Cleaning operations and precautions during offset printing

The cleaning of printing plates, rubber blankets, water rollers, ink rollers, etc. is one of the main contents of the daily operation of offset printing. Proficient and timely cleaning operations can not only improve the printing durability of the printing plate and the service life of the blanket, but also It is of great significance to guarantee the quality of the printed matter, compress the auxiliary production time, and make the production go smoothly.
PS Plate Cleaning and Protection Purpose of Cleaning Plates Cleaning plates means applying or scrubbing the plate with materials such as water, glue, fountain solution, and gasoline. Its main purpose is:
1. Protect the printing plate. During the stoppage of the printing process, water or glue is applied to the layout to form a water film or film, so that the non-graphic part of the printing plate is isolated from the oxygen in the air to prevent the layout from becoming dirty. In addition, freshly printed plates or plates that are not used for a long time can be protected by coating glue.
2. The layout is dirty. When the non-graphic part of the printing plate appears dirty, it can be removed with glue, fountain solution, dampening solution, dirt removing agent, cleaning solution, and gasoline.
3. Improve the clarity of the graphic. When the text of the layout is light or enlarged, it can be rubbed with materials such as gasoline, dampening solution, and glue to increase the clarity of the graphic and text.
Before the start of the cleaning work, various cleaning materials must be prepared in order to improve the cleaning quality and efficiency.
1. Water. It is mainly used for wetting paper, paper powder and other debris on the surface of the plate or cleaning plate or cleaning blanket. In order to ensure the quality of wetting and cleaning, the water stored in the bucket should be kept as clean as possible without oil, and the water must be changed in time.
2. glue. Also known as hydrophilic colloids, it is mainly used to coat plates, dirty or add fountain solution, to protect the printing plate and enhance the non-graphical part of the plate hydrophilic properties, improve the clarity of images and texts.
Common gums are gum arabic and carboxymethyl cellulose (CMC)
3. Fountain solution. Also known as the fountain solution, it is mainly used to wet the layout or remove the non-image part of the printing plate. It plays the role of stabilizing and enhancing the hydrophilicity of the non-graphical part and maintaining the balance of water and ink. The undiluted dampening fluid becomes a dampening stock solution, which can effectively remove the stain on the plate.
4.PS version cleaner. It has been widely used in many printing plants and can effectively remove dirt from the layout and enhance the hydrophilic properties of the blank part of the printing plate. The disadvantage is that the cost is too high.
Operation Method and Procedure 1. Selection of Cleaning Wipes. Wiping cloth is the main tool for cleaning printing plates. It must be kept as clean as possible, and it cannot have hard materials such as grit. The cleaning cloth cleaning cloths mainly include water wipes, rubber wipes and gasoline wipes. You must pay attention to the following four points when choosing a cleaning cloth:
1) Water wipes and wipes must use soft, absorbent cotton gauze instead of wrapping or yarn. Water wipes and wipes can be used together or separately, but they must be rinsed in clean water before use.
2) You can use ordinary cotton cloth (such as packing cloth, etc.) instead of chemical fiber fabric or yarn head.
3) Water and adhesive wipes must be strictly separated from gasoline wipes.
4) The size of the cleaning cloth should be appropriate, too large or too small is not conducive to operation. In general, the sum of the length and width is about 80mm, and the thinner cotton gauze can be slightly larger. Of course, we must also consider the operator's own handy.
2. Wipe the surface of the printing plate 1) Remove the water cloth after repeated rinsing in the water, and gently wipe the cloth with water by one hand and drop without water to determine the moisture content of the cloth. In addition, the downtime is short, the moisture content of the wipes can be less; otherwise it can be more.
2) The grip of the cloth is to hold the four sides and the four corners in the palm of the hand, and close to the palm of the hand (to prevent the edges of the cloth from scratching the printing plate or being caught in the machine).
3) Jog the machine or make the machine run at a low speed, take a “8” shape on the layout, and wipe the surface of the layout (this will ensure uniform and rapid application of water to the plate).
3. Erasing the surface of the printing plate 1) Unscrew the tape after repeatedly rinsing it in the water, and grasp the wipe with one hand without dropping drops of water to determine the moisture content of the wipe.
2) The grip of the tape is the same as that of the water cloth.
3) According to the printing plate area to take appropriate amount of glue, the glue can not drop naturally is appropriate.
4) The route of rubbing the rubber is the same as the route of rubbing the water. The rubbing glue is generally wiped 2-3 times to meet the requirement of the flat, thin, uniform and complete adhesive layer.
4. Use petrol to clean the plate and remove some of the original ink film from the image and ink with gasoline. Replace it with new ink before printing to ensure product quality. The operation process is as follows: First, the plate is washed with water cloth (if the new plate should be completely washed out), then the ink of the plate graphic is washed with a gasoline wipe, and then the plate is washed thoroughly with water cloth 1 or 2 times. The specific operation method for cleaning the plate with gasoline is basically the same as the method for cleaning water. (If the conditions permit, you can use Jie Jie liquid instead of gasoline to clean the layout, but pay attention to when the layout is clean, you should use water cloth to wipe the plate in a timely manner to avoid off-screen).
Easy to produce problems and precautions 1. Use water or glue to wash the printing plate (commonly known as water or wipe glue), can play a role in protecting the printing plate. Which method you choose to protect the plates depends on the length of downtime. When you have a long downtime, you must wipe off the glue.
2. If there is a certain amount of oil on the water wipe, it is easy to make the non-graphic part of the plate dirty after the water is wiped. Therefore, wipe the water before you wipe the water and rinse it in water. The water in the bucket should be replaced frequently.
