Elastic knitted fabrics are characterized by long routes, complex processes, multiple processes, and most of them are carried out in sections due to the weaving, pre-treatment, shaping, dyeing and finishing processes. If the control is not good, it is easy to form a fabric surface during the production process. folds. Moreover, most of the wrinkles are irreparable, directly causing quality problems of the fabric, causing the fabric to be downgraded, causing unnecessary losses and impacts to the company. This article focuses on some common wrinkle phenomena in the production process of knitted elastic fabrics, analyzes their causes and solutions, and hopes to provide useful help to the majority of knitting colleagues.
01 Main causes of fabric wrinkles
①Basic structure of knitted fabrics It is made up of countless coils that are looped around each other. During the weaving process, it experiences fluctuations in weaving tension, tensile deformation, or artificial pulling during the production process, resulting in deformation of some coils.
② Wrinkles caused by equipment, technology and human factors during the loose cloth, pre-processing or pre-shaping process.
③ The folding, squeezing, or heating and cooling rate of the fabric in the dye vat is too fast, and different fibers shrink differently in a short period of time, resulting in folds caused by coil displacement and deformation. .
④ When the fabric comes out of the setting machine, the cloth surface is not cooled enough and the cloth surface temperature is too high, causing the knitted fabric to be hot-pressed and deformed in the cloth car to form wrinkles.
⑤ Because the elastic recovery rate of elastic yarn is higher than that of other fibers, it shrinks together with other fibers after pulling, causing changes in the fabric structure during severe contraction, and then folded and extruded. Wrinkles formed by pressure.
⑥Some special elastic yarns will have mutual adhesion effects between “elastic yarn-elastic yarn” and “elastic yarn-main fiber” when encountering high temperatures above 120°C. , if the fabric surface is uneven or wrinkled at the moment of adhesion, the “curing effect” that occurs after adhesion will cause wrinkles on the knitted fabric surface.
02 Weaving creases
1. Weaving folds
Weaving wrinkles refer to the wrinkles formed during weaving. It mainly includes edge pleats, cloth head and tail pleats and both side pleats. This kind of wrinkle phenomenon should be discovered and adjusted in time during weaving, or focus on the initial inspection of gray fabrics, discover in time, adjust the weaving process, and deal with it in time.
2. Pressed edge wrinkles
Knitted gray fabric during weaving , if a square fabric stretcher is used to roll up, two folds from beginning to end will be formed at the fold. The reason is that the knitted gray fabric is folded in half and squeezed by the roller. One of the knitted fabrics will disappear after being cut by the slitting machine, and the other will remain in the middle of the gray fabric, which is called the blank line wrinkle.
The best way to solve the wrinkles on the edge line is to use automatic open-width and flat-width winding. Nowadays, most of the new circular knitting machines have automatic open-width and flat-width winding devices; if If there is no condition to adopt the automatic open-width winding method, the weaving roll tension should be appropriately lowered within a reasonable range, the roll pressure should be reduced as much as possible, and after weaving and dropping, use a slitting machine to cut the open width in time. Roll, try to reduce the degree of wrinkles on the edge line.
3. Cloth head and tail pleats
Automatic opening and flat width Although winding can effectively overcome the problem of the edge line, improper operation can easily cause wrinkles at the beginning and end of the fabric. The cloth head must be flat when rolling up. It is best to have two people work together to fully smooth the cloth head before turning on the machine, because once the cloth head is wrinkled or twisted, obvious wrinkles will be visible at the top of the cloth for more than ten yards after loosening. If the blank fabric is piled up for a long time after being dropped, it will cause indentation or even crushing on the fabric surface.
In order to reduce the wrinkles of the cloth end, some factories use double-sided adhesive tape on the rolled paper tube or rubber tube to make the cloth end as flat as possible. After the cloth tail is dropped, the cloth tail on both sides should be fully unfolded and knotted with the lower layer to avoid wrinkles when the cloth tail is relaxed.
In addition, it is best to use a hose when rolling up the gray fabric, which can ensure the quality of the roll and can be reused, which meets environmental protection requirements. Because the paper tube has poor hardness, it is easy to deform or break under pressure, causing new wrinkles, indentations or bruises on the cloth surface. Moreover, the damp paper tube will also cause stains on the gray cloth.
