The purpose of this experiment is to determine the parts that occur in the yarn while producing the yarn due to raw materials, equipment, workmanship and working method, according to the capacitive measurement method (according to the change in mass). Evenness in yarn is one of the most important factors affecting quality. Irregularity in the yarn; affects processing, use and other properties. Unevenness; It defines the value deviations occurring along the yarn in terms of fineness and count, as well as other structural features. It is expressed in two ways as % U (mean deviation percentage) and % CV (coefficient of variation). In principle, it is based on the principle of mass measurement of the fluctuations on it with the help of the electric field formed between the passage of two parallel sheet material (yarn) kept at a certain distance from each other.
Irregularities in the yarn cause a decrease in yarn strength, the formation of thin and thick spots, and abrage errors in the dyeing of fabrics formed with this yarn.( ISO 16549 )
Sample preparation
The number of samples for the determination of unevenness with the capacitive measurement method is determined as 10. The number of tests for each sample is 1. Test specimens or parts are conditioned for 24 hours until the standard atmospheric conditions for the test reach equilibrium.
The test should be carried out under standard atmospheric conditions.
Doing the Experiment
Prepared yarn samples are passed through the guide on the device, between the tension adjuster and the capacitors and given to the suction port. The device is started. Adjustments are made according to the yarn values to be measured. For the experiment; measuring range
(4 tex – 80 ktex for staple fiber materials. 7 tex – 3000 tex for filaments
up to), measuring speed (25, 50, 100, 200, 400 m/min, 800 m/min for filaments) test time (1, 2, 5, 10 or 20 minutes), according to the yarn count to be measured Information such as capacitor plate spacing (12 mm - 0,2 mm width and 20 mm - 8 mm height), desired results are selected from the computer. After the test is completed, the following results can be viewed and printed on the computer screen.
Values from Display and Printer
*** Unevenness (% U)
*** Coefficient of variation (% CV)
*** Coefficient of variation (CV(L))
*** Frequent errors
*** Thin place: -30%, -40%, -50%
*** Bold: +35%, +50%, +70%, +100%
*** Neps:+140%, +200%, +280%, +400%
Graphical Values From Screen and Printer
*** Normal Diagram
*** Mean Value Variations
*** Spectrogram
*** Three-dimensional Spectrogram
*** Length Change Curves
*** Three Dimensional Length Change Curves
*** Mass Density Diagram
Yarn unevenness as a result of the test; can be expressed as unevenness (%U) and coefficient of variation (%CV). These numerical values are compared with statistics (Uster statistics) prepared according to the measurement results taken from all over the world. Thin and thick places in the yarn, nep values and yarn hairiness are also determined in the yarn quality control. By comparing the obtained values with the standards, the quality of the roving or tapes is determined.