3. When the water is wiped, the water on the layout should be moderate and even, and there must be no omission. Otherwise, the ink or the dirty version may be washed down.
4. When wiping glue, the film should be as thin and uniform as possible. For a long period of time, wipe the film with a dry cloth after wiping. The film is too thick, which can easily cause a reduction in the ink absorption of dirty plates or graphics.
5. When the rubber is wiped off, glue drops should be avoided on the blanket; at the same time, the wiper must not touch the ink roller and the roller.
6. When the machine is stopped for a long time, the water roller should not touch the plate to prevent it from being dirty.
7. When cleaning plates with gasoline, pay attention to the sequence of operation; when rubbing gasoline, the action should be rapid; when the cleaning is completed, you should pay attention to ink and water immediately.
8. After cleaning the plate with the cleaning solution, be careful to clean the plate cleaning solution on the plate with water immediately to avoid ablation of the plate by the cleaning solution.
Blanket Cleaning Cleaning blanket material commonly used materials are water, gasoline, kerosene, pumice, sulfur powder, talcum powder, blanket cleaning agent, rubber blanket reducing agent.
Cleaning the New Blanket 1. The surface of the new blanket has a protective film. Therefore, before using a new blanket, this protective film must be removed, otherwise it will affect the ink absorption of the blanket.
2. Pouring a proper amount of kerosene on the blanket or pouring the kerosene onto a cloth.
3. Spread pumice powder on the blanket or pumice powder with a kerosene wipe.
4. Repeatedly wipe the blanket.
5. Pour gasoline and clean pumice powder with a cloth.
6. Wipe the blanket clean with a dry cloth.
7. Wrap talcum powder with 2-3 cotton gauze and apply talc evenly over the surface of the blanket.
Daily cleaning of the blanket In the daily printing process, the blanket continuously contacts the ink and the paper, and the ink on the printing plate graphic is transferred to the paper, so the blanket inevitably adheres to certain ink and paper hair. And paper powder (filler in paper) and other substances. This adhesion phenomenon is more serious when the blanket is sticky, printed with inferior paper, or the pigment used in the ink is coarse, with a large specific gravity and a low viscosity. Therefore, during the printing process, the rubber should be visually recognized. Cloth surface accumulation and different job requirements. Regular cleaning of the blanket ensures and enhances the clarity of the graphic and extends the life of the blanket.
1. Prepare the materials used for cleaning and prepare a piece of water, a cloth, and a dry cloth.
2. The grip of the cloth is the same as that when it is wiped.
3. Jog the machine or make the machine run at a low speed, wipe the water from the mouth of the blanket until it is slightly stretched.
4. Jog the machine from the blanket's drag to the mouth or when the machine is running to the mouthwash. Wipe the blanket with gasoline to dissolve the ink on the blanket.
5. When jogging the machine or when the machine is re-run to the mouthwash, use a clean cloth to remove grease and impurities from the surface of the blanket.
Special cleaning of blanket
If the blanket is used for too long or because of improper maintenance, a smooth film or stickiness will form on the surface of the blanket, which will not only affect the clarity of the printed text, but also cause the printing work to not proceed smoothly. Therefore, it is necessary to wash off the smooth film layer or to stick the blanket for processing.
1. Treatment of blanket smoothing film: Remove the blanket together with the splint from the machine and lay it flat on a flat surface with the same cleaning method as the new blanket; or clean it with water on the machine. Wipe with pumice powder with petrol.
2. The sticky remedy of the blanket: The blanket is sticky, which is mainly due to its poor durability and swelling or aging of the blanket. Severe stickiness will cause the blanket to continue to be used. Mild stickiness will also cause the printing paper to adhere to the blanket. Therefore, stickiness should be detected as soon as possible and the blanket should be cleaned in time.
3. The cleaning method is: first use gasoline to wash off the ink layer on the surface of the blanket, wipe it with a dry cloth, and then use volatile solvent gasoline or a small amount of industrial alcohol in gasoline (also can use rubber reducer ) Wipe the blanket, then use talcum powder to mix sulfur powder to wipe the surface of the blanket and reduce the stickiness of the blanket.
Easy problems and precautions:
1. When pumice powder is used, it must be ensured that the pumice stone does not contact the plate or fall into the underlay, otherwise it will accelerate the wear of the corresponding part of the plate.
2. The interval between daily cleaning of the blankets should be based on the blanket accumulation and different job requirements. The general rule is: when changing the color, it must be cleaned once; during regular printing, about 3,000-5,000 sheets should be cleaned once; Every day before work (after shut-down) should be cleaned once; the test printing process should be cleaned at least once.
3. The finger should be light when jogging the machine. At this time, the hand holding the blanket should leave the surface of the drum; after the jog is completed, the finger should leave the button during the scrubbing process.
4. When cleaning, avoid contact with solvents such as gasoline on both sides of the blanket.
5. The liner that is lined with the blanket should be narrower than the blanket to prevent the penetration of solvents such as gasoline.
6. Spare or long-term unused blankets, should be cleaned, talc powder, wrapped in protective paper, stored in a closed container or a well-ventilated, cool, dry place, avoid oil and acid, alkali, salt And other chemicals come in contact and avoid being squeezed. When printing on the machine, it must be cleaned like a new blanket.
7. Kerosene should not be used when cleaning the blanket daily.
8. When using a device that automatically cleans the blanket, strictly control the amount of cleaning agent.
In the printing process, the water transfer roller and the water roller (water roller type) are cleaned. Because the water roller and the printing plate are repeatedly contacted, after use for a period of time, on the other hand, ink and other debris are attached from the printing plate. one