Popular Science | The reason why fabric finishing and raising effect is poor has been found!

The purpose of fabric fleece processing is to improve the style and appearance of the fabric, and to increase the wool texture and warmth on the surface of the fabric. The fabric becomes bulky and thick, feels soft, improves the wearing effect, and increases the added value of the fabric.

Steel wire fleece machine is equipped with two types of fleece rollers on one drum. One fleece roller is equipped with a velvet roller that bends in the same direction as the movement of the fabric. Metal needles. Another type of raising roller is equipped with metal needles that bend in the opposite direction to the movement of the fabric, which are what we usually call carding raising rollers and brushing raising rollers. When the fabric runs on the raising machine, the rotating carding roller The raising roller and the brushed raising roller have a relative movement on the fabric at the same time. It is this relative movement that causes the needle tip of the raising roller to scrape the fabric in one direction and then in the opposite direction, causing the fluff of the fabric to rise, thus achieving the purpose of raising the fabric. The purpose of velvet, this is the principle of velvet fabric

There are three main reasons for the problems that occur during the fabric raising process: the fabric itself and its processing methods are not suitable. , caused by inappropriate or imperfect raising machine, caused by incorrect raising operation technology. The problems that often occur during the fabric raising process are mainly uneven raising and damaged fabrics. Excessive weft strength reduction, excessive pile reduction, yarn scratches, insufficient thickness, etc. The reasons for uneven velvet are very complex and extremely troublesome to solve. Other problems can be avoided as long as sufficient attention is paid during raising. Pilling defects originating from the fabric itself are caused by fiber, yarn or fabric preparation, weaving and pre-processing (scouring, dyeing, finishing) and other processes.

1. Problems caused by fibers and yarns and their solutions

(1) The weft strength is affected by the fiber type. The shorter the fiber length or the smaller the yarn twist, the greater the strength drop of the weft yarn before raising. In addition, there is a lot of waste during the raising process. , so the fluffing effect is poor. The length of the fiber used must be more than twice the length of the fluff pulled out of the fabric, and the best average length is more than 10mm.

(2) Yarns with long fiber length and small twist are suitable for raising even if the strength is not strong. On the contrary, when using yarn with long fiber length and strong twist, it is difficult to raise the yarn, but beautiful, uniform and neat pile can be obtained. When the twist of the weft yarn is too strong, not only is it difficult to raise the yarn, but the suede effect is also unsatisfactory.

It can be seen from the above conclusion. If yarns of the same count from different manufacturers or twists are woven into the same weave specifications, uneven pile will inevitably occur. Even if we work hard on raising methods, it is almost impossible to change the current situation. If the blended yarn is unevenly blended, fluffing defects will also occur.

The yarn tension during weft winding is uneven, and its moisture content is different. Weft defects will occur during raising. The reason is that after weaving Caused by different shrinkage rates of weft yarns. After the yarn with small shrinkage is raised, small groove-shaped raising defects will occur in the warp direction. Uneven thickness of weft yarn is a fatal flaw of pile. Hard yarn is more difficult to nap than soft yarn. Uneven yarn count and twist also have a serious impact on raising. Generally, the same yarn has a small twist in the thick part and a large twist in the thin part, which causes uneven pile.

Different dyeing conditions will also affect the raising effect to a greater or lesser extent. The amount of dyeing auxiliaries and softeners remaining in dyed fabrics can also cause uneven nap. Cotton staple fiber fabrics are dyed with direct dyes. Light colors are difficult to nap, but dark colors are easy to nap. Uneven raising caused by dyeing can be improved by properly softening the fabric before raising.

2. Problems caused by fabric structure specifications and weaving and their solutions

The structure of the fabric and The texture has a great influence on the raising effect. Uneven fabrics are not easy to detect at first and are mostly exposed after dyeing or raising. The key is that the tension of the warp and weft yarns should be uniform, which is the most difficult to solve when the edges of the fabric are tight and loose. At this time, the fabric needs to be finished again. Uneven pile occurs due to uneven weft tension. It is related to the weft winding and weaving. If the weft tension in a certain part of the fabric is small, the warp will appear in that part. The uneven weft density will not only cause uneven pile, but also the parts with small density will be strongly piled, and the strength will be significantly reduced. Generally, when fabrics with many floating points of weft yarn are piled, the method is to reduce the pile. Use the short dense pile method to increase the number of piles to improve the pile effect.

3. Problems caused by fabric preparation methods

(1) Improper moisture content

Light raising or raising that requires a reduced amount of raising, etc., if the moisture content is not appropriate, the expected effect cannot be achieved. Uneven moisture content will cause uneven pile. Cotton fabrics are always dry-naped, but fabrics that are over-dry will experience increased pile loss. If the moisture content is too high, creases will easily occur in the warp direction of the pile, making it difficult to pull out the pile.

(2) Unreasonable fleece pre-processing

The fabric before raising must not have warp wrinkles. If there are warp wrinkles, it needs to be soaked in water and then dried before it can be raised.

(3) Improper seams

The seam head needs to be straight and secure. If the seam head appears corrugated or the front and rear fabric connections are skewed, a large section of fabric at both ends of the seam head will be unevenly raised. When the seam head is not firm, the seam head is easily scratched during the raising process, causing the fabric to get entangled in the card clothing roller, which not only damages the card clothing but is also dangerous.

4. Problems caused by raising machines and raising methods

(1) Problems caused by the centrifugal force of the drum

The speed of the fleece machine is high. The high-speed operation generates centrifugal force, and the middle part of the drum is convex, which makes the central part of the fabric strongly raised.

(2) Problems caused by improper raising methods

If two narrow-width fabrics are fluffed for a long time and then wide-width fabrics are fluffed, the central part of the fabric will have strong fluffing, resulting in striped uneven fluffing. . Therefore, when raising narrow-width fabrics, the contact position between the fabric and the card clothing must be frequently moved.

If the normally open mid-width fabric is piled with a wide-width fabric, weak piles will appear on both sides of the wide-width fabric. The middle part has strong fluff. Because the tension on both sides of the fabric is large, the tension in the middle part of the fabric is slightly smaller, which causes the middle part of the fabric to be hairier than the two sides. Therefore, it is necessary to move more when opening medium-width fabrics in preparation for opening wide-width fabrics.

Excessive winding tension of the card clothing will cause the card clothing to lose elasticity, scratch the weft yarn, excessive pile reduction, uneven pile, etc. question. When some fabrics first start to pile, the fabric tension between the running card rollers is out of balance, which affects the pile operation. The relationship between the fabric tension and the speed between the carding and brushing rollers is very critical. Once the balance is obviously lost, the weft yarn tension increases, causing the weft yarn to be scratched or the warp yarn to be cut. The tension of the fabric is small, and the needle is inserted deeply into the fabric, which is prone to long lint and even uneven weft pile. If the fabric tension is too high, the belt of the card roller will slip, which will not improve the raising efficiency and easily cause the edges of the fabric to be damaged.

In short, it is necessary to choose fibers, yarns, etc. that are evenly processed, have small twists and high strength, so that the expected raising effect can be achieved after being woven into fabrics. Increasing the cloth speed may not necessarily improve the pile efficiency, and speeding up the drum speed may not necessarily improve the pile effect. If the rotation speed is raised too high, the contact time between the needle and the fabric will be shortened, and the brushing effect will be reduced.