The Effect on Top Length and Noilage of Fibre Loading on the Swift of the Worsted Card

2010

Carding is the primary step in the processing of staple fiber in which a disorganized matt of fiber tufts and clumps is converted into an even web of individualized and partially aligned fibers. The fiber to be opened is conveyed by a primary set of pinned rollers past a secondary set of counteracting pins, usually moving at a much lower relative speed. The secondary pinned surfaces are either rollers or flats and are called workers when in the form of rollers. The clearance between the pin sets is small, meaning that fiber tufts become caught in both sets of pins and the difference in speeds pulls the fiber clumps apart, individualizing and aligning the fibers.Fiber is fed into a card as a low-speed, high-density, entangled matt of fiber tufts and is conveyed through the card by a series of transfer rollers with progressively higher speeds. The speed of the final roller of this sequence, referred to here as the swift, is high and typical examples are 2400 m min -1 for a Trützschler TC03 cotton card and 1500 m min -1 for a Thibeau CA7 high-production worsted card. By the time the fiber has reached the swift, it has been converted into a low-density web of individualized and partially aligned fibers.After processing on the swift, the fiber is transferred to a slower moving surface, the doffer, which is the final step of the carding process. Unlike previous transfers in the card, the transfer to the doffer is not completely efficient, so some fiber recycles around the swift where it mixes with incoming less-carded fiber, complicating the opening process. Some of the problems associated with inefficient doffing include fiber breakage, loss of alignment, imperfect opening of tufts, and generation of nep. Since measurements show doffer efficiencies can be low, ~0.1 (see [1]), the difficulty is to optimize opening in the presence of significant levels of recycled fiber.Due to its significance for carding quality, doffing has long been of interest to textile engineers and researchers Abstract A parametric model of fiber transfer to a doffer, based on the geometry of the system and physical models of fiber transfer, was developed to describe the efficiency with which doffers collect fiber from the high-speed carding roller. Doffer speed, normalized to that of the cylinder, was adopted as the variable and parameters, such as wire height, pitch, width, and fiber-layer thickness on the cylinder, were introduced to describe the process of fiber transfer. The equation for doffer efficiency developed by this procedure was tested by fitting it to data on hauteur and noil from a worsted-carding trial employing a range of drafts and production rates. The calculated efficiency of the doffer for these trials was found to lie in the range 0.15-0.25. The effects of changes in the dimensions of the card wire and layer thickness were predicted by changing the values of the parameters.

Section: Discussionsupporting

confidence: 93%

Section: Mathematical Developmentmentioning

confidence: 99%

mentioning

confidence: 99%

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A Parametric Model of Fiber Transfer from Swift to Doffer

2010

“…A doffer draft of 9.1 % (doffer speed 41 m/min) was adopted as the draft for the control experiments because it minimizes fiber breakage [8], but an additional doffer draft of 5.3 % (speed ~24 m/min) was included as an extension of the study. Details are summarized in Table 1.…”

Section: Card Operation and Trial Designmentioning

confidence: 99%

Reversed Direction of Worker Rotation in Worsted Carding

2010

The effect of reversing the direction of rotation of workers on the swift of a worsted card was studied in a trial that included processing to top. Experimental conditions studied were worker draft (three levels), doffer draft (two levels), and wool type (two levels). Production rate was held constant throughout at values typical for worsted carding, ~1 gsm production fiber density on the swift and standard topmaking procedures were used after carding. The results showed that the only effect of reversing the direction of rotation identified was increased fiber breakage and noil at the lowest opening roller draft (0.4 %). A tracer fiber study failed to identify any effect of the direction of worker rotation on the fiber structure of the card web. The reason for the increased fiber breakage with reversed direction of rotation at very low draft was thought to be the increased loading in the nip due to the trailing ends of the fibers. The implications of reversing worker rotation for roller carding in general are briefly considered.

“…The consequences of this include additional fiber breakage, loss of alignment, imperfect opening of tufts, and generation of nep. 1,2 Since measurements show doffer efficiencies can be low, less than 0.1 for a flats card, 3 cards must be able to operate in the presence of significant levels of recycled fiber. This is most effectively achieved by restricting card production, which also increases processing cost.…”

mentioning

confidence: 99%

Design, function, and applications of high-retention doffer and worker wire

2014

The transfer of fiber from higher-speed rollers, licker-ins, breasts, or swifts, covered with forward-facing teeth, to relatively lower-speed doffers and workers with backward-facing teeth, is analyzed using the mechanics and geometry of the process. The analysis shows that the front angle of the doffer and worker teeth is too large to prevent fibers from slipping off as a result of the pull from the teeth of the swift. The capacity of the doffer and worker teeth to retain fiber is enhanced by cutting steps parallel to the base into the front edge of the tooth, effectively lowering the front angle of the tooth to zero degrees. Teeth with extremely low front angles support fibers until they are perpendicular to the doffer or worker, maximizing retention and transfer. Carding trials on worsted and non-woven cards in a pilot plant reveal benefits attributable to the new wire design. A survey of commercial non-woven processors using the high-efficiency wire on doffers and workers also identified various benefits.