Yarn evenness test method
There are many ways to test the unevenness of spinning yarn. Here are only two commonly used simple methods. 1. Cut-off weighing method: Use a yarn length measuring device to obtain several skeins of a certain length. Each skein is called a segment. The weight of each skein of spun yarn is weighed separately to obtain Xi. Substitute into Equation (2-12) To find the weight unevenness, substitute it into Equation (2-13) to find the unevenness between segments. The fragment length is specified as 100m for cotton type spinning yarn, 50m for box carded wool yarn, 20m for combed wool yarn, 50m for ramie yarn 49tex and above, 100m for below 49tex, and 450m for raw silk. 2. The final inspection method is also called the black-slat drying method. It uses a blackboard winding machine to wind the spinning yarn evenly on a blackboard of a certain specification at a certain density, and then places the blackboard under the specified finishing line and position in the darkroom, and uses the eyes to observe the shadows, thick spots, and serious defects of the blackboard. etc., and compare it with the standard sample to determine the evenness level of the spinning yarn. The evenness levels of cotton yarn are divided into first-class, first-class and second-class, and those other than second-class are third-class. The first grade evenness rate of woolen yarn is evaluated. The unevenness of the spun yarn tested by the visual inspection method reflects the uneven thickness of short segments of the spun yarn. The test is fast and simple, but it cannot obtain quantitative data, and the test results will vary from person to person. Figure 2-7 are two blackboards of yarns spun with different finenesses. You can see the differences in defects, hairiness and uneven evenness. Figure 2-8 shows the YG381 blackboard machine.
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