紡織類外文翻譯雙語(yǔ)

1、Rotor SpinningRotor spinning involves the separation of fibers by vigorous drafting, and then collection and twisting of the fibers in a rotor. In the actual rotor spinning machine, draw frame sliver is presented to a spring-loaded feed plate and feed roller. Fibers within the sliver are then indivi

2、dualized by a combing roller covered with saw-tooth wire clothing. Once opened, the fibers pass through a transport tube in which they are separated further and parallelized before being deposited on the inside wall of the rotor. Centrifugal forces, generated by the rotor turning at high speeds, cau

3、se the fibers to collect along the wall of the rotor, forming a ring. The fiber ring is then swept from the rotor by a newly formed end of yarn which contains untwisted fibers. With each rotation of the rotor, twist is inserted, converting the fiber bundle into yarn as it is pulled out of the rotor

4、through a navel. The yarn is then taken up onto a cross-wound package, eliminating the need for a separate winding process as in ring spinning. As the yarn is drawn from the rotor, some fibers lying in the peeling point may wrap around the yarn, resulting in the formation of undesirable, random wrap

5、per fibers which are characteristic of the open-end yarn structure. Rotor spinning can be divided into four major areas: fiber separation, fiber transport, fiber reassembly, and twist insertion.Schematic representation of the rotor spinning process.Fiber SeparationFiber separation is critical in rot

6、or spinning for effective orientation of the fibers before yarn formation within the rotor. The sliver must be separated into individual fibers for effective delivery to the rotor. If the fibers are not separated effectively, a quality yarn with the best possible fiber orientation cannot be formed.

7、The most common method for fiber separation incorporates the use of combing roller covered with saw-tooth wire. Sliver is fed into the rotational action of the combing roller by action of a feed roller/feed plate mechanism. As the sliver is fed into the wires of the combing roller, individual fibers

8、 are caught by the teeth on the roller and pulled from the sliver. At this point the centrifugal forces and aerodynamics of the system transport the fibers from the teeth on the surface of the combing roller to an airstream where the fibers are separated further and eventually deposited into the rot

9、or in small layers over many revolutions. Another critical function of the combing roller is the removal of trash from the sliver. Well-cleaned sliver should be presented to the system. Some dust and dirt particles, however, will still be present in the cleanest sliver, especially if cotton is being

10、 processed. The trash extraction unit of the combing roller is designed to allow lighter fibers to be carried by air to the transport duct while the heavy trash particles, because of their mass, will deflect through an opening below the combing roller and out of the system. If the fibers are not cle

11、an on delivery to the open-end system, excessive fine particles and dust will deposit in the rotor, preventing uniform fiber alignment. As a result of particle buildup, yarn of poor quality (with poor fiber orientation, lower strength, and increased imperfections) is produced.Fiber transportOnce rem

12、oved from the combing roller, the fibers must be transported to the rotor without becoming excessively disoriented. The fiber transport tube is responsible for moving individualized fibers from the combing roller teeth and transporting them via air currents to the rotor. The transport tube is genera

13、lly tapered to accelerate the air and fibers during movement through the tube. This fiber acceleration helps to straighten out some fiber hooks existing from the fibers leaving the combing roller.Fiber ReassemblyUpon exiting the transport tube, the fibers are accumulated in the rotor which is the he

14、art of the open-end spinning process. Within the rotor, fibers are collected into an untwisted strand against the rotor wall via centrifugal forces, and then the strand is drawn off as yarn. As the fibers are delivered to the rotor wall, the centrifugal forces cause them to slide down the wall into

15、a groove. It takes many layers of fiber to make up a strand of sufficient density for yarn; therefore, the yarn is built over a period of many revolutions. As a result, numerous doublings occur within the groove (approximately 100) wherein further blending takes place and short-term unevenness that

16、occurs at drawing is reduced. Consequently, the rotor yarns are extremely even with few thick and thin defects. For short staple spinning, rotor diameters range from 31 to 56 mm and may be constructed with a variety of shallow “groove shapes”. The rotor design has a significant effect on the yarn st

17、ructure and physical properties, resulting from the fiber orientation and the twist imparted on the yarn while it lies within the rotor groove. The rotor typically has a conical shape, and the inner surface along the wall is known as the collecting groove, the diameter of which is the specified roto

18、r diameter. The rotor diameter depends on the machine speed, as well as on fiber properties, such as fiber length. As a rule of thumb, the rotor diameter should be no less than 1.2 times the staple length of the fiber; ends down at spinning otherwise increase. Illustrations of different rotor profil

19、es available for rotor spinning.The shape of the rotor groove should be considered because of the effects on twisting forces that occur in the groove to form the yarn. A variety of different rotor groove shapes exist to allow for different final yarn properties, including yarn strength, bulk, torque

20、, and uniformity characteristics. For instance, the T-rotor, because of its narrow groove diameter, produces yarns with a tight configuration more nearly like ring spun yarns than does the G-rotor. However, the bulk of the yarns produced from a G-rotor provides for better knit fabric hand and cover.

