The main task of the double-twisting machine is to twist the combined yarn, so the most important indicator to evaluate the quality of the double-twisting effect is the strand twist unevenness. The unevenness of the strand twist refers to the discrete degree of the twist distribution of the combined twist on the strand. The twist cv value is often used to express the uniformity of the twist of the strand. Uneven twist will affect the physical and mechanical properties and appearance characteristics of the strands such as strength, elasticity, elongation, gloss, feel, and wear resistance, thereby affecting the style and quality of the fabric. An in-depth analysis of the uneven twist of double-twisted strands is also the basis for controlling and improving the uneven twist.
1. Double twist strand twist The classification of unevenness depends on different sampling methods. Twist unevenness can be divided into three types: unevenness between machines, unevenness between spindles and unevenness within a single spindle. Generally speaking, the uneven twist refers to the total uneven twist of the product, which includes uneven twist between machines and uneven twist within the same machine. Uneven twist within the same machine can be divided into two types: unevenness between spindles and unevenness within spindles.
Generally, uneven twist refers to the total uneven twist, which is a comprehensive reflection of uneven twist between machines, uneven twist between spindles and uneven twist within spindles. In this article, the twist unevenness is expressed by the twist cv value.
In production control, with reference to gb/t2543.1?2001, the yg331ii microcomputer semi-automatic yarn twist meter is used to test the twist of each variety of strands being produced every day and calculate the twist. Unevenness is expressed by the twist cv value.
Take the test data of jc 9.8 tex×2 on a certain day as an example. Number of sampling units: 3 units (represented by letters a, b, c); sampling volume: 10 packages of yarn; test volume: 2 packages/cone (represented by test 1 and test 2), with an interval of more than 1 m. The test data and calculation results are listed in Table 1. Table 1 Twist daily test data
The data sampling in Table 1 covers 3 double twisting machines, and the number of sampled spindles per machine is 3 or 4 samples are not equal, and 2 samples are measured on each spindle (tube) of yarn; the twist cv value is calculated using statistical methods for the 20 data in Table 1. It can be seen that the measured twist unevenness represents the total twist unevenness of a variety in one day. The average value of the twist unevenness measured every day during the entire production cycle represents the total twist unevenness of a batch of yarns. Because one sampling includes not only different machines, but also different spindles of the same machine, and the same spindle also needs to test two data. Therefore, when analyzing twist unevenness, it is necessary to gradually start from three levels: between machines, between spindles and within spindles.
2. Uneven twist between machines has the greatest impact on the twisting effect of strands. If the overall twist of a two-for-one twisting machine is low or high, the number of twists will be large and the impact will be wide, causing great losses to the weaving factory. Usually, uneven twist between machines is caused by differences in machine status, mainly spindle belt, tension, winding, etc.; it may also be caused by errors in the process parameters of the machine. In production control, uneven twisting between machines must be well controlled, mainly relying on good equipment maintenance and regular testing. Taking the data in Table 1 as an example, the average twist measured by three double twisting machines are 805, 807, and 818 respectively, and the step unevenness rate is 1.6%. The difference between the machines is small. To find the cause of the uneven twist, further analysis is required.
3. Uneven twist within the machine. Uneven twist within the machine includes uneven twist between spindles and twist within the spindle. Unevenness, under the premise that the twist unevenness between machines is well controlled, the uneven twist within the machine will naturally become the focus of attention.
3.1 Uneven twist between spindles. In actual production, it is generally believed that uneven twist between spindles is caused by speed differences between spindles and state differences between spindles. Therefore, in the use of double twisting machines Special attention should be paid to the speed difference and status difference between spindles during maintenance and maintenance. The smaller the difference, the better. Analyzing the data in Table 1, it is found that the twist ranges of single spindles of machines a, b, and c are 39, 54, and 52 respectively. The uneven twist between the spindles of machines b and c is obvious, so a stroboscope is used to detect the corresponding twist. The spindle speed, the results are shown in Table 2, and the twist extreme unevenness calculated from the data in Table 1 is also listed in Table 2 for comparison. </p
