The surface of a woven fabric consists of weft and warp threads. Here, it is aimed to determine the yarn density in the weft and warp directions. It is important to determine the frequency. Because the frequency in a tissue; It is a concept that can shed light on details such as the estimation of yarn count by yarn density per unit area, as well as affecting some physical properties such as air permeability, handling (hard or soft), unit weight and smooth stable surface of the fabric. Measurements can be made using three different methods.
These ;
1. Method Separating the fabric into thread elements
2. Method- Optical thread counting device (Lup)
3. Method-Moving yarn counting microscope on scale. (TS 250 EN 1049-2, ISO 7211-2)
Used materials
Standard atmospheric conditions, test samples, colored fine-tipped pen,
1. Material required for the method; clamp, two separating pins and heavy steel ruler
2. Material required for the method; loop (light receiving range should be 2 0,005 cm or 3 0,005 cm all around),
3. Material required for the method; low-power microscope thread counter (magnification 4x to 20x) and microscope eyepieces deemed suitable for measuring must have an index line).
Sample preparation
Except for Method 1, specially prepared test samples are not required. But the number of threads is determined in at least five different places so as to fully introduce the fabric. Before starting the experiment, the samples are conditioned for at least 16 hours in standard atmosphere.
Experimental Procedure
The density in woven fabrics is measured by 250 different methods according to the TS 1049 EN 2-3 standard.
1. Method- Separation of fabric into thread elements:
This method can be applied to any type of fabric.
It is also the only method that enables the examination of multi-layered and mixed textured fabrics.
A test sample containing at least 100 threads is used.
In narrow fabrics with a width of 10 cm or less, all warp threads are counted, including the edge threads, and the result is expressed as the number of threads in the full width.
First, at least 5 test samples are taken at random.
Samples should be longer than the length indicated in the chart below.
Needles at a distance of 0,2 cm to 0,3 cm from the ends of the gripper are inserted into the test sample.
The yarns outside the needles and in the measuring direction are removed and counted so that the distance of the fabric to be measured between the needles is left.
Threads in which the needles are stuck are counted as half threads.
It is appropriate to use pointed tweezers for removing the threads.
It is convenient to divide the threads into groups of ten in order to facilitate the counting process.
In the absence of a clamp, an alternative accepted method can be applied by placing a heavy ruler along the sample edge and inserting two needles into the sample at the appropriate distance.
Minimum measuring distance
2. Method- Optical yarn counting device (Lup):
The warp threads remaining between the two parallel edges of the light receiving aperture of the optical counting device are counted, the same process takes place in the weft threads.
As a result, the number of threads per centimeter is calculated.
A measuring distance suitable for the values given in the chart above is used.
The test sample is laid flat on a horizontal plane and one side of the light receiving aperture of the optical counting device is brought to a position parallel with the warp threads.
In some fabrics, it is not possible to see and count each yarn separately.
Then the repetition of thread reports is counted.
For this The easily distinguishable yarn is selected within the yarn pattern, and one edge of the light receiving aperture of the optical yarn counting device and the selected yarn are brought together.
The number of report repetitions and the number of remaining threads within the measuring distance are determined.
The number of threads in a report is determined by counting the threads in the tissue or by removing the threads from the fabric.
The warp yarns remaining between the two parallel sides of the light receiving aperture of the optical yarn counting device or the number of repetitions of the pattern or the warp yarn units and the warp yarns remaining from these units are counted.
Likewise, the weft threads remaining between the two parallel edges of the light receiving gap of the optical thread counting device or the number of repeats of the pattern or the weft thread units and the weft threads remaining from these units are counted.
Some satin twill etc on the face of the fabric. If a yarn type dominates, as in knitting, counting can be done on the back of the fabric, where it is possible to recognize the texture pattern more easily.
3. Method- Moving yarn counting microscope on scale:
In the third method, there is a frequency measurement with the help of a moving yarn counting microscope on the indicator chart.
With the help of a microscope moving along the selected distance on the fabric, the number of threads in that distance in the weft direction and in the warp direction is determined.
First, the test specimen is laid flat on a horizontal plane.
When the moving yarn counting microscope on the scale is moved with the screw, it is placed on the fabric in a position parallel to the warp or weft yarns, according to the yarns to be counted.
The yarns within the selected minimum measuring distance are counted.
Threads are counted one by one as the index line or indicator needle moves across the fabric.
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