Roving

This power point describes about the roving process. Roving is the last spinning preparation process in Ring yarn manufacturing.

1. Roving Frame By Bewuket Teshome (Lecturer) Bahir Dar University

2. 1.1. Introduction 1.2. Operating sequence 1.3. The operating zones of the roving frame 1.4. Machine drive systems 1.5. Automation 1.6. Process parameters and production calculation

3. Today’s Objectives: To understand the necessity of roving process To understand the objectives of roving frame To know the working principle of roving frame To understand false draft and its cause To identify the creel and the drafting arrangement components To understand the principle of drafting To understand the difference between draft and attenuation To understand the importance of all components in the drafting zone To identify the different roller weighting systems To understand the cradle length

4. 1.1. Introduction Draw Frame/Comber Roving Drafting Twisting Winding The draw frame sliver already exhibits all the xs required for the creation of a yarn. Fibers Ordered, Clean Laying parallel

5. Why roving frame is necessary? The required draft . Sliver is a thick, untwisted strand that tends to be hairy and to create fly. The fine, twisted roving is significantly better suited to this purpose. The draw frame cans represent the worst conceivable mode of transport and presentation of feed material to the ring spinning frame.

6. Objectives of the roving frame Drafting: The chief task of the roving frame is the attenuation of the sliver. Twisting: since the resulting fine strand has scarcely any coherence, protective twist must be inserted in order to hold it together. Winding: winding the roving into a package that can be transported , stored and donned on the ring spinning machine.

7. Sliver can Driven transport rollers Drafting arrangement 5. Roving 6. Flyer 7. Spindle 8. Bobbin 9. Bobbin rail 10. lever . 1.2. Operating sequence

8. Draw frame sliver is presented to the roving frame in large cans (1). Driven transport rollers (2) draw the slivers from the cans and forward them to drafting arrangement (3). The drafting arrangement attenuates the slivers with a draft of between 5 and 20 . The strand delivered is too thin to hold itself together. A protective twist is inserted , usually in the range of 25 – 70 turns per meter . The turns are created by rotating flyer (6) and are transmitted into the unsupported length of roving (5). The flyer itself forms part of driven spindle (7) and is rotated with the spindle.

9. The roving runs through the flyer top and the hollow flyer leg to the wind-up point, and is wound 2 – 3 times around the presser arm before reaching bobbin (8). To enable winding to be performed, the bobbin is driven at a higher peripheral speed than the flyer so that the roving is drawn off the flyer leg. The coils must be arranged very closely and parallel to one another so that as much material as possible is taken up in the package. For this purpose, bobbin rail (9) with packages on it must move up and down continuously. This can be affected, for example, by continual raising and lowering of lever (10), on which the bobbin rail is mounted.

10. 1.3. Operating/Working regions of the roving frame The creel The drafting arrangement Roller drafting system The apron Applying pressure to the top roller The condenser The spacer Winding of bobbin Package build Bobbin drive Cone drive transmission The lifter motion The builder motion Spindle & flyer Imparting twist Spindle Flyer Design of flyer Pressure arm

11. Due to high degree of parallelization of the fibers in the slivers (especially in the case of combed sliver), strand coherence (sticking together) is often not very great. Accordingly, transport at this place can easily create false drafts . Guide rollers should run smoothly to avoid false drafts. Above the cans there are several rows of driven rollers to help the slivers on their way to the drafting arrangement. A perfect drive to the rollers is effected by chains. The Creel

12. The drafting arrangement Draft? The distribution of an approximately constant total number of fibres over a greater length of the product . Drafting is effected mostly on roller drafting arrangements. The fibres are firmly nipped between the bottom steel rollers and the weighted, top, pressure rollers. The rollers are so rotated that their peripheral speed in the through flow direction increases from roller pair to roller pair , then the drawing apart of the fibres, i.e. the draft, takes place. Attenuation? Attenuation = Draft * 100 (100-P)

13. Double apron drafting system with 3/3 or 4/4 (for high drafts) roller arrangements It is used in the roving frame since it enables drafts of 20 while holding the fibers more or less under control during their movements.

14. Three-cylinder, double-apron drafting arrangement

15. Drafting Rollers Bottom drafting rollers They are usually fluted. They get motion from motor. They are not continuous, connected together by roller bearing. Knurled Spiral Plain

16. Top drafting rollers They are rubber coated pressure rollers. Hardness = 80 – 85 o Shore, Rollers over which the apron runs often have a hardness only slightly greater than 60 o Shore to enable better enclosure and guidance of the fiber strand during drafting.

