As one of the important parts of the offset printing machine, the rubber roller has a close relationship with the printing quality. Therefore, how to use and maintain the rubber roller scientifically and correctly is very important. Take a 4-color offset printing machine as an example: the complete set of ink rollers with 4 color groups of the machine is worth about 50,000 yuan. If carefully cared for and scientifically adjusted, its average service life can reach 2 years; if it is used improperly, its average use The life span will be shortened to 1 year or half a year. Therefore, strengthening employees' sense of responsibility and improving their operating skills are of great significance for ensuring product quality, reducing maintenance costs, improving economic efficiency, and promoting enterprise development.

1 Reason analysis of abnormal damage of rubber roller

According to the author's many years of practical experience, the reasons for the abnormal damage of the rubber roller are generally as follows.

(1) During installation and disassembly, the roller body or the rubber surface was damaged.

(2) The rubber roller shaft head and the bearing are not tightly matched or the bearing performance is poor, causing the rubber roller to be rubbed, squeezed, etc., and it is easy to accelerate the rubber roller's cracking and aging.

(3) There are too many impurities such as ink skin and ink residue on the rubber roller, which accelerates the friction and aging between the rubber rollers, so that the surface of the rubber roller is covered with numbs and cannot accurately transfer water and ink.

(4) Improper selection of the cleaning agent of the rubber roller, such as gasoline, reducing agent, strong acid, strong alkali, etc., will cause the surface of the rubber roller to crack and drop slag.

(5) The pressure between the rubber rollers is too large, causing the rubber rollers to be deformed due to extrusion, and the rubber heats up and expands, and the rubber rollers are shelled directly from the rubber roller core, resulting in the rubber rollers being scrapped.

(6) The high temperature in the workshop caused the rubber roller to fail to dissipate heat in time during operation, and the cohesive temperature of the rubber continued to rise, which accelerated the aging of the rubber.

(7) The ink dries too fast and the emulsification is serious, and it will continue to accumulate on the two ends of the rubber roller, thereby increasing the pressure between the rubber rollers here in disguised form, accelerating its wear,

Ageing.

(8) The ink discharge keys at both ends of the ink fountain are closed, causing the rubber roller to fail to receive ink replenishment at both ends, and the rubber roller is often in a dry friction state and damaged.

(9) In a multi-color printing machine, due to the small number of colors of a certain printed product, the rubber rollers of other color groups are idling for a long time, causing them to be in a dry friction state and damaged.

(10) If the printing plate is not pulled tightly or clamped tightly, the trailing edge of the printing plate often breaks. When the rubber roller runs close to the printing plate cylinder, the rubber surface of the rubber roller will be scratched, causing the rubber roller to be scrapped.

(11) Improper storage of the rubber roller, for example, it is not stored in the dark, which causes the rubber roller to be crushed and scratched by sharp objects.

There are many reasons for the abnormal damage of the rubber roller, but as long as you carefully analyze and find the root of the problem, the damage of the rubber roller can be avoided.

2 The correct use of rubber rollers

1. Install rubber roller bearings correctly

First of all, clean both sides of the rubber roller, and then select bearings with specifications and models that meet the design requirements of the machine, and apply a layer of lubricating oil evenly on each mating surface, and then use the special sleeve for mounting the bearing to evenly force the bearing. Make it smoothly installed in place. Never apply force directly to the bearing surface to avoid damage to the bearing.

2. Regulate the pressure between the ink rollers

During the printing process, the water roller and the ink roller must continuously and evenly provide an appropriate amount of water and ink to the printing plate, so as to obtain printed products with consistent ink color. Therefore, proper pressure must be maintained between the rubber roller and the rubber roller, between the rubber roller and the printing plate, in order to achieve good ink transfer. In order to ensure the pressure between the water roller and the ink roller, the width of the ink roller must be used, which mainly includes the following points.

