Research On Two-Channel Differential-Drafting Ring Spinning And Yarn Structure

Ring spinning,as the most important production technology of yarns at present,shows great advantages in adaptability for raw material,spinning a wide range of yarn count,producing good evenness and strength of yarns.However,with the emergence of new spinning technologies,the disadvantages of the ring spinning technology are highlighted,such as low spinning speed,small volume capacity,low automation degree,as well as the long process flow.In particular,rotor spinning and vortex spinning of high spinning speed,high automation degree,short process flow and big volume capacity bring another tremendous impact on ring spinning,forcing the ring spinning to open up new application fields and technical innovation.The ring spinning device has a great advantage in spinning fancy yarn because of its strong control ability of fiber strand and high control precision.At the same time,ring spinning technology is an effective way to expand yarn categories and increase the added value of products.The existing ring spinning fancy yarn devices mainly include slub yarn,fragment colored slub yarn and fragment colored constant count yarn.However,the single drafting channel of the aforementioned fancy spinning device can not give full play to the advantages of double roving fancy spinning.Therefore,the research of developing a ring spinning device that can realize independent drafting of double roving is of great significance to further expand ring spinning fancy yarn categories and increase the added value of products.In this paper,a two-channel differential-drafting ring spinning system is constructed based on two coaxial gear rings with independent rotating degree of freedom.The single spindle of this system has two drafting channels,which can give full play to the advantages of double roving fancy yarn spinning.Moreover,it can realize multi-functional spinning by taking into account the spinning of slub yarn,fragment colored slub yarn and fragment colored constant count yarn.It is helpful to further develop ring spinning fancy yarn categories and increase the added value of products.Furtherly,based on the two-channel differential-drafting ring spinning system and the self-developed yarn appearance structure characterization method,this paper systematically studied the yarn spinning principle and yarn structure of two-component variational blending yarn and two-component alternating yarn.It is helpful to provide theoretical guidance for spinning practice.The main research contents and achievements are summarized as follows:Firstly,according to the two coaxial rollers differential-drafting principle,a two-channel differential-drafting ring spinning system was constructed on the basis of the innovative design of the key components of the spinning machine and control software.The compact spinning technology was used in the two-channel differential-drafting ring spinning,which facilitated the actual application of the developed spinning method.Moreover,the roller gauge of the back zone and the drafting ratio for the roving of a high percentage of the blending yarns were also optimized,and under the premise that the roving in the back zone does not slip with the nippers,the optimal back zone gauge tends to be minimized,and the drafting ratio for the roving of a high percentage of the blending yarns was selected as 1.05.In order to study the appearance features of the two-component variational blending yarn and the two-component alternating yarn,four indices,i.e.Fiber Distribution Proportion on yarn surface?FDP?and Coefficient of Variation of Fiber Distribution on yarn surface(CV_fd)of the two-component variational blending yarn,as well as Appearance length of single component fragment and Appearance length of two component overlap joint fragment of the two-component alternating yarn were also defined.A test method based on image processing technology for featuring the appearance structures of the two kinds of yarns were proposed.The corresponding device used for the continuous acquisition of yarn images was constructed with the optimized acquisition parameters,achieving the effective characterization of the designed yarns.In order to reduce the measurement error caused by the color difference of two-component fibers,the two color rovings in experiments were optimized according to the relevant color space theory,and the feasibility of the test method was verified by experiments.For two-component variational blending yarn,the variable coefficient of the FDP of the yarn after 10 repetitions was 1.44%;for two-component alternating yarn,the variable coefficient of the segment length of the yarn after 10 repetitions was 1.52%.In terms of the two-component variational blending yarns,the effect of twisting fibrous strand form,twisting direction and blending ratio on the internal and external fiber distribution in yarn forming process based on the fiber geometric transfer mechanism of ring spinning.The distribution trend of the two-component fibrous strands as the two-component bundles twisted in adjacent flat ribbon form and two approximate cylindrical sirospun form was analyzed theoretically.The two-channel differential-drafting ring spinning with the compact spinning technology was used in this paper to achieve the independent processing of the converging process and twisting process,where two fibrous strands were converged first and then were independently twisted to form yarns by adjusting the airflow at the converging area to ensure the stable state without rotary movement in the strands.The range of fiber ratio changing on the surface of two-component variational blending yarns was enhanced at the same blend ratio of the two components,and the verification test was done based on the two-channel ring spinning method.The results showed that the linear relationship between the fiber distribution ratio of the yarn surface and the blend ratio is high as indicated by the relatively high coefficient of determination?R²=0.995?,and the range of the fiber distribution proportion is higher?the slope of the linear fitting is 0.955?than the other two cases?the slope of the linear fitting are0.771 and 0.572,respectively?.Finally,the spinning principle of the two-component alternating yarns was analyzed in detail.Based on the random distribution of fiber in the roving,the longitudinal gradient distribution of fiber in roving wedge end is formed in the process of stretching roving at breakage or extraction fiber from roving head,and the complementary joint of the two-component roving wedge ends can maintain yarn count constant during the dynamic drafting.The spinning principle of the two-component alternating yarns was clarified referring to the breakage mechanism of the rovings.The length model of two-component overlap joint fragment of the two-component alternating yarns was derived.Moreover,the spinning principle of the two-component alternating yarns was verified by the spinning experiments using the two-channel differential-drafting ring spinning system.It can be concluded that the average length of overlap joint fragment become larger with the increase of the drafting ratio,and the actual average length measured from the surface of the yarns was smaller than the predicted length from the length model.The study also found that the force state of the rovings at breakage,the variation range of the breakage area and the overlap joint fragments can be changed by adding two confined points.