Because of the characteristics of knitted fabric, the operation in the printing process is certainly different from that in the printing process of woven fabric. Reasonable and correct printing operation is the key to ensure and improve the quality and output of knitwear printing.

01

sewing

In order to prevent skew defect of woven fabric, the most effective way is to tear the seam. Knitted fabric and woven fabric structure is different, it is impossible to take the operation of tear head seam head.

Knitted fabric in order to prevent the deviation caused by improper sewing head, the work to be done before the sewing head is: to see the fabric pattern, if necessary, the two cloth head along the cloth pattern. To distinguish the positive and negative sides of the fabric, so that the front is facing the front, the cut head along the edge of the cloth, then the seam head, and do the seam head to be firm and straight.

02

Section size and seam edge

Woven fabrics produced by the textile mill to the embryo are flat width, so in the printing and dyeing production process without cutting and seam; But knitted fabric is different, it is produced by the knitting mill to the embryo is more cylindrical.

In the production process of knitted fabrics, some processing processes need to be carried out in open width, such as tensioning, printing, evaporation and so on. Some processing procedures also require the fabric cylinder, such as knitting fabric pretreatment, dyeing, post-printing flat washing, etc., to reduce and prevent knitting fabric yarn damage caused by loose crimping, and the edge is not easy to hold.

Therefore, with the needs of knitting production and processing, the cylindrical knitting fabric should be dissected into flat width. And sometimes the flat knitted fabric or seam into a cylinder, so that the smooth production. Knitting is done on a loom.

03

Pulp edge and cut edge

Some specifications of knitted fabric are prone to crimping, which will seriously affect the quality of knitted fabric printing products and the smooth production of printing. Want to catch the pulp edge of knitted fabric for this, cut edge, basically be aimed at those in the production process easy to produce the knitted fabric that roll edge character. Woven fabrics also have the situation of edge rolling, such as cotton yarn card, cotton-ammonia elastic fabric in the wet and hot conditions of strong alkali, it is easier to have the situation of edge rolling, generally by improving the fabric edge, predetermined shape and clamping measures can be solved.

The above method is not effective in the production process of knitting fabric, and it is necessary to adopt the method of pulp edge and cutting a small amount of useless edge outside the pulp edge to ensure uniform fabric width and meet the needs of printing production. Insoluble slurry is generally used for slurry edge. The width of the slurry edge is about LCM, and the hardness of the slurry edge should be moderate. Excellent sizing is too thick, will make the edge and cloth thickness difference, affect the contact surface of the flower net and cloth so that the color of the printing is not uniform. Hardness can be mastered by knitting fabric on the rotary screen printing machine, not too thick.

04

Preparation before printing

Knitting fabric printing preparation includes two parts:

1. Pretreatment of printed embryo fabric of knitted fabric

The natural and artificial impurities in the printed blank fabric can be removed by pre-scouring treatment to provide qualified printing semi-products for knitted fabric printing.

2. In order to ensure the quality of printing products and the smooth progress of printing process, the processing content must be carried out before printing:

(1) Knitwear pretreatment, different fiber components to take the pretreatment process is different.

Synthetic fiber, artificial regenerated fiber. Such as polyester, polyamide, acrylic, viscose, modal, fiber texture itself is relatively clean, without boiling bleaching, bleaching, its to remove, clean are artificial impurities; Such as oil stains, dust, stains, etc on fabric. Natural fibers such as cotton, hemp, silk, etc., are accompanied by symbiotic growth in the growth process, which will affect the printing and dyeing processing of these fibers and affect the wearability of these fiber knitted fabrics. These symbiotic are natural impurities that must be removed.

In the case of cotton knitting, the most important pretreatment process in the traditional pretreatment process is scouring. Knitted fabrics do not need sizing when weaving, so there is no desizing process before bleaching of knitted fabrics, and most cotton knitted things do not go through singeing and mercerization.

With the improvement of consumer demands for knitted fabric quality and the development of science and technology production, production of high-grade fabric has become a trend, now use yarn singeing, mercerizing, then knitted fabric in the process of printing and dyeing fabric singeing, mercerizing process, in order to improve the luster of the knitted fabric color, improve the grade of knitted products has formed in the bulk production. In order to improve the finish of the fabric, reduce the velvet of the fabric, in the enterprise without burning equipment, some use cellulase method for hair treatment.

The preparation work before knitted fabric printing

In order to meet the requirements of printing and ensure the quality of products and smooth production on the basis of pretreatment, the following work should be generally carried out according to the induction of production practice.

① Prepress tensioning and shaping. To improve the flatness of half-finished products to be printed, improve the dimensional stability of half-finished products. Do a good pulp edge, cut edge.

(2) Pre-press filling. Weft slant fabric, after printing, will form slant defect and cannot be repaired. In order to prevent the deviation of knitted fabric, the weft must be straightened before printing.

③ Whitening of printing embryo. Polyester knitted fabric is washed and whitened on a tensioning and shaping machine. Bleaching of cotton, nylon and acrylic can be carried out in overflow dyeing machine or dyeing VAT by dipping method.

