Some quality issues in spinning, such as hairiness, neps, foreign fibers, strong weak loops and immature fiber content percentage, are important issues that directly affect yarn quality, even fabric quality and the production efficiency of downstream processes, and should be paid great attention to. , set up defenses one by one, and use various high-tech testing instruments to monitor and solve the above problems online and offline. At least we can detect problems in time and take measures to reduce the quality problems found, in order to further improve the quality of spinning. Here we take strong weak loops and unevenness as examples to introduce ideas for improving yarn quality.
Average strong and strong weak rings
The strength characteristics of raw yarn include average strength, strength unevenness, average elongation and elongation unevenness. Generally, the average strength of warp yarns is 15 cN/tex, and the uneven strength is 9% to 10%. The average strength of weft yarns is 12 cN/tex, and the uneven strength is 9% to 10%. The average elongation at break is generally controlled within 2%.
An important strength indicator for the stop of the air-jet loom is the weak link, which is the lowest strength. It is generally believed that when the linear density of the yarn is only 40% of the normal yarn, this detailed weak link will inevitably cause end breakage and cause the stop. If the strength is weak If the ring is at 4 cN/tex and the elongation is less than 2%, it will inevitably cause breakage.
In addition to detailed defects in other strong and weak links, which account for 61%, other weak twists, poor joints, and thick sections can also cause stops between longitude and latitude, accounting for about 39%.
In addition to average strength and uneven strength, the strong factors that cause warp and weft yarns to stop are strong and weak loops, especially the index of strong and weak loops of 100,000 wefts. Therefore, some relevant enterprises in my country should be equipped with strength meters as much as possible to control the quality of raw yarn.
There are three main types of details on the raw yarn: short velvet details, thick details at the knots, and long filament knots or multiple short details connected together that will cause breakage.
In order to reduce strong weak links and provide good raw yarn for downstream processes, corresponding measures must be taken, such as the use of a new roving frame with four-unit transmission and four-roller drafting. On the one hand, it eliminates the details caused by the switch car, and on the other hand, it improves When drafting the sliver, it is necessary to reduce coarse and detailed defects, etc. It is also necessary to strengthen the coordination of the transmission teeth and keys of the drafting part to prevent loosening gaps and ensure the synchronization of the drafting process. This is also one of the important methods to reduce details.
In addition, rational configuration of the process and selection of good drafting components, such as rubber rollers, rubber rings, upper and lower pins, pressure mechanisms, etc., are also factors that reduce details.
Unevenness
The unevenness index includes two indicators: quality unevenness and evenness unevenness. Generally, spinning mills pay more attention to unevenness and have a high level of monitoring.
The new blowing and carding double cotton box feeder uses a pressure sensor and a variable frequency speed motor to control the cotton density in the cotton box, so that the cotton layer fed to the carding machine is consistent vertically and horizontally, and the uneven quality of the sliver can be controlled within 2 %～2.5%.
The open-loop, closed-loop and mixing loop auto-levelling mechanisms in each process of pre-spinning equipment such as carding machines, draw frames, and combing machines all play a positive role in improving uneven yarn evenness and uneven quality.
The drafting components of the draw frame, such as the cradle, rollers, bushings, etc., have been greatly improved, which has greatly improved the unevenness of the medium and short segments.
The final draw frame is equipped with a slub monitoring device and the roving is equipped with a tension monitoring system, both of which have a positive effect on improving the evenness of the finished yarn.
Most spinning mills are equipped with offline evenness monitoring instruments, which have a high frequency of monitoring and can detect evenness, coarse details, and nep defects in a timely manner and resolve them in a timely manner.
The advanced final draw frame is equipped with an online USTER auto-levelling and monitoring system, which can monitor the evenness level of the draw frame online, and offline monitoring can generally be cancelled.
The implementation of a series of online and offline monitoring technologies has ensured the spinning quality, which can generally reach the level of 25% of the bulletin, and some can reach less than 5%.
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