No abstract

Double apron drafting is an important unit in yarn spinning; the motion of fibers during the double apron drafting zone directly determines the quality of the final yarn. In this research, we sought to study how the motion of the fibers and the irregularities introduced during the double apron drafting process were affected by the processing settings and fiber properties. The fiber acceleration point under different drafting conditions was investigated using the tracer fiber technique. The results showed that both the drafting parameters as well as the input sliver properties have a certain influence on the fluctuation of fiber acceleration points, but the difference is small. In addition, the irregularity caused by the fluctuation of the fiber acceleration point during the drafting process (CVFAP) was also calculated under the same drafting conditions based on the irregularity of the input sliver and that of the spun yarn. By comparing the relationship between the CVFAP and fiber acceleration point fluctuation, it was found that the trend of the change between the two is in fairly good agreement. This is consistent with theoretical research and practical experience, and it can prove the accuracy of the fiber acceleration point test results from another aspect as well. Studying the dynamic motion of floating fibers during the double apron drafting process sheds light on the correlation between spinning conditions and yarn quality, which can provide a reference for process optimization.

Fiber tufts were modeled as random fibrous materials based on the statistical orientations of the observed fibers. The tufts with different fiber properties were analyzed experimentally and simulated well. It was found that the distribution of fiber orientation angles is not uniform. The simulations of tufts have confirmed that the sizes of tufts could also be affected by the orientation angle distribution of the constituted fibers. The model was verified by the simulated tufts and the tested ones. Good agreement was achieved between the sizes of simulations and the observed ones. The above model can further explore the underlying principles of carding in yarn manufacture. Furthermore, the modeling method can also be widely used to simulate other fibrous materials where fibers are highly tangled.

Double apron drafting is the general drafting form in the front zone of the ring spinning frame. In the double apron drafting system, the top apron and the bottom apron form an elastic tensor gauge, which can better control the movement of floating fibers and improve yarn quality. In order to investigate quantitatively the influence of the top apron and bottom apron on fiber movement and yarn quality in the double apron drafting system, the differences of fiber acceleration point distribution, yarn irregularity and yarn strength spun by double apron drafting, single apron drafting and simple roller drafting under different process conditions were compared. Compared with simple roller drafting, double apron drafting and single apron drafting can effectively control the fiber movement in the drafting zone. With the increase of fiber length, the difference between the distribution of fiber acceleration points obtained by double apron drafting and that obtained by single apron drafting gradually decreases. When the fiber length is greater than 32 mm, the difference is small. Besides, by analyzing the improvement rate of the top apron and bottom apron on yarn irregularity and yarn strength under different drafting settings, it was found that the overall improvement rate of the bottom apron on the yarn quality was higher than that of the top apron, especially for manmade fiber yarns. Even in some cases, the strength of viscose yarn spun by the single apron drafting process is higher than that of the double apron drafting process.