Second, the relationship between the yarn body and the spinning process
The spinning process directly affects the yarn defects and their distribution state.
2.1 Cleaning and carding process
Excessive opening and carding will cause fiber damage, increase the short linter and decrease the strength of the yarn, the average fiber length of the yarn will become shorter than the average length of the cotton fiber, and the yarn body of the yarn will increase and the yarn defects will increase in the range of 1-4 cm. Therefore, the rationality of the process parameters in the production process can be understood through the yarn morphology.
The type of carding wire, carding interval, carding speed and the proportion of back-flushing also affect the yarn shape and the average fiber length.
Fig.11 Viscose and acrylic blended corespun yarn
2.2 Effect of tight spacer spinning on yarn defects
The spinning yarn is spun with tight spacers, which can cause the fibers to be pulled apart.
In order to pursue quality indicators, some enterprises use extended spinning yarns and use too small roller spacing, which is easy to cause a large number of fibers to be broken when producing long-staple cotton and its blended varieties. Especially in the production of high-count yarns, due to the small number of fibers in the main drafting area, the long fibers will be broken due to excessive drafting.
Fig.12 Trend of fiber length in each process of combed yarn. JC60S, 100% cotton, UQ3iMH C15
As can be seen from Figure 2, the fiber length of the spinning process is shorter than that of roving, and the content of staple fiber is higher than that of roving.
Therefore, in order to improve product quality, the straightening and parallelism of the fibers in the whisker should be increased as much as possible, the fiber arrangement structure should be improved, the roving twist coefficient should be appropriately increased, and the internal friction between the fibers inside the roving should be increased to achieve flexible drafting.
2.3 Measures
(1) Adopt new upper and lower pins to appropriately increase the length of the floating area and reduce fiber damage.
(2) AFIS and UT test indexes were used to compare the fiber length of AFIS L(n) and spectrogram to understand the fiber damage.
(3) Observe the average fiber length of UQ3, which corresponds to L(n) of AFIS.
Fig.13 Same roving
Fig.14 Same roving
The UQ3 scatter plot of medium and low count yarns of the same roving raw material was compared (Fig. 13-14).
图15 100%棉,精梳,Nec32,UQ3iMHC15
Fig.16 100% polyester, Nec21, ring spinning, deterioration of drawing quality, UQ3iMHC15
Poor running status of spinning equipment or unreasonable spinning process parameters (Fig. 13) can also cause yarn body abnormalities.
2.4 Semi-combed
Fig. 17 shows J32Nec semi-combed yarn blended with 7 combed strips and 1 plain comb strip. Compared to 100% combed yarn, there is a wider zone of variation in the 1-4 cm range. This is due to the addition of a carded sliver in the drawing process, which causes an increase in the number of short and coarse joints in the yarn.
Carding and roving use a larger quantitative, and spinning yarn uses a larger drafting multiple, resulting in unstable drafting of the spinning yarn, which will cause an increase in coarse details of more than 8 cm.
图17 FTC28tex，UQC2iMKC15
Fig. 18 T65/JC3520Nec, due to the influence of the large drafting process, there are more coarse knots and details of more than 8 cm near the long and thick and long thin variation regions, UQC3iMH C15
3. The relationship between the yarn body and the spinning equipment
When using different equipment to spin the same number of yarns, due to the differences in the drafting form, transmission mode, drafting structure, process configuration, and operating status of the equipment, the quality of the spun yarn will be different, which can also be seen in the NSLT scatter chart of UQ3 (C sensor).
图19 100%,粘胶,环锭纺,Nec30,UQ3iMHC15
Fourth, the relationship between yarn body and temperature and humidity
Temperature and humidity affect the carding and drafting effect of fibers, thereby affecting the state of yarn defects.
(1) The control of temperature and humidity in the carding workshop will directly affect the opening and carding effect of raw materials. If the humidity fluctuates greatly or the individual bales are damp, the reflection on the spinning yarn is that the number of short yarn defects increases dramatically and the yarn body widens.
(2) In a cotton batch of polyester fibers, if there are several bales of damp bales, it will also cause poor carding and widening of the yarn.
(3) The high humidity in the spinning workshop will cause the increase of drafting defects.
(4) The low humidity of the spinning workshop will cause the increase of yarn defects.
(5) The humidity of the spinning workshop is low, and the mesh circle accumulates flowers, which will cause the increase of yarn nep defects.
(6) The blockage of the negative pressure compact spinning mesh circle will cause the increase of yarn hairiness and neps.
(7) In the production of long-staple cotton or fine-staple cotton high-count yarn, the roller interval is too small and the fiber is easy to be broken.
(8) Compact spinning is more sensitive to temperature and humidity. When there is a large difference in temperature and humidity between the two sides of the spinning frame or the front and rear of the car, there will be a difference of 1.5-4 cm short roving defects.
Editor: China Yarn Network New Media Team
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