Study on effects of structural parameters on untwisting performance in pneumatic yarn splicing

Abstract

The internal airflow of an untwisting chamber clearly affects the untwisting performance as determined by the appearance of the untwisted yarn end. This study established a geometric model of an untwisting chamber comprising an intake tube and untwisting tube, and adopted the renormalization-group k-" turbulence model to simulate the airflow patterns inside chamber structures having three varying parameters. These were the chamfer angle of the intake nozzle, rotation angle of the intake nozzle, and eccentric distance between the intake nozzle and untwisting tube. The chamber angle of the intake nozzle mainly induces a radial flow from the axial flow in the intake nozzle. The strength of the circumferential airflow in the untwisting tube, which is converted from the radial flow, is affected by the combined effects of the rotation angle of the intake nozzle and the eccentric distance between the intake nozzle and untwisting tube. An experimental bench that employed a high-speed camera to capture yarn movement was designed to verify the numerical results. Comparisons between simulation and experimental data show that the structural parameters of the untwisting chamber affect the airflow patterns and consequently the performance of untwisting the yarn end.Pneumatic yarn splicing used to join two separated yarn ends is a key technology for promoting yarn quality. As a complex process, pneumatic splicing can be obviously divided into an untwisting stage and a mingling stage. Firstly, a high-speed jet generated from compressed air is used to untwist two yarn ends intermingled by fibers in a helical manner, causing the yarn ends to become individual fibers, in an untwisting chamber. The two untwisted yarn ends are then dragged into a mingling chamber in an overlapping relationship using yarn clamps. Finally, another strand of airflow opposed to the rotation of untwisting airflow is applied to join the two separated yarn ends to form a neat strong yarn.There are many factors affecting the performance of the pneumatic splicing of yarn, such as the splicing inlet pressure, splicing duration, overlap length of the two yarn ends, and physical characteristics of the yarn. 1 Owing to the importance of splicing parameters, researchers have investigated the effect of such factors on the quality of twisted yarn normally characterized by strength and diameter, both experimentally and theoretically.Li presented the working principle of the pneumatic splicer and described how the factors affect the performance of splicing yarn. 2 Focusing on the dynamic response characteristic of the pneumatic actuator in the air splicer, Chattopadhyay et al. 3 realized rapidity of splicing by modifying the mechanism parameters.

A Research on Determining Optimum Splicing Method in Terms of Fiber Types and Yarn Count

“…Their findings showed that the Spandex © filament angular position is influenced by the important splicing conditions (splice length and duration of water joining) and, by providing the adequate splicing condition adjustments high splice physical performance is given and a particularly good appearance. Wu et al (19) revealed that pneumatic yarn splicing is a complex process concerning the winding of multi-filaments in a spiral airflow field. They indicated that a proper overlapping length is of benefit to achieve enough winding loops at the free-end of the filament to resist the dragging force exerted by axial airflow and obtain a successful splice subsequently.…”

Simulation of the dynamics of a flexible fiber in the swirling airflow in a nozzle containing cylindrical and divergent conical sections

“…3 In the air splicer of the auto-winder, a swirling airflow is used to untwist, unravel and open up a yarn to prepare for the piecing process. 4 In the JetRing and JetWind processes, swirling airflows are formed in the air-jet nozzle through which the yarn passes to make the yarn hairs wrap around the yarn body. 5,6 Considering the wide and important applications of swirling airflows in engineering fields, progress in studies on swirling flow is being continuously made.…”

“…3 In the air splicer of the auto-winder, a swirling airflow is used to untwist, unravel and open up a yarn to prepare for the piecing process. 4 In the JetRing and JetWind processes, swirling airflows are formed in the air-jet nozzle through which the yarn passes to make the yarn hairs wrap around the yarn body. 5,6…”

Numerical prediction and experimental analysis of ends-together yarn splicing

“…By analyzing the flow field, they discussed the principal of yarn untwisting and their conclusions confirmed the pneumatic splicer maker's suggestions about the principal of yarn untwisting. Wu et al 5 investigated the structural parameters that affect the untwisting stage. They made comparisons between the flow field simulation and experimental data.…”