The first line printer must master the printing quality management skills!
Time:2023-10-26
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To this end, today we have sorted out the five magic weapons that affect the stability of ink.
1 -- Before printing, do a good job of pre-adjustment with experience
First of all, according to the sample or printing plate graphic area, roughly adjust the amount of ink under the color group ink fountain. This is easier to do on machines with ink remote control systems. There should be an estimate of more than 80%, and do not adjust the ink amount in a large range while printing, so as not to cause a large color difference.
Secondly, according to the requirements of the production process sheet and the characteristics of the product, the various links such as Feida, paper receiving, ink performance, and pressure are adjusted in advance to avoid confusion in the formal printing. Among them, ensuring Feida reliable, continuous and stable paper delivery is the most important. Experienced operators are first according to the size and thickness of the paper, pre-adjust the blowing, suction, press foot, press spring, press wheel, side gauge, front gauge, etc., to smooth the movement between the components of the relationship, to ensure that Feida smooth paper delivery, to avoid due to Feida padden caused by different shades of ink. It is suggested that experienced workers can pre-adjust Feida.
In addition, it is also necessary to adjust the viscosity, fluidity and dryness of the ink in advance for the quality of the paper and the size of the graphic area of the printing product, so as to improve its printability and ensure the normal printing process, and it can not be caused by frequent shutdown to clean the paper wool and ink skin on the rubber blanket and printing plate. If you add a variety of adhesives and ink oil halfway through printing, the color deviation is certain.
In short, the pre-adjustment work before the boot can be done, which can greatly reduce the fault after the official opening of the press, and the captain has time and energy to focus on the ink.
2 -- Correctly adjust the pressure of water and ink roller
In the printing process, the graphic part of the plate must be continuous, uniform and appropriate amount of ink in order to obtain a consistent ink color. Therefore, between the ink roller and the ink roller, between the ink roller and the plate, must maintain the appropriate contact and rolling relationship to achieve a good transfer of ink. If this work is not done carefully and correctly, the ink will not be consistent. Therefore, each time the installation of water and ink rollers, adhere to the method of rolling ink bars to adjust the pressure between them one by one, rather than the traditional method of testing the pull force, because the latter due to various human factors caused by the actual error is large, in the multi-color, high-speed machine to be disabled. As for the width of the ink bar, it is generally appropriate to 4 ~ 5mm. First adjust the pressure between the ink roller and the ink roller, then adjust the pressure between the ink roller and the ink roller and the plate roller, and finally adjust the pressure between the water roller, the plate water roller, the water roller, the middle roller, and the pressure between the plate water roller and the plate roller, the ink bar between these several waterways is 6mm.
The equipment should be re-adjusted after two or three months of use, because the diameter of the ink roller will become smaller after a period of high-speed friction, especially in the transmission. The pressure between the ink rollers becomes smaller, the ink accumulation on the ink roller will not be passed down, when Feida dun or stop to continue printing, due to the large amount of ink at this time, resulting in the first dozens or even hundreds of ink color is darker, the ideal ink balance is difficult to achieve. This fault is generally not easy to find, and is more obvious only when printing finer prints. In short, the operation in this area should be meticulous and the method should be scientific, otherwise it will cause the ink depth of the water, ink bars, and the mouth and drag parts of the printing part to be different, which artificially causes faults and increases the difficulty of operation.
3 -- To achieve ink and wash balance
As we all know, ink balance is an important content in offset printing. If the water is large and the ink is large, the ink will be oil-in-water emulsification, and the quality of the printing product will not be ideal. Through long-term practice, we have developed some techniques.
First of all, ensure that the pressure relationship between the water and the ink roller is properly adjusted, and the content of the moistening solution and isopropyl alcohol meets the general standard. On this basis, turn on the machine, close the water and ink roller, and then stop the machine to check the printing plate. It is better to have a slight sticky dirt of about 3mm at the mouth of the printing plate. The water amount at this time is used as the initial water amount for printing, which can ensure the normal printing of general graphic products and basically achieve the balance of ink and wash.
Secondly, flexibly adjust the water consumption according to other factors, such as the printing plate graphic area is large, the paper surface is rough, the ink needs to add additives, the printing speed and air temperature, humidity and other changes.
In addition, we also found that when the machine just opened the printing, the body temperature is low, and when the machine ran at high speed for an hour or two, the body temperature, especially the roller temperature will rise more than double, or even higher, at this time the water consumption will gradually increase until the ink reaches a new equilibrium state.
It can be seen that it is not easy to achieve the balance of ink painting, and operators need to weigh and use it dialectically. Otherwise, the stability of the ink is difficult to control, and the printing quality cannot be produced.
4 -- Proofreading and color sequence arrangement
In production, it is often encountered that the sample provided by the customer is very non-standard, or only a color spray draft is provided without proof. At this time, it is necessary to analyze the specific situation, and it is not possible to use the method of hard increasing the amount of ink or reducing the amount of ink to chase the effect of the sample. Even if it is close to the prototype at the beginning, it cannot guarantee the stability of the ink color, which cannot guarantee the final quality of the print. In this regard, the printing plant should actively exchange views with customers in a serious and responsible attitude, point out the problems and modification suggestions of the sample, and obtain consent before appropriate adjustment and re-printing.
Production is usually based on ink viscosity to determine the printing color sequence of the multicolor machine, because in multicolor printing, the ink is overprinted in a wet press wet way, only to obtain the best overprint rate, in order to print ink color stability and consistency. The arrangement of the printing color sequence must obey the characteristics and quality requirements of the printed product, and cannot be unchanged. At the same time, the ink viscosity can also be adjusted. Such as a purple based cover and a sky blue based cover, the printing color order is different, the former first green after magenta, the latter first magenta after green, otherwise the overprinted color will be spot-like, neither flat nor stable. If the printing is mainly black, the black should be arranged in the last color group as far as possible, so that the printed product has a better gloss of black, and also avoids the occurrence of scratches and color mixing inside the machine.
5 -- Cultivate good operating habits and strengthen the sense of responsibility
Do any work must have a high sense of responsibility and a strong sense of quality, must standardize the process operation, adhere to the "three flat", "three Qin" and other good traditional habits. Taking the sample as an example, when comparing the signature sample on the template, due to the difference in distance, Angle, light source, etc., it will cause visual deviation, resulting in inconsistent ink color, then it is necessary to take the signature sample from the template to carefully compare it; Long live plates need to bake plates to reduce the ink deviation caused by plate change; The rubber cloth should be cleaned frequently, and more blotting paper should be put in after each cleaning to make the ink steady; After Feida, the five or six pieces of ink that have just been printed are too deep to be extracted, and the printing speed cannot be greedy. The important thing is to keep the machine stable and normal. When adding ink to the ink hopper, because the new ink is hard and poor fluidity, it is necessary to stir several times to avoid affecting the amount of ink and causing ink color deviation.
Operators should continue to learn, carefully observe and analyze, from all aspects to find out the factors affecting the change of ink, and take appropriate measures to properly prevent and overcome, and strive to improve the stability and consistency of ink color, effectively improve the quality of printing.
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Anna Zhang