17. The top rollers are pressed down with sufficient force on to the bottom rollers to ensure proper grip of the fibers so that there will be proper guidance of the fibers . Pressure are in the range of 100 to 250 N per roller which may vary as per raw material and its volume . Top roller weighting can be carried out by: Spring (all manufacturers) Pneumatic pressure (Reiter) Spring + magnet

18. Condensers At the back of back roller they are mounted on a reciprocating bar. The traverse motion spreads wear evenly over the whole width of the roller coatings. In the main drafting field which rest on the moving fiber strand without being fixed. Function: Spreading sliver masses are condensed to improve evenness and lead to drafting zone. Advantage: Reduce the high fly level and hairiness of roving .

19. Aprons They are made of leather or synthetic rubber. They are usually about 1mm thick. The upper aprons are short. The lower aprons are longer. They run over the guide bar, usually known as nose bar, to position close to the delivery roller. They are used to guide and transport fibers during drafting. They should extend as closely as possible to the nip line of the front rollers. The guiding length, referred to as the cradle length , must be adapted to the staple length.

20. They are held taut by tensioning devices (4). In contrast, the lower aprons (1) are longer and usually made of leather, although synthetic rubber is also used. They run over guide bars (nose bars) (3) to positions close to the nip line of the delivery rollers . Cradle L (mm ) Cotton 36 29-31 mm 43 32-39 mm 50

21. Spacer As the top apron are forced by spring pressure against the lower apron, the arrangement of this apron should permit precise adoption of minimum distance to fibre volume . In order to be able to maintain this minimum distance , spacer are replace ably inserted between the nose bar of the lower apron and the cradle edge of top apron . Spacer size is 4 to 7 mm in accordance with roving hank.

22. In the roving frame we can witness two drafting zones 1. Break draft ( at the back zone) The main objective is to enhance the fiber orientation instead of drafting itself. Break drafts for cotton = 1.05 – 1.15 (usually 1.1), and for synthetics and strongly compressed cotton sliver delivered from high performance draw frames = 1.3. Break draft affects roving evenness. 2. Main draft ( where the real drafting is taken place) The total draft is the product of break and main draft. Maximum Total Draft = 20 Minimum Total Draft for cotton = 5 and for synthetic fibers = 6. If drafts below lower limits are attempted, then the fiber masses to be moved are too large, the drafting resistance becomes too high and the drafting operation is difficult to control.

23. Reading Assignment One Make a note on Bottom apron tensioner Drafting Clearer Suction system

24. Today’s Objectives: To understand the principle of twisting To identify the twist inserting parts and their technological impact on the roving To understand the effects of arrangement of bobbins into two rows

25. Imparting Twist TWIST: The number of turns about its axis per unit of length of a roving or other textile strand. Twist is expressed as turns per inch ( tpi ), turns per meter ( tpm ), or turns per centimeter ( tpcm ). Twist per unit length depends on the delivery rate of front roller. Twist per inch (TPI) = rpm of flyer s s of front roller (inch/min)

26. Spindle It is a long steel shaft mounted at it’s lower end in a bearing. It is a support and drive element for the flyer. The spindle tip is conical and is provided with a slot . When the flyer is set on the spindle cone, a pin on the flyer projects into the slot so that the flyer and spindle are converted into a unit for drive purposes.

27. The Flyer Flyer has two legs , one with hollow path or slot and presser arm another for balancing the flyer while rotating. Flyer is placed on spindle, it gets motion by gearing. Flyer speed has direct influence on production. Flyer can be varying in sizes which are specified in inch. For example, 12”X 5.5”, 12”X6” and 14”X6” (max. height X max.dia. of package) Flyer top Roving inlet Spindle end Flyer leg Presser arm Presser eye Spindle

28. Functions of the flyer: 1. Inserting twist Each flyer rotation creates one turn in the roving. The flyer rotation rate is held constant. High levels of roving twist always represent production loses. Low twist levels can cause roving breaks during bobbin winding. 2. Leading the very sensitive strand from the flyer top to the package without introducing false drafts .

