During the dyeing and finishing process, textiles are subject to greater tension in the warp direction, resulting in length elongation and width narrowing. In order to overcome this unstable state and ensure the dimensional stability of the textile, the cloth feeding speed is adjusted during tentering or setting. This is called overfeeding.
The cloth feeding speed is greater than the speed of the tenter or setting machine, which is called positive overfeeding (or overfeeding, shrinkage). Positive overfeeding causes the warp to retract, the weft density to increase, the weight to increase, and the warp shrinkage to decrease.
If the cloth feeding speed is lower than the speed of the tenter or setting machine, it is called reverse overfeeding (or negative overfeeding, or pulling code). Anti-overfeeding causes the warp to elongate, the weft density to decrease, the weight to decrease, and the warp shrinkage to increase. There are many dyeing factories in China that do not hesitate to do things that violate their principles in order to pursue their own profits.
Tenter setting is the finishing work after dyeing, and it is also a very important process. In the tenter setting process, some dyeing factories work hard on the tenter setting process in order to process more cloth than the input amount of gray cloth. They objectively believe that most customers do not understand the reasons and allow themselves to do whatever they want.
Now we have compiled some overfeeding knowledge during stenter shaping, for reference only.
During the dyeing and finishing process, the fabric is subject to greater tension in the warp direction, which can easily lead to elongation in the warp direction and narrowing in the weft direction. This is an unstable state. This kind of fabric will shrink in the warp direction in water.
In order to reduce the warp shrinkage of the fabric and stabilize the size of the fabric, overfeeding is required during tenting or setting, and the fabric feeding speed is greater than that of the tenter or setting machine. The speed of the machine causes the warp yarns to retract completely and the weft yarns to be pulled to the specified width.
Generally, cloth with a light weight is fed when it is being shaped. In order to make the weight meet the customer’s requirements, overfeeding will make the cloth surface wavy and the garment factory cannot cut it. The cloth needs to be reshaped.
In the fabric shaping process, there are sayings of “overfeeding” and “anti-overfeeding”. Generally speaking, after the weft width is determined, the radial direction is under tension. This is reflected on the machine , that is, the speed of the fabric entering the machine is greater than the speed of the setting machine (chain speed), which is “positive overfeeding”, causing the weft density of the finished fabric to increase, that is, the gram weight increases. Then “anti-overfeeding” is just the idea. But it is worth noting Yes, with “positive overfeed”, the fabric will shrink to a certain extent. But “positive overfeed” should reduce the warp shrinkage. The warp shrinkage will become larger and the shrinkage will become smaller.
Analysis of some important proper nouns:
Overfeeding: Yes Provide the action process of specific proportion required according to the requirements of the next step.
Specific proportion: positive, negative or one, that is, positive, negative overfeeding or zero overfeeding.
Required quantity: can be reflected in speed, flow, quantity, quality, etc.
The requirements of the next step: based on its The processing purpose to be achieved is determined.
Overfeeding amount: It is completed by the overfeeding mechanism through the measurement and control of the data relationship between the front and rear mechanisms.
To complete the processing purpose: it is the main functional mechanism.
To complete the overfeeding: it is the auxiliary mechanism.
Measurement and control instrument : is a necessary matcher.
Actual operation example:
1. In order to eliminate the longitudinal stretch of the fabric in the bleaching and dyeing process before setting, and to meet the size requirements of the customer and the design structure, the setting machine needs more fabrics to be pre-fixed on the needle plate. For example, feeding The mechanism feeds 120M per minute, and the needle plate that fixes the fabric travels 100M per minute. In this way, 120M fabric is squeezed into the 100M position (positive overfeed + 20%), and then is set at high temperature. After the machine is off, the fabric is 100M, eliminating longitudinal stretching. Stretch. At the same time, increasing the needle plate distance will control the fabric width and eliminate the lateral shrinkage in the bleaching and dyeing process before fabric setting. On the contrary, if only 95M fabric is fed, it will be stretched to 100M setting (negative overfeeding -5%). This is also a way for sellers to make money, so buyers specify the longitudinal and transverse shrinkage and square meter weight (knitting) to allocate the amount of money.
2. Spinning and winding Even weaving will involve or adjust the amount of overfeeding. For example, the spinning of double-stranded fancy yarn must be positively overfeeded to make one of the strands loop; the process of roving and spinning is negatively overfeeded (feeding hundreds of meters of cotton top and spinning it into Thousands of meters of yarn); (precision) winding machine winding (positive overfeed controls the lower and constant winding density of the winding); loom weft feeder (controls the tension of the yarn, especially the elastic yarn, Ensure non-negative overfeeding).
3. Many continuous processing equipment (other industries) also often have this mechanism. For example, the tensioner of a dyeing machine is a mechanism that coordinates the front and rear speeds. , control the negative overfeed amount of the fabric transported by the front mechanism so that the fabric will not be over-stretched. </p
