Analysis of weft bias problem of woven fabrics
General twill fabrics have large internal stress due to improper handling during the production process, which will produce weft skew. The fabric is twisted and the weft is divided into left and right.�� Latitude oblique, commonly known as “turning direction” and “turning direction”. The degree of weft skew = (h/H) X 100%. The greater the weft skew, the greater the change rate of the weft skew after washing. “Latitude slope” is also called “latitude slope change rate”. The larger the weft slope, the more severe the weft slope of the fabric.
1. Draw a 50cmX50cm square 15cm away from the edge of the cloth
2. Send for washing. Remember to iron it with an iron after washing, and measure the change after leaving it for 2-3 hours
3. Measurement and calculation method, measure the difference between the diagonals, the unit is mm, 100X2 (long diagonal – short diagonal Line)/sum of two diagonals = latitude and slope percentage
Generally, the amplitude of the latitude inclination must be less than 2%-3%. Otherwise, the garment will appear twisted or bent.
When the cloth surface is vertical, first find a balance line as a reference, and align one end with that straight line , then measure the height of the balance line from the high/low side on the other side, and divide the height of the high/low side by the width of the door, which is the number of weft inclinations .
Tear off a piece with your hands, then align the edges of the fabric and fold it in half. Check the difference by a few centimeters and divide it by the width to get the percentage. It’s hard to say, it depends on the style. Those with stripes are more troublesome. It’s basically no problem if it’s below 5%. When laying out materials beyond this, you should consider the left and right bone positions to be in the same direction to avoid twisting the barrel.
Different weft straighteners can be used according to the type of weft skew. The weft straightening principle is to adjust each warp of the fabric through the mechanical action of the overall mechanism. The relative running speed between the weft yarns makes the corresponding part of the weft yarn skew “lead” or “lag behind”, thereby restoring the state where the weft yarns and warp yarns intersect vertically in the entire width.
Why fabric Will the fabric and knitted fabric become skewed? Or will the fabric be twisted in a meandering manner? There are two reasons for this phenomenon.
Cause 1: If the fabric design or knitted fabric design is poor, weft skew will form. In this case, the design itself must be completely changed.
Reason two: Although the fabric is made based on normal fabrics and designs, weft skew is formed during the coloring and finishing process and the printing and finishing process. This kind of weft skew accident mostly occurs in plain weave fabrics of short fiber fabrics and filament fabrics in coloring and printing factories. The reason is that cloth colored and washed in a rope shape is prone to weft skew. Because the softer the fabric, the easier its tissue is to deform.
Therefore, when dyeing in a rope shape or using a coloring machine similar to this, the occurrence of weft skew in plain fabric is very obvious, and the weft skew in the fabric is easily formed. and the snaking (S-shaped) state.
When bending produces defective products and the fabric’s structure bends, all fabric products (dips dyeing, continuous coloring, printing) using the fabric will become defective products. Especially when finishing after printing, the bending status is clear at a glance. A state in which fabrics with skewed wefts are used for post-printing finishing, resulting in “bending” accidents. The printed pattern curves against the fabric. If the squeegee guide belt of a rotary screen printing machine or an automatic flat screen printing machine sticks to the fabric without weft adjustment, it will easily cause weft skew.
To solve this problem, pass the cloth through the cloth’s diagonal rod in front of the adjuster to form a tension difference on the left and right sides of the cloth and correct it. . In addition, there are many factories that use the weft bias and serpentine edge of the correction cloth to install the adjuster. However, this method cannot completely remove the latitudinal slope. There are many factories like this.
When an adjuster is used to correct the weft skew and meandering state of the cloth through human visual inspection and manual operation, if an error occurs during visual inspection and manual operation If so, there is a danger of the fabric becoming skewed or snaking in an instant. The way to completely prevent weft skew is to install a weft skew correction device (weft straightening machine) in front of the regulator or in front of the printing machine. If the fabric is passed through this device, the weft skew can be removed. It is possible to correct the weft skew in an unmanned manner if three appropriate devices (weft straightening devices), which are interconnected with sensors and microprocessors and specially designed guide devices, are used.
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