During the weaving and dyeing process of knitted fabrics, defects of different shapes will more or less occur due to factors such as raw materials, machines, processes and operations. Some phenomena are close and similar, and are confused together and difficult to distinguish. Especially dyeing and finishing factories that mainly process imported materials often cause disputes with customers, blame each other, unclear responsibilities, and even cause compensation, which brings consequences to the enterprise. unnecessary loss. This article combines production practice to discuss the identification and prevention of some common weaving defects and dyeing defects.
1 Crochet yarn
With the rapid development of the knitting industry, various ultra-fine denier, New products of ultra-thin fabrics are constantly emerging, but they make weaving and dyeing more difficult. A little carelessness can easily cause snagging.
1. Weaving hook yarn
Hook yarn refers to gray cloth The phenomenon that the surface is brought out by sharp and hard substances or hooked. When weft-knitted fabrics form crochet yarns, the phenomenon of flower stitches often occurs at the same time. The reason is that during the loop-forming process, the old loops do not exit the needle hook and form new loops, and the old and new loops overlap together. Appears as straight bars and scattered points. In addition, if the needle latch of the loom is incorrect, it is easy to cause straight yarn hooking. There are also burrs on the cloth inspection machine roller or careless scratches and scratches during transportation, which are all causes of yarn hooking.
2. Dyeing crochet yarn
Knitted fabrics from gray fabric to finished product The conventional process flow of dyeing processing: collecting → distribution → loose cloth (section) → washing → booking → sewing edges → distribution → dyeing → dehydration → intermediate inspection → shaping → finished product inspection → packaging.
3. The difference in identification and treatment of hooking yarn phenomenon
Weaving Whether it is cloth crocheting or dyeing crocheting, the key is to start with the initial inspection. The key point is to control loose cloth, slitting, washing and predetermined processes. The turner is required to pay attention to the surface of the incoming billet and promptly detect and reflect abnormalities in the incoming billet. When checking that there are no obvious burrs at the contact point between the equipment you are using and the gray fabric, and excluding other defects that may cause yarn hooking, once you find that the yarn is hooked from the gray fabric, you should notify the customer for confirmation.
If the initial inspection misses the hook yarn, the responsibility will be borne by the dyeing factory.
The hooking phenomenon in the dyeing vat is very messy and irregular. In severe cases, the loops are completely pulled out, and even the hooks break into holes.
Causes:
① The broken needles were not cleaned in time after the loom broke down, and were wrapped and brought into the gray fabric. It is formed in the dyeing vat;
② It is caused by other foreign objects (metal objects, small stones) entering the dyeing vat with the gray cloth and hitting the nozzle mouth, cloth guide wheel, and the surface of the vat wall to form burrs. cause.
Once it is found that the hook yarn formed in the dyeing vat, the vat should be stopped immediately for inspection. Enter the vat and use transparent ultra-thin stockings to repeatedly rub the vat wall and every surface in contact with the gray fabric. For every detail, wipe the burrs smoothly with a hand grinding wheel or fine emery cloth, and clean up any foreign matter in time.
If obvious hook yarn is found on the finished fabric surface, if it is in a straight line, the rear machine operator or quality controller should promptly notify the front machine operator to intermittently check all areas in contact with the cloth surface. The cloth guide wheel and exhibition roller should be used to deal with burrs in time if they are found.
If the crocheted yarn area on the fabric is large and there is no crocheted yarn on the unshaped fabric, it should be judged to be caused by the dragging of the gray fabric on the air duct after large reduction. Adjust the excessive yarn in time. The feeding amount and the weight per square meter are mainly based on the cloth surface effect to achieve the best.
2 Oil spots
Oil spots refer to gray fabrics that have been washed, After being scheduled and dyed, the cloth surface appears in the shape of irregular yellow clouds. Some are intermittent straight strips, and some are scattered spots, which are similar to dyeing defects, auxiliary spots, and silicone oil spots stained on the cloth wool in the shaping rolling groove. They are often found in weaving factories. An anomaly that has caused much controversy with dyeing factories.
1. Oil spots on the fabric
Weft knitted fabrics are being woven During the process, the loom must be refueled regularly and quantitatively to maintain lubrication. Especially important components such as knitting needles, needle grooves and needle tracks, the purpose is to reduce wear and tear of machine parts and achieve good processing performance. Warp knitted fabrics use an oiling device to oil the yarn surface during the warping process in order to improve fiber bundling, smoothness, softness, antistatic and other properties.
The purpose is to reduce the friction coefficient between the fiber and the metal yarn guide parts, protect the fiber surface, make it pass through each reed and yarn guide parts smoothly, and make the yarn have good knitting performance.
