Common Printing Faults and Solutions for Offset Printing Process

Abstract: From the ink point of view, the common faults in the offset printing process and their solutions are described.

Keywords: ink, offset printing, printing failure

The various failures that occur in the printing process are, in general, seldom caused by a single factor, and are often caused by inconsistent and inconsistent conditions of the ink, paper, printing press, and printing environment. Here is a common printing failure, from the ink point of view to propose solutions for your peer reference.

1, from the dirty

Dirty refers to the occurrence of many ink stains in the non-graphic area of ​​the printed matter, which is a common and representative failure in lithographic printing.

This phenomenon is mostly caused by various factors such as ink, paper, printing plate, and printing syrup. From the ink point of view, it usually occurs when the ink is thin, soft, and the yield value is too high and the viscosity is insufficient. The performance, adding the appropriate viscosity of the resin varnish or bright paste, help to overcome the dirt; ink deployment, desiccant, low viscosity varnish, detackifier added too much, the ink will be thin The stickiness and smallness are important reasons for this disadvantage. The ink can be properly prepared and replaced with quick-setting light ink.

Second, uneven plateau grains, abrasive material residues, insufficient non-lipidation, partial oxidation of the plate, or insufficient development, etc., are also important factors that cause dirt, and should also be checked and resolved. At the same time, the printing roller is poorly arranged. , Water roller dirty, ink roller rubber aging, blanket loose, can also cause dirt, should be checked and adjusted.

2, thick

Thickness means that the pigment is separated from the ink and accumulated on the plate and the blanket, resulting in the printing dots being crushed.

Under normal circumstances, the ink is poor in water resistance, and this phenomenon often occurs during emulsification. Can add appropriate amount of high-viscosity resin varnish, bright lacquer or printing varnish, improve ink viscosity, transferability and water resistance, while increasing the PH value of printing syrup, reduce the amount of water, reduce the amount of ink, can be improved Or overcome this failure.

3, dirty

Dirty, also known as "dirty", "stained back", the printing speed is too fast, when the time fixed on the paper is not enough ink or paper pressure is too large, the ink layer is not yet dry, the phenomenon of ink retransfer occurs. Dirty.

This phenomenon is easy to occur in high-speed four-color and two-color printing. The most fundamental measure is to use fast-fixing light, fast-fixing ink printing and dusting, adjust and control the amount of powder to be sprayed, and reduce the supply when the ink color and concentration allow. The amount of ink reduces the pressure on the accumulation of printed matter and reduces the amount of water supply, helping to overcome the dirtiness.

4, paste version

Paste refers to the printing process, the ink in a very light color, a large area of ​​the layout of the blank space, wiped off after another phenomenon will soon appear.

The appearance of stencil printing is generally due to the poor water resistance of the pigment in the ink, improper adjustment of the ink formulation, excessive use of a de-adhesive agent, low-viscosity grading oil, and the over-thinning of the ink. To solve this problem, one is to use ink with good water resistance, and second is to adjust the amount of various printing auxiliaries to ensure the ink's water resistance and ink balance.

5, pull the paper

Printing high-grade coated paper, glass cardboard, matt paper, generally do not have this problem. If the surface of the paper is rough, the strength is not good, the paint adhesion of the paper is not strong, and the viscosity of the ink is relatively large, all of them can cause a paper pull phenomenon, resulting in a decrease in print quality. In such a case, it is a simpler and more economical method to reduce the viscosity of the ink by using a de-adhesive agent or to reduce the viscosity of the ink as small as possible so that the ink film is easily split during imprinting, and the printing speed is reduced. better.

6, crystallization

Crystallization is also called vitrification. The phenomenon is that the first printed ink is dry, and then the ink is not printed on the printing or even if it is printed, the ink layer is also easy to fall off after the printing. The fast-setting light ink and resin offset printing ink after the ink is resinized. Problems are rare, and occasionally this phenomenon occurs when printing large-scale or thick inks. The solution is mainly to properly grasp the next color of the overprint time, when the previous color is not completely dry when the overprint, followed by the control of a good dry oil blending amount, dry oil added too much to promote the crystallization of the main factors.

7. No ink

Not to ink, also known as ink roll, refers to the print marks, the hue is also relatively light phenomenon.
This phenomenon is mainly due to the ink's poor ink property, too high yield value, high pigment content in the ink, short cheese-like ink, cheese-like ink, gelled ink, or water entering the ink to cause partial flocculation. The ink and the ink roller in the printer ink tank are detached and cannot be transferred well. To meet this problem, the ink property and ink fluidity must be improved from the ink design. Secondly, during printing, inks with high viscosity are properly prepared to improve the flowability of the ink, which can help to overcome the large thixotropy, ink with a good viscosity and fluidity. The ink in the ink tank is often agitated with a knife or ink. Installing a stirrer directly in the ink tank can also overcome this disadvantage.

8, flying ink

Flying ink refers to the fact that during the printing process, the ink is rotating between the ink rollers, and when disconnected, the broken ink filaments become charged particles due to the surface tension, and the driven printing machine is driven out of the space and scattered. phenomenon.

The phenomenon of flying ink increases with the thickening of the ink layer of the roller, and the speed of the printing machine increases rapidly. In serious cases, the pollution equipment and the printing environment even affect the quality of the printed product. This phenomenon occurs because the viscosity of the ink and the speed of the printing press do not adapt. Generally, the viscosity of the ink is large, the length of the ink is long, and the ink is soft. The ink is poor in water resistance, and it will also fly when it is easily emulsified. The main solution is to remove the viscosity of the ink properly and improve the water resistance of the ink. The use of harder, higher-concentration inks reduces the amount of ink supplied. The roller's ink layer is thin and the flying ink phenomenon is improved.

9, dry too fast

Too fast drying refers to the fact that the ink has thickened and dried in the ink fountain, on the ink roller, and on the blanket.
This phenomenon is mainly caused by too much desiccant in the ink, the ink contains too much solvent that volatilizes too quickly, and the temperature in the printing shop is too high, the air is too dry or the air circulation is too good. The solution is mainly to add a small amount of Vaseline to the ink to reduce the conjunctival drying rate; add a small amount of anti-skinning agent or antioxidant; workshop ventilation should not be too good.

10, network expansion

The expansion of outlets is mainly reflected in the outlets of the edition and cannot be faithfully reproduced. As a result, outlets are distorted or connected, and the contrast is insufficient, which affects the quality of printed products.

This phenomenon is mostly caused by improper ink blending, over-excessive and soft ink, and insufficient concentration. When the ink is formulated, an appropriate amount of de-adhesive agent should be added. No more dilute ink is needed to stick, or a higher concentration of ink is used to reduce the amount of ink. This phenomenon can be overcome, the hardness of the second printing ink roller is not suitable, the roller pressure is too large, the blanket is loose, and the poor arrangement of the rollers is also an important reason for this problem, also due to inspection adjustment.

Ink and printing workers are very clear that there will be no universal ink, can adapt to a variety of printers, paper, printing environment and different printing needs, so printing should be based on different circumstances, the deployment of ink is essential , It is also very important, properly deployed, you can reduce a lot of printing failures, the above is only for your peer reference, hope correcting!

Source: Ink Information