When cotton knitted fabrics are subjected to scouring, bleaching, printing and dyeing wet processing, even if loose or low-tension equipment is used as much as possible, they will inevitably be stretched by a certain tension, making the width smaller. At the same time, during processing There will also be skewing of the threads. Although it has been through overfeeding wet expansion and overfeeding drying, its width and flatness have not yet met the requirements. Especially after being dried with a rotary screen, the fabric surface will show numerous wrinkles, the yarn will be more bent, and the undulations will increase. , causing the cloth surface to be uneven and unable to show good luster. In addition, there is fluff on the surface of the fabric, which makes the surface not smooth and the reflected light diffuses in all directions at different angles, so the luster is darker.
Calendering finishing of cotton fabrics
In order to make the surface of cotton knitted fabrics smooth and smooth, feel soft and elastic, and make the fabric Calendering is required to ensure that the width of the fabric meets the specified requirements, corrects the skewness of silk threads, reduces shrinkage, and improves the luster of cotton knitted fabrics, especially single-sided fabrics.
Cotton knitted fabrics with higher gloss requirements can be electro-optically finished. Calendering finishing uses cotton fiber to have certain plasticity under hot and humid conditions and passes mechanical requirements.
The process of calendering cotton knitted fabrics using an overfeed calender is generally as follows: After drying, the fabric is placed in a pile, turned over, seamed and joined, calendered (expanded, steamed, wetted, hot rolled One cooling and one dropping) Among them, the cloth speed is 14m/min, the steam box temperature is 98-100℃, and the roller pressure is 3.8×104-19.8×104pa.
Electro-optical finishing uses the effects of mechanical pressure, temperature, etc. to make the fabric have a smooth surface or fine parallel lines and good luster.
Electro-optical finishing is generally carried out in cross-section. The finishing principle and processing process are basically similar to calendering finishing. The main difference is that electro-optical finishing not only smoothes the knitted fabric, but also rolls parallel lines on the surface of the fabric. Threads cover up the irregular arrangement of fibers or yarns on the surface of the fabric, thus producing regular reflections of light and obtaining a strong luster and silky feel.
The structure and working principle of the electro-optical finishing machine are similar to those of the calender. The electro-optical machine mostly consists of two rollers, one hard and one soft. The hard roller can not only be heated, but also, under the action of gauge pressure, flatten the yarns on the surface of the knitted fabric, suppress the erected fluff, and change the surface of the fabric. It is smooth and smooth, and the degree of diffuse reflection of light is reduced, thereby improving the gloss of the fabric. In addition, before calendering, the knitted fabric is first reasonably expanded by the expansion support plate, so that the door width is increased and the longitudinal length is shortened. This state will be stabilized after calendering. Therefore, calendering has the functions of smoothing the surface of knitted fabrics, stabilizing the width, reducing shrinkage and producing luster.
A summary of common quality problems.
Longitudinal strands are skewed
1. Reasons
① When the fabric is calendered by three rollers, the number of windings is insufficient or Too much and wrong winding direction.
②When feeding the cloth, the cloth head is skewed.
③Three-roll calender, the pressure of the calendering roller is uneven.
④Three-roll calender, prevent improper burring (too slanted or too straight).
⑤When the felt and damping are calendered, the seam ends are not straight.
⑥The tension at both ends of the felt is different, and the gap between the knife and the damping roller is different at both ends during damping calendering.
2. Preventive measures
①After inspection, make corrections.
②The head of the cloth should be flush when entering.
③The tension at both ends of the drum must be adjusted evenly.
④ Stop the machine immediately and correct the position of the burr.
⑤The seam head should be straight.
⑥Adjust the tension at both ends of the blanket; adjust the gap between the damping and the knife.
Figure 1 Calendering of knitted fabric
The horizontal strands are skewed
1. Reasons
①The pressure at both ends of the three-roll calender roller is uneven.
②The surface of the fiber drum of the three-roll calender is uneven.