4. Put on antistatic agent. In the process of synthetic fiber knitted fabric, static electricity, dust adsorption, color adsorption and other defects occur, so antistatic agents should be used to overcome them. Antistatic agent can be done on tensioning and setting machine. The electrostatic agent on polyester knitted fabric can be soaked and rolled in the same bath with polyester and whitening to dry.

Printing embryo sizing. For some thin and creased knitted fabrics need to be sizing, in order to increase the body bone of knitted fabrics, easy to print.

6. Printed embryo dyeing. For some patterns that require a dye base, semi-finished knitwear is dyed before printing. Dyeing process and operation are basically the same as knitting fabric dyeing process operation.

⑦ Printing embryo roll to ensure the uniformity of fabric into the tension, for the yarn is easy to move light knitted fabrics such as color, chiffon, silk and other fabrics before printing to roll, easy to cloth.

05

Stenter setting

Tensioning can be divided into blank tensioning, prepress tensioning, finished tensioning and so on. The arrangement and frequency of shaping should be determined according to whether the production quality can be guaranteed and whether it is favorable for smooth production.

The processing purposes and advantages and disadvantages of the above kinds of tensioning are summarized as follows:

(1) Blank shaping is to stretch and shape the knitted fabric blank cloth. The advantage of this kind of tensioning is that it can reduce the serious deformation of the processed fabric in the subsequent processing. Remove the tensile deformation and residual tension of knitted fabric caused by strong force during weaving.

For elastic knitted fabrics can prevent shrinkage in the heat and humidity conditions, reduce and overcome the generation of wrinkles. But the process requirements to the embryo is relatively clean, can not contain after high temperature treatment becomes difficult to remove impurities. With the development of knitted fabrics containing spandex fiber, the output of blast-shaping has been improved.

(2) pre-press stretch setting, that is, the stretch setting before printing of knitted fabric printed cloth after pre-treatment. Through this process, the fabric can be wrinkle-free and the fabric size can be stable. At the same time, the fabric can be pulp edge, edge cutting, whitening, anti - static agent and so on to ensure the smooth production of printing.

06

Measures to prevent fabric deformation during printing

Knitted fabric structure characteristics of loose, easy to deformation in the printing process under tension warp length, weft narrow situation. Deformation of fabric in printing will bring a series of problems, resulting in weft deviation. Wrinkles and printing defects in the printing process. Therefore, it is the key to ensure the quality of knitting fabric printing and ensure the smooth progress of knitting fabric printing to prevent and overcome the series of problems caused by the printing machine.

Of printing and dyeing enterprises in knitted fabric printing production, considering the characteristic of knitted fabric printing production and problems, often before a large number of formal production, test grope and summarizes the knitted fabric deformation data on the printing machine and the situation of the pattern changes, using the pattern color separation in the tracing proper zoom processing, such as pattern vertical amplifier, Method of zonal reduction.

When the knitted fabric is printed on the printing machine, the pattern is enlarged longitudinally and reduced weft. Then, when finishing and setting, the weft is stretched to the finished door width and widened longitudinally and shortened longitudinally, in order to conform to the size of the customer's sample pattern. This approach is no lack of a way, but this approach to solve the above problems of knitted fabric printing, can not fundamentally solve the problem, because there are too many factors affecting knitted fabric deformation, too many variables. Different enterprises have different equipment, the operation status of the equipment of each enterprise is different, and the operation characteristics of the operator are not completely consistent.

If the variety of printed knitted fabrics is relatively single, it is ok to adopt the above method. If there are many varieties of printed knitted fabrics, with different thickness and tightness, and the warp and weft scale of knitted fabrics, the shape will certainly be greatly different. If the above approach is adopted, it is necessary to do various experiments and gropes, which brings certain difficulty and trouble to the operation. In addition, when printing the same variety, the speed of printing, pressure, fabric tension and other changes will affect the expansion of the fabric, affecting the printing effect of the fabric.

When printing knitted fabric on the printing machine, it is necessary to ensure the printing effect of knitted fabric, prevent and overcome the series of problems caused by the easy deformation of knitted fabric structure. In addition to paying attention to the operation of machine printing and pulp blending, ensuring the penetration of printing pulp, the amount of color, the accuracy of the print and the clear printed outline, it is also necessary to pay attention to the following measures and operations:

(1) When the printed knitted fabric is input into the printing machine, it must be carried out under the condition of low tension or no tension. The knitted fabric should be input straight on both sides, which is very important.

The cloth must be plain, to stick firmly. To choose a good paste, stick cloth operation, knitted fabric on the machine after the guide tape pasted flat, stick firmly. This ensures that the knitted fabric does not move during printing, which is conducive to printing and printing effect.

(3) Attention should be paid to the drying equipment, the use of high capacity air jet oven. The air-jet oven is required to have large steam flow circulation and high flow velocity to reduce energy consumption. Finished printing knitted fabric, from the end of the printing table is lifted into the oven import, by the oven conveyor belt without tension into the oven to complete the fabric drying work, and complete the printing task.

