5 typical cases that teach you to use offset inks
We are a big printing company in Shenzhen China . We offer all book publications, hardcover book printing, papercover book printing, hardcover notebook, sprial book printing, saddle stiching book printing, booklet printing,packaging box, calendars, all kinds of PVC, product brochures, notes, Children's book, stickers, all kinds of special paper color printing products, game cardand so on.
For more information please visit
http://www.joyful-printing.com. ENG only
http://www.joyful-printing.net
http://www.joyful-printing.org
email: info@joyful-printing.net
Regarding the practical application of ink, the author wants to focus on the relationship between the correct adjustment of ink and the quality of printed products through the most typical cases that I have experienced.
Case 1: Poor ink overprinting
When our company was printing a batch of handbags, the magenta dots of the latter color group and the cyan field overlay of the previous color group appeared to be bad, resulting in many spots on the printed matter. Although the author has repeatedly lowered the viscosity of magenta ink and hopes to increase its overprinting rate, it has no obvious effect. Reluctantly, I had to reverse the order of green and magenta, and the problem was completely solved.
Case study: The multi-color machine finishes printing in a short period of time. The overprinting method of the ink is wet and wet. If the printing color sequence is improperly arranged, the ink overprinting rate will be greatly reduced. Therefore, according to the characteristics of the multi-color machine, the following basic principles should be followed when arranging the printing color sequence.
(1) The printing color sequence is arranged according to the transparency of the ink. The ink with a lower transparency is printed first, and the ink with a higher transparency is printed later, which can improve the color rendering effect after the ink is overprinted.
(2) Arrange the printing color sequence according to the area of the printing plate. That is, the printing plate has a small area with a small ink color, and a large image with a large ink color.
(3) Arrange the printing color sequence according to the viscosity of the ink. The ink with a large viscosity is printed first, and the ink with a small viscosity is printed, and the viscosity of the ink is lowered by color. If the color ink with high viscosity must be placed in the next color group, the viscosity should be reduced first with the de-adhesive. Otherwise, the overprinting failure will occur, that is, the ink mixing phenomenon will occur. For example, when the machine's gripper is worn and the black character has a ghosting fault, the color sequence can be adjusted, and the black ink is arranged in the second, third or fourth color group printing, but the viscosity of the black ink should be lowered in time.
(4) Arrange the printing color sequence according to the characteristics of the original. For example, when printing originals such as warm colors and Caixia, the cyan should be placed in the previous color group, and the magenta should be placed in the back. If the originals such as glacier and snow are mainly printed in cool colors, the magenta should be placed. The former color group, the cyan is arranged behind.
In the above case, the cause of the failure is that the cyan ink is in the ground, the ink layer is thick, and the magenta ink is a light net, and the ink layer is thin. When the magenta ink is printed on the wet and thick cyan ink layer, the ink is surely produced. The phenomenon of poor overprinting, the printed outlets are vain, irregularly enlarged, and even appear to be streaked, very uneven. When the color sequence is reversed, the fault is eliminated.
Case 2: Overprinting caused by the problem of peeling tension of the ink on the paper
When a machine is printing a full-color sauce of beef sauce logo (paper is 80g/m2 single-coated coated paper), it is always overprinted, and the fourth color group blanket is constantly stuck and peeled. Long suspected tooth decay, repeated cleaning and lubrication of the tooth decay, still can not be resolved. After the author has checked, first remove the viscosity of the black, magenta, and yellow inks with the de-adhesive agent, and then reduce the printing pressure of each color group as much as possible, and troubleshoot.
Case study: For full-size large-volume prints, the viscosity and printing pressure of the ink should not be too large. Otherwise, if the paper is thin, the paper will be difficult to overcome the excessive printing peeling tension, resulting in inaccurate overprinting and paper curling. Even the tooth decay can not peel the paper from the blanket to complete the normal handover, so that the paper is continuously torn and peeled. When the author takes measures to add the de-adhesive agent and reduce the printing pressure, the peeling tension of the ink on the paper is greatly reduced, and the production can naturally proceed normally.
Case 3: The coloration effect of the ink is dark
There is a four-color bank passbook order, and the main color of the passbook cover is overprinted by 100% medium yellow and magenta. When the customer signs up on the machine, it is considered that the red color is slightly darker than the golden red and bright, which is far from the official printing. In the face of this situation, the author is very embarrassed, because if you re-plate, time is too late, and will increase the cost, so you can only use the brain color.
Later, according to the changing rules of ink color, the author decided to change the medium yellow used in the four-color ink to light yellow and the magenta to big red. When the first sample was printed, we found that the main color of the cover of the passbook had completely reached the golden red effect, the color was very bright, and the customer was very satisfied.
Case study: It is undeniable that in the commonly used three primary color inks, different batches of inks tend to have a certain deviation in hue due to factors such as cost and price, such as reddish yellow, reddish magenta, and reddish blue. Overprinted colors, whether red or green, have lower color saturation and greater grayscale. At this time, we must analyze the original, grasp the most important color, choose the most suitable ink, and print the best results.
