"Yarn Defect Scatter Diagram" is a kind of graph that reflects the distribution of yarn defects, which is depicted by the sensor in the form of "points" on a two-dimensional matrix according to the size of the yarn defects. It directly reflects the size, number (frequency) and distribution of all defects on the yarn. In the scatter plot, the dense area formed by the "yarn defects" that occur more frequently is called the "yarn body".
The differences in raw materials, processes, equipment, temperature and humidity and other production conditions in the yarn production process will affect the size and number of yarn defects, thereby affecting the yarn body shape.
The UQC scatter plot is equivalent to marking all yarn defects on the yarn on a two-dimensional logarithmic coordinate, so the yarn quality, equipment condition and raw material changes can be understood through the shape of the yarn body and the distribution status of yarn defects.
1. The relationship between the yarn body and the spinning raw materials
Different types of fibers will have differences in physical indicators such as length, length uniformity, fineness, etc., and the spinning properties will also be different, so they will also affect the shape of the "yarn body".
Compared to cotton fibers, modal/wool blended yarns have longer fiber lengths and better length uniformity, resulting in a thinner yarn body (see Figure 1). Due to the difference in the length of modal and wool fibers, the length distribution of the blended fibers was wider (Fig. 1A), and the NSLT variation area decreased at about 5.5 cm.
Fig.1 Modal/wool blend, ring spinning, 20.8tex, UQ3iMH C15
In the scatter plot of UQC3 (C sensor), the abscissa length corresponding to the lowest point of the yarn in the detail (T) area is equivalent to the average fiber length of the yarn (see Fig. 2 and Fig. 3), and the horizontal length at the lowest position of the yarn body also reflects the length uniformity of the fiber. The longer the horizontal line, the higher the CV% value and the higher the linter rate. Excessive proportion of backflower can also lead to yarn variation.
Fig.2 100% cotton, carded, ring spindled yarn 32S (18.2tex) The average fiber length is less than 21mm. UQ3iMH C15
Fig.3 The raw material is 50% long-staple cotton + 50% fine-staple cotton, 100S, ring spinning, and the average fiber length is 20mm. UQ3iMH C15
In the case of no damage to the fibers, the average fiber length reflected on the yarn body diagram is also different when the fine wool cotton is produced using different spinning processes:
(1) Cotton combed yarn, the average fiber length of the spinning yarn = the main body length - 5 (mm).
(2) Cotton carded yarn, the average fiber length of the spinning yarn = the length of the main body - 7 (mm).
From this, it is also possible to determine the information about fiber damage and linting processes in the production process (clearing, carding, combing, spinning, etc.).
Several years of field service have also found that the average length of cotton fibers has generally decreased. Among them, there is a yarn that uses Xinjiang cotton, and there is also the problem of reducing the fiber length. This also confirms that the quality of Xinjiang cotton grades has declined this year, and the average fiber length has decreased by 1-2mm compared with previous years.
The moisture regain rate of the new flowers is larger, and the physical properties of the fibers are better, when matching with the old flowers. As a result, the internal physical indicators of the whole batch of cotton blending are very different, which leads to the problem of opening and carding. It is mostly reflected in poor grooming. At this time, attention should be paid to the adjustment of the carding process.
1.1 Fiber damage from the yarn body diagram
Affected by the processing performance, equipment operation status and process configuration of lyocell fiber, fiber damage occurred in the process of opening and carding, and the average fiber length of the finished yarn was short on the yarn body diagram (see Figure 4).
Fig. 4 100% LF (lyocell), 14.8tex, ring spinning, cut-off length of 39 mm, shown as around 23 mm on the NSLT scatter plot UQ3iMH C15
At present, in order to pursue the indicators such as dry yarn slivers, coarse details, and neps, some enterprises adopt the process configuration of "tight spacing, strong carding, heavy pressurization, and small spacing", which causes fiber damage and shortens the average length of the fibers of the yarn.
The speed of the flower beater is too high, causing fiber damage.
For raw cotton and its blended varieties, the damage of fibers in the spinning process can be understood according to the relationship between the AFIS L(n) index of raw cotton and the average length of fibers reflected by UT spectrogram and UQ3 NSLT scatter plot.
Fig.5 100% acrylic, 27S, ring spinning. The average fiber length is greater than 40mm, UQ3iMH C15.
For long-staple cotton or fine-staple cotton high-count yarns, the use of roller spacing is too small for the spinning yarn, which is also easy to cause the fibers to be pulled off.
Fig.6 Wool acrylic fiber yarn, 32.5tex, ring spinning, average fiber length 70mm, UQ3iMH C15.
Figure 7 100% viscose, 40S, ring spinning, UQ3iMH C15
Fig.8 Polaris/Modal 40S, ring spinning, UQ3iMH C15
Fig.9 Lyocell/viscose, 40S, ring cello spinning, UQ3iMH C15
Fig.10 Cotton/viscose, 26S, ring spinning, UQ3iMH C15
1.2 Summary
The yarn spun by raw materials (such as chemical fibers) with good length uniformity has a thinner yarn body.
Yarns spun from raw materials with poor length uniformity (such as chemical fiber and cotton blend, chemical fiber and natural fiber blend, natural fiber) have a wide yarn body.
If cotton is blended with chemical fibers with low moisture regain (such as polyester 65% cotton 35%), if the mixing is uneven (uneven weight is qualified), or there is a problem with the carding of a certain component, it will cause the yarn body in the 8-200cm range to be wider.
(To be continued)
Editor: China Yarn Network New Media Team
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