Nondestructive Test Technology Research for Yarn Linear Density Unevenness

Yarn linear density and linear density unevenness between fragments involve the mass and mass variation of yarn per unit length, which are important indices to reflect the uniformity of yarn thickness. Aiming at the shortcomings of the traditional testing method, which uses a yarn length tester to test these indices by counting length first and then cutting and measuring weight, a testing device that measures weight and counts length synchronously is designed and developed, so that the yarn can be continuous, recyclable, and reusable. Length counting is conducted by a length-counting disk connected to a photoelectric coded disk, and the result of length counting can be accurate to 0.01 m. The original skein frame with a perimeter of 1 m is replaced, so that the error caused by yarn overlapping is avoided. Through program control, the testing of a plurality of groups of linear density values can be completed at one time to calculate the linear density unevenness of different fragments of yarn, and the yarn can be led to a recovery spool through a yarn guide cylinder to form a new package. Polyester/viscose 65/35 blended yarn was taken as a test sample and subjected to statistical analysis using SPSS software. It is found that the results of the newly developed device are closer to the arbitration value; the whole experiment is completed at one time, which avoids the secondary error and reduces the labor intensity; and the raw materials can be recycled, which saves labor and raw material costs. The device has high value for industrialization and popularization.

Design and manufacture of three-dimensional auxetic warp-knitted spacer fabrics based on re-entrant and rotating geometries

Warp knitting technology is a fabric-forming technologies that is very suitable to fabricate three-dimensional (3D) auxetic fabrics due to its high efficiency and powerful pattern designing possibilities. In this study, two typical auxetic geometries, namely the re-entrant hexagonal network and rotating square solids, were selected as the design prototypes for the design and manufacture of 3D warp-knitted spacer fabrics. While two 3D warp-knitted spacer fabric structures with representative units of different sizes designed based on the re-entrant hexagonal geometry were manufactured by using a RD7 double needle bar Raschel machine with seven yarn guide bars, two 3D jacquard warp-knitted spacer fabrics with different base fabric structures designed based on the rotating squares geometry were fabricated by using a RDPJ4/2 double needle bar jacquard machine with two ground yarn guide bars and four jacquard guide bars. The Poisson’s ratios of these 3D warp-knitted fabrics in the course direction and wale direction were evaluated respectively through constant-rate tensile tests. The results revealed that the re-entrant hexagonal fabric structure with double chain stitches has auxetic behavior across a wide range of tensile strains along the course direction, while the rotating square fabric structure with elastic chain stitches as the base is auxetic within a narrow range of tensile strains along the wale direction. The study provides an alternative method to directly produce auxetic warp-knitted spacer fabrics through a single knitting process instead of using an additional post-compression and heat-setting process.

A novel method of analyzing spinning tensions for yarn breakage detection in ring frame

To reduce yarn breakage rates in spinning and increase production efficiency, we developed a detection device for spinning tension of the ring-spinning system by implementing the stress and displacement sensors with the yarn guide plate. The as-developed device receives data through signal acquisition system, and then the yarn tension at the thread guide and the displacement of the guide plate are obtained by solving the coupled physical-mathematical equations describing yarn tensions in twisting, ballooning, and winding processes, which gives the real-time dynamics. We found that the yarn tensions show periodical fluctuations along with the reciprocating movement of the yarn guide plate. In particular, the maximum tension at the initial winding stage has increased 12.6% when compared to the second winding stage, while the maximum tension at the third winding stage has increased 10.6% when compared to the second winding stage.

In situ measurement of the dynamic yarn path in a turbo ring spinning process based on the superconducting magnetic bearing twisting system

The yarn tension and balloon form are the most important physical process parameters to characterize the dynamic yarn path in ring spinning. The present research work focuses on the in situ measurement of yarn tension in different regions of the yarn path in a developed turbo ring spinning tester with a friction-free superconducting magnetic bearing (SMB) twisting system and at an angular spindle speed of up to 50,000 rpm. The influence of different parameters, such as angular spindle speeds (15,000–50,000 rpm), yarn counts (15–40 tex) and balloon control ring (one or multiple), were evaluated to identify the influence of acting forces, for example, centrifugal forces. The effects of these process parameters were analyzed statistically using an analysis of variance. The yarn tension between the delivery rollers and the yarn guide was measured using a modified one-roller tensile yarn tension sensor. The yarn tension between the yarn guide and the SMB system was determined with an already existing optical approach at a higher angular spindle speed. As the highest yarn tension theoretically occurs between the SMB system and the cop, it was estimated in this region by measuring the coefficient of friction between the yarn and the yarn guide using the friction module of the constant tension tester equipment. The maximum balloon diameter was determined from the recorded balloon form between the yarn guide and the SMB system with respect to different angular spindle speeds. The results provide valuable information about the highest possible spinnable speed and enable a better understanding of the dynamic yarn path in the SMB spinning system.

Development of auxetic warp knitted fabrics based on reentrant geometry

This paper reports a novel method to fabricate auxetic warp knitted fabrics on a tricot warp knitting machine based on a special structure design and knitting process. Three auxetic warp knitted structures were successfully developed and all of them were designed to form a reentrant hexagonal geometry to acquire an auxetic effect. To provide the fabrics with reentrant frames, elastomeric yarns and stiff yarns were used to form the elastic underlaps and stiff underlaps, respectively. While the elastic underlaps can keep the reentrant structures stable, the stiff underlaps can support the reentrant structures to keep their reentrant frames. To alleviate the transfer of yarns in the loops under tension, an additional front yarn guide bar was used to feed binding yarns to basic reentrant structures. After knitting, all the fabrics were subjected to a heat setting process to keep their shape and a tensile test to assess their auxetic behavior. The experimental results showed that all the fabrics exhibited an obvious auxetic behavior within a wide range of strain. In particular, the fabrics retained auxetic behavior until breaking when stretched in the wale direction, and the Poisson’s ratio of the fabrics could be as low as –0.5. On the other hand, the fabrics exhibited a large tensile elongation when stretched in the course direction and their Poisson’s ratios changed from negative to positive after the tensile strain exceeded a certain value.

FORMATION OF PACKAGES WITH PERIODIC CHANGE OF FORCES OF PRESSURE OF THE DRUM TO WINDING SHAFT

For the formation of high-quality packaging of cross winding on machines with a constant speed, release into the composition of the winding mechanism introduce a dispersion device of the bundle winding, providing a change in the speed of the yarn guide according to the law with a long cycle of work. When laying the thread with a slotted drum, as on a spinning self-rolling machine PSK-225 SH there is no way to influence the movement of the yarn guide. In this case, effective dispersion can be achieved by periodically changing the clamping force of the bobbin to the winding shaft. When the effort of pressing the bobbin to the winding shaft changes, the contact radius of the bobbin changes, and hence its rotation frequency, which in turn leads to a change in the angle of elevation of the coil. A mathematical model is obtained that describes the change in the angle of the coil on the package from the effort of pressing the bobbin to the winding shaft. It is shown that such a device can effectively eliminate defects in the structure of the winding in the form of bundles and ribbons.

Composition Analysis of Spooling Tension about Automatic Winder

The spooling tension of the automatic winder is the critical factor influencing on the quality of the finished textile. The satisfying creel package depends on the constant spooling tension. However, the complex spooling tension is subjected to many factors, such as the unwinding tension, additional tension and yarn guide tension. In this paper, the composition of the spooling tension was studied theoretically and the main factors giving rise to the tension fluctuations were obtained. The gained results could be applied to controlling the tension fluctuations of the winder.