Simulation Of Roller Drafting Process And Calculation Of Accelerated-point Distribution During The Drafting Process

Drafting procedure runs through the whole spinning process so that the simulation of drafting process will be a significant section to realize virtual spinning.Drafting procedure in the process of drawing,roving and spinning is to gradually draw out and narrow the sliver,which realizes the rearrangement of the fibers in the sliver,as well as the straightening and separating of fibers in the sliver.Therefore,if the fiber arrangement and morphology in the sliver can be simulated according to the sliver parameters,then the drafting process will carry out the simulation of straightening and separating the fibers and rearranging the distribution of the fiber in the sliver.The realization will provide theoretical basis for intelligent manufacturing of the spinning processing,which is what textile scholars had been expected,too.Currently,fibers were assumed to be completely straight and separated in the yarn in the drafting simulation,which is inconsistent with the actual sliver,and cannot reflect the straightening and separating effect of the drafting process on the fibers.Moreover,the distribution of the accelerated points of the drafting process is based on the mathematical fitting of the actual test,which has certain limitations.In this paper,the simulation of the roller drafting process was carried out and continuously improved based on the model of fiber arrangement in the sliver,which realized the simulation of redistribution of fibers in the sliver and straightening and separating on the fibers.The influences of drafting process parameters on the sliver motion during the drafting process and the sliver quality after the drafting process,including sliver unevenness,fiber straightness,fiber separating degree were discussed by these drafting models,which provided the theoretical reference for optimizing the drafting parameters.Besides,the accelerated-point distribution of floating fibers in the drafting process was derived based on the measured distribution of fibers and frictional forces in the drafting zone.The specific research contents are as follows:The second chapter firstly established the sliver before drafting based upon the straight fiber arrangement in the sliver,and then the movement time and distance of low-speed and high-speed can be calculated on the basis of the accelerated-point distribution,which realized the simulation of roller drafting process.The sliver unevenness,and additional unevenness by the drafting,with different drafting parameters can be calculated by the arrangement of fibers in the sliver after drafting,which will evaluate drafting effect.Moreover,the drafting model can be used to simulate the drafting procedure of spinning process,and the simulated yarn unevenness was significantly compatible with the measured value.The results can provide a theoretical basis for predicting the yarn unevenness by simulating the drafting process of roving with more straight fibers.Moreover,the fiber arrangement in the sliver can be recorded,then the dynamic change of the sliver can be analyzed according to the motion state of fiber during the drafting process.The attenuation curves of viscose sliver calculated from the fiber arrangement during the drafting process were consistent with the tested ones.The relative errors between simulated values and tested values were almost lower than 5%,which verified the reliability of this model again.The third chapter optimized the roller drafting simulation based on the model of the second chapter by applying the arrangement of hooked fiber into drafting simulation.The new roller drafting model realized the motion simulation of fibers during the low-speed stage,straitening stage and high-speed stage,which reflected the straightening influence of drafting on the hooked fibers.The straightening influence of the drafting parameters on the hooked fibers were quantitative analyzed,especially on the hooked fibers on both ends and the other hook fibers,which provided the theoretical basis for setting the drafting parameters.The simulated straightness of the first drawn sliver and the second drawn sliver for cotton are in according with the actual values.The relative errors between simulated ones and tested ones were all lower than 8%,which verified the necessity of introducing the hook fiber arrangement into the drafting simulation.In addition,the fiber arrangement and the distribution of different fibers in the drafting zone obtained by this perfected model were closer to the tested values compared with the simulated from the model of the second chapter.It can be concluded that the model is more suitable in the roller drafting simulation of sliver with more hooked fibers,such as cotton sliver.Based on the model of the second and third chapter,the fourth chapter developed the model of fiber arrangement in the sliver considering the influence of the fiber bundle on sliver quality,which is more in line with the actual sliver.The number of separated fibers and fiber assemblies were calculated by the ideal sliver density and the actual sliver density.The simulation of the separated fibers and fiber assemblies were realized during the simulation.The sliver irregularities of three kinds of cotton slivers simulated by this new model were more consistent with the actual test values even though there were also certain difference with the measure ones.The prediction precision of the sliver unevenness was improver by 50%-60% compared with the simulated values based on the model without considering separation degree.According to the model of fiber arrangement in the sliver considering the fiber separation degree,the drafting model was established to carry out the simulation of separating fibers during the drafting process.The quantitative analysis of the influence of drafting parameters on the sliver quality was operated to compare with the simulated results by the model of the third chapter.It was induced that the fresh drafting model can provide more effective and more accurate theoretical reference in the optimization setting of drafting parameters.Besides,the drawing process from the carding sliver to the drawn sliver can be simulated based on this drafting model combining the doubling simulation.The simulated sliver qualities from the carding sliver to the drawn sliver had the same trend with the tested ones and were closer to the actual results compared with the simulated results with the model of the third chapter.The relative errors between simulated straightness and tested ones were all lower than 5%.The relative errors between simulated separation degree and tested ones were all less than 11%.The forecasting accuracy of the sliver unevenness was improved by 30%-50%.Based on the actual distribution of fibers and frictional forces in the drafting zone,the fifth chapter carried out the simulation of the accelerated-point distribution.Specifically,9 contact relationships between the floating fiber with equal length and the other fibers and 36 contact relationships between the floating fiber with unequal length and the other fibers were completely considered for the fibers with equal length and unequal length firstly,then the contact fibers were randomly selected in the drafting zone according to the contact relationship to obtain the contact lengths,the forward force and backward force of floating fiber were calculated based on the distribution of frictional forces so as to realize the simulation of accelerated position lastly.The accelerated-point distribution of viscose and cotton with different drafting parameters were separately simulated and compared with the tested ones.The results indicated that the simulated values were conforming to the measured values,especially the results of viscose.The correlation coefficients of regression analysis between the simulated ones and tested ones were all greater than 0.90,which indicates that they have the same variation trend with the drafting parameters.The results verified the feasibility of the simulation method and the rationality that the actual contact between the floating fiber and other fibers is considered.Above all,compared with the previous drafting simulation,the roller drafting models in this study based on the fiber arrangement in the sliver can reveal the dynamic change of the sliver.Then the influence of drafting process on the fiber redistribution in the sliver can be can be full reflected by this drafting model.Besides,the drafting model was significantly improved by the application of straightness and separation degrees.The influences of the drafting process on the straightening and separating fibers were more comprehensively reflected by the optimized model.In addition,the simulation accuracy of drafting process and the prediction accuracy of sliver quality after drafting were improved by the optimized model.In the simulation of accelerated-point distribution,the contact relationship between the floating fiber and other fibers due to the arrangement position of fibers in the draft area was fully considered.Then the simulation of accelerated-point with different drafting parameters can be completed based on the distribution of fibers and the frictional force distribution in the drafting zone by the simple and time-saving testing methods.