the cylinder and doffer in doffing disposition ( Point to Back ). But , it may reduce the cohesiveness , So, the strength of the web would not be sufficient for a stable operation. Therefore, they are arranged in carding ( Point to Point ) disposition ; Because, fibers get randomly arranged in the doffer which provides necessary cohesiveness required in the web. Why doffing by doffer is through point to point rather than point to back? 46 Cont…

47. However, the disadvantages of point to point arrangement are: Parallel arrangement of fibres achieved in carding cylinder is not retained . It leads to the formation of hooks . Poor efficiency of fiber transfer (0.2-0.3), and consequently more load on the cylinder clothing. Of course, it is a fact that the fibers rotate with the main cylinder about 5 to 10 (15) times before passing to the doffer , this results has some important improvements: It is an additional carding point; The fiber-to-fiber blending effect increases, i.e. A high degree of intermingling results there, which is important, e.g. for man-made fiber/cotton blending); 47

48. The detaching apparatus Web detaching using detaching rollers and transverse belts. On conventional cards, web is doffed from the doffer by an oscillating comb . It oscillates up to 2500 strokes per minutes. In all high production cards, it is replaced by a roller . Counter-rotating belts carry the web into the center or a circulating band carries to one side of the card. 1. Take-off roller 2. Delivery rollers 3. Web collection to center 5. Suction system 6. Clearing brush Fig: Web detaching using detaching rollers and transverse belts 48

49. Doffer Stripping roller equipped with a special clothing which prevents looping. The guding profile The crush roller ensures an even web transfer. Web guiding bridge supports the web. Sliver former from web Funnel and sensor for sliver quality monitoring is integrated. Calender roller condenses the sliver to ensure its proper delivery in to the can. Fig:Flat revolving Card(Schematic diagram) 49

50. Crushing Rollers (Web Crushing) Immediately after the detaching roller , almost all high production cards have two smooth steel rollers ( 2 ), one above the other. They are usually loaded with a pressure of 15 N/ m 2 . Additional cleaning can be carried out here by squashing the foreign particles. The fragments fall away immediately afterwards or in the subsequent machines. 50

51. In conventional cards and also in modern cards with roller doffing, web is condensed by narrow shaped condenser, just before the calendar roller. Up to the condenser, it runs a distance of 30-50 cm in a freely suspended form in a wedge shape. Sliver formation zone 51

52. However, in high production modern cards , web exposed falls apart due to high speed, and So, web must be condensed immediately after the detaching rollers. This can be done in various ways , such as: Several transversely guide rollers Traverse sliver condenser, giving central delivery. Calender roller condenses the sliver to ensure its proper delivery in to the can. 52

53. Coiling zone The sliver must be  coiled in cans  for  storage   & transport. Cycloidal deposition  of sliver has proved to be the most advantageous method of filling a can.  In this process,  two shifting movements  of the deposition point are  carried out simultaneously . The rotating plate R , with its guide passage L , draws the sliver away from the delivery cylinders D and continuously deposits it on a circle . The  turntable can plate C  continually rotates the can , the  deposition point of the circle is constantly shifting .  Fig: Can filling device (coiler) Fig: Laying down sliver  in cans 53

54. Can diameters are in the range of 600-1200 mm . Heights : 1000-1220 mm. Cans used subsequently in open end machines are smaller: 350-400mm diameter. Most of the modern high production cards have automatic can changing mechanism. Fig: Can filling device (coiler) 54

55. Recycling Layer and Transfer Coefficient The presence of a fiber layer on the cylinder clothing in the bottom transfer zone, observed by Lauber and Dehghani, indicates that: Not all the fiber mass on the cylinder leaving the carding zone becomes part of the doffer web on first contact with the doffer clothing. Using the tracer fiber technique of different-colored fiber ends, Ghosh and Bhaduri found that fibers generally went around with the cylinder for several revolutions before being incorporated in the doffer web . They found that, on first contact with the doffer clothing, only 20% of fibers became part of the doffer web. 55

56. The following fiber mass values per revolution of the cylinder are important to understanding fiber transfer : Qo : the operational layer , i.e., the fiber mass leaving the carding zone. Q1 : the mass transferred from cylinder to doffer . Q2 : the mass of the recycling layer The ratio of Q1 to Qo is termed the transfer coefficient ( K ), and can be measured as described below. Figure: Representation of the fiber mass distribution within a revolving-flats card. 56

