For the Indian iron reference principle
The quality of offset printing products is inseparable from the balance between ink and water. In the printing process, the amount of water supplied is too large or too small, which is often prone to occur because the size of the printing plate moisture is manifested from the dirtiness of the printing plate. However, the so-called dirt is not caused by the small amount of water. Operators often mistakenly increase the amount of water supply to cause the ink and moisture to lose balance and form a vicious circle. What kind of printing consequences does the water produce?
1, dilute the ink to make the ink pale, dull, affect the color of printed products. If we use the method of increasing the amount of ink to save the ink color, it will cause the ink to be large and the water to be large, making the image rough, paste, and the print is not clear.
2, causing ink roller deinking. In severe cases, there will be accumulated moisture on the entire ink roller, so that the printing plate graphic part can not get the normal ink supply, causing the printing plate graphic “floweringâ€.
3, affect the drying of the imprint. If the ink is mixed with excessive moisture, it will play a role in suppressing the drying of the ink. Together with the absorption of more moisture in the paper, the product will dry more slowly.
4, paper fibers absorb too much moisture, will have a deformation, resulting in overprinting is not allowed. It will also make the paper texture loose, easy to lose hair, and accumulate on the blanket or plate, which will seriously affect the quality of the printed product.
5, the ink emulsification, so that the ink loses its viscosity. After the ink is emulsified, it can't protect the printing plate picture and text, it is easy to cause "flower plate", at the same time, it will reduce the printing plate's resistance to printing force.
Through the above analysis, it is shown that the balance between ink and ink is a key link in offset printing. In addition to the experience of the operator, it is more important to master the correct use and adjustment of the offset printing machine's water delivery mechanism.
In order to adapt the water supply capacity of the water delivery system to the requirements of the printing production, the water delivery system is provided with a device for controlling the moisture and regulating the amount of water. This can be divided into three parts according to the nature of their work: First, the water supply device; the second is a uniform device; third, the water supply device.
The water supply device mainly consists of a water tank, a fountain roller, and a water transfer roller. The sink is used to store water, and there is a water bucket roller (also called water outlet roller) at the upper part. The lower half of the fountain roller is immersed in the fountain solution. They do not touch each other and do not support each other. In addition to automatically adding water to the water (it has been used by many manufacturers), it is also possible to add water manually. Manually adding water requires the operator to constantly add the previously prepared solution to the sink. Since the amount of water supplied in the fountain roller is related to the height of the fountain solution, the water supply must be uniform so that the fountain solution in the sink must maintain a certain water level. The operator can't be impatient when he adds the water bucket solution. Slowly add the water bucket solution to the sink. Do not swing the solution in the sink. Such as swinging, one is caused by normal local moisture suddenly increased, affect the quality of the product; Second, the bucket solution will be sprinkled to the front of the sink part of the sink, resulting in paper, clutch pressure is not normal (This is because the solution Dropped to the front of the teeth section, the formation of conductive); third is the drop of printed products, resulting in water spots on the paper, and then print a color when prone to double sheets.
The water transfer roller, also known as the draught roller, is a rubber roller installed between the water roller and the water roller. The regulation requirement of the water transfer roller is that the draught should be kept in parallel with the water roller, and there is an appropriate pressure, which is regulated by the tension springs on both sides. The pull force of the tension spring must be kept constant during adjustment to ensure that the water transfer roller works parallel to the water roller during draught. When relying on the cam for water supply, the water transfer roller must be leaned on the string water roller with appropriate pressure. On both sides of the water roller there is an adjustment screw and a positioning backing. The adjustment also requires that the transfer roller and the skewer roller remain parallel. The water transfer roller also has a draft device for draught. When the pressure is released, the normal draught feed water is swung back and forth through a 0.7 kg iron suction of 220V. When the pressure is released, it stops swinging back and forth, that is, no longer depends on the outlet roller. The buttons for controlling the water supply and water supply on the operation console are to control the iron absorption. They work according to the production conditions. We sometimes find that after the normal printing, we will find that the pressure of the plate will increase after the pressure is released. why? This is because the pulling force of the top jaw of the suction iron is not enough after the suction of iron stops working, causing the roller to remain in draft from the pressing water transmission roller, and the machine stops feeding after one or two revolutions. The strength of the tension spring is not enough, causing the suction iron to shrink slowly one or two beats. This is the reason that causes the layout moisture to become larger. It is very easy to solve this problem by replacing a new tension spring or shortening the old tension spring by one or two.
