How to improve printing quality?
Time:2023-11-20
Views:2106
Below, let‘s take a look at the core elements that affect ink stability and printing quality from the perspective of actual production.
Temperature
Keeping the temperature and humidity constant is very important to ensure the stability of the ink.
In summer printing, due to the high ambient temperature, it is easier for the roller of the printing machine to transfer ink, and with the increase of printing time, the fluidity of ink is enhanced, in the case of the same amount of ink, the ink color of the printing will be deepened, so in the printing process to constantly detect the density of the signal bar, often compared with the sample, if necessary, the amount of ink can be appropriately reduced. Make the color of the printed and signed samples uniform.
In winter, due to the overall low ambient temperature, when the machine is started in the morning, the temperature of each part of the machine is low, and the printing operator must do the following two points to start printing.
First, improve the temperature and humidity of the workshop, so that it meets the standard (temperature is 20 ~ 24℃, humidity is 60% ~ 70%).
Second, heat the ink or add additives or ink oil to the ink to increase the fluidity of the ink, and then start. This is because even if the ambient temperature and humidity are just up to standard, the temperature of each roll of the printing press is still at a low level, which will lead to weakened ink transfer performance, so that the printing press can not ink well, the printing speed is very slow, and the ink stability is difficult to control. It is necessary to increase the amount of ink to twice the usual printing of the same live parts in order to barely make the ink look saturated; Or the whole page turns gray; Or when printing thinner paper (105g/m2 or less), the paper is easy to stick to the rubber cloth, resulting in the rubber cloth being crushed.
Moistening solution concentration
Today, many printing presses use an automatic printing system, which eliminates the need for operators to adjust the concentration of the printing fluid, here, only the need to manually add the printing fluid described.
This printing machine requires the operator to deploy a good version of the liquid before starting, this is because the water and alcohol added to the water tank in the printing process and the original version of the liquid in the water tank are different in temperature and concentration, easy to cause printing with dirty, and if you want to eliminate floating dirty, you need to increase the water, the ink will become lighter because of the increase in water, which has little impact on the general living parts. However, it has an impact on high-speed operation and high quality living parts, and is prone to failure.
In addition, the concentration of the printing solution must meet the printing requirements, which can be measured by pH test paper or concentration meter. If the concentration is too large, the ink color will not meet the requirements in any case, and the ink will quickly emulsify; If the concentration is too small, the floating dirt of the living parts will be eliminated when the water is added to a large amount, and once the printing is accelerated, the floating dirt will easily appear in the mouth position, the ink will become lighter when the water increases, forming a vicious circle, making the stability of the ink simply uncontrollable, the ink will change very large when printing after running empty or stopping, and it is easy to cause sticky dirt.
Therefore, the operator should measure the concentration of the plate liquid every 2 hours, and add a trace amount of alcohol as needed, because the alcohol is volatile during the printing process, and the printing plate and the rubber blanket will cause alcohol volatilization during the process of pressing and rotating. If you do not add alcohol for a long time and do not measure the concentration of the moistening solution, the concentration of the moistening solution will be very low after six or seven hours, resulting in faults such as dirty version and emulsification, resulting in ink stability that cannot be controlled at all. It‘s easy to overlook.
Control of the amount of ink given
Pre-inking before printing is very important, after adjusting the ink color, we must first print out the standard printing sample, usually called signing sample (generally signed by the captain and the workshop director), and then hang it in the sample table. Some press captains decided not to worry about it after signing the samples. This view is actually wrong, with the speed of printing and printing time becomes longer, the viscosity and emulsification of ink will change, and the ink color has not really achieved stability. This requires us to do the following two things before printing:
First, reduce the amount of water before pre-inking, because the density of different pages is different, and the amount of water required will be different.
Second, when printing samples, the field density value of the signal bar should be in the standard range (Y is 0.85 ~ 1.10, M is 1.25 ~ 1.50, C is 1.30 ~ 1.55, K is 1.40 ~ 1.70).
The reason for ensuring the above two points is that if the amount of ink in the last live part is very large, and the amount of ink in the current live part is very small, and the water is not reduced in advance before the pre-inking, then the color of the sample is not normal ink color at all, and it will change during printing. Moreover, in the case that the amount of ink given in this way cannot be absorbed by the plate, it will slowly accumulate on the roller and gradually emulsify, and it is difficult to eliminate the floating dirt after the water roller pressing, and the printing will stick and dirty under the same amount of powder. Operators through the ink roller rotation that occur when the sound of "yi yi", or the ink roller inking and shiny can judge the situation.
Therefore, the printing captain must develop a good habit of reducing water before signing the sample, observe whether there is floating dirt in the mouth during the ink mixing process of running through the plate paper, until the water is gradually increased to eliminate floating dirt, and then the density of the signal bar meets the standard, so that the ink is really in line with the theory of "printing standard prints with the smallest ink and the smallest water". This will make it easy to make the ink stable and easy to control.
After signing the sample, with the increase of speed, it is necessary to frequently sample to test whether the ink color is stable. Generally, the new machine has the ink characteristic curve, and the machine will automatically add ink and water according to different parts. The relatively old printing models should be controlled manually, and do not think that after signing, you can rest assured to accelerate the printing, which is actually easy to cause waste.
Acceleration should be slow, and then frequently sampling, often adjust the amount of ink, printing speed must not be increased from 6000 / hour to 10000 / hour or more, otherwise it is easy to cause light ink, printing mouth is easy to dirty, resulting in waste products. When you slowly accelerate to the appropriate printing speed, observe hundreds of pieces, if the color is stable, then this is the real sense of the "rest assured" printing stage, as long as you do frequent sampling, fine observation, the stability of the general live parts will be easy to control.
Printing speed
This is throughout the stability of the ink, because the color can only remain stable if the stable paper is maintained. If the paper is not smooth, improper adjustment, empty and stuffy car, it will not only cause ink instability, but also waste a lot of paper, in the encounter of electrostatic large offset paper (generally 100g/m2 paper), it is easy to appear non-regulatory empty and paper is not smooth. Then it is necessary to find a way to increase the humidity of the air, and place metal rods to eliminate static electricity above the Feida paper to eliminate static electricity.
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Anna Zhang