Operation essentials of the hottest ink balance co

Operation essentials of ink balance control

in offset printing production, poor ink balance control will produce a series of printing faults. Among them, too much water in the printing plate will cause the following hazards

(1) the printing ink is dim and lusterless, the saturation decreases, and the color is light

(2) ink is over emulsified, resulting in stencils

(3) the drying speed of the imprint slows down, causing the back of the print to rub dirty

(4) due to the blocking effect of water, the ink cannot be transferred normally, resulting in poor ink supply

(5) the printing sheet is soft, the paper receiving is uneven, and there are water stains on both sides of the drum, which will cause local rust of the machine in the long run

if the water volume of the printing plate is too small, the following hazards will occur

(1) printing ink becomes darker, dot increases, and it is easy to paste

(2) the blank part of the printing plate and sheet is dirty

according to the information, during normal printing, the ink layer thickness of the graphic part of the printing plate is 2 ~ 3 μ M, the water film thickness of the blank part is 0.5 ~ 1 μ m. The volume percentage of the fountain solution contained in the ink is 15% - 26% (preferably 21%, up to 30%), which can basically achieve the balance of water and ink. However, in the actual printing, the operator does not have enough time to use instruments to measure, and the factors affecting the ink balance are complex and constantly changing, so in the actual work, the operator mainly judges and controls the ink balance based on experience. The following work experience is for your reference

I. pre adjustment of water and ink before startup

advanced printing machines are equipped with printing plate reading devices (such as Heidelberg cpc3, Komori PSS printing plate scanning device, etc.), which can provide preset data of water supply and ink, and can automatically complete the setting. But colleagues who have used similar devices must know that in fact, this preset is not accurate, and it often needs real-time adjustment to achieve the required ink balance. For machines without printing plate measuring and reading devices, it mainly depends on experience to complete the preliminary water and ink presetting

before pre adjustment, the installation, pressure adjustment and testing of water roller and ink roller should be carried out first to avoid water and ink transmission failures

the preset method is as follows

1. Analyze and set

(1) observe the graphic distribution of the whole printing plate, determine the water and ink volume of each printing unit, and conduct preliminary setting operation. The principle is: large graphic area of the layout, more water consumption, otherwise less; The ink layer thickness uses more water, and vice versa

(2) according to the nature of the ink used, the ink with large emulsification value needs large water consumption, and vice versa

(3) when the printing speed is fast, the environmental humidity is low and the temperature is high, the water consumption is more, and vice versa

(4) the smoothness of paper is high, and the water consumption is less, otherwise it is more

(5) the sand mesh of the new printing plate has more water storage and consumption; Old printing plates use less water. PS version uses less water; The gravure plate uses a lot of water

2. Discharge water and ink

(1) first adjust the gap between the ink bucket and the ink bucket roller to make the ink output of the whole ink bucket roller uniform. During operation, rotate the ink bucket roller by shaking the one-way rotating handle to observe the distribution of the output ink layer on the ink bucket roller

(2) according to the graphic distribution of the printing plate, their common standards and the requirements for equipment in each standard, the gap between the ink bucket and the ink bucket roller is adjusted accordingly below. If the graphic density is large or there are many fields, the gap is correspondingly larger; The gap is correspondingly smaller if the density of pictures and texts is small or high-profile

(3) according to experience, estimate the number of teeth of the ink bucket roll in advance and adjust it well

(4) start the machine, turn on the water and ink transfer switches, and force the water and ink supply

(5) comprehensively and rapidly deliver ink to the ink roller

(6) comprehensively and rapidly increase the water volume of the water roller. When adding water to the water supply roll, it should be added to the water string roll. During operation, hold the sponge block with your fingers, suck enough fountain solution in the bucket tank, and evenly add it to the water roller. The operation posture should be correct and pay attention to safety. On the operating side of the machine, hold the safety part with your left hand and add water with your right hand; When on the transmission side of the machine, hold the safety part with your right hand and add water with your left hand

(7) during the operation of the machine, listen to the separation sound of the ink layer on the ink roller. If the separation sound is large, it means that the ink volume is large, and the separation sound is small, it means that the ink volume is small or moderate. When checking the water content of the water roll, you can gently touch the surface of the water roll with your fingers after stopping the machine. When your fingers feel the humidity similar to that of the wringing wet cloth, it basically meets the requirements

