Unevenness is expressed as the variation of any measurable yarn property or variation in linear density.
Due to the variation within wide limits in terms of fineness and length properties of the fibers and the uneven distribution of the fibers caused by the random placement of the fibers along the yarn length, the yarn count, strength, twist, etc. changes in properties occur along the yarn. These types of changes that occur in the textile material sometimes tend to repeat with a certain period of time, such changes are called "periodic irregularities" or "periodic errors". Today, irregularity control is carried out in order to detect and correct these errors as early as possible.
Main causes of yarn unevenness
1-Natural irregularities due to raw material properties and random fiber arrangement.
2-Irregularities resulting from the grouping of fibers due to the drawing process.
3- Periodic irregularities in linear density as a result of mechanical errors.
4-Irregularities resulting from random changes.
İFactors caused by yarn unevenness during processing
1-An uneven yarn will tend to break during spinning, winding, weaving and knitting, or any other process where tension is applied to the yarn. This also reduces efficiency.
2-Obviously visible defects occur on the fabric surface.
3-Because of their low resistance to deformation, more twist is collected in thin places in the yarn.
4-Fabric properties such as resistance to pilling, attitude against dirt, degree of moisture absorption, light reflection and gloss are also affected by yarn unevenness.
5- In knitted fabrics, yarn unevenness is evident on the fabric. The number variation that continues smoothly in the yarn has created light and dark areas on the surface. Thick areas in the yarn created darker areas in the knitted fabric, and thin areas formed the lighter areas.
6-After the dyeing process, the differences become more obvious because the thick areas of the yarn take more dye than the thin areas. Especially plain weaves show yarn faults more clearly than other knitting types.
Yarn Unevenness Device
One of the most widely used of these devices is the “Uster Unevenness Measuring Device”. The analysis of the spectrogram obtained in the Uster unevenness measuring device is a very useful method for examining and determining the source of errors that cause periodic changes in tape, roving and yarns.
The unevenness device uses the electrical capacitive principle to measure mass variations of sliver, roving and yarn. In capacitive measurement, an electrically non-conductive material passes between two parallel capacitor (channel) plates. Mass variations of the test material will alter the electrical signal from the sensor. Electrical signals are amplified, analyzed and recorded. In this way, mass variations of the material being tested are measured very quickly and accurately.
Benefits of the Uster evenness device
1- Irregularity of tapes, rovings and threads,
2-Frequency of thick places, thin places and neps,
3- Frequency of rare errors,
4-Strength and elongation of yarns,
5-Thread number change,
6- Yarn hairiness,
7-Change of thread diameter,
8- Trash and dust in the threads,
9-The roundness of the threads can be determined.