The evenness of yarn is an important index of quality control of textiles, so the researches about the yarn evenness test method have been the hotspot in the textile measurement for recent years. In this article, yarn evenness testing by uster evenness tester
Wednesday, May 16, 2012
10:07 PM
Uster Evenness Tester or Uster Tester-5 | Principle of Uster Tester | Advantages/Disadvantages of Uster Evenness Tester | Uster Statistics
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| Uster evenness tester |
The evenness of yarn is one of main indexes to measure the quality of yearns. The unevenness of yarns will deteriorate the mightiness of yarns, and increase the end breakage rate in the spinning, and the increase of the end breakage rate will directly limit the speed of the machines and reduce the productivity. In addition, the unevenness of yarns will seriously influence the appearance quality of textiles.
Disadvantages of Uster Evenness Tester:
Uses of Uster Evenness Tester:
The uster company takes test result from the whole world, tested by their own equipment. They disclose statistics of the representative sample periodically. This statistics is known as Uster statistics.
The usual yarn evenness testing methods mainly include the length measurement and weight measurement method, the visual measurement method and the Uster evenness tester method. Because of large computation, the length measurement and weight measurement method is only used in the research works requiring higher nicety or adjusting and measuring unevenness instruments, and it is rarely adopted in general tests. Because the visual measurement method is quick and convenient, and it can comprehensively evaluate the appearance quality of yarns, and it is a very usual method in productions, but it has many deficiencies such as large man-made factor influences, random character, non-objectivity and bad repetition character, and its testing results are hard to be reserved.
The Uster evenness tester can get rid of the influence of man-made factors to the testing results, and it can quickly and objectively measure the unevenness of yarns, so it is applied widely. However, as viewed from its testing principle, it still has certain deficiencies. First, the Uster CV value of yarn evenness can only denote the unevenness degree of yarns, but can not reflect the uneven structure of yarns. Second, the Uster CV value of yarn evenness only considers the average of the unevenness degree of yarns, and can not reflect the uneven waves with different characters on yarns, i.e. it ignores the discrete character of yarn unevenness. But these uneven waves of yarns would largely influence the unevenness of cloth cover. Third, when measuring blended yarns, because both the properties of fiber materials and the dielectric coefficients are different, and if the blended evenness of fibers in yarns is bad, the capacitance will change, which will influence the CV values. If above factors can not be controlled effectively, the nicety of the testing result of yarn unevenness will be influenced. Fourth, the nicety of testing values will be impacted by the testing conditions (the atmosphere state, the historical reversion condition of samples, the time of humidifying treatment).
Principle of Uster Evenness Tester:
Raw material as well as spinning problem can be detected by the measurement of yarn unevenness which is done by Uster evenness tester or uster tester-5.
The quality parameter is determined by a capacitive sensor. In this case the yarn, roving or sliver is passed through the electric field of a measuring capacitor. Mass variation of the material causes the disturbance of the electric field which are converted into electric signal. Which is proportional to the mas variation of the material. The unevenness is recorded as a diagram.
Advantage of Uster Evenness Tester:
- The CV% measured by Uster give a measure of variation of weight per unit length.
- This instrument measure the irregularity of material at high speed (2-100ft/min)
- It can show both % of M.D & C.V. of material.
- The recorder of pen can work at a high speed of 100yds/min
Disadvantages of Uster Evenness Tester:
- The result obtained by this M/C is affected by moisture content of material .
- This M/C can not detect the thick and thin place.
- In this instrument material up to a certain thickness can be tested .
Uses of Uster Evenness Tester:
- Evenness measurement of yarn, roving and sliver.
- Measurement of imperfection ( thick,thin place, eps)
- Mass analysis.
- Spectogram analysis/frequency analysis.
- Yarn hairiness measurement
- Fabric simulation i,e before making fabric. The yarn gathering knowledge about the quality of the fabric.
- Variation of trend analysis.
The uster company takes test result from the whole world, tested by their own equipment. They disclose statistics of the representative sample periodically. This statistics is known as Uster statistics.
The uster statistics are quality reference figures which permit a classification of fiber, sliver, rovings and yarn with regard to world Production.
Last uster statistics for cotton fiber and yarn was published in 2007
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