Tenter finishing: During the printing and dyeing process, the fabric is subjected to greater tension in the warp direction and smaller tension in the weft direction. Therefore, the longitudinal direction (warp direction) of the fabric is elongated, and the transverse width will become wider. The warp direction is slightly shortened, so the finished product should be tentered before leaving the factory to reduce the width change of the fabric during use. During the tentering process, the skew and bending of the warp and weft yarns can also be corrected to ensure that the finished product is beautiful and neat.
Concept of overfeeding
During the dyeing and finishing process, textiles are subject to greater tension in the warp direction, resulting in elongation of length and narrowing of width. In order to overcome this This unstable state ensures the dimensional stability of textiles, so the speed of fabric feeding 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 yarns to retract, the weft density to increase, the gram 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 drawing code).
Reverse overfeeding causes the warp yarns 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 reason.
Common sense about overfeeding
Collate some overfeeding tips when setting tenter shapes Feedback, for reference only.
During the dyeing and finishing process, the fabric is subject to greater tension in the warp direction, which is prone to elongation in the warp direction and narrowing in the weft direction. This is an unstable state, and this kind of fabric will occur in water. Meridional shrinkage.
In order to reduce the warp shrinkage of the fabric and stabilize the fabric size, overfeeding is required during tenting or setting. The speed of feeding the fabric is greater than the speed of the tenter or setting machine, so that all the warp yarns Retract and pull to the specified width in the weft direction.
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 cause the cloth surface to become wavy, and the garment factory cannot cut the cloth and must re-shape it. …In the fabric shaping process, there is a saying of overfeeding and “anti-overfeeding”. Generally speaking, after the weft width is determined, the radial tension is exerted.
This is reflected on the machine, that is, the fabric enters The speed of the machine is greater than the speed (chain speed) of the setting machine, which is “positive overfeeding”, which causes the weft density of the finished fabric to increase, that is, the gram weight increases. Then “anti-overfeeding” is just the right idea.
However, It is worth noting that with “positive overfeeding”, the fabric will shrink to a certain extent. But “positive overfeeding” should reduce the warp shrinkage. The warp shrinkage will become larger and the shrinkage will become smaller.
Overfeeding: It is an action process that provides a specific proportion of the required amount according to the requirements of the next step.
Specific proportion: there are positive, negative or one, that is There is positive, negative overfeeding or zero overfeeding.
Requirement: can be reflected in speed, flow, quantity, quality, etc.
The requirements for the next step of the process: are determined based on the processing purpose to be achieved.
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 instruments: are necessary matchers.
Production should be implemented
For example: 1: In order to eliminate the longitudinal stretch of the fabric bleaching and dyeing process before setting, and to meet the size requirements of customers and design structures, the setting machine needs more fabrics in advance. Fixed on the needle plate. For example, the feeding mechanism feeds 120M per minute, and the needle plate that fixes the fabric travels 100M per minute, so that 120M of fabric is squeezed into the 100M position (positive overfeed + 20%), and then is set at high temperature, and then The fabric after machine is 100M, which eliminates the longitudinal stretch. At the same time, increasing the needle plate distance will control the width of the fabric and eliminate the transverse shrinkage in the fabric bleaching and dyeing process before setting.
On the contrary, if only 95M is fed The fabric will be stretched to 100M and set (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, winding and even weaving will all involve or adjust the amount of overfeeding. For example, the spinning of double-ply fancy yarn should be positively overfeeded to make one of the strands loop; the roving and spinning process is negative overfeeding. (Feed hundreds of meters of cotton top and spin into tens of millions of meters of yarn); (Precision) Winding of the winding machine (Positive overfeed controls the lower and constant winding density of the winding); Weft feeder of the loom (Control the tension of yarn, especially elastic yarn, to 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 and controls the negative overfeed amount of the fabric transported by the front mechanism. So that it won’t be overextended.
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