57. After the card has reached a steady running state , the feed, doffer, and flats (or workers and strippers) are stopped while the cylinder continues running. The doffer is then restarted with the feed and flats (workers and strippers) out of action. This is easily detached along a visible dividing line formed when the feed roller was stopped . The mass of the remaining part of the web will be Qo . 57

58. Within a single revolution of the cylinder , a point on the doffer would travel a distance of: Where: Rc = the cylinder radius (m) = doffer travel distance (m) Vc = cylinder surface speed (m/min) Vd = doffer surface speed (m/min) If T is the sliver count in Tex, and P is the card production rate in kg/h, then:   P[kg/hr] = 60 *T   58

59. Hence, from the measurement of Qo , K can be calculated for known production parameters. Reported values for K are within the range of 0.02–0.18 , This means that, with each cylinder rotation , 82 to 98% of the fiber mass (Qo) remains on the cylinder as the recycling layer, Q2 . 59

60. From the figure, if QL is the fiber mass on the taker-in, then this will be drafted to give the mass QLC fed to the cylinder with each cylinder revolution, Where: Vt and Vc = the taker-in and cylinder surface speeds, respectively. The mass going into the carding zone with each revolution of the cylinder is QLC + Q2 and, Is called the cylinder load. 60

61. The mass leaving the carding zone (Qo) is: Qo = QLC + Q2 – Qf Where; Qf = the fiber mass per cylinder revolution contributing to the flat waste. An equation for the roller-clearer card would not include Qf. Although an important parameter , Qf is much smaller than QLC + Q2. Therefore, Qo may be taken as a practical estimation of the cylinder load for the card. 61

62. Hence, from the start of carding, the buildup of cylinder load (Qo) , the doffer web (Q1), and the recycling layer ( Q2 ) will follow the geometric progression given in the following table. 62

63. 63 When n is very large , there is continuity of fiber mass and, ignoring the flat strap waste : The mass from the taker-in onto the cylinder per revolution of the cylinder, equals the mass transferred to the doffer . i.e., Q1 = QLC .

64. There are two actions that form the recycling layer: Retaining power of the cylinder Cylinder clothing taking back from the doffer web of previously transferred fibers According, the mechanism of fiber transfer particularly in the top zone , and the transfer coefficient is governed by: Tooth angle Tooth density Circular motion Diameters of cylinder and doffer 64 Factors that Determine the Transfer Coefficient, K

65. The Importance of the Recycling Layer: Reported values show K to be small, ranging from .2 to 18%. This means, that the recycling layer constitutes a significant part of the cylinder load . Q 2 is therefore important in two respects. First, fibers will be subjected to several cycles of the carding action before permanently being incorporated in the doffer web. Second, by contributing to the cylinder load, it tends to reduce irregularities in the fiber mass transferred from the taker-in to the cylinder and is said to contribute to the evening action of the card . 65

66. Types of card clothing The term card clothing is used to describe the large number of pins covering the roller or cylinder surfaces. The type of card clothing required depends on many factors such as: Type and design of card Rotational speed of the cylinder Material throughput Production rate Fiber type and characteristics Quality requirements and price of clothing 66

67. There are three groups of clothing: Flexible clothing Semi-flexible clothing Metallic clothing I. Flexible clothing: It is mostly found in woolen cards, and In high production short staple cards found only in flats. Mostly, flexible card clothing is made in the form of fillet, It’s a narrow continuous length of clothing helically would around the roller. Cross-section of wires 67

68. Sectoral & ovoid wire commonly used, because: More strength is given in the carding direction of the wire, and More resistant to bending by increasing the lengthwise dimensions of the cross section. Flat cross-sectional wire is commonly used for fancy roller in woolen card. In most of modern cards, rubber-cushion (thick cellular rubber) foundation is used enable to: Increases the stability of the teeth, and Withstand greater amount of stress 68

69. The angle 'a' determines: The card clothing's ability to catch fibers The ease ways of the fibers can be stripped from the teeth The angle depends on the position and function of roller is mounted. The angle 'b', called back prick, is important in regards to the stability of the teeth. Wire geometry 69

70. Tooth of the card clothing at (A) is bent back the point of travel through an arc, and Overall height of the tooth is consequently increased. This can impose restriction on fine settings. In case of wire having a knee ('B'), the point would be forced down rather than up. 70