In order to do well the above measures, in addition to the printing operation should pay attention to the selection of printing machine equipment, and it is not easy to obtain satisfactory printing effect by adopting the shuttle fabric into the printing machine. As fabric printing machine ever more emphasis on the accuracy of the printing area, convenience operation, the printing effect of satisfaction, and choosing a knitted fabric printing machine in addition to the note and pay attention to the above, also must pay attention to printing fabric into cloth to tension, low tension, no need to be able to absorb stick tightly to the conduction band, printing end and into the drying equipment must also low tension and no tension, Only in the use of suitable knitted fabric printing equipment and good operation combined, in order to prevent, overcome the knitted fabric changeability caused by the series of problems.

07

Causes of shrinkage of knitted fabric and its overcoming

The shrinkage of cotton knitting is mainly related to the fiber properties, wet thermal plasticity and the structural characteristics of knitted fabric. In the process of printing and dyeing and weaving, the following situations inevitably exist:

The hot and humid environment of printing and dyeing processing.

(2) In the process of knitting fabric printing and dyeing, efforts have been made to create conditions for knitting fabric to be carried out with little tension and no tension, but so far, it is impossible to completely avoid tension in the process of knitting fabric processing. The existence of tension makes the fabric be stretched lengthwise, the fabric density is reduced and the fabric is deformed.

The knitted fabric is dried in an unsteady state.

(4) There is also latent tension in knitting process.

Due to the existence of the above situation, it will bring a series of problems causing shrinkage hidden danger to knitted fabric, which is embodied in:

(1) Because the dyeing and finishing process is in the hot and humid state of water molecules into the amorphous region of the fiber, so that the intermolecular chain force is reduced. At this point, under the action of external forces, molecular chain segment displacement, elongation of the fiber. If the fiber is dried in this elongation state, hydrogen bonds are formed in the new position between the fiber molecular chains, and the elongation part of the fiber fails to shrink back to the original state. The stability of deformation under such hot and humid conditions is unstable.

(2) Knitted fabric is made up of coils of each other, which has one of the most stable structure. If knitted fabric is in a stable structure, it is in a stable state of size and does not shrink when it meets water. However, in the actual production process, the fabric, especially the longitudinal fabric is subjected to large repeated tensile action, resulting in plastic deformation of the yarn fiber, longitudinal elongation of the fabric, narrow width, coil transfer, fabric structure away from the stable state of the fabric. This state is unstable and tends to restore the original stable state under appropriate conditions.

(3) Knitted fabrics are dried at an extended state, which appears to be stable on the surface, but in fact this "stability" is temporary.

(4) Knitted fabric yarn processing, fabric weaving process is affected by drafting, tension has potential tension, will also cause yarn, fiber retraction.

1. To sum up, the reasons for knitted fabric shrinkage are as follows:

(1) Recovery of fiber deformation under hot and humid conditions. Cotton knitting thing is washed below flabby state, water molecule can destroy the hydrogen bond that produces newly, make internal stress flabby, elongate part retracted namely produced shrink.

The recovery of knitted fabric deformation. When knitted fabric structure is far away from the stable state of knitted fabric, during wetting and washing, fiber plasticity is enhanced, recovery force is strengthened, deformation recovery, elongation retraction, cotton knitted fabric shrink and restore to the original stable state. This is the main cause of cotton knitting shrinkage.

(3) Fiber moisture absorption, yarn diameter increases, leading to yarn shrinkage caused by shrinkage. The increase in yarn diameter results in the shortening of yarn length, resulting in fabric shrinkage (including length and width) and increased density.

These are the basic causes of cotton knitting shrinkage. As for the knitted fabric under different circumstances, to shrink effect factors and shrink condition, for example: different fiber ingredients knitted fabric, knitted fabric, different organizational structures in different dyeing and finishing processing technology and equipment, whether the fabric after mercerizing, stenter setting and preshrinking processing, etc., has yet to be practice, summarize perfected and improved.

Two, the measures and methods to overcome cotton knitting shrinkage rate

To overcome the problem of large shrinkage of cotton knitted fabric, the following measures and methods can be taken in combination with the characteristics of knitting fabric printing under the condition of flat profile:

(1) Loose processing.

Minimize the tension of each process in the printing and dyeing production process, avoid plastic deformation of the fabric in the wet state as far as possible, avoid fabric and fiber elongation, which is the most ideal way to prevent fabric shrinkage.

In fact, printing enterprises have adopted a lot of loose processing methods in the dyeing and finishing of knitted fabrics. Regardless of the selection of textile printing and finishing equipment before treatment, many effective loose processing methods have been taken into account. We believe that with the development of knitwear printing and knitting printing equipment, knitwear loose processing will continue to improve and improve. In addition, the shortening of printing process has also caused attention in production and put into production practice, the adoption of the above measures will reduce the knitted fabric in the wet state of plastic deformation, will inevitably avoid the elongation of fabric and fiber, reduce the fabric shrinkage has great benefits.

⑵ superfeed drying.

That is, to achieve relaxation drying, reduce tension, so that the fabric near the full balance state. Before knitting fabric printing, overfeed drying can be connected with prepress drawing-setting process