Uster Evenness Tester: Principle, Uses, Advantages and Disadvantages | Uster Statistics

Last Updated on 01/02/2022

What is Uster Evenness Tester?
The instrument or machine by which unevenness (U%), co-efficient of variation of mass (CVm%), yarn hairiness, imperfection index (IPI) and thick, thin place, neps etc. of yarn, roving sliver can be measured or calculated is called USTER Evenness Tester. It is a legendary quality control instrument for fibers and yarn testing in the world.

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

Uster Evenness Tester is a capacitance testing equipment for measuring mass evenness and imperfections in staple yarn.  May also be used for measuring mass evenness of sliver and roving.

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.

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.

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.

The USTER evenness tester finds the variations in thickness of a yarn by using capacitive techniques. The yarn to be examined is passed through a pair of parallel capacitor’s plates whose capacitance is continuously measured electronically. The capacitance of system changes continuously due to the presence of the yarn between the capacitor’s plates. The capacitance depends on the mass of material (yarn) between the plates and its dielectric constant (type of raw material used). For the same dielectric constant, the signals are directly related to the mass of the yarn between the capacitor plates. To get the same relative permittivity for yarn, it should be made up of the same type of fiber and it must have uniform moisture content throughout its length. The varying moisture content or an uneven blend of two or more fibers will vary the dielectric constant in different parts of the yarn and this variation will be signaled as unevenness. The readings made by the USTER tester are equivalent to weighing successive 1 cm lengths of the yarn.

The following can be the possible reasons for yarn unevenness:

  1. The number of fibers in the yarn cross-section is not constant; it varies widely depending upon the fiber parameters. This is the most significant reason of yarn unevenness.
  2. The staple spun yarn made up of natural fibers having the variable fineness, this variation leads to a difference in yarn thickness even when the number of fibers in the cross-section remains the same.

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.

Advantages of Uster Evenness Tester:

  1. The CV% measured by Uster give a measure of variation of weight per unit length.
  2. This instrument measure the irregularity of material at high speed (2-100ft/min)
  3. It can show both % of M.D and C.V. of material.
  4. The recorder of pen can work at a high speed of 100yds/min

Disadvantages of Uster Evenness Tester:

  1. The result obtained by this machine is affected by moisture content of material .
  2. This machine can not detect the thick and thin place.
  3. In this instrument material up to a certain thickness can be tested .

What is Uster Statistics?
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. Uster Statistics have become a common language of quality for yarn producers and yarn users.

The uster statistics are quality reference figures which permit a classification of fiber, sliver, rovings and yarn with regard to world Production.

The latest 2013 edition of Uster Statistics covers 101 quality parameters in 123 chapters, using over 2,500 graphs. In 1957, Uster Standards included just three quality parameters, contained in two chapters across only six pages, including six graphs. “The standards are far more than figures to compare yarn quality around the world,” said Gabriela Peters, Product Manager Yarn Testing within Uster Technologies.

You may also like:

  1. USTER HVI 1000: Principles of Fiber Testing
  2. Features, Functions, Components and Applications of USTER HVI 1000
  3. An Overview of USTER CLASSIMAT
  4. Main Parts and Functions of USTER TENSORAPID 4 (UTR4)
  5. Classification of Textile Testing: Fiber Testing, Yarn Testing, Fabric Testing

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