Occurrence of a Singular Point in a Bundle Flow System and the Sensitivity of the Bundle Thickness to Perturbations in a Steady State Draft Process

2021

Roller drafting is an indispensable and fundamental procedure in attenuating the sliver to an adequate linear density during the spinning process. In this study, the drafting dynamic process was reflected in the arrangement containing hooked fibers and straight fibers, and the fiber straightness in the drafting zone in real-time. The drafting process was implemented from the initiation of the sliver head moving into the drafting zone to the achievement of the straightening process for all fibers in the sliver. The developed model demonstrated that the simulated weight distributions of various fibers, including the total fibers, back fibers, front fibers and floating fibers, were more in line with the actual results than the simulative ones based on the previous drafting model with the simulation of the straight fiber arrangement in the sliver. In conclusion, the drafting model with the application of the hooked fiber arrangement was effective and precise in quantizing the drafting process of a sliver with many hooked fibers, such as a cotton card sliver. Moreover, the drafting model can offer the theoretical foundation for setting the drafting parameters from the perspective of the distributions of slow-floating fibers and fast-floating fibers.

mentioning

confidence: 99%

Simulation on the fiber arrangement and distribution in the drafting zone

2021

“…The dynamic behavior of the fiber bundle and sliver thickness variation in the drafting zone were also simulated by using some mathematical models. 2,9–14 Recently, the discrete-event model was applied into simulating the variation tendency of fiber number qualitatively and fiber distribution in the drafting zone. 15–17 A simple multi-field coupling model of fiber mechanics based on conserving momentum has been proposed that considers the distribution of the fiber speed point, slip rate and friction mechanics.…”

mentioning

confidence: 99%

Simulation of drawing process based on fiber arrangement in the sliver with straightness and separation degree

2021

Sliver irregularity, straightness and separation degree of fibers are three crucial factors in sliver quality. Considering the straightness and separation degree, the drafting model based on the fiber arrangement in the sliver was applied to simulate the drawing process. First, the fiber arrangement in the carding sliver was developed. Then, the drafting process was divided into the low-velocity stage, straightening stage and high-velocity stage to carry out the redistribution of the fiber arrangement so that the sliver quality after drafting can be recalculated from the new fiber arrangement after the drafting procedure. Combining the doubling procedure, the simulated sliver quality of each drawing process was demonstrated to be close to the actual values, taking the straightness and separation degree into consideration. The relative errors between the simulated straightness and percentage of separated fibers and the tested one were all less than 10%. The prediction accuracy of sliver irregularity was raised by about 40%. In addition, the simulated results strongly confirmed the theory that the drawing process has an influence on straightening the hooked fibers, separating the fiber in the assembly and improving the sliver evenness, which cannot be reflected in previous models.

“…An assumed random sliver and fiber end distribution were applied in the computer simulation by Johnson. 9 Huh and Kim [10][11][12] tried to formulate and simulate the dynamic behavior of a fiber bundle in the roller drafting and derive the attenuation curves of linear density. Kim et al [13][14][15][16] also analyzed the sliver thickness variation and fiber behavior theoretically.…”

mentioning

confidence: 99%

“…Figure12. The simulated mean and CV of fiber velocities in the sliver in the drafting zone for various distributions of fiber accelerated points.…”

mentioning

confidence: 99%

Modeling fiber arrangement and distribution during the roller drafting process

Yang

2019

During the spinning process, the roller drafting operation plays a significant role in attenuating the sliver to an appropriate linear density. In this study, the model of fiber arrangement was applied to simulating the roller drafting process in order to shed light on the sliver dynamic behavior in the drafting zone. The drafting process was operated from the high-velocity motion of the first accelerated fiber to the high-velocity motion of the last accelerated fiber. The proposed model showed that the simulated sliver attenuation processes were highly corresponded to the actual sliver attenuation results. In addition, the results revealed that the draft ratio, gauge length, input sliver linear density and accelerated-point distribution form had effective influences on the attenuation curves of sliver linear density, whilst the delivery speed scarcely had any effect. The fiber distributions of various forms were also investigated specifically and quantitatively from the fiber arrangement during the drafting procedure in real time. Furthermore, the sliver dynamic was also described by the mean and CV of fiber velocities within the drafting zone. The obtained simulation results demonstrated that the draft ratio, gauge length and delivery speed had a bearing on the mean velocity of fibers, while the CV of fiber velocities was significantly influenced by the draft ratio, gauge length and input sliver linear density. Besides, the distribution pattern has a valuable contribution to the mean and CV of fiber velocities. In consequence, the new drafting model was validated to be effective in quantizing the drafting process.