Yarn quality evaluation includes two aspects: intrinsic quality and appearance quality:
Basically based on physical indicators and appearance Defects are detected. However, the physical index items and appearance defect items of different types and different uses of yarn are different.
Yarn quality standards have national standards (National Science and Technology Committee approved and promulgated), ministry standards (approved and promulgated by the Ministry of Textile Industry), enterprise standards (promulgated by provincial and municipal industrial departments)
The basis for common yarn quality evaluation and grading are as follows:
Cotton yarn quality assessment
Cotton yarn refers to all cotton-type yarns. The production volume of three shifts a day and night is used as a batch to evaluate. Its grades are divided into superior, first-class, second-class, and third-class. Superior is equivalent to the international advanced level. , first-class is equivalent to the international general level
Cotton yarn rating items
1. Variation coefficient of single yarn breaking strength
2. Weight variation coefficient per 100 meters
3. Evenness
4. Number of neps in one gram
5. The total number of nep impurities in one gram
Cotton thread rating basis: 1.2.4.5.
Rating method: Rating based on the lower one from 1 to 5, and then see if 1.2. is out of range. Regardless of whether one or two items are exceeded, it will be downgraded to one level, down to the second level for this reason. For high-quality cotton yarn, 100,000 meters of yarn defects are added as a grading indicator.
1. Single yarn (thread) breaking strength, breaking strength variation coefficient
Measure 60 times for single yarn and 30 times for strands. Substitute into the coefficient of variation formula to obtain. The formulas for n>50 or n<50 are different.
2. Weight variation coefficient per 100 meters
30 yarns, 1 meter long per week, 100 weeks. 30 are weighed separately and substituted into the coefficient of variation formula. Based on this, search for products, etc. in the technical specification table.
3. Weight deviation per 100 meters
Actual special number and Design features
The deviation percentage between the two is called the weight deviation or special number Deviation. Actual evaluation is measured in weight deviation of 100 meters.
4. Evenness
The evenness coefficient of variation (using electronic uniformity When there is a dispute, the former shall prevail.
Measurement of dry uniformity of blackboard strips: randomly select 10 tubes and shake 10 blackboards evenly , each block 250mmx220mm, compare them with the standard photos in turn under the specified light, and evaluate them as excellent or good according to their shadows, thick spots, serious defects, serious regular unevenness, etc. Those that are equal to or equal to first grade will be rated as first grade, those that are worse than first grade or have serious defects will be rated as second grade, and those with serious regularity and unevenness will be rated as third grade based on 10. The proportion of first-class, first-class, second-class, and third-class blackboards determines its evenness.
5. The number of neps in 1g and the total number of neps and impurities in 1g
The number of neps and impurities within 10 spaces of the positive and negative points, the total number of neps na and the total number of neps and impurities nb within 10 blackboards can be calculated as follows:
The number of neps in 1g=na/ Ntex x10
Total number of nep impurities within 1g =( na+nb)/Ntex x10
6. One hundred thousand meters of yarn defects
Yarn defects refer to major defects attached to the yarn, which are divided into short slubs (more than 100% thicker than normal and less than 200px in length) and long slugs (more than 45% thicker than normal and more than 200px in length). , Long slender knots (30~70% thinner than normal, longer than 200px) will affect the quality of the fabric and cause short ends. The inspection requires a large sample size, otherwise it will be difficult to detect, so the yarn defect tester takes a length of 100,000 meters.
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