29. This is very difficult task because: i) The strand has only protective twist and is very liable to break; ii) The flyer, along with the roving, is rotating at a high rate (up to 1500rpm). The fiber strand must, therefore, be protected against strong air currents. For this purpose, one of the two flyer legs has been grooved , i.e., open in a direction opposite to the direction of rotation. New designs are no longer provided with this easily accessible, “service-friendly” groove. Instead , they have a very smooth guide tube set into one flyer leg . The advantages are: the strand is completely protected against the air flows and frictional resistance is significantly reduced so that the strand can be pulled through with much less force. These reduce false drafts and strand breaks while allowing high production speeds. The disadvantage is that piecing of strand break is difficult.

30. Presser Arm A steel end attached to the lower end of hollow flyer leg is called presser arm. The roving is wrapped 2 or 3 times around it. The no. of turns determine the roving tension. For higher tension, a hard compact package is obtained and if it is too high false draft or roving breakage can be caused. Therefore, the no. of wrap depends upon material and twist level .

31. The flyer top The way in which the roving is carried along and guided at the entrance to the flyer determines the degree of twist and the winding tension. low twist or coarse , the strand passes through the flyer top to the guide groove without wrapping . A half-turn of wrap is selected for high speed frames winding large packages with high twist levels. The wrap enables better control of roving tension and the package build becomes more even owing to harder coils . Old flyers have flyer tops of smooth metal. Modern flyers have an insert of rubber formed with grooves.

32. Effect of Arrangement of Bobbins in two Rows In fly frames, the spindles are arranged in two rows (in a zigzag manner). This arrangement is made in order to economise on the space requirements. It has some technological disadvantages .

33. The free unsupported lengths (L1 & L2) are different. (Fig. (a)). The rolling angles (β) are different (Fig. (b)). The spinning triangle sizes are different.

34. These differences result in: More complicated design Operation of the machine is made less convenient Automation is hindered uneven twisting uneven binding of fibres and ultimately count variation between front and back rows.

35. Various designs of the flyer   Depending upon its form and drive , there are three flyer types: Spindle mounted flyers: Simple as far as design and drive are concerned. Piecing is easier. automation is difficult. 2. Top-mounted (suspended) flyers: Facilitates automation of the doffing operation, piecing is difficult. 3. Closed flyers: Reduced spreading of the legs at high operating speeds.

36. Today's Objectives To understand the principle of winding To identify parts involved in winding process To understand the motions/movements involved in cone winding process (Builder motion) To understand the drive elements for the parts involved in cone winding process

37. Winding Principle Winding is the process of transferring roving from flyer to roving bobbin to facilitate subsequent processing. Cylindrical body with tapered ends. Created by building layer upon layer of parallel coils of roving. The angle of taper of the ends is normally between 80° and 95°. Large angle - to wound more roving onto the package . Small angle - to ensure that the layers do not slide apart . [Slough-off]

38. Mechanical drive systems Electronic drive system T o create the desired shape the following motions are required; Bobbin Rotation – to wind the roving on the roving bobbin [bobbin speed must be higher than the flyer speed] Reduction of rotation by belt shifting – to achieve constant winding speed [bobbin dia. increases, the winding on speed must be decreased-constant] Bobbin rail Lifter motion - to wind over the whole length of the tube, the winding point must be continually shifted. Reversing the direction of movement Shortening of traverse/stroke after each layer has been completed – to make tapered ends.

39. Let, Front roller delivery= L inch/min Bobbin speed at any instant point of winding = N B rpm Spindle speed at any instant point of winding = N S rpm Bobbin dia. at that point of winding = d So, bobbin circumference =  d  Winding on speed , N w = (N B – N S ) rpm Total winding length / minute =  d ( N B – N S ) Therefore, L =  d ( N B – N S ) In this formula, L,  & N S are constants. So, with the increase of bobbin dia , bobbin speed decreases. .

40. 1.4. Mechanical drive system: 41 Bobbin drive: Variation in bobbin speed originates from the cone drums . When the builder motion shifts the cone belt , the rotation speed of the lower cone is changed. This declining rotation speed is transmitted via gearing to the differential and superimposed on the constant speed of the main shaft. Further gearing then transmits the resulting rotation speed to the bobbin drive .

