In the dyeing and finishing of textiles, the warp direction is subjected to a large pulling force, resulting in elongation and narrowing of the length. In order to overcome this unstable state and ensure the dimensional stability of the textile, the speed of feeding into the cloth is adjusted during stentering or setting, which is super-feeding.
The speed of feeding into the cloth is higher than the speed of the Hot Air Stenter machine called positive super-feeding (or over-feeding, shrink-code). The positive overfeeding causes the warp yarn to retract, the weft density rises, the gram weight increases and the warp direction shrinks.
If the speed of the cloth is less than the speed of the Hot Air Stenter setting machine, it is called anti-overfeed (or negative overfeed, pull code). The anti-overfeeding causes the warp yarn to elongate, the weft density decreases, the gram weight decreases, and the warp direction shrinks. There are many dyeing factories in China that are willing to make some violations of the principle in order to pursue their own profits.
Stretching is a finishing work after dyeing, and it is also a very important process. In the process of stentering, some dyeing factories have worked harder than the amount of grey cloth input in order to process the fabric. They are very objective in thinking that most customers do not understand the reasons for this, letting them do whatever they want.
Now I have compiled some knowledge of overfeeding during tenter setting, for reference only.
In the dyeing and finishing process, the warp direction is subjected to a large pulling force, which tends to cause a narrowing of the warp direction, which is an unstable state, and the fabric undergoes warp shrinkage in water.
In order to reduce the warp shrinkage rate of the fabric and make the fabric size stable, in the tentering or setting, overfeeding is required, and the speed of feeding is greater than the speed of the Hot Air Stenter machine, so that the warp yarns are all retracted and the weft is pulled to specify the width of the door.