Covered yarn, also known as wrapped yarn, is a composite structure yarn made of filament or spun yarn as the core yarn and wrapped with another kind of filament or spun yarn. At present, the vast majority of covered yarns on the market are produced and processed by hollow spindle fancy twisters. The process is that the core yarn is fed into the hollow spindle by feeding the roller at a certain speed, and the outer covered yarn is withdrawn from the hollow spindle bobbin. Wind down and form a true twist on the core yarn to play a fixed role.
The covered yarn is divided into single and double packages. In the double-wrapped yarn, since the two layers of the wrapped yarn are wrapped in the Z direction and the S direction respectively, forming an "X"-shaped coating, when the yarn is subjected to a certain external load, the bidirectional wrapping length The silk can be squeezed inwards, so that the core yarn is always kept in a straight state, which is helpful to improve the breaking strength of the yarn, and can well eliminate the deformation and uneven twisting problems that occur when the single layer is coated. And industrial textiles have broad application prospects. However, during production, it was found that the production process of double-clad covered yarn has an uncertain effect on the quality of the finished yarn, and sometimes even leads to user claims. To this end, this paper adopts the second general rotating combination design to arrange experiments, establish mathematical models, analyze the influence of coating process parameters on yarn quality, discuss its changing rules, and establish a new yarn design combining production practice and market demand Ideas and design methods.
01
test
1.1 Raw materials and test equipment
The core yarn is 14.5 tex viscose spun yarn, and the two covered yarns are 111 dtex/36 F polyester low-elastic yarn.
Yarn strength test: YG021B electronic single yarn strength tester, drawing speed 500 m/min, 20 samples. Strip test: YG137 type strip uniformity test analyzer with a test speed of 200 m/min and 20 samples. Hairiness test: YG171B-2 hairiness tester with a test speed of 30 m/min and 20 samples. Test conditions: temperature 18℃, relative humidity 60%.
1.2 Experimental design
Taking winding speed, upper twist (Z), lower twist (S) and other coating process parameters as the research object, the test is arranged and arranged by the second general rotation. The factor level coding table is shown in Table 1.
1.3 Test results
On the WF series double-layer double-sided coating machine, according to the test arrangement in Table 1, 20 test schemes are selected (the number of center point tests is 6). The indicators for examining the quality of the covered yarn are the breaking strength of the yarn, the CV of the sliver, and the number of hairiness of 3 mm.
Firstly, the original data is processed to remove outliers, and the normality test and variance consistency test are performed. The test results show that after removing the outliers, the index data of each scheme meets the normality to varying degrees, and the corresponding index data between the schemes also meets the variance consistency to varying degrees. Then separately obtain the average value of each program index data.
Conclusion
In the WF series double-layer double-sided coating machine, the coating process parameters such as winding speed, upper row twist and lower row twist have different effects on the performance of polyester low-elastic yarn double-coated viscose staple fiber composite yarn. With the decrease of the winding speed or the increase of the twist of the lower row, the breaking strength of the yarn increases; with the increase of the winding speed, the CV value of the yarn spool first decreases and then increases; With the increase of the twist of the upper and lower rows, the CV value of the yarn strand gradually decreases; the hairiness of the yarn is only related to the twist of the lower row.
The study also found that from the perspective of the yarn forming performance and covering effect of the covered yarn, the twist of the coating should be too large, but when the coating is too large, the yarn feels hard and the production cost increases. Therefore, in the production, under the conditions of ensuring that the yarn index meets the requirements and maximizes the productivity of the equipment, the coating twist should be reasonably selected.
