10 common problems in printing and their solutions

10 common problems in printing and their solutions

Printing, the process of printing floral patterns with dyes or pigments on fabrics with certain dyeing fastness. So, what problems may be encountered in the printing process? How to solve it?

1.The problem of sticky hand after printing the printing glue

The phenomenon of sticky hand after printing paste drying becomes more serious with the increase of temperature.

Reason: the main raw material of printing glue is acrylic resin. The characteristics of the resin determine the selection of a harder resin and the problem of sticky hand can be solved, but the adhesion is very serious. If the adhesion is increased, the soft resin must be selected, but the soft resin is easy to stick back.

The solution:

The use of printing adhesive adhesive, add printing adhesive and mix evenly. After printing, printing adhesive adhesive can form a film on the surface, which does not affect the adhesion of printing adhesive, and solve the problem of sticking hand.

2.Flat - screen fabric printing plug - net phenomenon solution

Reason: manuscript film density is not enough; Flat screen plate-making operation process is improper; Printing paste quality problem.

The solution:

Manuscripts are currently produced by computer. The higher the black density, the better the shading effect. Such as blackness is not enough, the worse the shading effect, UV light is easy to pass through, will cause plug net; The gray fog of the manuscript film is low, such as the high gray fog, blocking the transmission of ultraviolet light, need to lengthen the exposure time to complete, so it is easy to cause excessive exposure time and plug net.

Flat screen plate development, curing process improper, will lead to plug. When developing, take into account that UV light is transferred from the printing surface of the screen to scratch the printing surface, the printing surface is fully illuminated, you can use a large pressure of water rinsing; The scraping surface light cross-linking degree is smaller than the printing surface, the film is tender, rinse should use no pressure water slurry residue slurry leaching clean, avoid residual slurry blocking mesh. Two exposures should be carried out before curing, so that the adhesive layer is fully sensitized and then coated with curing agent.

Printing, the use of paste containing impurities or undissolved particles plug the mesh, so that printing paste can not be scraped out of the mesh, so before the use of the paste to filter impurities. Make the coating adhesives to choose good quality adhesives and good compatibility of thickening agent, scraping the conjunctiva should not be too fast.

3.The process by which the edges of a pattern change from clear to fuzzy

At the beginning of printing, because the fluidity of the slurry is good, so the scraper does not need a lot of force to cut the slurry clean. With the continuous evaporation of water in the slurry, the slurry gradually thickens and the viscosity becomes larger. The particle size of the ink scraper must be increased to clean the excess slurry. Due to the increase in strength, the screen elastic deformation of the pattern displacement, with the disappearance of the squeegee force, screen rebound after the screen printing surface of the pattern edge will stick to the paste, in the second printing, the paste will move to the edge of the pattern, resulting in pattern edge blur phenomenon.

The solution:

(1) with a small elastic screen, such as polyester wire mesh;

(2) improve the tension of the screen;

(3) reduce the resilience of the screen;

(4) Adjust the viscosity of the slurry at any time.

4.Pattern acute Angle rounded, small dot loss of the cause

Due to paste in the printing process has thickened gradually, make its liquidity decreases, through the mesh must increase the pressure of scraping knife can through the mesh, but on the edge of the screen pattern due to the effect of cushion of the sensitive glue, make scraping knife not to squeeze pulp mesh at any time, make the slurry particles stay in the mesh form a membrane, cause photosensitive glue on the edge of the mesh plug.

The solution:

(1) Selection of low mesh, monofilament, thin screen;

(2) photosensitive adhesive can not be too thick;

(3) The slurry should keep a certain fluidity at any time.

5.The reason of the coating phenomenon in the printing process of glue

Any printing material has a common characteristic, that is: the thinner the ink layer, the faster the drying, the same is true of the glue. Because the network version is greater than design, network version of the pulp has enough space to pile up, scraping blade can't clean the slurry closed at every time of printing, especially in the upper part of the design often produce thinner ink layer, the ink layer will form in a short time half dry membrane, the membrane was scraping blade into slant hole plug mesh, form a local version of the phenomenon.

The solution:

In the screen between the pattern area and the screen frame with wood to do isolation, the size control in a certain range, ink scraper can each screen pattern edge of the size of the clean, is also said that the size in this range is impossible to produce a thin ink layer, so that you can put an end to the skin phenomenon.

6.Causes and solutions of seepage of paint colorant prepared by oneself

Self - matching paint paste is a water - based paste used in textile printing. Yin can be found in the following aspects.

(1) Synthetic fabrics: such as polyester, nylon, polypropylene, etc., or blends with a high proportion of synthetic fibers. Synthetic fiber: Fabric is a hydrophobic substance, with the general printing of cotton fabric coating water prone to bleeding. When printing synthetic fabric, thick emulsion paste should be used to avoid dilution with water. If dilution is necessary, dilute it with dilute emulsified paste. Do not dilute directly with water.

(2) The humidity in the air is too large, such as the long rainy weather in the south, the slurry should be added with less water or no water.