71. These are similar in structure to flexible type. But, the backings are less elastic than flexible clothing. Flat wires are not formed with a knee, but round wires may have one. They do not choke with fibers like flexible clothing. However: Less capable of yielding when subjected to a bending load. Used in flats only in cotton cards. II. Semi-flexible clothing: 71

72. This is manufactured in two forms; Inserted pin, and Rigid metallic wire III. Metallic clothing It is set in a rigid foundation such as metal or wood. Such types are found in Jute and Flax cards, and It may be on early rollers of a woolen card. Pin concentration ( pin/sq cm ) is usually within the following limits: Jute breaker card: 0.3 - 1.25 Jute finisher card: 0.8 - 1.4 Flax breaker card: 5.6 - 9 Inserted pin: 72

73. It is extensively used in licker-in and cylinder of cotton cards, and It’s becoming popular for worsted and semi-worsted cards. The use of rigid metallic clothing is the key to success for high speed and high production cards. Wire is hardened during manufacturing by passing through flame and a quenching bath. High carbon alloy steel is used to manufacture a cylinder wire. Rigid metallic wire: 73

74. 74 Specifications and geometry of the teeth a 1 : Base width a 2 : Tooth thickness at the root a 3 : Tooth thickness at the tip h 1 : Overall height of the tooth h 2 : Height of the base h 3 : Depth of the tooth T: Tooth pitch (when the wire is stretched out)  : Carding angle (face angle)  : Tooth apex/tip angle  : Trailing angle

75. 75 Some important parameters in card clothing Point Density : It is the number of points per square area. In general, high point density gives a better carding effect. However, if point density is above the optimum, Then loading of clothing would take place and carding effect would be deteriorated. Point density largely depends on: Fiber fineness (coarse fibers require low density ) Roller speed Material throughput Total available carding surface in the machine

76. 76 Number of points presented to the number of fibres in a given time is a very important factor that determines the efficiency of carding. Calculation of point density: Points /sq cm = Points /sq inch =

77. 77 Fibers Card components/devices Points/inch 2 Fine cotton Cylinder wire 800 to 1000 Man-made Cylinder wire 450 to 650 Coarse cotton Cylinder wire 600 to 800 Fine cotton Flat clothing 500 Man-made Flat clothing 270 Coarse cotton Flat clothing 350 to 400 Universal wire Doffer clothing 340 Special wire for fine fibers Doffer clothing 400 Cotton, general Licker-in clothing 36 at 10 o +ve Synthetics and rayon Licker-in clothing 27 at 0 o – 5 o +ve Suggestions of clothing in card

78. 78 If angles were to remain the same , then a shorter tooth gives a low pitch , thereby density can be increased . A short tooth reduces choking and thereby better carding over the total surface can be achieved. On the cylinder, tooth height is kept short, Usually, 2mm - 3.8mm. If height is too short , then fibre control will be less ; If height is more , then fibre transfer to doffer will be less and recycling will take place resulting in neps . Height of clothing :

79. 79 Angle : The carding angle (  ) is the most important angle of the tooth. Aggressiveness of the clothing Fiber retaining power determined The normal range is usually kept as follows: Licker-in + 5 to -10 Cylinder +12 to +27 Doffer +20 to +40 Negative angle is used in licker-in for processing man-made fibres, since cleaning is not the objective . Even in cylinder, for man made fibres, low angle is used.

80. 80 Trailing angle: A lower trailing angle reduces the fibre loading , but higher angle helps better penetration. - sharp edge b - land /surface The tooth point: For optimum operation, the point should not have a needle form but, should have a land as shown. In order to provide retaining power , the land should terminate in a sharp edge.

81. 81 Cut -to -point tooth Most of the recent cylinder wires have the smallest land or cut-to-point tooth . Sharp point penetrates better , thus reduces friction , which in turn reduces the wear on the wire and increases working life However, flat top wire is used in wool carding where burr removal is required. It improves the action of burr beating roller provided in the woolen card. - sharp edge b - land /surface

82. Fiber Configuration and Mechanism of Fiber Transfer The fibers transferred from the cylinder to the doffer is not in the form of a web of fibers but as individual fibers . This gives rise to the shapes of fibers have in the doffer web , i.e., the fiber configurations . The fiber shapes observed were grouped into the five classes of configuration, 82

