Yarn evenness control is the measurement of mass changes in yarn structure (diameter) as it passes through the capacitor.
İyarn Irregularity Deviationsı Purpose of Detectionı
In order to eliminate the periodic errors that occur during the yarn production processes, the irregularities must be detected in the yarn irregularity devices. Irregularity is detected to detect and correct these errors at an early stage.
İTaking Yarn Samples
5 or 10 different sample bobbins are taken from the filament spinning machine. Coil picking is done by selecting a certain interval on the machine. The received coils are taken to the laboratory to be checked.
Unevenness deviceı; not to withdrawş yarns, POY, k in plain and textured yarnsıhr period variationsı showing kpassively measuring unevenness is the capacitor.
The parts that make up the unevenness measuring device
2-Signal processor with monitor and processor
Doing the Experiment
For irregularity control;
1-All samples must be conditioned before starting the experiment.
2-Thread; The yarn guide is passed through the tension adjuster and rollers (plates) and fed to the suction mouth.
3-In order to obtain error-free results, the test speed, inlet pressure, twist direction and tension force settings for each sample are adjusted to obtain minimum unevenness.
4-The test is started by pressing the Start button.
5-The resulting test result (% U) is compared with the irregularities found in the previous tests.
If there is a mass change along the length of the textile material passed between the capacitors consisting of two parallel plates located at a certain distance, the capacitance of the capacitor changes. The resulting signal change is amplified in the amplifier (image changer) and transmitted to the electronic circuits. The information about unevenness is distinguished as thick place and thin place errors in the indicator (indicator). Deviations in the signal are determined as % CV or % U. In the spectrograph unit of the device, periodic errors with the same length, repeating magnitudes and wavelengths are classified. The printer, on the other hand, outputs all the values obtained. It is sufficient to examine the weight change in unit length in the detection of unevenness. In the unevenness device, the following information is obtained by determining the unevenness in the yarn:
1-Irregularity (% U and % CV )
4-Spectograms and diagrams
5-Average deviation percentage ( U % )
6-Coefficient of variation (variation) (% CV)
7-Individual value M: Mass
8-Xort: Arithmetic mean
9-T: Experiment time
10-A: The area between the single value and the mean is also expressed as a % Unevenness.
Subjective (Black Plate İle) Irregularity Control
It is a method based on observation by wrapping the yarn in a contrast color (dark color plate for light yarns, light color plate for dark yarns) in order to indicate unevenness in yarn. Generally, black colored sheet is used. The yarn is wound on the plate at regular intervals in a smooth and parallel manner. It is necessary to pay attention to some points during this winding. It is the foremost rule that the yarn winding intervals are equal. It is a preferred feature that the plates are conical so that the faults can be seen more clearly. The yarn, which is placed on the feeding spindle of the machine that will perform the winding, passes through the guide and comes to a moving shuttle. The shuttle moves and wraps the yarn on the conical plate in a parallel and smooth manner. After the set amount of yarn is wound, the sheet is removed. General information about the yarn is obtained by comparing it with the standards prepared under the appropriate light. Checks should be made in daylight or artificial light, with the light coming from behind.
Irregularity AlsoğReading your men
Diagrams and spectrograms taken from the device are used to read the yarn unevenness values.
Diagram; They are graphs showing mass changes of fibers or yarns, flowing against time on a scale.
The diagram is arranged to show the magnitude of the deviations on a linear scale. This scale is valid for various materials within certain measurement limits.
For strip: 12,5% or 25%
For wick: 25% or 50%
For yarn : 100%
Spectograms are graphs of material mass change versus error repetition frequency.
By analyzing the spectrogram, the errors that cause periodic changes in the yarns are examined and their source is determined.
After reading the unevenness values, the result is evaluated. According to the results, the continuation of production or the elimination of errors are ensured. It is evaluated whether the number of twists of a 1 meter long filament yarn is between 20 and 40 according to the yarn number. The twist between the values is transmitted as an error. Generally, according to the evaluation results:
1- Rarely occurring errors,
2-Long wavelength variations,
Periodic errors of wavelength greater than 3-40 meters,
4-Very thick and thin places,
5-Slow changes in mean value,
6- Gradual changes in the mean value,
7- In periodic errors, it is determined whether the error occurs continuously or if it occurs rarely in the batch.