(3) Cotton fabric is a natural cellulose fiber fabric, which is a hydrophilic substance. Generally not easy to permeate. But if the capillary effect is too high, it will also lead to infiltration. Therefore, the appropriate capillary effect is controlled at about 7-8cm. It is very important to ask for the manufacturer's technical specifications before feeding. Too low capillary effect will be impenetrable, too high resulting in infiltration.

(4) Some enterprises use emulsified paste as thickening agent, commonly known as A help pulp. It is emulsified with white flame oil, flat and synthetic dragon gum under high speed stirring. If the A-side pulp has quality problems and is not fully emulsified, the "oil ring" will be produced after printing, which is easy to cause the misunderstanding of "seepage" or "watermark". Therefore, we should choose good quality A-band pulp or use synthetic thickening agent to overcome the "oil ring".

(7) There are many comprehensive factors causing "bleeding" and "Yin", such as too thin, too thin and too light fabric fabric; Pattern area is too large; The mesh number is too low; Excessive pressure during operation; The blade section does not correspond to the pattern, the amount of pulp is too large and so on.

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7.How to mix different colors of paste?

Color science is a deep knowledge, and color blending needs the accumulation of practice. Learn theory, practice bravely, brilliant colorful will belong to you. A good colorist can roughly determine the basic formula of color composition from one look. More some color old technician, in the mass production that is out of the time, found the problem, additional color material in time, too late sample, a hammer, do eight or nine out of ten, this is hard time, so it is necessary to start from the beginning, practice basic skills.

First of all, from the three basic colors of red, yellow and blue to test the secondary colors: orange, green and purple. Modulation of three colors: yellow gray, blue gray, red gray.

Then put each monochrome in each chromatogram from light to medium to dark, the dosage is 0.1%, 0.5%, 1%, 3%, 5% respectively, scratch and leave the sample paste formula.

In addition, to each batch of business samples, formula file, for reference, perseverance, will be harvested.

The general principles of color mixing are as follows:

Try to reduce the number of dyes or paints when coloring, can use one, not two, can use two, not three. To facilitate the control of color light, generally three the following color is good. Second, the same kind of dye or paint, different manufacturers, different brands are best not mixed, such as necessary for the "color head", then the "color head" can only be very small, not two brands equal.

Another principle is: dye or paint has its saturation value, more than its saturation value, washing is easy to drop, resulting in contamination. Even if the coating is black, the dosage should also be controlled in 8%-10%, do not exceed 10%.

8.How to select and use elastic cover printing paste to ensure its color fastness?

(1) If it is clothing, choose water-based elastic cover printing glue. Because dress printing requirements odorless, soft feel, especially export clothing or high-grade products especially strict printing.

(2) There is a very important relationship between the type of cloth and the color fastness of the elastic cover printing glue. Elastic cover printing paste used on cotton fabric should not be used on synthetic fibers, because it can not guarantee the color fastness, should choose polyester or nylon special glue.

(3) rainproof nylon or polyester, used as banners, umbrellas, etc., outdoor environment requires good weather fastness, should withstand sun and rain, soft smell and feel is not too demanding, solvent ink can be selected, such as polyester ink, nylon ink to print. Coating fabric, should be based on the coating material to choose the appropriate ink is better.

(4) Due to the different materials and production process of each manufacturer, please read the instructions carefully to know how to use it. Some products require drying after baking 130-150℃, 3-5min, to increase color fastness. And many individual workers often put their energy on the quality of printing, ignoring the post-processing process. The baking process is eliminated, resulting in a wash off, all the previous work is wasted.

Even the low-temperature type of "glue" or paint paste, can not be washed after printing. It should be fully dried for 24h, preferably for 7 days, so that its color fastness reaches the highest value. If it is dried at about 100℃, it is better to iron it.

9.Why does thermosetting ink printing not block the screen and wet to wet printing

This is the traditional textile clothing printing industry people's biggest question. When they see the full automatic garment printing machine at high speed (one piece every five seconds), they are surprised; When they see thermoset ink printing without cleaning the screen, the next day or even ten days after a month can continue to print is incredible. Why is that? Because we all think that printing coating must contain adhesives, and adhesives must have viscosity (so in the case of not dry will stick version) and self-curing (of course, will block).

10.Is thermosetting ink a textile printing paint?

Is, of course! But it is a new type of printing coating, that is, does not contain any adhesive printing coating. Therefore, the thermosetting ink does not have the adhesive adhesive has the viscosity and self-curing, it also has the conditions of the never block and non-stick screen version.

With the conditions of non-stick screen version, is not equal to the absolute non-stick screen version, because thermosetting ink is paste after all. In order to achieve wet - to - wet high-speed printing, it is necessary to master the technology of thermoset ink dot printing.

Textile printing coatings have been divided into two categories: adhesives and non adhesives.

Thermosetting ink for non-adhesive textile printing paint, its accurate name should be: hot melt curing PVC textile printing paint.