Abstract: Roving elongation is a comprehensive indicator that reflects the quality of the roving. It has a great influence on the quality of the roving, so it must be controlled. By optimizing the tension parameters of the roving frame, the winding process parameters were adjusted. After adjustment, the roving elongation and the elongation difference between large and small yarns are effectively controlled, the evenness and quality unevenness of the roving are improved, and the roving breakage is reduced. The roving will generate tension during the winding process. If the twist of the roving is small, it is easy to produce unexpected draft after being tensioned. At the same time, if the tension is uneven during the winding process, it will have a great impact on the evenness, uneven weight and breakage rate of the roving. The roving elongation is an important indicator that indirectly reflects the roving tension. Therefore, regular testing of the roving elongation can promptly understand the trend of roving tension changes and adjust unexpected elongation, which is very important to maintain production stability and improve yarn quality.
01
The impact of roving elongation on products
The elongation difference between roving frames or between small, medium and large yarns within a doffer is too large, which affects the quality of spinning yarns Unevenness; excessive roving elongation can easily worsen the evenness of the roving; too large or too small roving elongation will increase the end-breakage rate of the roving frame.
During the winding process, the roving from the front roller to the bobbin is basically in a free state except for the support and friction of the spindle wing. When the roving winding speed is different from that of the front roller, Improper coordination of the roller output speed will cause excessive local or overall doffing elongation, thus affecting the uniformity or quality deviation of the roving. In order to ensure the quality of the roving, the elongation of the roving must be controlled.
02
Detection control and requirements for roving elongation
Currently , most roving frames use mechanical or electronic methods to detect and control the tension of small, medium and large yarns. The roving frames currently used by our company are Tianjin Hongda’s JwF1415 type and Qingdao Universal’s FA491 type. In fact, they belong to the same series. , the mechanical structures such as forming, upper and lower cone wheels, cone wheel control and length gauge are cancelled, and the corresponding functions are completed by the computer. The elongation detection and control method of the new roving frame is simpler, more advanced and more accurate. The general roving elongation testing method is the length measurement method. The new roving frame computer system has a special control module to measure roving elongation, which is more convenient to use and improves the test efficiency.
Use the length measurement method to measure the average roving elongation on a machine-by-machine basis. Our company’s combed variety requirements are 1% to 2%. The elongation difference between the front and rear rows and between large and small yarns is required to be no more than 1%. The monthly roving elongation pass rate is 80%, and the elongation difference pass rate is 90%. If it exceeds the range, it should be adjusted.
03
Control method of roving elongation
The roving quality of the original combed variety is: roving elongation 2.33%. The elongation passing rate is 34%, the elongation difference rate is 1.2%, the elongation difference passing rate is 64%, the roving evenness is 3.84%, the unevenness rate within the roving is 1.0%, and the roving breakage is 1.5/100 spindles.
Due to the large fluctuations in various indicators of roving and the quality variation of spun yarn, statistical analysis of monthly data found that the elongation index of roving has been poor, and the elongation and difference The qualification rate was beyond the standard range, so we started to control the roving elongation and then control the unexpected draft. We first made statistics and analysis of the data of the two roving frames 10# and 11#. The results are shown in Table 1.
As can be seen from Table 1, there is not much difference between the large and small yarns in the front and rear rows of the 10# roving frame, but the average elongation All are outside the control range, and the 11# roving frame shows a large difference in large and small yarns. Next, the elongation is adjusted and controlled. The adjustment methods of the new roving frame are different from those of the traditional roving frame, but the principle is the same. Taking the JWF1415 model as an example, the tension control parameters of the roving frame are: draft coefficient, thickness of each layer, bobbin diameter, etc.
The drafting coefficient p affects the tension of the whole yarn. If the tension is tight, p will decrease; if the tension is loose, p will increase. The thickness of each layer affects the yarn tension. If the tension is tight, the thickness of each layer increases; if the tension is loose, the thickness of each layer decreases. The bobbin diameter affects the yarn tension. If the tension is tight, the bobbin diameter increases; if the tension is loose, the bobbin diameter decreases.
First check the axial winding density of the two cars of this type. The inspection method is that when the yarn is small, it is required that there is a gap of less than 0.5 mm between adjacent yarn circles. With the naked eye, when the yarn is wound, The surface of the bobbin can be vaguely seen in one layer. After determining the gear of the winding part, start adjusting the elongation of large, medium and small yarns. The original parameters on the car are as follows: the drafting coefficient p is 1.02; the thickness of each layer of 10# is 0.421 mm, the bobbin diameter is 44.05 mm; the thickness of each layer of 11# is 0.428 mm, and the bobbin diameter is 44.16 mm.
Based on the elongation and difference rate of large and small yarns on each machine, multiple tension parameter optimization tests were conducted. It is believed that the following configuration is better for roving quality. The adjusted winding process parameters are: 10# and The drafting coefficient p of 11# is all 1.017, the thickness of each layer is 0.428 mm, and the bobbin diameter is 44.34 mm. Therefore, the winding process parameters of this variety were adjusted to control the roving elongation and improve the elongation of the 10# and 11# roving frames after adjusting the roving quality, see Table 2.
The adjusted monthly roving quality index is: roving elongation 1.81%, elongation qualification rate 90%, elongationThe difference rate is 0.7%, the elongation difference passing rate is 100%, the roving evenness is 3.54%, the unevenness within the roving is 0.7%, and the roving breakage rate is 0.8 pieces/hundred spindles·h. The test results show that by optimizing the process parameters of the winding part, the roving elongation and the elongation difference rate of large and small yarns are effectively controlled, the evenness and quality unevenness of the roving are improved, and the roving breakage is reduced. Improved production efficiency.
04
Conclusion
(1) Same variety, same machine The process parameter settings of the winding part of the roving frame must be consistent. Generally, the roving elongation remains basically unchanged after being adjusted.
(2) When the relative humidity in the workshop changes greatly, the variety is changed (fiber type or length changes greatly), a new machine is tried spinning, or the test elongation is significantly different from the target, The roving elongation must be adjusted.
(3) When adjusting the elongation of the roving, first adjust the axial winding density, then adjust the elongation of the small yarn, and finally adjust the elongation of the medium yarn and large yarn, but The winding process parameters should be determined according to the actual situation, and the optimization test should be coordinated with the data. </p
