Horizontal stripes are a common weaving defect caused by factors such as machine adjustment and poor raw material quality during the production process of circular knitting machines. There are generally two types of weaving defects: hidden horizontal stripes and single-filament horizontal stripes. This article introduces the characteristics of circular knitting fabrics, analyzes the causes from the aspects of raw materials, mechanisms, machine components and adjustment processes, and proposes corresponding preventive and rectification measures.
Causes of hidden horizontal bars and preventive and rectification measures
Hidden horizontal stripes refer to the phenomenon of sparse and uneven appearance on the cloth surface due to periodic changes in coil size during a cycle of machine operation. Generally speaking, the possibility of hidden stripes caused by raw materials is small. It is mostly caused by periodic uneven tension caused by untimely adjustment after mechanical wear, thus causing hidden stripes.
1.1 Reasons for occurrence
a. Due to low installation accuracy or severe wear due to equipment aging, the horizontality and concentricity deviation of the circular knitting machine needle cylinder exceeds the allowable tolerance. A common problem occurs when the gap between the positioning pin of the large transmission gear plate and the positioning groove of the machine frame is too large, causing the needle cylinder to be unstable during operation, seriously affecting yarn feeding and unwinding.
In addition, due to equipment aging and mechanical wear, the main drive gear plate shakes longitudinally and radially, increasing the concentricity of the needle cylinder and causing deviations, causing fluctuations in the yarn feeding tension, causing abnormal coil sizes, and in severe cases, hidden horizontal stripes appear on the gray fabric. .
b. During the production process, flying flowers and other foreign objects were embedded in the adjustment slide of the speed plate of the yarn feeding mechanism, which affected the roundness. The speed of the synchronous toothed belt was abnormal, and the yarn feeding amount was unstable, resulting in the occurrence of hidden horizontal stripes. .
c. The circular knitting machine uses a passive yarn feeding mechanism, which is difficult to overcome the shortcomings of large differences in yarn tension during the yarn feeding process. It is easy to cause unexpected yarn elongation and differences in yarn feeding amount, thus forming hidden horizontal stripes.
d. For circular knitting machines that use intermittent coiling mechanisms, the tension fluctuates greatly during the coiling process, and the length of the coil is prone to differences.
1.2 Preventive and corrective measures
a. Appropriately thicken the gear plate positioning surface by electroplating, and control the shaking of the gear plate between 1 and 2 wires. Polish and grind the bottom ball track, add grease to flatten the bottom of the syringe with soft and thin elastomer, and strictly control the radial shaking of the syringe to about 2 wires. The sinker triangle needs to be calibrated regularly, so that the distance between the sinker triangle and the tail of the new sinker is controlled between 30 and 50 wires, and the triangle position deviation of each sinker is controlled within 5 wires as much as possible, so that the sinker can be retreated during the retreat. Keep the yarn tension consistent while looping.
b. Control workshop temperature and humidity. Generally, the temperature is controlled at about 25℃ and the relative humidity is controlled at 75% to prevent the adsorption of flying dust caused by static electricity. At the same time, necessary vacuuming measures are taken to maintain cleanliness and hygiene, strengthen machine maintenance, and ensure the operation of each rotating part. normal.
c. Transform the passive mechanism into a sequential active yarn feeding mechanism to reduce the tension difference during the yarn guiding process. It is best to install a speed monitoring device to stabilize the yarn feeding tension.
d. Transform the intermittent coiling mechanism into a continuous coiling mechanism to ensure continuity during the cloth curling process and ensure stable and uniform roll tension.
Causes of monofilament strips and preventive and rectification measures
Monofilament horizontal stripes refer to the phenomenon that one or several rows of coils on the surface of the fabric are too large or too small and unevenly dense compared to other rows of coils. In actual production, monofilament strips caused by raw materials are the most common.
2.1 Causes
a. The quality of the yarn is poor, and there is color difference in the single filament, such as tightly twisted yarn, chemical fiber filament without batch number, non-colored filament, or mixing of yarns with different yarn counts, which directly leads to the production of single filament stripes.
b. The size of the yarn bobbin is greatly different or the yarn cake itself has convex shoulders and sagging edges, resulting in uneven yarn unwinding tension and easy to produce single-filament horizontal stripes. This is because the different sizes of the yarn packages will result in different winding points and diameters of the unwinding balloons, and there will inevitably be large differences in the change patterns of the anti-heat tension. During the knitting process, when the tension difference reaches the maximum value, it is easy to cause different yarn feeding amounts, resulting in uneven coil sizes.
c. When processing porous and ultra-fine denier raw materials, the silk path should be as smooth as possible. If a certain yarn guide hook is slightly rough or the grease is solidified, it is easy to cause multiple single filaments of the raw material to break, and the color difference of the single filaments will also occur. Compared with conventional raw material processing, the requirements for equipment are more stringent, and the finished fabric is more likely to produce monofilament horizontal stripes.
d. The machine is not adjusted in place, and the needle triangle is too deep or too shallow somewhere, causing abnormal yarn tension and resulting in differences in coil size.
2.2 Preventive and corrective measures
a. Ensure the quality of raw materials, use raw materials from famous brand manufacturers as much as possible, and have strict requirements on the dyeing and physical index changes of raw materials. The dyeing requirement standard is above 4.0, and the coefficient of variation of each physical index should be small.
b. It is best to use fixed-weight silk cakes for processing. For fixed-weight silk cakes, select silk cakes with the same roll diameter for use on the machine. If any silk cakes with poor appearance, such as convex shoulders and sagging edges, are found, they must be removed for use. When dyeing and finishing, it is best to follow the dyeing sample. If horizontal streaks appear, choose to change the dyeing to a non-sensitive color or add a horizontal streak treatment agent to eliminate or reduce the horizontal streaks.
c. When processing porous and ultra-fine raw materials, the raw materials must be processed first.��Mao silk is strictly controlled. In addition, it is best to clean the wire path and check whether each guide wire structure is smooth. During the production process, observe whether there is tangled wool on the weft feeder. If found, stop the machine immediately to find out the cause.
d. Ensure that the depth of the pressure gauge triangle of each yarn feeding channel is consistent. Use a yarn length gauge to finely adjust the bending position of each triangle to keep the yarn feeding amount consistent. In addition, check whether each bending triangle is worn. The adjustment of the bending triangle directly affects the yarn tension, and the yarn tension directly affects the size of the loop formed.
in conclusion
1. In the production of circular knitting fabrics, monofilament horizontal stripes caused by the quality of raw materials are the most common. It is very necessary to select raw materials with good appearance and good quality for circular knitting production.
2. Routine maintenance of machinery is very important. The wear and tear of some machine parts that have been running for a long time will increase the horizontality and concentricity deviation of the circular knitting needle cylinder, and it is easy to cause horizontal stripes.
3. During the production process, the adjustment of the needle triangle and the sinking arc is not in place, causing abnormalities in the coils, increasing the difference in yarn feeding tension, resulting in inconsistent yarn feeding amounts, and horizontal stripes.
4. Due to the characteristics of its coil structure, circular woven fabrics have different sensitivities to horizontal stripes in fabrics of different organizations. Generally speaking, the probability of horizontal stripes appearing in single-area fabrics such as jersey is relatively high, and the requirements for machinery and raw materials are relatively high. high. In addition, fabrics made from porous and ultra-fine denier raw materials are more likely to have horizontal stripes.
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