21、 As a result, specific rotors must be chosen to generate the appropriate yarn appearance and physical properties desired in the end product. S-rotors and U-rotors are generally used for sock, blanket, and towel yarns. G-rotors are normally used for apparel knitting yarns, and T-rotors are most often

22、 used for weaving yarns.Twist InsertionTwist occurs in the open-end spinning process as a result of the action of the rotor, navel, and take-up rollers. Once a sufficient number of fibers has collected in the rotor, twisting action from the rotation of the rotor propagates from the rotation of the r

23、otor propagates from the navel back to the peeling point at the rotor (the point at which the fibers leave the rotor). At the peeling point, the fiber strand is slightly twisted and peeled off the collecting surface at which time full twist is imparted. The strand is then carried perpendicularly out

24、 through a navel along the axis of the rotor. Figure schematically diagrams the yarn formation process within the rotor during open-end spinning. The rotor rotates in direction “a” at a fixed rate. At point “B” the newly formed yarn moves through the yarn withdrawal tube (or navel) where it is remov

25、ed form the rotor and wound onto a package. The actual yarn formation occurs in area “c”, wherein the individual fibers begin to collect twist. Once slightly twisted, the fibers reach point “p”, the peeling point, and the bundle is directed out of the rotor groove where it is fully twisted. Each rev

26、olution of the rotor theoretically introduces about one turn of twist into the yarn; however, slippage occurring during actual twist insertion is believed to cause lower actual twist than the number of rotor rotations. Because the fibers are not held firmly by the nip of a pair of rollers, as in rin

27、g spinning, the fibers can migrate independently during twisting. In fact when tsist is measured in rotor yarns, the measured twist is usually 15 percent to 40 percent lower than the machine twist. Machine twist is determined by the following formula: Not all twist imparted to the yarn is directly c

28、aused by rotor rotation. As the yarn travels through the navel and doffing tube, a significant amount of contact occurs. This rolling action on the navel surface produces a false twist that is trapped in a section of the yarn inside the rotor. In addition, a proportion of the real twist arising from

29、 the rotation of the rotor projects backward into the rotor. Therefore, the total twist is the sum (or difference) of the two kinds of twist. Overall, the false twist provides for more stability of the yarn between the navel and the rotor groove than does the genuine preset twist. The final yarn at

30、the package contains only real twist, yet the false twist has definite effect on final yarn characteristics. With increases in rotor speeds, false twist is increased correspondingly due to higher yarn tension and more centrifugal forces in the rotor. This increase in false twist tends to increase th

31、e amount of wrapper fibers in the yarn.Wrapper Fiber FormationThe inner core structure of rotor yarn resembles that of ring spun yarn structure; however, rotor yarn has a unique structural buildup of outside yarn layers that affects the aesthetic as well as the physical characteristics of the yarn.

32、Once each revolution some fibers entering the rotor from the transport tube interfere with the yarn peeling from the collecting surface. Portions of the fibers entering the rotor are captured inadvertently into the yarn. Instead of being twisted into the inner yarn structure, these fibers wrap aroun

33、d the outside of the yarn. The formation of these fibers, called “wrapper fibers”, is illustrated in figure. The fewer wrapper fibers that are present, the more that rotor yarns resemble ring spun yarns. However, methods to reduce wrapper fiber formation in rotor spinning cause reductions in product

34、ivity, as the minimum twist required for spinning increases. In general, wrapper fibers should be minimized to achieve an aesthetically appealing yarn while maintaining productivity. Also, the presence of wrapper fibers in rotor yarn has been shown to contribute to increased needle wear in knitting.

35、 It is theorized that wrapper fibers move across the knitting needles like “speed bumps on a highway,” sending waves of vibration through the needle and contributing to accelerated wear. The formation of wrapper fibers is largely affected by several machine-related and fiber-related factors includin

36、g: rotor speed, rotor diameter, fiber length, friction between the fiber and rotor groove, and aggressiveness of the navel. With increasing rotor speed, the levels of both false twist and yarn rotation become higher; hence, wrapper fibers are wrapped around the Sequence of illustrations showing one

37、mechanism of wrapper fiber formation on the surface of a rotor yarn with: (A) the fiber peeling point which moves slightly clockwise during the above sequence, (1) a fiber entering the rotor, (2) this fiber beginning to wrap around the body of the yarn rather than being twisted into the tail of the

38、yarn, (3) the fiber continuing to wrap, and (4) the final view of such a wrapper fiber.core more often. At higher speeds the rotor diameter or the navel should be changed to reduce false twist; otherwise, the yarn qualities will deteriorate. With smaller rotors the presence of wrapper fibers is less

39、 pronounced than with larger rotors. Even though more wrapper fibers exist owing to the fact that more fibers are delivered to the peeling point of the rotor, the wrapper fibers are wound fewer times around the yarn core than with large rotors. Therefore, yarns produced on smaller rotors tend to be

40、more hairy, but less bulky than similar yarns produced with larger rotors. Overall, the factors relating to wrapper fiber formation must be adjusted so that the minimum number of wrapper fibers are produced for a given speed. Wrapper fibers cannot be entirely removed, or productivity would be restri