③After the fabric is bleached and dyed, it is not washed enough or softened poorly.
④The roller speed of the three-roll calender is slow and the fiber roller is fast.
⑤When the felt and damping are being adjusted, the seam head is skewed, and the left and right overfeed wheels have different speeds.
2. Preventive measures
①Adjust the pressure at both ends to promote uniform pressure at both ends of the three-roller calender drum.
② If the surface of the fiber drum is found to be uneven, correct it immediately.
③ Strengthen the final washing of fabrics and enhance softness and finishing.
④ Strengthen equipment maintenance to ensure normal operation.
⑤ Strengthen the maintenance of overfeeding parts, and the seams must be straight and flat.
Rolling width size
1. Causes
①Uneven drying and wetting of the fabric.
②Overfeeding is sometimes more and sometimes less.
③The shrinkage of the finely bleached gray fabric is uneven
④The pressure at both ends of the three-roller and two-roller calenders is uneven, and the steam box is wetted inconsistently.
2. Preventive measures
① Strengthen drying to make the fabric dry and wet evenly.
②The overfeeding amount should be adjusted when starting the machine, and the overfeeding situation should be checked frequently during operation.
③ Strengthen the process operation of gray cloth reduction.
④ Apply pressure at both ends of the optical machine to make it uniform. Control the pressure change of the steam box and adjust the steam supply volume at any time
Figure 2 Knitted fabric calender
The fungus edge
1. Causes
①The cloth is unevenly fed.
②The tension is unevenly adjusted.
③Three�The surface of the calender fiber drum is uneven.
2. Preventive measures
① Check whether the incoming cloth is flat.
②Adjust the tension frame to make the tension on the edge of the fabric uniform.
③Reinforce the maintenance of fiber rollers.
Yin and Yang sides
1. Reasons
①The temperature of the rollers on the three-roll calender is too high; between the two rollers The temperature difference is large.
② During the first pass of the three-roll calendering machine and the two-pass calendering, the gray fabric is in contact with the roller on one side.
2. Preventive measures
① Check and adjust the temperature of the three-roller calender drum in a timely manner; adjust the drum temperature of the damping preshrinking machine and felt finishing machine , to prevent automatic adjustment failure.
② Strengthen operations and make corrections in time.
Small holes are produced after calendering
1. Reasons
① The angle of the burr of the three-roll calendering machine is too high Obliquely, the needle point of the thorn nest is lying down, and the thorn nest is reversed.
② Regular holes appear on the fabric due to loose screws on the support plate or other debris embedded in the fiber roller.
③The adjusting screw on the support plate of the three-roll calender is resting on the steel rod of the support plate
Figure 3 Three Roll Calender
2. Preventive measures
① Place the thorn nest at the right angle and height, correct the lodging needle tip, and check when installing the thorn nest. .
② Check the fiber roller and the rolled out gray cloth, and remove debris in time.
③After the support plate is adjusted, inspection should be strengthened to ensure that the textile screws are in contact with the steel roller.
Water stains
1. Causes
① The water accumulated in the steam box tube has not been removed, and it is sprayed on the gray cloth, and the steam The box is too wet.
②The steam box is not kept warm, causing condensation water to drip on the cloth.
2. Preventive measures
① Before starting the machine, remove the accumulated water in the pipeline, and the moisture supply to the steam box should be strictly controlled in accordance with the process requirements.
② It is best to make a steam box with an interlayer and a waterproof ditch to prevent water from dripping on the cloth.
Stains
1. Causes
① Poor cleaning of steam boxes, floors, etc.
② The calendering roller, damping roller and felt are stained with oily clothes, etc., causing fabric contamination.
2. Preventive measures
① Strengthen the cleaning of the machine, steam box, and floor.
② Strengthen the cleaning work of the machine, felts, damping rollers, tool rests, etc., and at the same time check the rolled fabrics, and remove oil stains and other dirt in a timely manner. </p
