The general process of sewing is: grey cloth inspection, material laying, cutting, sewing, ironing, quality inspection and evaluation, folding packaging, etc. Sewing is not only an important link in the process of fabric garment, but also a key factor determining the quality of garment. In the process of fabric sewing, improper treatment of fabric, sewing process parameters and environmental temperature and humidity may lead to the formation of needle holes in the sewing process and seriously affect the product quality，In particular, the separation characteristics of the coil make the knitted fabric more prone to damage. Therefore, some scholars at home and abroad have studied this since the early 1950s. Their research results are summarized as follows.
(1) There are two types of fabric sewing damage: mechanical damage and melting damage. That is, when the sewing needle punctures the fabric, the yarn is broken due to yarn expansion, or the yarn cannot slide away from the sewing needle and is directly stabbed, broken or partially broken by the sewing needle. The damage of the yarn is called mechanical damage (commonly known as needle hole). Needle holes are divided into visible needle holes and invisible needle holes. Visible needle holes refer to that in the sewing process of knitted fabric, the coil of knitted fabric is cut off by sewing needle or sewing thread, the needle trace hole is expanded, and the coil is separated; Invisible needle hole refers to the hidden danger caused by the puncture of the coil by the sewing needle during the sewing process. With the increase of fabric taking time and washing times, the puncture yarn is broken and the needle trace hole is expanded, resulting in the separation of the coil. Mechanical damage usually occurs in fabrics made of natural fibers. For synthetic fibers or fabrics blended with synthetic fibers, when sewing at medium and high speed, the needle heat caused by the friction between the needle and the fiber softens and melts the fabric yarn or suture, which is called melting damage.
(2) Research on the force between sewing needle and fabric at home and abroad: patent 3979951 invented a force when testing machine needle punctures fabric. It simulates the operation of sewing machine needle puncturing fabric and continuously reads the force when machine needle penetrates fabric. Through this test, the possibility of sewing damage can be effectively predicted; S. Simmons also designed a machine that can control the speed, which is equipped with a pressure sensor to test the needle puncture force at the sewing time; Matthews and little installed sensors on the needle and presser foot plate of the sewing machine to measure the force between the needle and the fabric. It mainly studies the feeding process; The sewing needle force sensor developed by Zhang Peihua and Wang Shanyuan dynamically measures the needle puncture resistance of knitted fabrics by using the method of tracer fiber, and obtains the relationship between the needle puncture resistance and the needle holding space of knitted fabrics; Buhler and hennric invented a new method to test suture tension and needle puncture force. It is to install the sensor on the needle plate. When the needle presses the fabric towards the needle plate, the sensor senses the force. This measurement method is not applicable to the test of needle pulling force; Zhang huaizhu and Wang Zhangming used glass bronze with excellent performance to make cantilever sensors, discussed the relationship between sewing resistance and sewing needle thickness, sewing speed and the number of layers of sewn fabric, and came to the conclusion that the thickness of sewing needle has the most significant effect on sewing resistance and the number of layers of sewn fabric; (chmielowiec and Lloyd are equipped with a pFAF flat sewing machine with sensors to measure the presser foot pressure and displacement, suture tension and needle puncture force, and detect “presser foot rebound” Correlation between effect and some presser foot pressure and sewing crease; Rocha invented a needle rod sensor device to measure the presser foot pressure, which can be used to evaluate the needle puncture force and extraction force of the machine; Lomo V established a mathematical model of fabric puncture force to predict the needle puncture force under the influence of multiple factors, which is very different from industrial high-speed sewing; Malt and Du proposed the finite element model technology to predict the puncture force. Leeming and munden found that the greater the puncture force, the more severe the damage during sewing.
(3) The main factors affecting the sewing damage of fabric in the sewing process: yarn properties, fabric properties, dyeing and finishing conditions, sewing conditions and climate. Accordingly, the measures to prevent and reduce fabric sewing damage are put forward Dorkin and NH Chamberlain discussed the causes of stitch holes in cotton and man-made fiber fabrics From the analysis of the causes of yarn breakage, it is concluded that the sewing breakage depends on the elongation and deformation of the fabric yarn during the puncture process of the sewing needle When the elongation percentage of yarn before and after puncture exceeds its breaking elongation the fabric will break.
Softening the fabric can reduce the occurrence of sewing needle holes. As early as the early 1950s, some scholars pointed out that lubricating and emulsified paraffin can reduce the friction between fiber and needle, so as to reduce the degree of suture damage in the process of sewing clothes; Hurt and Tyler’s research results show that the friction between the sewing needle and the fabric or yarn has an important impact on the sewing needle hole, and the finishing lubricant can reduce the penetration of the machine needle and change the friction performance of the fabric; Xu Hong and ye Wei found out the best scheme and process of softener a-920 epoxy silicone by establishing mathematical model and orthogonal design, which effectively reduced the occurrence of sewing needle holes.
Throughout the research history of fabric sewing damage, it can be found that most of these research work is to analyze the causes of damage in the sewing process and constantly improve the testing method of stitchability puncture force. There is little research on the sewing needle hole of knitted fabrics, especially on the sewing performance of high count and high density knitted fabrics. Based on the above research, this paper will focus on the analysis and discussion of the influence of high count and high density knitted fabrics on sewing needle holes; In actual production, it is sometimes found that the fabric feels soft after finishing, but there will be needle holes. This is because most kinds of softeners reduce the friction coefficient and greatly reduce the yarn strength. This paper will also study and analyze this situation, and select the best finishing additives and finishing process, in order to avoid or reduce sewing needle holes and improve the sewing quality of knitted fabrics.
