Offset cleaning operation and precautions

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 version cleaning and protection

First, the purpose of cleaning the printing plate

Cleaning plates refers to painting or scrubbing plates 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 graphics. 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.

Second, the preparation

Before the cleaning work begins, 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.

Third, the operation method and steps

1. Choose the cleaning cloth.

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. Plate surface rubs water

1) Remove the water cloth after repeated rinsing in the water, and gently wipe the cloth with one hand without water drops 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. Printing plate surface eraser

1) Unscrew the tape after repeatedly rinsing it in water, and grasp the wipe with one hand without water drops 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. Clean the layout with gasoline

The original ink film of the graphic part is washed away with gasoline, and the new ink is printed before printing to ensure the 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 problems and precautions

1. Clean the plate with water or glue (commonly known as water or wipe) to protect the 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 stain 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 gluing, the film should be as thin, uniform and complete 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 the plate with gasoline, pay attention to the sequence of operation; when rubbing the gasoline, the operation should be rapid; when the cleaning is completed, the ink and the water should be noticed 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.