【Popular science】Weft knitted fabric of knitted fabric
Editor: SunHing │ Date: April 16, 2021
【Knitted fabric】I believe that older ladies have had the experience of knitting sweaters, or everyone has worn sweaters made by mothers! The balls of yarn turned into warm sweaters in the hands of the ingenious mother, accompany us through the cold time.
Actually, the sweater mentioned above is a knitted fabric, so let's spread the relevant knowledge for everyone.
The so-called knitting is the use of knitting needles to bend the fed yarn into loops, and the loops are stringed and connected to each other to form a knitted fabric. This kind of textile processing in which the knitting needles are used to form loops, and then the loops are stringed into cloth. Technology is called knitting. As a craft, knitting has many different classifications. According to the weaving method, knitting production can be divided into two categories: weft knitting and warp knitting. Today, let’s introduce the weft knitted fabric.
Weft knitted fabric is a kind of fabric in which one yarn or several yarns are drawn from the bobbin, placed on the corresponding knitting needles of the weft knitting machine along the transverse direction to form loops, and are intertwined with each other in the longitudinal direction.
01 Composition of loop
Loop is the basic structural unit of knitted fabrics, and its geometric form presents a three-dimensional curved space curve. In the weft-knitted loop structure shown in the figure below, the loop is composed of leg1-2, needle loop2-3-4 and sinker loop5-6-7.
In knitted fabrics, a row of loops along the transverse direction of the fabric is called a course, and a row formed by intertwining in the longitudinal direction is called wale.
The characteristic of the weft knitted fabric is that the loops on each yarn are generally arranged horizontally, and a course is composed of one or several loops.
02 How is weft knitted fabric formed
The knitting needles of weft knitted fabrics mainly use latch needles, and the loop formation process of latch needles is generally divided into the following eight stages.
No matter how complicated weft knitted fabrics are, they are composed of three basic structural units: knit, tuck, and float combined with a certain rule.
03 Classification of weft knitted fabrics
The organization of weft knitted fabrics can generally be divided into three types: basic organization, change organization and pattern organization.
Basic organization, there are flat needle, rib weave, double reverse weave.
Change organization, it is composed of two or more basic structures, such as double rib knitted fabrics.
Pattern organization, on the basis of the basic structure or the changed structure, the loop structure is changed, or some colored yarns, auxiliary yarns or other textile materials are additionally knitted to form colored knitted fabrics with significant color effects and different properties.
04 The main parameters and performance indicators of knitted fabrics
Coil length, generally refers to the length of 100 coils, in millimeters (mm). The actual yarn length that composes a loop can be measured by hand unraveling method.
Density, It is used to indicate the density of knitted fabric under the condition of a certain yarn fineness, which can be divided into horizontal density and vertical density. Horizontal density (WPI) is the number of wales within one inch along the course of the stitch, and vertical density (CPI) is the number of courses within one inch along the wale of the stitch. It can be read directly with a density ruler or through a mirror. The higher the density, the tighter the structure of the knitted fabric.
Gram weight, Expressed by the weight (g) of 1m2 round cake. The larger the weight, the thicker the knitted fabric.
Thickness, in millimeters, can be measured with a thickness gauge.
Hemming, because the internal stress in the curved yarn tries to straighten the yarn, the edge of the knitted fabric is wrapped in a free state. Generally speaking, the left and right edges of the fabric are rolled to the opposite side of the fabric, and the upper and lower edges of the fabric are rolled to the front of the fabric.
Divergence, the phenomenon in which the loops of the pointer fabric lose their sleeves, and the loops separate from the loops. This is actually the reverse process of knitting. The escaping caused by the yarn hooking in the stockings is a typical detachment phenomenon.
Tensile performance, refers to the degree of elongation when the fabric is stretched by a certain external force, divided into warp and weft directions. If the value is larger, it means that it has better elongation.
Snagging and pilling, the fibers or yarns in the fabric are hooked by external objects to form silk loops on the surface, which is the snagging. When the fabric is constantly subjected to friction during wearing and washing, so that the fiber ends are exposed on the surface, it is called fluffing. If these fiber ends can't fall off in time during the subsequent wearing and washing process and are entangled and kneaded into many small spherical particles, it is called pilling.
05 Weft knitting machine classification
In the knitting industry, currently commonly used weft knitting machines are divided into three categories: circular knitting machines, flat knitting machines and circular hosiery knitting machines. Well-known manufacturers of weft knitting machines include Mayer&Cie in Germany, Santoni in Italy, Pai Lung in Taiwan, Santec in Taiwan, Fukuhara in Japan, and Wild horse in Shanghai.
The needle bed of the circular knitting machine is cylindrical and disc-shaped, the diameter of the needle cylinder is generally 356~965mm, and the machine number is generally E16~E44.
Gauge is expressed by the number of knitting needles, which indicates the density of needles on the needle bed. The higher the gauge, the more knitting needles within one inch, that is, the smaller the needle pitch, the finer the yarn that can be processed.
06 The production characteristics of weft knitted fabrics
● The production process of weft knitting is short (warping needs to be warped), and the production efficiency is high. On the weft knitting machine, at least one yarn, as many as dozens of yarns (depending on the loop-forming system) participate in the knitting, and the cheese yarn is directly on the machine, and the production is flexible and flexible;
● The raw materials are highly adaptable, and all kinds of staple fibers and filaments can be produced;
● The machine has low noise, low energy consumption and small floor space;
● The variety of changes is convenient and fast, the product range is wide, and the products are rich and diverse;
● Weft knitting can not only produce grey fabrics, but also semi-formed and fully-formed products, which is unmatched by other production methods.
07 Application of weft knitted fabric
Weft knitted fabrics are still mainly used in the field of clothing due to their soft hand feel, comfort and good air permeability, including traditional underwear, outerwear, casual wear, sportswear, etc. The sweaters, socks, gloves, underwear, warm tops, and many other clothes we usually wear are weft knitted fabrics, which can be seen everywhere in our lives.