The function and adjustment of the water-discharging mechanism of offset press (2)

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 skewer roll is equal to the surface speed of the plate to keep the platen roller moving at equal speeds. The axial movement 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 may be referred to as a plate water roller or a water roller. Generally uniform for the two rollers, the surface of the water transfer roller is wrapped like a good absorbent water roller velvet. The role of the reel water roller is to evenly transfer the aqueous solution from the water transfer roller and the string water roller to the printing plate.

Its surface speed must be equal to the speed of the printing plate surface. It is not allowed to have axial turbulence and radial runout, otherwise it is easy to cause damage to the printing plate. 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 adjusting the cone head, only the pressure between the plate roller and the string roller is changed, and the pressure between the plate roller and the string roller is constant. When adjusting the plate roller, the nozzle roller should be adjusted first. Adjust the upper water roller.

The pressure of the upper water roller is better than the pressure of the lower water roller, because it can use the upper water roller to collect excess water on the plate, which 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 between the two ends will be easily generated. .

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 to prevent the water roller from being in parallel. The contact pressure between the printing roller and the printing plate cannot be too heavy. Otherwise, the plate friction force will be increased and the printing plate will be subject to wear. This will make the plate “texture” and the printing force reduced, and it will also cause the water roller and printing. When the touch occurs in the touch screen, the jumped parts are dirty, and the parts that fall again have "water bars" (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 inappropriately increasing the amount of water, it will cause the layout water to be too large. So how do you determine if the contact pressure is in the optimal adjustment position? According to the experience, by pressing the water roller and the plate together, the machine is turned on, and then the plate holder is pressed by hand to determine if there is a beating phenomenon during operation.

Since the plate cylinder has the difference between the printing surface and the neutral position, the pressure of the contact pressure of the printing plate roller is easily felt. Under normal circumstances, the feeling of a slight jump is the most appropriate. If the jump is serious, it means that the pressure is too heavy. Then you should adjust it again.

To adjust the water transfer mechanism, the following work must be done: First, the pad of the printing plate should meet the standard; second, the water solution in the water tank should be free of impurities; third, the water roller must be changed frequently; and the fourth is the water roller and string water. The rollers must be cleaned and must be kept clean.