Simulation Design For Draft Ratio Of Back Drafting Zone During Drawing In Spinning Process

Drafting exists in the processes of drawing,roving and spinning.The quality of the sliver after drawing is the main index to evaluate the drafting,so the main purpose of study on drafting is to obtain low irregular slivers.Draft ratio of back drafting zone is a key factor in determining the quality of the sliver.slivers was become longer and thinner during the tensile,Tensile was used to simulate drafting of the back drafting zone on drawing frame.which provided reference for the design of draft ratio of back drafting zone.The device which was designed and constructed on drafting frame by the predecessor to measure the dynamic force during roller drafting was improved in this paper,the experiment was carried out based on the measuring device and measuring method.The drafting force was tested the device.The relationship between variation of drafting force and the irregularity of output slivers was discussed and analyzed.Tensile and drawing are both pulling process during which the slivers become longer and thinner,tensile curve and drafting force-drawing multiple curves are very similar.Tensile method was used to simulate the drafting of the back drafting zone on drawing frame.Polyester and rayon slivers were used in the experiments,respectively.Tensile,and drawing were carried out in this paper.Tensile and drawing in spinning process were investigated in the study.The conclusions can be obtained as follows:(1)According to the experimental scheme,the drafting force of the back zone was tested and analyzed on the condition of different parameters.According to the experiment results of drafting force,it can be concluded that the variation of draft force curve was consistent with the drafting theory,which can be concluded that the testing method and precision of this testing device were still accurate.When the number of slivers and the the back roller ratch were constant,there is a critical draft ratio of around 1.50 to 1.60 for polyester and rayon slivers,at which the drafting force reaches its maximum,while the CV of drafting force and unevenness of output slivers can reach their minimum.(2)The results show that the draft ratio that translated from the critical elongation in tensile stress-strain curve is very close to the one that calculated from the drafting experiment when the maximum drafting force occurs.Obviously,it is feasible to design the draft ratio of the back drafting zone during drawing in spinning process by using tensile to simulate drafting.Different fiber slivers have different critical draft ratio of back drafting zone different fiber sliver is different.The critical draft ratio of the polyester sliver is slightly larger than that of the viscose sliver.Whether it is polyester or viscose,when the draw ratio is less than the critical draw ratio,the draft force increases gradually and the CV of drafting force and the CV of output slivers decreases gradually.The drafting force reaches its maximum at the critical draft ratio,however,at which the CV of drafting force and unevenness of output slivers can reach their minimum.In the end,the critical draw ratio obtained from the tensile method was verified on the other drawing frame in the lab.The results showed that the CV of the output slivers was low when the draft ratio obtained by this method occurred,so the tensile method can be used to design draft ratio of back drafting zone during drawing.(3)The critical draft ratio obtained from the tensile test was very close to the draft ratio of the back zone at which the property of output spinning yarn was very excellent.Similarly,tensile method can be used to simulate drafting during drafting in the spinning process,which also can be used to design the draft ratio of back drafting zone on spinning frame.Whether cotton,polyester or viscose,when the draft ratio is less than the critical draft ratio,the unevenness of the spinning yarn gradually decreased.The yarn strength reached its maximum at the critical draw ratio that obtained from roving tensile curve,however,the unevenness of the spinning yarn reached its minimum at the critical draw ratio.