Fujio Konda

Effect of Suction Air Pressure in Friction Spinning on Yarn Properties

We have studied the effects of suction air pressure on the structural parameters and mechanical properties of yarn. Changing the amount of suction air pressure improves the fiber extent in yam and yarn appearance. Therefore, photographic and fiber tracing methods are used to evaluate, respectively, yam appearance and fiber extent in the yam. To consider the effect of suction air pressure on yarn diameter, yam tension at the yarn-forming zone and yam diameter are measured simultaneously on a friction spinning machine using various levels of suction air pressure, and then the relationship between them is considered using the cross correlation method. The results show that at high suction air pressure, yarn di ameter, yarn unevenness, and yam irregularity decrease, while fiber extent in the yarn and twist efficiency increase. On the other hand, the value of the correlation coefficient demonstrates that there is a high correlation between variations in yam tension and yarn diameter. The results of yam mechanical property measurements show that at high suction air pressure, yam tenacity increases and yarn elongation decreases. Results are reported from experiments on 100% cotton yams.

Filament Pre-tension in Core Yarn Friction Spinning

Core yams are known to improve cotton yam properties. In this research, core yarns are spun by introducing filaments under tension into the yarn-forming zone of an ex perimental friction spinning apparatus. A 30-denier (3.3 tex) nylon monofilament and a black 75-denier (35f) nylon multifilament make up the core, and cotton fibers are used as the sheath. The effect of filament pre-tension on the structural parameters and mechanical properties of the core yarn is examined, and core yarn properties are com pared with those of equivalent 100% cotton yarns. The photographic and fiber tracing methods are used to consider the appearance of the yarns and the geometric position of the core in the core yarns. The results show that the appearance of the core yarn is similar to that of regular cotton yarns, with the exception of core yarns produced with 00 gf/fil pre-tension. Core yarn irregularity does not change with filament pre-tension, and it is less than that of cotton yam. Core yam strength significantly increases as filament pre-tension and filament percentage increase, and it is greater than that of cotton yarn. Core yarn elongation is less than that of cotton yarn at a low filament percentage and greater than that of cotton yarn at a high filament percentage.

ANALYSIS OF YARN TENSION IN THE YARN-FORMING ZONE IN FRICTION SPINNING

We have analyzed the tension distribution along the yarn tail in the yarn-forming zone of a friction spinning machine by considering the effective parameters of the torque applied to the yarn tail. Tension is applied to the yarn tail by suction air pressure and rotation of friction rollers. The yarn tension in the yarn-forming zone is measured for various yarn counts and suction air pressures. The effects of the parameters on yarn tension are considered in a theoretical analysis based on tension distribution along the conical yarn tail. Theoretical results are compared with me experimental data. The results of this research show that yarn tension increases with increasing suction air pressure and yarn size in tex, and yam diameter decreases with increasing suction air pressure for the same yarn size. Therefore, because of the low tension experienced with fine yarns, it is difficult to properly produce such yarns through friction spinning.

False Twist in Core Yarn Friction Spinning

We have analyzed false-twist distribution in filaments along core yams produced on a friction spinning machine, considering the effective parameters for imparting twist to the filaments and yarns. The theoretical analysis is based on twist distribution along the conical yarn tail. Twist is applied to the yam tail by suction air pressure and rotation of the friction rollers. The theoretical results are compared with the experimental data. The results show that although, theoretically, the twist imparted to a filament is zero, there is still some twist in the filament in both directions (S and Z) in a short yarn length. As the sample length increases, these twists combine and cancel each other. The resulting twists tend toward zero in longer yam samples. Filament pre-tension also affects the false twist of the filament. The results show that the remaining twist in filaments in non-pre-tensioned yams is greater than that in pre-tensioned yams.

Fiber Speed and Yarn Tension in Friction Spinning

To investigate fiber speed inside the transport channel, fiber flow and yarn tension are measured at the same time on a friction spinning machine. Fiber speed at the fiber flow detection point is calculated using the number of fibers in a cross section of the channel at the detection area, the number of fibers in the cross section of sliver, and the speed of sliver feeding. The cross correlation method is used to obtain the time lag between the variation of yarn tension and the number of fibers in the channel cross section. The mean fiber speed between the fiber flow detection point and the yarn-forming zone is calculated from the time lag. Fiber speed in both cases is calculated for various levels of suction air pressure. The results of this research show that fiber speed decreases from the beginning to the end of the transport channel, and increases with increasing suction air pressure in the yarn-forming zone. On the other hand, calculating the value of the correlation coefficient demonstrates that there is a high correlation between yarn tension variation in the yarn-forming zone and the number of fibers in the channel cross section.