83. A disadvantage of web formation at the card that is the formation of hooks . According to investigations it can be assumed that the fibers in the web show the following hooks: More than 50 % have  trailing hooks (Group II); About 15 % have  leading hooks (Group I); About 15 % have  doubled hooks (Group III), and Less than 20 % have  no hooks (Group IV). The fibres are found to be hooked at their forward ends termed ‘’leading hooks‘’. The fibres are found to be hooked at their rear end (back end) termed ‘’trailing hooks“. The bulk of fibres as they leave the doffer have ‘'Trailing Hooks" 83

84. Cylinder surface Doffer surface Before transfer, fibers remain caught at the cylinder teeth. During transfer, projecting ends are caught by doffer clothing. As a result of higher surface speed of cylinder compared to doffer, It sweeps the rest part of the projected fibre (tail) caught by doffer. The tail of the fibre emerges first and, so it comes out as a trailing hook . The actual mechanism of hook formation: Clothing configuration between cylinder and doffer 84

85. The presence of hooked fibers in the sliver: Reduces the effective length of fiber, and Influence properties that benefit from length of constituent fibers. If hooks exist into the yarn, The yarn will be weaker, and More ends down will be observed in spinning. 85 Influence of hooks:

86. Straightening-out of fiber hooks Machine vibration, improper settings, and disturbing air current in the drafting zone have adverse effects and fresh hooks tend to appear . Hook formation tendency is proportional to: The fiber length, As well as its fineness characteristic. Due to the natural reversal of material at each stage of processing , the hooks can be fed either as leading or trailing . During drafting , i f a hook is presented as trailing hook; Then it gets straightened out . 86

87. If fiber is presented to the nip of the front roller , it is rapidly accelerated , but trailing end is caught by more number of slowly moving fibres controlled by the back roller . This results in straightening of hooks . This is more likely to happen when draft is more. Straightening-out of fiber hooks Fig: Trailing hooks in the drafting arrangement 87

88. Since maximum draft is available in the ring frame , number of passages between carding and ring frame is so adjusted that majority hooks are introduced to the ring frame as trailing hooks . Therefore, odd number of passages should be provided between card & ring frame to feed majority hook as Trailing hook , to the Ring frame. 88

89. If a hook is presented to the combing machine as leading hook , it is straightened out by the revolving comb . However, if the hook is presented as a trailing hook , straightening does not happen and the fibre is removed as a short fibre; So that, waste in combing will be reasonably high. Fig: Leading hooks in the comber 89

90. The increase in waste is not because of the comber extracting more short fibre, but because of hooked long staple fibre ( trailing hook ) go into waste . Therefore, even number of passages (two or four machines) should be provided between carding and comber for presenting major hooks as leading to the comber . C: Card D: Sliver - lap E: Ribbon - lap F: Comber 90

91. 91 Drafts Equations in the Card Let us consider surface speeds of the machine components moving the fiber mass through the card, which eventually forms the sliver that is coiled in the can. For simplicity, we can ignore the speed of the flats , because this only govern the rate of removal of the flat strips from the carding zone. Based on the above description of the operating principles, Where, Vf = feed roller Vt = taker-in Vc = cylinder Vd = doffer Vs = stripping roller Vcr = crushing rolls Vca = calender rollers Vsc = sliver coiler rollers

92. 92 The relation of these surface speeds shows that the fiber mass is subjected to a sequence of drafts as it moves through the card. Draft (mechanical draft) = = Actual draft = ……..[ in case of direct count .] Actual draft = …….[ in case of indirect count .] Relation ship between Actual and mechanical draft If the waste of the material during processing is not considered Actual draft = mechanical draft  

93. 93 If the waste of the material during processing is considered Actual draft = Where, p= percentage of waste(%) Draft constant = Therefore;   =   =   =   =   =  

94. 94 =   =   All drafts are >1 except Dcd . The drafts Dds; Dscr, Dcrca, and Dcasc are sufficiently close to one and to be ignored . The total draft for the card is given by: Total mechanical draft ( ) = * =   Actual (Total fiber) draft ( ) =   =  

95. 95 Waste calculations in card Licker in waste(%) = Fan waste (%) = Cylinder and doffer fly waste (%) = Flat waste (%) = Total waste in a card(%) = Lickerin waste + fan waste + cylinder and doffer fly + flat waste Nep removal efficiency (NRE) in card can be calculated as: NRE(%) =  

96. Gearing diagram of carding machine 1000 rpm 96