41. Bobbin drive (side view); drive transmission to the bobbin Bobbin drive (gearing plan) 42

42. Cont … On the bobbin rail, bevel gears fixed to the longitudinal shaft drive the bevel gears of the bobbin supports. Flexible connection is needed between the main drive shaft in the gear box and the longitudinal bobbin shaft - swinging joint . 43 Swinging joint at the bobbin drive shaft

43. Cont… Cone drive transmission Transmission occurs in small steps through shifting of the cone belt after each lift stroke . Bobbin rotation must be changed with a linear function. Straight-sided cones does not vary the transmission ratio in a linear manner and thus does not produce the required linear variation in bobbin rotation speed. The cone faces convex on the upper driving cone and concave on the lower driven cone - difficult to design. Straight sided - the belt must be shifted through steps of varying magnitude , the initial steps being relatively large (  W1 ) and the later ones smaller. 44

44. Convex and concave cones Shifting the belt with hyperbolic (a) and straight-sided cones (b) 45

45. Shifting the belt Is controlled by the ratchet wheel (on axle). After each stroke, the ratchet wheel is permitted to rotate by a half tooth . This ratchet steps out the wire rope ( 1 ) and hence permits movement of the belt guide ( 5 ) to the right. The tensile force required to induce movement of the belt is exerted by a weight . Bobbin diameter increases more or less rapidly depending upon roving hank . So degree of shift is modified by replacing the ratchet wheel or by substituting change wheels. ratchet wheel with fewer teeth - then the belt is shifted through larger steps, i.e. it progresses more rapidly, and vice versa When the bobbin is fully wound, the belt must be moved back to its starting point- today by auxiliary motor. 46

46. Belt-shifting device 47 Rope 10. Ratchet wheel 5. Belt guide 7. Weight 4. belt

47. Bobbin rail a. Lifter motion: In the package, each turn must be laid next to its neighbors. So the lay-on point must continually be moved, by raising and lowering the bobbins supported on a movable rail. Not by raising and lowering the flyers – b/c the unsupported roving length, withdrawal angle and approaching angle will vary. Raising and lowering can be carried out by – - Racks attached to the rail. - Lever mounted on the rail The lift speed must be reduced by a small amount after each completed layer. The lift drive is also transmitted via the cone transmission as bobbin drive but not via the differential . 48

48. Lifter motion with racks (a) Lifter motion with levers (b) 49

49. b. Reversal of the bobbin rail movement: Reversing drive must be provided so that the bobbin rail is alternately raised and lowered. Reversal of the rail movement originates from the reversing gear (1/2/3 ) . Electrically operated valve pressurizes the left- and right-hand chambers of double-acting cylinder ( 9 ) alternately. Thus left-hand clutch (1) and right hand clutch (2) are operated successively. So that pinion (3) engages with either gear wheel 1 or gear wheel 2. The rotation itself comes from the shaft 10 , on which gear wheels 1 and 2 are mounted, always rotating in the same direction. Operation of clutch (1) or (2) causes left- or right-hand rotation of pinion 3 and shaft 4 , accordingly. The bobbin rail is correspondingly raised or lowered via bevel gear 5, pinion 6, sprocket 7 and lifting chain 8. 50

50. a. The reversing assembly of the lifter motion b. Mechanism for reversing the bobbin rail movement 51 1/2/3 – reversing gears 4 – shaft 5 – worm gear 6 – pinion 7 - sprocket 8 – lifting chain 9 – cylinder 10 – drive shaft

51. c. Shortening the lift: Rods 5 and 6 (a) are inclined. The inclination is adjustable and corresponds exactly to the taper of the bobbin ends (angle alpha). During winding of a package, the ratchet is rotated at every change-over, and the micro-switch (4) is also gradually shifted further to the right on a slide . Therefore , the rods engage the micro-switch steadily earlier in the lift stroke, reversal occurs correspondingly earlier. This results in a continuous reduction in the lift of the rail. The bobbins are thus built with a taper. c. The assembly for building conical ends on the bobbins 52 1- Bobbin rail frame 2 – bobbin rail 3/7 – bracket 5/6 – rods 4 – micro switch

52. Builder motion Has to perform three important tasks during winding Shift the cone belt corresponding to the increase in bobbin diameter; Reverse the direction of movement of the bobbin rail at the upper and lower ends of the lift stroke; Shorten the lift after each layer to form tapered ends on the bobbins. 53

53. Today's Objectives To understand electronic drive system and its advantage To identify possible automation areas in roving frame To understand the process parameters in roving frame To understand how production is calculated in roving frame