Analysis of Blend Irregularity in Yarns Using Image Processing Part III: Evaluation of Blend Irregularity by Line Sense and Its Application to Actual Blended Yarns

In Parts I and II of this series, we discussed the precision and efficacy of an image processing system for evaluating blend irregularity in blended yarns using three kinds of model yams, and reported on the application of that system to actual blended yams. That system involved converting original images into trivalued images (black fibers, white fibers, and gray background), which enabled quantitative evaluation of the blend irregularity on the surface of a short length of yarn (about 4 mm). However, that system required threshold values for converting original images into trivalued images, and also needed a considerable amount of processing time and experience. This study deals with a new system to evaluate blend irregularities by measuring line sense (a series of intensity values) around the center line along a yarn axis without converting the original image and by analyzing the distribution of the intensity values. This method saves processing time and provides a real-time evaluation of the blend state ( fiber arrangement). We have studied the feasibility of evaluating blend irregu larities by means of measuring line sense with this system using two kinds of model yams, where the numbers of component fibers, blend ratios, and blend states are known. We also discuss application of the system to actual blended yams.

Analysis of Blend Irregularity in Yarns Using Image Processing: Part I: Fundamental Investigation of Model Yarns

In this research, a computer image processing system is used to evaluate the blend state (fiber arrangement) or uneven distribution in blended yarns. Part I presents an investigation of the precision and effectiveness of the system using three kinds of model yarns, whose numbers of component filaments, blend ratios, and blend states have been predetermined. The method of image input, various image processing techniques, and a statistical analysis are examined based on the model yarns. The results show clearly that with this system, the diameter and area of one fiber can be measured, the blend ratio of black and white fibers in a short sample length can be accurately determined, and the size of a cluster can be quantitatively evaluated.

Analysis of Blend Irregularity in Yarns Using Image Processing: Part II: Applying the System to Actual Blended Yarns

Image processing has been applied to actual blended yarns made from wool/wool and wool/mohair, and the blend state (fiber arrangement) of the yarns analyzed. Yarn about 4 mm long (310 pixels) was processed in each image. The projected area of white and black fibers on the yarn surfaces, the blend ratios, and the sizes of clusters were determined. Further, when several scores of yarn images laid in a row were put into the system, blend irregularity curves could be obtained. From these curves, variance-length curves of blend irregularity were calculated, and a total variance, average values, etc., were determined. The analysis showed that the wool/wool yarn was well blended compared with the wool/mohair, because the former was smaller in blend ratio variance than the latter, was also smaller in cluster size and its variance, and further was smaller in the total variance of the variance-length curve for blend irregularity. With this system, such differences in the blend state of an actual blended yarn, which can hardly be distinguished with the naked eye, can be estimated.

Yarn Tail Structure in Friction Spinning

We have analyzed the yarn tail structure in the yarn-forming zone of a friction spinning machine by considering the shape of individual fibers in the yarn. We use photographic and fiber tracing methods to consider the shape of individual fibers in the yarn structure. In this research, we try to demonstrate that the shape of the yam tail in friction spinning can be obtained from the fiber configuration in the yarn structure. The results of our research indicate that the yarn tail in the yarn-forming zone has a complex shape. The tip of the yarn tail is thicker than in theory, not only because of the volu minous structure in this part of tail in the yarn-forming zone, but also because it may be affected by the quality of fibers feeding in to the yarn tail through the outlet of the transport channel. The experimental results of the twist imparted to the yarn tail also show that the twist in the inner and outer layers of the yarn is different and increases in the yarn center 2-2.5 times compared with twist in the yam surface.

Analysis of Blend irregularity in Gill Sliver by Image Processing. Part 1: Quantification of Blend Irregularity.

A general-purpose image processing analyzer was used to evaluate the blend irregularity in sliver by mean and standard deviation of detected blend ratio, which was obtained from the brightness of the image. The image of the black and white blended sliver was taken with a CCD camera. The influence of number of gilling, fiber length, blending system and feeding direction on the blend irregularity was discussed. In sliver blending, as the number of gilling is increased, the blend irregularity is remarkably reduced. In stock blending process, the blend irregularity is small and it shows nearly the same value irrespective of number of gilling. This fact indicates that the sufficiently blend has been obtained in the stock blending process. In sliver blending process, the sliver composed of fibers with the same length shows better blending than that of different length fibers. In reverse direction feeding, the blend irregularity of sliver is better than that of the forward direction feeding. (Received July 28,1997) (Accepted for Publication May 8,1998)