(1) Add appropriate amount of yellow ink evenly on the clean rubber roller, and then run the machine to make the ink evenly distributed on the surface of the ink roller.

(2) Jog the printing machine to check the width of the pressure bar. It is worth noting that before checking the width of the pressure bar, the printing machine should be kept stationary for about 20 seconds, and then the printing machine can be moved to get a clear pressure bar again.

(3) Priority should be given to adjusting the pressure between the inking roller and the inking roller, and then adjusting the contact pressure between the inking roller and the printing plate, and then adjusting the pressure between the other inking rollers respectively.

(4) Refer to the operating instructions of the printing machine, the width of the pressure bar between the ink rollers is generally 4mm. But for the ink roller with smaller diameter and better sensitivity and elasticity, the appropriate width of the pressing bar is 3mm; on the contrary, the appropriate width of the pressing bar is 5mm.

(5) The width of the pressure bar between the water rollers should be 5~6mm. The pressure of the water roller to the metering roller should generally be such that the water film layer at both ends of the water roller just has no obvious water droplets.

(6) When the pressure of all the water rollers and ink rollers are adjusted, the adjusting screws must be fixed in time to prevent the printing press from running out of position after rotating.

3. Remove the rubber roller correctly

Each time the rubber roller is disassembled, the employees should coordinate and unify the adjustment screw to loosen 2 turns. When reinstalling the rubber roller, only need to tighten 2 turns in the opposite direction. Even if there is an error, it can be fixed quickly. At the same time, check the quality of each bearing. If it feels swaying, blocking, etc., it must be replaced immediately.

3 Correct maintenance method of rubber roller

1. Ensure the lubrication of each shaft sleeve and shaft seat

In actual work, the water roller seat and the ink roller seat are often severely worn, and the roller will be damaged after the bearing is broken, which will cause greater losses. Therefore, before all the rubber rollers are installed, the bearings, bushings, shaft seats, brackets, etc. on both sides of the rubber roller should be coated with lubricating oil to minimize the friction of the inking roller due to the back and forth movement of the inking roller. Its friction on the bearing seat.

2. Maintenance of the rubber rollers of each color group of the printing machine

The rubber roller of any printing machine will gradually become smaller in diameter after 2 to 3 months of use, which will affect the accurate transfer of water and ink. At this time, the rubber rollers of each color group of the printing press should be maintained in sequence, and the pressure between the rubber rollers should be re-adjusted.

3. Cleaning of rubber roller

The rubber roller should have good ink absorption and ink transfer. Generally, the surface of the high-quality rubber roller is fine and smooth. However, since the rubber roller has to be in contact with water, ink, paper, etc. for a long time, residues will inevitably accumulate on the rubber roller. Although the rubber rollers have to be cleaned every time, some residues cannot be completely cleaned. Over time, a smooth crystalline layer similar to calcium will form, which firmly adheres to the surface of the rubber rollers, blocking it. The capillaries lose their elasticity and become harder, which seriously affects the performance of ink transfer and water transfer, so that the ink color of the printed product cannot be controlled stably.

At present, although many companies have developed a fountain solution to prevent the calcification of rubber rollers, and the effect is good, but the price is relatively expensive and cannot be widely used. In order to solve this problem, printing companies should often use special accumulation paste and accumulation water to clean the rubber rollers, but this method is time-consuming, laborious, and virtually increases production costs. Therefore, the author thinks that a better way is to wash the rubber roller with a small amount of citric acid water every time after washing the rubber roller to make some calcium impurities on the surface chemically react, and then clean it.

Some people think that such careful use and maintenance of rubber rollers will waste a lot of time. Don't you know that the ancients said that "knife sharpening does not cut wood by mistake" and "practice makes perfect". As long as you stick to standardized operations for a long time and continuously improve your technical skills, it will naturally become more complicated. In order to simplify, greatly reduce the labor hours consumed by this, so that the rubber roller can be more fully utilized.