Later, based on this successful experience, the author used a combination of light yellow ink and hole blue ink to print a relatively pure green color, which made the customer very satisfied. This method can sometimes correct some of the color cast problems in the plate making and achieve unexpected results. Such innovative measures are quick and easy, and do not need to add any cost.
Case 4: "Ghosts" caused by ink
On one occasion, the machine printed a cover for a child's book. The mouth of the print was a pattern of small trees, and the tip of the print was a large apple pattern. During the printing process, it was found that there was a "ghost" of small leaves in the apple pattern at the tip of the mouth. At first we thought that there was a problem with the ink path of the cyan group. First, the pressure of the water and ink rollers of the color group was adjusted again according to the standard. As a result, the "ghost shadow" still existed. So, we re-adjust the relevant parameters of the yellow group behind, and the result is still not good. After calm thinking, the author guessed that it was caused by ink, so immediately added 3% de-adhesive agent to the yellow ink, and then started printing, "Ghost" immediately disappeared.
Case Study: We know that the main reason for the production of “ghosts” is the improper design of printed products and poor ink transmission. In this case, there is no such problem. In terms of printing color sequence arrangement, yellow ink has the highest transparency and the smallest stickiness, and it is correct to put it in the last color group printing. And we use high-grade environmentally friendly inks, ready to use, without the need to add any adjuvants. Why did you produce "ghosts" this time?
Originally, due to the large difference in the graphic area of the printed four-color printing plate, the consumption of the blue ink is small, the ink on the rubber roller is less replenished, and the ink is continuously eroded and emulsified by the dampening solution, and the viscosity of the ink is greatly reduced; The yellow ink consumption is very large, and it can be continuously replenished with new ink, and the ink viscosity does not change much. When the machine is pressed, the yellow ink will stick the residual blue ink on the blanket under the action of the printing pressure to form a slight reverse overprint, and then transfer through the yellow group by the plate roller, at the tip of the printed product. In the apple pattern, there is a "ghost" of small leaves. That is to say, the viscosity of the two inks of cyan and yellow is relatively close, which leads to the generation of “ghost shadow”. When the author adds the detacking agent to the yellow ink, the viscosity of the yellow ink drops a lot, and the “ghost shadow” is naturally eliminated.
Case 5: Poor ink transfer, printed ink color is light
The common causes of the ink color of the printed products are: (1) the ink supply is too small; (2) the ink is excessively emulsified, forming an oil-in-water state, so that the print becomes shallow; (3) the pressure of the rubber roller is uneven, or the glue Crystallization of the surface of the roller causes the ink to fail to pass normally; (4) The ink-repellency of the printing plate is poor, or the printing plate is printed in the printing process due to wear and tear, so that the ink color is light; (5) The blanket piles paper powder, aging, etc., resulting in poor ink transfer.
For the above problems, we have a way to solve them quickly, but there are some special cases that require careful analysis and patience. When a four-color machine captain of our company printed a book, it found that the ink color of the printed product was very light, and even if conventional measures such as reducing the amount of water supply and increasing the amount of ink supply were used, it would not help. When the captain reflected the situation to the author, the author immediately went to the site to check and found that there was a lot of ink on the rubber roller. As long as the machine was slightly clicked, the ink could be heard when the ink was separated on the rubber roller. It shows that the viscosity of the ink is very high, and the author gently touches the surface of the rubber roller with his hand, which seems to be somewhat hot. At this point, the author has understood most of the reasons, that is, the temperature of the rubber roller is too high.
Case study: This problem is not caused by excessive emulsification of the ink, but because the temperature of the production workshop is high, and the machine speed is too fast, the temperature of the machine itself rises rapidly. Under such high temperature environment, the evaporation rate of the organic solvent in the ink Accelerate, so that the ink becomes dry and thick on the rubber roller, and the fluidity is deteriorated; at the same time, the dry and thick ink will continuously increase the friction between the rubber rollers, so that the temperature of the rubber roller further rises. Question: In this case, how can the ink be delivered normally? How can it be suitable for high speed printing?
In this regard, it is necessary to take the following measures in a comprehensive manner:
(1) cleaning the ink on the rubber roller while gradually lowering the temperature;
(2) Control the printing speed to prevent the temperature of the printing machine itself from being too high;
(3) appropriately lowering the set temperature of the alcohol fountain solution to quickly absorb heat from the surface of the plate cylinder, thereby lowering the temperature of the printing machine;
(4) Adding certain 6# varnish to the ink to increase the fluidity of the ink and prevent the ink from drying too fast on the rubber roller;
(5) Correctly adjust the pressure between the ink rollers to prevent the rubber roller from heating up too high due to excessive pressure.
Through the implementation of the above measures, the temperature of the rubber roller was finally lowered, and the color of the printed product was again brightened and full.