Study On The Effects Of Navel In Rotor Spinning

The effects of navel on the yam twist propagated in the rotor spinning are studied using integrated methods.Compared with ring spinning system, rotor spinning system has many predominant performances as follows: less neps and piecings, higher productivity and output, bigger package, shorter technological process, lower labor strength and better environment, rotor spun yarn has better evenness, thickness, nip, hairness, curling, pilling, extension, elasticity and dyeability, and so on. As a result, rotor spinning has been making great developments around the world.Twist is an important property of a yarn. Investigate of the influencing factors of twist is very important to improve the yarn quality. There are many factors that influence the yarn twist in rotor spinning. Navel is one influencing factor. Many researchers studied the functions of navel in rotor spinning, but they have not obtained a uniform viewpoint whether the navel has the function of false twist, twist deterrent or twist fault.In order to analyze effects of the navel in rotor spinning and accelerate the development of technology and equipment of rotor spinning, researches in this paper are carried on as below:1. Based on the definitions of false twist, twist deferent and twist fault, together with the analysis of forces and moments acting on the yarn, a method is established to distinguish these three effects and a method to evaluatethe degree of these effects.2. Based on the locomotion and forces of yarn relative to the surface of the navel, the effects of the navel on the twisting procedure are analyzed in rotor spinning with different instances.3. By analyzing the forces and moments of yarn relative to the surface of the navel, a mathematical model of twist of the yarn on the navel is established.4. Using the mathematical model, the relationships between the effects of the navel and some relative factors are analyzed.Based on above analysis, the following results are obtained:1. By analyzing the forces and locomotion of the yarn relative to the surface of the navel, the effects of the friction part on the twist of the yarn can be used to distinguish the false twist, twist deterrent and twist fault of the friction part. The degree of these three effects can be evaluated by the change of the twist of the input yarn relative to the friction part.2. Based on the locomotion and forces of yarn relative to the surface of the navel, the navel has the effect as false twist, twist deterrent or twist fault with different instances. Details are showed as follows:(1) When the friction force is not big enough to cause the yarn to revolve around its axis, and the friction angle is in the range of [-n/2, n/2], the effect of the navel is twist deterrent in rotor spinning.(2) When the friction force is not big enough to cause the yarn to revolve around its axis, and the friction angle is in the range of [n/2, 3ti/2], the effect of the navel is twist fault in rotor spinning.(3) When the friction force is big enough to cause the yarn to revolve around its axis, the effect of the navel is false twist in rotor spinning. As the normal component of the composition of forces along the yarn axis is greater than zero, the navel conducts the function of false twist, which will increase the twist on the input yarn relative to the friction part. As the normal component of the composition of forces along the yarn axis is less than zero, the navel also conducts the function of false twist, which will reduce the twist on the input yarn relative to the friction part.3. By analyzing the yarn on the navel, the mathematical model of the yarn twist is established, which shows the mainly factors affecting the functions of the navel. These factors are the raw material, friction coefficient between the yarn and the navel, yarn diameter, the radius of circular generatrix of navel surface, the inner radius of yarn doffing tube, rotating velocity of rotor and rotating velocity of the navel, etc.4. By solving the mathematical model based on the Runge-Kutta method, factors as the radius of circular generatrix of navel surface, the inner radius of yarn doffing tube, rotating velocity of the navel and rotating velocity of rotor have different effects on the function of the navel in different conditions. So the functions of thenavel can be controlled by varying or designing thosefactors.The above results will contribute to understanding the processing mechanism of rotor spinning, enriching the twisting theory of rotor spinning, investigating the twist of rotor yarns, and optimizing the design of navel, etc.ZHANG Guolian (Textile Engineering) Supervised by CHEN Ting...