Experience of high speed strength testing in the h

2022-08-01
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Experience in high-speed strength testing of spinning mills in 1992, the first high-speed strength testing system - Uster tensojet high-speed strength tester appeared in the market. Compared with the traditional detector, the detection speed of the powerful detector is increased by more than 40 times

this instrument introduces new concepts to the textile industry, especially in the field of discrete weak rings. It can be proved that the broken warp on the shuttle loom is related to these weak rings. In order to find these weak rings, it is necessary to greatly improve the detection speed. Therefore, it is necessary to know not only the average strength and average elongation of the yarn, but also these weak rings

each point in the scatter diagram not only causes the relative error of indication to exceed the tolerance, but also indicates the strength and elongation value corresponding to a strength test

a large number of discrete points on the left of the scatter diagram with a large number of weak rings indicate that the spinning process is not controlled. These weak loops will greatly reduce the efficiency of the loom, so there is a high wind. The subsequent tests only need to call the risk. Since a large number of broken warp ends need to be repaired, the weaving process is likely to consume too much time

strength test of knitted yarn

many spinning mills often mistakenly believe that knitted yarn does not need strength test, because the strength of yarn used in knitting process is far lower than that used in shuttle weaving process. Contrary to this view, some researchers have analyzed the physical characteristics of yarn (including strength and elongation) and found that these characteristics play an important role in the weaving performance of yarn

for example, Iyer et al. Mentioned that the strength of the yarn must be sufficient to resist the tensile strain during knitting, especially in the knitting needle, sinker and triangle areas during unwinding from the barrel yarn and during looping. This also indicates that the yarn must have sufficient elongation to resist bending strain, or a certain amount of elongation to suppress strain, so that the yarn will not break

the high-speed motion of the knitting needle in modern knitting machinery increases the requirement for yarn strength. The strength of staple yarn is largely related to the twisting degree (twist coefficient) during spinning α e) Directly proportional

when considering the knitting performance of yarn, the term "knittability" should also be explained

The weavability of the yarn indicates whether the yarn is easy to weave. Knittability is a factor that directly affects the downtime, output, quality of knitted fabrics and production cost of knitting machines. This characteristic depends not only on the fiber characteristics in the yarn, but also on the physical and structural properties of the yarn itself. Before knitting, it is very important to know whether the yarn can be knitted well or not

some researchers also studied the weavability of yarn before knitting. There are 30 different kinds of cotton yarns used in the experiment, some of which are of commercial value

Uster tensojet test scatter diagram (tube yarn at slow spindle position)

among them, 12 samples (pure cotton, ring spinning yarn) were selected. All the yarns are woven into 1 × 1 rib structure and constant fabric tension and machine speed. The samples were woven according to three different loop length values, representing tight, medium and loose fabrics respectively

observe and record the number of stops, yarn breaks and holes in the knitting process of 2000 revolutions. By using multiple regression analysis, the friction equations between yarns and between yarn and knitting needle based on yarn characteristics are established, and the friction torque of bearing surface is reduced to 40%. Finally, the weavability is determined by these equations, machine density setting and machine speed

according to the statistical analysis, it is found that the yarn characteristics not only have a significant impact on the fabric quality, but also have an impact on the friction coefficient

in the knitting process, from tube yarn to knitted fabric, the friction between yarn and yarn, and between yarn and knitting needle occurs between yarn and knitting machine components, which will cause the increase of yarn tension

the increase of yarn tension will lead to a large number of yarn breaks and the decline of production capacity in the knitting process. Therefore, it is hoped that the friction between yarns and between yarns and needles can be controlled at a low level

some examples can be given from previous studies to explain the importance of yarn characteristics, so as to determine the knitting performance of yarn. As mentioned earlier, these yarn characteristics can be measured quickly and easily by using the yarn evenness and strength detection system

based on the experience of using USTER tensojet for more than 15 years, it is known that spinning defects can be detected by this instrument, but can not be found only by measuring the evenness of sliver

when the testing speed of this instrument can reach 30000 times per hour or 500 times per minute, some weaving problems that cannot be found in other textile testing can be exposed. A large number of tests form a reliable statistical platform

many events in the spinning plant will lead to the reduction of strength and elongation, but many of these events cannot be found through the evenness test, because these defects will not cause quality variation

the experiment shows that for the tube yarn (yarn specification: pure cotton combed ne16 ring spinning) from the same spinning frame, if the regular maintenance of the spinning frame is not in place, there will be various contaminated spindle positions, resulting in insufficient twist of the yarn (slow spindle position)

the experimental lineation diagram shows the variation of strength and elongation. Production problems are more reflected by the drawing of elongation

an individual test represented by each vertical line in a scribed graph. Line length is related to strength and elongation. Pay attention to the end of the line

the scribing diagram also shows that 9 tube yarns are tested, and each tube yarn is tested for 1000 times. Due to production problems, the scatter distribution below is very long

in order to successfully evaluate the quality level of yarn, many physical characteristics of yarn need to be determined in the laboratory

according to the laboratory test results, the performance of the yarn in the subsequent process can be predicted. The two most important yarn characteristics are strength and elongation

depending on the type of textile process, the yarn needs to have a certain minimum tensile strength and elongation. For example, the yarn used on shuttle looms requires great strength; On the other hand, yarns used in modern knitting machines require better elongation properties

as mentioned above, the tensile strength and elongation values can be used to predict whether the yarn is suitable for a specific subsequent process. Another use is to analyze yarn production process and problems caused by production

because tensojet can run at high speed, the strength detection and evenness detection can be carried out synchronously. In this way, the weak ring and physical characteristics of knitting and woven yarn are also detected at the same time of evenness detection and high-speed strength detection. (end)

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