However, the quality, amount and method of adding oil will bring difficulties to the dyeing process. This is because in addition to the different oil content, the oil also contains some silicon-containing additives and lubricants with macromolecular structures. If the pre-treatment is not completely removed, it will not only affect the levelness of dyeing, but also coagulate with the oligomers in the dye liquor to form color spots and tar stains that are difficult to remove, called fabric oil spots.
2. Dyeing auxiliary stains
during the dyeing process or dyeing For post-processing, choose appropriate dyeing auxiliaries (such as dispersants, leveling agents, bath softeners, defoaming agents, color fixing agents, etc.) to achieve good level dyeing, improve the feel of the fabric, and prevent wrinkles on the fabric surface. , which is beneficial to the smooth operation of the fabric in the dye vat and improves the color fastness after dyeing.
However, attention should be paid to the compatibility, alkali resistance, acid resistance and the order of addition between the auxiliaries, and the operation must be strictly in accordance with the process requirements; otherwise, it is easy to cause dyeing auxiliaries to spotstrace phenomenon.
②The cloth end is rolled up
It must be flat because once the cloth end is wrinkled or twisted, it will be more than ten meters above the cloth end after loosening. Obvious creases can be seen everywhere. If this kind of cloth is stacked and pressed heavily (layered layer by layer) after being dropped, it will cause indentations and even crushing on the cloth surface over time. When dropping the cloth and changing the paper tube, it is best for two people to fully smooth the cloth head together before turning on the machine, which can reduce the creases on the cloth head.
③ For products with high elasticity and high spandex content, the cloth is dropped using automatic open-width winding. After the cloth is loosened, the two edges of the cloth will still be affected by the elasticity of the spandex. Large creases caused by double-sided cotton, thick colored cloth, etc. Therefore, pay attention to reducing the parking time after loosening such products and ordering them in time to reduce the phenomenon of creases.
2. Creases and prevention in the dyeing process
Before dyeing Loose cloth and water washing are most likely to produce creases. Pure cotton, viscose, modal, bamboo fiber and some milk silk, T warp knitted swimming fabrics generally do not need to be washed. Loose cloth can be dyed after ordering. Stretch knitted fabrics containing spandex cannot be stretched mechanically or artificially.
Therefore, the slitting and loosening machines must have adjustable speed devices to control the loosening process, which will reduce many creases. In addition, the cloth cart after loosening should not store too much gray cloth or park it for too long to prevent squeeze creases on the cloth surface.
Nowadays, the new open-width washing machine has been equipped with a speed-adjustable loosening device. The open-width rolled blanks can enter the washing tank after loosening. Solved the crease problem very well. Machine failure in the scheduled process can also cause creases on the fabric.
For example, if the gray fabric enters the exhibition area before the roller, if the belt slips for a long time, the gray fabric cannot be unfolded to form a fold, and creases will be formed after being rolled by the roller. The cloth in the dyeing vat is blocked or the amount of dyeing vat is too large. The gray fabric has been subjected to high-temperature heat treatment for a long time, and the cloth surface can easily form chicken claw marks or creases. This requires dyeing operators to stick to their posts, observe the operating status of the gray fabric in the dye vat at any time, and deal with the clogged fabric in a timely manner. The dyeing master should pay attention to the size of the cylinder when arranging the cylinder. Generally, the production is arranged according to 60% to 70% of the fabric capacity to avoid creases caused by poor operation in the cylinder.
6 Postscript
“Re-inspect the initial inspection and grasp the rules “, fine screening” is the key to distinguish elastic fabric weaving defects or dyeing defects:
1. The initial inspection is to focus on inspecting the defects of the incoming blanks, each piece of incoming blanks All have to inspect the cloth. The factory must also formulate quality inspection standards for gray fabrics so that employees can become familiar with and master the methods and requirements for identifying various defects. For incoming defects that exceed the factory’s allowable range, the quality manager must be reported in a timely manner, and the customer must be notified to confirm and record the handling. If the customer approves, the defect shall be signed and kept on file. Employees who miss inspections or report errors should be punished and their responsibilities should be clarified.
2. Pay attention to the defects caused by regular dyeing, which are generally irregular. For example, color patterns, color spots, color stains or spandex damage are mostly scattered spots with different shapes and sizes. However, defects caused by weaving are formed in a weft or longitudinal sequence along the cloth surface, so there are rules to follow. As mentioned above, The hidden breaks of spandex in the example are clearly visible from the cross path or longitudinal direction of the coil; the defects caused by the warping of warp knitted fabrics will show obvious pan head marks or straight strips on the cloth after dyeing.
3. Careful screening When defects appear on the cloth surface, the entire cloth should be inspected first to check whether the defects are whole or partial. For example, when the yarn hooking phenomenon is found, you should carefully check whether there are hooking yarn points from the beginning of the cloth to the end of the cloth, whether it is straight along the direction of the knitting needle, or intermittent, etc. Quality abnormalities should be discovered in time in each process. The fewer the processes, the easier it is to analyze the cause of the anomaly. </p
