Ink roller maintenance and common troubleshooting
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The printed ink roller mainly transfers ink on the offset printing machine. In order to make the ink transfer evenly and meet the needs of various printing products, in addition to a certain number of ink rollers, the ink roller usually has three forms: ink supply, Evening ink and squeezing ink require ink roller to have good ink absorption and ink transmission during printing, and it is resistant to organic solvents, gasoline, kerosene and other oils, and is easy to clean. At present, the surface rubber of the rubber roller commonly used in offset printing presses generally uses nitrile rubber.
Whether the daily maintenance of the ink roller is reasonable or not has a direct relationship with the service life of the ink roller. Since the offset ink roller is made of rubber, it is easy to expand and deform, the surface is dry and conjunctiva or aging cracks, which affects the normal transmission of the ink. Therefore, it is very important to use and maintain the ink roller in daily use.
1.Every day after work and after the product is printed, when cleaning the rubber roller daily, it must be carefully cleaned to avoid the surface layer of the rubber roller and the ink pigment and resin oxidized to form a smooth and hard film, which is called vitrification and affects the offset printing. ink. Cleaning is usually done first with kerosene and then with gasoline. Because kerosene is not easy to evaporate, the gasoline is easy to evaporate, which makes the ink roller clean and dry, and protects the ink roller. Nowadays, many manufacturers use ink detergent (car wash water) to clean the rubber roller. When cleaning, pay attention to cleaning the two ends of the ink roller, because the two ends of the offset roller are easy to accumulate ink and produce crust drying. You can't rely solely on the wiper to clean it, use clean linen to clean the wiper, and clean both ends.
2.Prevent the ink roller from being deformed under pressure. When the offset printing machine is in normal operation, the pressure of the rubber roller is comprehensive and uniform, so that the rubber roller does not have a concave protrusion or the like in a certain part. The offset printing device presses the ink roller in a fixed position after a long shutdown, which creates the possibility of partial depression. Therefore, if you have long downtime or encounter holidays and long holidays, the best way is to remove the ink roller and put it on the ink roller shelf. Do not put the ink roller on the ground or work table to prevent pressure. Deformation.
3.Prevents the ink shovel of debris and ink fountains from scratching and crushing the ink roller. When working, the offset printing machine should be kept clean and tidy. The tools used in various tools and offset printing cannot be randomly placed. Do not accidentally drop debris, ink shovel, coins, etc. into the running ink roller. This will crush the ink roller. When evaluating the ink roller, adjust the pressure between the ink roller and the printing plate, and the pressure between the various ink rollers and the ink roller, measure with a thick gauge steel sheet, and try to insert the number of times as much as possible to prevent scratching the ink. Roller.
4.The ink roller is used to oxidize the conjunctiva after a long time. In the offset printing process, the bright-light fast-drying resin ink is commonly used. The quick-drying feature is that the drying oil and the diffusing agent are added to the surface of the rubber roller for a long time, and the coarse capillary pores are closed to form an oxidized conjunct film to make the rubber roller. The effect of reducing the fatness affects the effect of ink absorption and ink transfer. The way to eliminate this drawback is to remove the conjunctiva layer by manual or mechanical polishing, but it should be noted that the diameter of the ink roller cannot be changed too much, otherwise it will affect the ink transfer. performance.
5.The surface of the ink roller is composed of nitrile rubber. There are two forms of rubber aging: one is the photoaging of rubber, which will affect the ink transfer performance of the ink roller; the other is the thermal aging of rubber, which affects the softening and softening of the rubber surface. Sticky, even cracks, require the printing ink roller to maximize the adsorption and transfer of ink, while at the same time minimally adsorbing moisture, but also have good oil resistance and certain acid resistance, because of the water, ink, paper, etc. Continuous contact may cause adsorption to the surface of the rubber ink roller to form a film state, which weakens its lipophilicity and enhances hydrophilicity.
The aging of the ink roller is always a phenomenon. The ink roller should be stored in a place where there is no direct sunlight, dry and clean, and avoid excessive humidity or overheating. The ink roller should be straight at the journal end and the surface should not be Contact with each other or with other surfaces.