4. Pleats on both sides
High elastic silk content Products, such as double-sided pure cotton, thick satin, etc., will also form wrinkles on both sides of the gray fabric due to the excessive elasticity of the elastic yarn. Generally, this kind of product does not need to be washed with water. It needs to be loosened first and then pre-shaped. Attention should be paid to minimizing the parking time of loosened gray fabrics in the cloth car, and pre-shaping in time to prevent the edges of the gray fabrics from curling and stacking for too long and aggravating wrinkles. In some weaving mills, wrinkles have formed on both sides of the fabric when the fabric ends are not fully unfolded during the initial roll. Feedback should be provided in time to solve the problem.
03 Loose cloth folds
For some that do not need to be washed with water (pre-treatment ), only the gray fabrics that need to be dyed directly after pre-shaping are required to be arranged first. To prepare for pre-shaping or dyeing in the vat, if the loose cloth equipment or process operation method is improper, it is easy to cause wrinkles on the cloth surface during the loose cloth stage.
1. Loose cloth equipment
Traditional loose cloth equipmentIt is lower, about 10~30℃ lower. According to experience, the fabric surface effect after the finished product is set will reduce wrinkles as the setting temperature increases. A small number of wrinkles after leaving the dye vat can be improved by appropriately increasing the setting temperature of the finished product, but it cannot be completely solved.
2. Operating status of the shaping machine
Attention should be paid to the shaping of finished products Observe the operating status of the machine to prevent weft deviation or even wrinkles caused by fabric deviation, needle loss, or abnormal expansion.
3. Cooling of the finished fabric surface after finalization
The fabric is heated After setting, the fabric surface should be cooled at an appropriate rate in the back section of the setting machine. If the cooling is insufficient, the speed is too fast or the cooling effect is not achieved, it may cause new wrinkles in the fabric.
At present, there are two main cooling methods for the stenter setting machine: one is to blow cold air; the other is to enter the cold water roller after passing through the cold air zone, and the fabric is cooled by contacting the surface of the cold water roller . From the perspective of practical application, if the temperature of the cloth surface during dropping drops to below 50°C, the wrinkles on the cloth surface will be significantly improved.
4. Stacking of finished products
How to stack finished products after they are finalized Also very important. The finished fabrics should always be kept in an open width state when placed in the fabric cart, to prevent random throwing, throwing, and random placement, and to avoid artificial wrinkles on the fabric surface.
08 Packaging wrinkles
Finished product packaging It is the last process in the dyeing and finishing process of elastic knitted fabrics. Poor packaging quality control will also cause new wrinkles on the cloth, making all previous efforts in vain. The main factors that affect packaging quality are: the hardness of the paper tube and the method of rolling the cloth.
1. Hardness of paper tube
Selection of paper tube for rolling It is very particular. The paper tube needs to be plump, round and straight, with good verticality and a certain hardness and strength. Fullness and roundness can ensure that the cloth surface is smooth and wrinkle-free during rolling; a certain hardness and strength can withstand the handling, carrying and pressure during transportation, and prevent the paper tube inside from deforming or breaking to form indentations and wrinkles on the cloth surface.
2. Cloth rolling operation
The most important thing about rolling cloth is When rolling the fabric on the paper tube for the first time, you must fully smooth the fabric with both hands and do not wrinkle or twist it at will. First, cut the cloth ends neatly, and do not stack them too much or too loosely. The cloth winding machine should start slowly. After ensuring that the cloth surface is flat and even, and the cloth edges are neat, it can slowly increase the speed and keep running at a constant speed.
09 Postscript
To reduce and overcome stretch knitted fabrics The problem of wrinkles must be dealt with throughout the entire production process, and the three-character sutra of “Loose, Check, and Strict” must be recited:
① “Loose” means that it must be processed on the machine in this process Minimize tension and maintain a loose handling process, which is required to ensure that the finished product is wrinkle-free.
② “Check” means to check the situation of the previous process to see if there are any improper wrinkles; to check whether there are any wrinkles on the fabric caused by equipment failure or illegal operation during the processing of this process. , should be discovered in time and dealt with in time.
③ The word “strict” is at the forefront, strictly control the quality, and strictly follow the process operating procedures.
As long as all production links pay attention to “looseness, inspection and strictness”, the basic work of preventing and overcoming fabric wrinkles will be guaranteed. </p