41、cted; however, excessive wrapper fibers will result in low quality, aesthetically displeasing yarn.Advantages and Disadvantages of Rotor Spun YarnThe primary attraction of rotor yarn is its production cost advantage over ring spun yarn. Because of its high degree of automation and higher productivit

42、y, a pound of rotor yarn can be produced with approximately one third the labor needed to produce ring spun yarn. Part of the labor reduction is attributed to the high automation of the system. Some other primary advantages include: (1) Lower defect levels compared to the other spinning systems, par

43、ticularly fewer yarn long thick and thin places; (2) Superior knit fabric appearance; (3) Lower fiber shedding at knitting or weaving than ring spun yarn; (4) Less torque than ring spun yarn; (5) Less energy per unit produced required than for ring spinning; (6) Less floor spaced required compared t

44、o ring and air jet spinning; (7) Sophisticated real time quality and production monitoring on each yarn position; and (8) Superior dyeability compared to ring spun yarn. As with any spinning system, some disadvantages exist with rotor yarns. From the initial development of rotor yarn, concerns have

45、existed regarding the harshness of the yarn compared to ring spun yarn. Some developments have been made to offset the difference through special spinning setups or fabric finishing; however, fabrics produced from rotor and ring spun yarn are still readily distinguishable. These are other disadvanta

46、ges of rotor yarn: (1) Low strength (approximately only 70 percent of ring spun yarn); (2) High pilling propensity compared to air jet yarn; (3) Accelerated needle wear at knitting compared to ring spun yarn; and (4) High maintenance costs compared to ring and air jet spinning.Critical Spin box Fact

47、ors for Spinning Performance and QualityDraftOne of the first decisions that must be made when beginning to produce a yarn at rotor spinning is the weight of the sliver that should be fed into the machine. The relationship between the sliver weight and the yarn weight is the draft required by the ma

48、chine. The machine draft can be calculated with the equation:The preferred draft is different for the various machines available. For the Rieter R1, draft levels above 200 generally help yarn strength, evenness, and IPI defects. Because the Schlafhorst machines have a smaller combing roller, the pre

49、ferred draft level is lower, usually less than 200.Rotor SpeedRotor speed has a strong correlation with yarn strength, elongation, evenness, shedding, and yarn breaks if all else is held constant. Increases in rotor speed cause increases in spinning tension, which disrupt fiber formation in the roto

50、r. However, if a rotor speed increase is made in conjunction with a rotor diameter decrease, it is possible to avoid a spinning tension increase and preserve yarn quality and ends down levels. SuctionA vacuum is generated at the end of the rotor spinning machine to provide suction at each spinning p

51、osition. The suction helps to remove the fibers from the combing roller and to move them through the fiber transport channel. The removal of fibers occurs before the fibers make a full turn on the combing roller. The air that travels with the fibers through the transport channel is accelerated by ap

52、proximately 50 percent as it moves into the rotor because of the taper of the channel and the extra air generated by the rotor and vacuum. The air then exits around the edge of the rotor. If any turbulence exists (because of improper setting of the rotor), if air leaks occur due to worn seals, of if

53、 the vacuum level is insufficient, yarn formation in the rotor will be adversely affected, and quality and efficiency will deteriorate. Combing Roller ZoneThe combing roller zone is schematically illustrated in figure. The sliver is delivered to the combing roller by the feed which turns at a speed

54、that is based on both the draft and the yarn delivery speed set on the machine. The critical factors in the combing roller zone for optimal quality and running performance include: feed clutch wear, feed tray-to-combing roller spacing, combing roller speed, combing roller wire selection, and combing

55、 roller wire condition. Rotor ZoneThe rotor zone can be defined as the combination of the rotor, twin disc assembly, and rotor drive belt. Critical factors influencing quality and machine performance in this zone include: rotor speed/diameter, rotor groove, rotor stem wear, rotor cup wear, twin disc

56、 wear, and rotor belt wear and alignment.Yarn Withdrawal Zone (Navel and Doff tube)The fiber bundle formed in the rotor is withdrawn through a navel and doff tube. These components not only guide the newly formed yarn out of the spin box, but contribute significantly to spinning performance and to y

57、arn characteristics As mentioned previously, movement of yarn against the navel introduces a false twist that strengthens the yarn between the rotor and delivery roller. Similarly, inserts can be added into the doff tube to increase friction on the yarn and therefore to increase false twist. However

58、, some measure taken to increase false twist cause evenness of the yarn to deteriorate. Critical factors in the yarn withdrawal zone include navel selection, navel spacing (the distance from the navel surface to the peeling point of the fibers from the rotor), and doff tube selection.Critical Windin

59、g and Piecing Factors for Spinning Performance and QualityWinding ZoneThe winding zone consists of the area from which the yarn exits the spin box to the drum that turns the package. The optimal setup of the winding zone is strongly dependent on the end use of the yarn. For instance, if the yarn is to be dyed, the desired