6.Due to the emulsification of the ink, the oleophilic performance of the offset printing machine is often easy to deink, and the hydrophilic film on the surface of the squeegee roller is relatively easy to remove. If the polar inorganic salt layer is formed, sodium hydroxide must be used. The 5% solution was completely removed. On the other hand, it should be noted that if the moisture particles in the emulsified ink contain an oxidizing agent, once it is excessive, black copper oxide is formed on the copper surface of the iron squeegee roller, and deinking may occur.
7.The ink roller is deinked. Since offset printing is a unique printing method for water, there is an ink emulsification phenomenon in water, and a hydrophilic foundation is formed on a smooth rubber roller to cause deinking of the ink roller. The solution is to remove the emulsified ink. The deinked ink roller is cleaned with a hydrophilic base and an emulsified ink. The 5% sodium hydroxide aqueous solution is mixed with the pumice powder to polish the surface of the ink roller to remove the hydrophilic foundation and let the ink The roller has oleophilic properties, and at the same time, it should also pay attention to the proportioning method of the offset water hopper solution, control the pH value of the water hopper solution, use the minimum amount of water under the premise of not being dirty, and reduce the degree of emulsification, gum arabic, The amount of surface active material added should not be too much.
Common faults and solutions for ink rollers
1. The ink roller becomes flat
Main reasons: 1 The position of the ink roller is not properly placed. It is not placed on the special rubber frame, but placed on the floor and stored on the work table. 2 Long-term shutdown, holiday holiday, rubber roller stop, rubber roller and The rubber rollers are still in a working state and have pressure. In short, it is caused by the deformation of the ink roller.
Solution: 1 Place the ink roller correctly. When the ink roller is not in use, it should be placed upright on the rubber frame. 2 The rubber roller under pressure deformation can be rotated in hot water to correct the deformation and make it round; 3 can not be corrected The rubber roller is ground and physically rounded.
2. The entire surface of the ink roller and the local crack
The main reason: 1 If the ink roller produces deep cracks on the whole surface, it will not continue to be used in the case of fine cracks, and will continue to be used by ozone. 2 The fine cracks appear on the whole surface due to the ink roller and ink. The pressure between the rollers is too large, and the ink roller is stored for a long time under inappropriate conditions, such as long-term exposure to direct sunlight or heat aging. 3 Localized cracking of the ink roller is uneven pressure between the ink rollers, and the ink roller is partially affected. Caused by uneven pressure.
Solution: 1 For the slightly cracked ink roller to be ground, the ink roller is very deep, it is necessary to replace the ink roller; 2 to avoid the offset printing machine directly exposed to sunlight, photoaging, heat aging, adjusting the ink roller and ink roller The gap between the two, reduce the pressure, when the rubber roller appears fine cracks, it is necessary to grind the surface in time; 3 adjust the pressure between the ink roller and the ink roller to be uniform.
3. The ink roller is partially uneven
Main reasons: 1 The pressure between the ink roller and the ink roller is too large, and the contact surface or the rubber sleeve layer is peeled off; 2 The surface of the ink roller softens into unevenness, is soaked by an organic solvent, or is impregnated with other chemicals.
Solution: 1Adjust the pressure between the ink rollers and replace the new rubber sleeves in time; 2 Prevent the ink rollers from being soaked in organic solvents such as banana water, benzene solvents and trichloroethylene.
4. Ink roller surface hardening
Main reasons: 1 The rubber roller is used for a long time and is caused by long-term erosion of light, heat and chemicals. 2 The ink roller is in contact with the ink for a long time, and it is easy to adhere to the hardening ink film.
Solution: The ink roller will grind off the hardened surface and replace the rubber sleeve if necessary.
5. The ink roller is completely peeled off
The main reason is that the pressure between the rollers is too large, and the pressure should be adjusted to an appropriate level.
6. The rubber sleeve at both ends of the ink roller is peeled off from the core
The main reason: because of abnormal heat, find the friction and heat, and heat it.
7. The roundness is slightly larger
The main reason: long-term compression of the ink roller, causing its deformation to appear aging or wear.
Solution: Grind in time to make it round.