54. Electronic drive system Electronic devices - frequency converters and individual servomotors - enabled the drive system of the roving frame to be simplified. Spindles and flyers are driven directly by individual servomotors. The control system ensures synchronized running throughout package buildup. The drives are controlled by frequency converters and are thus especially gentle in their treatment of the material. Controlled machine stop is assured in the event of power failure . 55

55. Electronic drive system 56

56. Advantages of Electronic Drive System: Much simpler than mechanical drive versions Lower energy consumption and reduced maintenance No need of heavy counter weight for bobbin rail balancing and differential gear,

57. 1.5. Automation replacement of human workers by technology: a system in which a workplace or process has been converted to one that replaces or minimizes human labor with mechanical or electronic equipment . Cleaning: by means of cleaning aprons, clearer rollers and suction systems at the drafting arrangement and also by the traveling blowers that keep the machine clean.

58. Equal roving geometry for front and back row roving Deposition of roving spindles in two rows leads to variation in roving twist and count . Modern speed frames have raised flyer top of the back row as compared to the front row to maintain the roving delivery angle.

59. Roving tension sensors These tension sensors do not actually contact the roving while measuring the tension. The tension is measured at periodic intervals. The required change in tension is actuated by changing the bobbin speed through servomotor.

60. Bobbin doffing: Manual: Costly Frequent and time consuming labor intensive Ergonomically unsatisfactory decreases efficiency Automatic: reduction in doffing time.

61. Bobbins transport Manual Transport: Labor-intensive Damage to the roving 60 % wages cost can be attributed to cost of transport Automatic transport: Reduced labor costs Roving bobbins are not touched, the bobbin surface is not damaged substantial increase in quality and productivity No intermediate storage which might result in damage, soiling, or ageing of the roving, space-saving No confusions between different roving bobbins ensuring the application of the “first-in, first-out” principle Clearly structured material flow, speeding-up processes

62. Machine monitoring (stop motions) In case of roving or sliver break machine should stop immediately in order to avoid production loss and creation of faults in the roving. Sliver stop motion: By light emitter and photocell Located between the last transport roller of the creel and the drafting system m/c should stop , in case of sliver break Roving stop motion: Light beams fall on flyer tops In case of a roving break, broken roving ends whirl around (hood), Interrupts light beam, m/c stops Production monitoring by Zellweger Uster : records, evaluates and stores interruptions in operation of all machines in the preparatory installation.

63. Reading Assignment two Make a note on Other Possible places for Automation

64. 1.6. Process parameters and production calculation Parameter: variable quantity determining outcome , a measurable quantity. Process parameters Speed of rollers (draft) Diameter of rollers Roller setting Pressure (100 – 300 N) Pressure range for pneumatic (1.5 bar-5 bar) Speed of flyer/spindle (twist) Speed of bobbin (winding) Condenser size Spacer size Shore hardness Cradle length Number of spindles/flyer Twist multiplier 65

65. Cradle length (mm) Cotton Synthetic fibres 36 Cotton up to 29-31 mm 40mm 43 Cotton up to 32-39 mm 50mm 50 60mm Roving hank (Ne) Condenser size (mm) Below 0.8 10 0.8-1.0 8 1.0-2.5 6 2.5-6 4 Roving count (Ne) TM 0.8-1 1.3 1.1-1.2 1.2 1.3-1.5 1.1 1.6-2.0 1 2.1-4 0.9

66. Production calculation Feeding Rate = π * D( dia of back roller) * Rpm(back roller) Delivery Rate = π * D( dia of front roller) * Rpm(front roller) TPI = TM TPI = spindle speed________________ Delivery rate or F.R delivery in inches / min Production(lbs/hr) = front roll delivery * 60 * 1 * ŋ 36* 840 * count Production(lbs/hr) = flyer rpm * 60 * No. of spindles * ŋ TPI * Hank roving * 36 * 840

67. Example : Find out the production per shift of a modern speed frame at 85% efficiency to produce 1.5 hank roving. Assume necessary parameters. Given, Efficiency=85%, Roving hank=1.5Ne = 1.1* No. of spindle = 120, Spindle speed = 1200 rpm. Production = Spindle speed*no. of spindle*hr*shift*efficiency / TPI*36*840* hank = 1200*120*60*8*0.85/ 1.34*36*840*1.5 = 96.6 lbs/shift ( Ans ) Let, TM = 1.1 TPI = TM = 1.34

68. Thank You!!!