(8) run the car empty for 1 ~ 2 minutes to make the water and ink even

II. Ink balance control in printing

1 Cleaning and maintenance of printing plate

before trial printing, the printing plate should be cleaned with water to remove the protective adhesive film on the surface of the new printing plate; When the printing stops halfway, the layout should be coated with water or glue to form a layer of water film or glue film, which will isolate the non graphic part of the printing plate from the air and prevent the layout from getting dirty. If the non graphic department pays the conference fee before March 31, it will enjoy a discount of 1500 yuan/person. When the dirt is separated, it can be removed with glue solution, fountain solution, etc. When the image and text of the layout become shallow, you can use gasoline, glue liquid, plate cleaning liquid, etc. to clean it, so as to improve the grease sensitivity of the printing plate and make the image and text clear. These details that control the ink balance must not be too cumbersome to ignore

let Jinan Shijin take you to know more about it

2 The method of identifying the amount of water and its control

(1) the sheet fed printing machine can preliminarily estimate the amount of water according to the reflective intensity of the page

when viewing the page, the operator can stand on the side of the machine and observe the water on the surface of the printing plate with the help of natural light or light. When the ink balance is correct, the layout has weak brightness, which feels like the reflection of ground glass. If the surface of the printing plate is dark black and there is no reflective feeling, it indicates that the water content on the surface of the printing plate is too small; If the reflection of the plate is very bright and watery, it means that the water on the surface of the printing plate is too large. The reflective intensity of the layout will be affected by factors such as the light above the printing machine and the printing speed. You need to observe more at ordinary times to form a memory in your brain. When you feel the water is large, you should slowly reduce the water. Every time you reduce the reflection of the layout, check whether the print is normal. Until the print is slightly dry, add some water. At this time, the moisture of the layout is the best, that is, the ink and water reach a balance state

when observing and analyzing, we should also pay attention to whether the printing plate is a new version or an old version. The new version has complete sand mesh, large water storage, and the layout is not easy to reflect light. It should be gray and slightly shimmering during visual inspection. The sand on the surface of the old version has been worn, and water cannot be stored well. The water floats on the surface of the printing plate, and the layout should have some reflective feeling

judge whether the water volume is appropriate, and observe the sample. If the ink color of the sample is light, and the ink color is still light after inking, the water is large; If the sample is soft and the shaking sound is not crisp, the water is large; If the sample is dirty and the page is not dry after a long shutdown, the water will be heavy; If the printed matter is Matt, embossed, or the printed sheet curls, uneven delivery and other phenomena, it indicates that the moisture in the layout may be too large

there are water drops on the ink roller and in the ink tank, which is also a feature of large water

(2) judgment and control of slight water drying in printing

when slightly water drying (less water), there is usually a slight ink stain on the mouth of the mouth other than the text, but it is considered as water drying if this phenomenon cannot be seen. If the water is slightly dry, sometimes there will be no ink on the mouth. At this time, the most effective way to judge whether the water is dry is to use a magnifying glass to observe whether there is a paste in the graphic area with a large amount of ink on the print. When such paste is serious, it is easy to see with the naked eye; If it is slight, you need to use a magnifying glass to see whether the edge of the pattern is smooth and whether the dots are clear

during printing, it is necessary to frequently sample sheets for observation, control the ink balance according to the observation, and do not rush for success. The amount of water and ink should be well known, and the adjustment effect should be predictable to avoid repeated adjustment

3. The influence of printing speed on the balance of water and ink

the printing speed is fast, the ink transfer rate decreases, and the ink color will become lighter. At the same time, due to the increase of the layout temperature and the rapid evaporation of water, the China Association for science and technology released the survey results organized by them in March 2007: the demand for water in the main analytical instruments in China's instruments and meters will increase, which is particularly evident in the high-speed rotary machine. When speeding up, many operators found that the color became lighter compared with the printing sample. They thought that the water was large, so they increased the amount of ink, but did not immediately increase the amount of water. Therefore, the water dried paste version will soon appear, and the ink color will become darker. At this time, we quickly add water to reduce the amount of ink. After printing a certain amount, there is a large amount of water and a small amount of ink. Such repeated adjustment has always been poorly controlled, resulting in the color instability of the same batch of products

to sum up, there are many factors that affect the ink balance of offset printing, but as long as we carefully analyze and accumulate rich experience, it is not difficult to control the ink balance

source: Printing Technology