The water distribution device is mainly a series of water rollers. It is usually made of a corrosion-resistant metal material. In order to achieve uniform water on the water roller, the water roller has not only rotary motion but also axial motion. The surface speed of the squeegee roll is equal to the surface speed of the printing plate to keep the platen roller moving at an equal speed. The axial convolution of the string water roller is adjusted by the eccentric link, which is relatively simple and does not need to be adjusted in the printing process under normal circumstances.
The water supply device can be called a plate water roller or a water roller. They are generally two. Its surface is the same as the water transfer roller. The role of the reel water roller is to evenly transfer the aqueous solution from the water transfer roller and the water roller to the printing plate. Its surface speed must be equal to the speed of the surface of the printing plate. It is not allowed to have axial turbulence and radial runout, otherwise the printing plate may be damaged. The requirements for adjusting the reel water roller are relatively high and must be adjusted according to the steps. Adjust the eccentricity first, so that the pressure between the plate roller and the skewer roller is just right. Then adjust the cone head so that the pressure between the plate roller and the printing plate is appropriate. The above method should explain that when the eccentricity is adjusted, not only the pressure between the plate roller and the string roller will be changed, but also the pressure between the plate roller and the plate will be affected.
When the cone head is adjusted, only the pressure between the plate roller and the printing plate is changed, and the pressure between the plate roller and the string water roller does not change. When adjusting the water roller, adjust the water roller and adjust the water roller. It is better that the pressure of the upper water roller is smaller than the pressure of the lower water roller, because this can use the upper water roller to collect the plate with excess moisture. This is an experience gained from practice. When adjusting the pressure of the printing roller, special attention should be paid to the position of the adjustment eccentric at both ends. If the difference is too large, the position of the printing roller and the printing plate and the string of water rollers will not be parallel, and the problems of loosening and tightness in the middle will be easily generated. . Therefore, when adjusting the reel water roller, it is necessary to use the method of correcting the center-to-center distance to measure the problems at both ends and in the middle. Therefore, when adjusting the water roller, it is necessary to use the method of correcting the center distance to measure the two ends and the middle three points so as to prevent the contact pressure of the water roller and the printing plate from being too heavy. Otherwise, the state can cause the plate friction to increase. Large wear and tear, so that the plate version of the "flower", the resistance force is reduced, but also will cause the water roller and the printing plate to contact when the jump occurs, so that the jumped parts with dirty, and re-fall part of the "water bar "(ie, white bars). However, the contact pressure between the plate roller and the printing plate should not be too light, which may cause the plate to be insufficiently supplied due to insufficient moisture supply. If the amount of water supply is inappropriately increased, it will cause excessive water in the layout. So how do you determine if the contact pressure is in the optimal adjustment position? According to the experience, it is necessary to determine whether or not there is a beating phenomenon during operation by pressing the plate-type water roller and the plate to press the machine to start the machine and then touching the plate holder of the plate-printing roller by hand. Because the plate cylinder has a printing surface, the contact pressure of the plate roller can be easily felt. In general, there is a slight feeling of beating. Under normal circumstances, the feeling of a slight jump is most appropriate. If the jump is serious, it means that the pressure is too high. At this time, it should be adjusted again.
To adjust the water delivery system, the following work must be done: First, the pad of the printing plate should be compounded; second, the water solution in the sink should be free of impurities; third, the water roller must be changed frequently; and the fourth is the water roller and the string water. The rollers must be cleaned and must be kept clean.
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